Adding splitting screen and buffer switching

assets/beluga.txt

@@ -9,7 +9,7 @@
     #----------------------------------------------------------##                   
    #=--------------------------------------------------------------##                
   +--------------------------+@#-%*-----------------------------------#*         
-  +--------------------------%@@@@#-------------------------------------**                              BELUGA - VERSION 2.2.1
+  +--------------------------%@@@@#-------------------------------------**                              BELUGA - VERSION 2.3
   *-=-------------------------#@@*---------------------------------------=%
   %*#==--------------------------------------------------------------------+#                           ----- KEY-BINDS -----
   *%%=-=--------------------------------------------------------------------=#                          CTRL-x CTRL-c  leave

config/init.lisp

@@ -81,5 +81,10 @@
 (map-key "f" editor-open-file "user")
 (map-key "TAB" editor-insert-tab "no-prefix")
 (map-key "CTRL-k" editor-del-row "no-prefix")
-(map-key "CTRL-s" editor-find "no-prefix")
+(map-key "CTRL-s" buffer-find "no-prefix")
 (map-key "CTRL-r" editor-move-to-end-of-word "no-prefix")
+(map-key "ARROW-RIGHT" editor-switch-next-buffer "user")
+(map-key "\"" editor-split-screen-vertical "user")
+(map-key "o" editor-switch-next-pane "user")
+(map-key "*" editor-unify-panes "user")
+

include/buffer.h

@@ -1,8 +1,58 @@
+/**
+ * @file buffer.h
+ * @brief Buffer management for handling multiple open files
+ */
+
 #ifndef BUFFER_H_
 #define BUFFER_H_
 
 #include "data.h"
 
-int new_buffer(enum buffer_type type, char * filename, int width, int height);
+/**
+ * @brief Creates a new buffer for a file
+ * @param filename Path to the file
+ * @return Buffer ID on success, -1 on failure
+ */
+int bufferCreate(const char *filename);
+
+/**
+ * @brief Switches to a specific buffer by ID
+ * @param buffer_id The buffer ID to switch to
+ * @return 0 on success, -1 on failure
+ */
+int bufferSwitch(int buffer_id);
+
+struct buffer_t *bufferFindById(int buffer_id);
+
+/**
+ * @brief Closes a buffer by ID
+ * @param buffer_id The buffer ID to close
+ * @return 0 on success, -1 on failure
+ */
+int bufferClose(int buffer_id);
+
+/**
+ * @brief Gets the current active buffer
+ * @return Pointer to current buffer_t, NULL if none
+ */
+struct buffer_t *bufferGetCurrent(void);
+
+/**
+ * @brief Lists all open buffers
+ * @return Number of open buffers
+ */
+int bufferListAll(void);
+
+/**
+ * @brief Saves current buffer to disk
+ * @return 0 on success, -1 on failure
+ */
+int bufferSave(void);
+
+/**
+ * @brief Saves all buffers to disk
+ * @return 0 on success, -1 on failure
+ */
+int bufferSaveAll(void);
 
 #endif

include/builtins.h

@@ -3,45 +3,53 @@
 
 #include "lisp.h"
 
+// Mouvement
+
 Lisp moveCursor(Lisp args, LispError *e, LispContext ctx);
-
-Lisp mapKey(Lisp args, LispError *e, LispContext ctx);
-
-void registerBuiltin(char * key_sequence, LispCFunc f);
-
-Lisp editorQuit(Lisp args, LispError *e, LispContext ctx);
-
-Lisp l_editorSave(Lisp args, LispError *e, LispContext ctx);
-
-Lisp l_editorInsertNewLine(Lisp args, LispError* e, LispContext ctx);
-
 Lisp moveCursorBeginLine(Lisp args, LispError *e, LispContext ctx);
-
 Lisp moveCursorEndLine(Lisp args, LispError *e, LispContext ctx);
-
-Lisp l_editorInserTab(Lisp args, LispError *e, LispContext ctx);
-
-Lisp deletePreviousChar(Lisp args, LispError *e, LispContext ctx);
-
 Lisp editorMoveCursorPageUp(Lisp args, LispError* e, LispContext ctx);
-
 Lisp editorMoveCursorPageDown(Lisp args, LispError *e, LispContext ctx);
 
-Lisp editorOpenFile(Lisp args, LispError *e, LispContext ctx);
+// Text editing
 
+Lisp l_editorInsertNewLine(Lisp args, LispError* e, LispContext ctx);
+Lisp l_editorInserTab(Lisp args, LispError *e, LispContext ctx);
+Lisp deletePreviousChar(Lisp args, LispError *e, LispContext ctx);
 Lisp editorPrintC(Lisp args, LispError *e, LispContext ctx);
-
-Lisp addPackage(Lisp args, LispError *e, LispContext ctx);
-
 Lisp editorDelRow_L(Lisp args, LispError *e, LispContext ctx);
-
-Lisp editorFind_L(Lisp args, LispError *e, LispContext ctx);
-
 Lisp editorReadChar_L(Lisp args, LispError *e, LispContext ctx);
 
-Lisp editorSetPrefix(Lisp args, LispError *e, LispContext ctx);
+// Editor
 
+Lisp editorQuit(Lisp args, LispError *e, LispContext ctx);
+Lisp l_editorSave(Lisp args, LispError *e, LispContext ctx);
+Lisp editorSetPrefix(Lisp args, LispError *e, LispContext ctx);
 Lisp editorPrefix(Lisp args, LispError *e, LispContext ctx);
+Lisp mapKey(Lisp args, LispError *e, LispContext ctx);
+void registerBuiltin(char * key_sequence, LispCFunc f);
+Lisp editorOpenFile(Lisp args, LispError *e, LispContext ctx);
+Lisp addPackage(Lisp args, LispError *e, LispContext ctx);
+
+
+// Buffer
+
+Lisp editorSwitchNextBuffer(Lisp args, LispError *e, LispContext ctx);
+Lisp bufferFind_L(Lisp args, LispError *e, LispContext ctx);
+
+
+// Pane
+
+Lisp l_editorSplitScreenVertical(Lisp args, LispError *e, LispContext ctx);
+Lisp editorSwitchNextPane(Lisp args, LispError *e, LispContext ctx);
+Lisp editorUnifiedPanes(Lisp args, LispError *e, LispContext ctx);
+
+
+
+
+
+
+// Other
 
 void free_structs(void);
 

include/data.h

@@ -13,12 +13,50 @@
  * \param
  * */
 
-typedef struct erow {
+typedef struct frow {
   int size;     /**< Size of the line */
   int rsize;    /**< Size of the render line */
   char *chars;  /**< Characters of the line */
   char *render; /**< The actual line we will print */
-} erow;
+} frow;
+
+
+/**
+ * @brief Split modes for screen layout
+ */
+typedef enum {
+    SPLIT_NONE = 0,      // Single buffer fullscreen
+    SPLIT_VERTICAL,      // Left-right split
+    SPLIT_HORIZONTAL     // Top-bottom split
+} SplitMode;
+
+/**
+ * @brief Represents an editor viewport/pane
+ */
+typedef struct {
+    int buffer_id;        // Which buffer this pane displays
+    int start_row;        // Starting row on screen
+    int start_col;        // Starting column on screen
+    int height;           // Height of this pane
+    int width;            // Width of this pane
+    int cursor_x;         // Local cursor x in this pane
+    int cursor_y;         // Local cursor y in this pane
+  int rx, ry; 
+    int row_offset;       // Scroll offset for rows
+    int col_offset;       // Scroll offset for columns
+    int is_active;        // Is this pane currently active
+} EditorPane;
+
+/**
+ * @brief Screen layout manager
+ */
+typedef struct {
+    SplitMode mode;
+    EditorPane *panes;
+    int num_panes;
+    int active_pane;      // Index of active pane
+} ScreenLayout;
+
 
 typedef struct theme {
   char *BACKGROUND_COLOR;
@@ -31,7 +69,7 @@ typedef struct theme {
 
 } theme_t;
 
-enum editorStatus_e {
+enum bufferStatus_e {
   IDLE,
   READ_ONLY,
   READ_AND_WRITE,
@@ -60,8 +98,14 @@ struct buffer_t {
   enum buffer_type type;
   int buffer_id;
   int width, height;
-  int x, y; /**< Position of the buffer*/
+  int x, y; /**< Position in the buffer (cursor) */
+  frow *row;
+  int numrows;
   char *filename;
+  enum bufferStatus_e state;
+  int dirty;             /**< Has this buffer been modified since last save */
+  int row_offset;        /**< Scroll offset for rows in this buffer */
+  int col_offset;        /**< Scroll offset for columns in this buffer */
 };
 
 /**
@@ -69,17 +113,12 @@ struct buffer_t {
  * \brief Containing our editor state.
  */
 struct editorConfig {
-  int cursor_x, cursor_y; /**< Cursor position */
-  int rx;                 /**< Position in the render*/
-  int row_offset;         /**< Position scroll of lines */
-  int col_offset;         /**< Position scroll of colomns*/
   int screenrows;         /**< Terminal height*/
   int screencols;         /**< Terminal width*/
-  int numrows;            /**< Number of rows contained */
+
-  erow *row;              /**< Store all the rows printed */
+  ScreenLayout layout;
+  
   int dirty;
-  char *filename;
-  enum editorStatus_e state;
   int prefix_state;
   char status_msg[80];
   time_t status_msg_time;
@@ -102,7 +141,6 @@ struct editorConfig {
   int number_of_prefix;
 
   struct buffer_t buffers[64];
-  struct buffer_t ***screen_layout; /**< Which buffer is the current cell*/
   int number_of_buffer;
 
   theme_t theme;

include/editor_op.h

@@ -2,11 +2,11 @@
 #define EDITOR_OP_H_
 
 #include "data.h"
-void editorInsertChar(int c);
+void bufferInsertChar(int c);
 
-void editorInsertNewLine();
+void bufferInsertNewLine();
 
-void editorDelChar();
+void bufferDelChar();
 
 void editorSetStatusMessage(const char *fmt, ...);
 

include/file_io.h

@@ -8,15 +8,15 @@
 #include <stdlib.h>
 #include <sys/types.h>
 
-char *editorRowsToString(int *buffer_len);
+char *bufferRowsToString(struct buffer_t *buf,int *buffer_len);
 
 
 void editorCloseFile(void);
 
-void editorOpen(char *filename);
+void editorOpen(struct buffer_t *buffer);
 
 void editorSave();
 
-void editorFind();
+void bufferFind(struct buffer_t *buf);
 
 #endif // FILE_IO_H_

include/output.h

@@ -1,11 +1,7 @@
 #ifndef OUTPUT_H_
 #define OUTPUT_H_
 
-#include "append_buffer.h"
 #include "data.h"
-#include "define.h"
-#include "row_op.h"
-#include <stdio.h>
 #include <unistd.h>
 
 /**

include/row_op.h

@@ -8,22 +8,22 @@
 #include <time.h>
 #include <unistd.h>
 
-int editorRowCxToRx(erow *row, int cursor_x);
+int bufferRowCxToRx(frow *row, int cursor_x);
 
-int editorRowRxToCx(erow *row, int rx);
+int bufferRowRxToCx(frow *row, int rx);
 
-void editorUpdateRow(erow *row);
+void bufferUpdatfrow(frow *row);
 
-void editorInsertRow(int at, char *s, size_t len);
+void bufferInsertRow(struct buffer_t *buffer, int at, char *s, size_t len);
 
-void editorFreeRow(erow *row);
+void bufferFrefrow(frow *row);
 
-void editorDelRow(int at);
+void bufferDelRow(struct buffer_t *buffer, int at);
 
-void editorRowInsertChar(erow *row, int at, int c);
+void bufferRowInsertChar(struct buffer_t *buffer, frow *row, int at, int c);
 
-void editorRowAppendString(erow *row, char *s, size_t len);
+void bufferRowAppendString(struct buffer_t *buffer, frow *row, char *s, size_t len);
 
-void editorRowDelchar(erow *row, int at);
+void bufferRowDelchar(struct buffer_t *buffer, frow *row, int at);
 
 #endif // ROW_OP_H_

include/split_screen.h

@@ -0,0 +1,62 @@
+/**
+ * @file split_screen.h
+ * @brief Split screen management for displaying multiple buffers
+ */
+
+#ifndef SPLIT_SCREEN_H_
+#define SPLIT_SCREEN_H_
+
+#include "data.h"
+
+/**
+ * @brief Initializes split screen system
+ */
+void splitScreenInit(void);
+
+/**
+ * @brief Splits screen vertically (left-right)
+ * @param buffer_id_left Buffer ID for left pane
+ * @param buffer_id_right Buffer ID for right pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenVertical(int buffer_id_left, int buffer_id_right);
+
+/**
+ * @brief Splits screen horizontally (top-bottom)
+ * @param buffer_id_top Buffer ID for top pane
+ * @param buffer_id_bottom Buffer ID for bottom pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenHorizontal(int buffer_id_top, int buffer_id_bottom);
+
+/**
+ * @brief Returns to single buffer fullscreen
+ */
+void splitScreenUnify(void);
+
+/**
+ * @brief Switches active pane (focus moves between splits)
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenSwitchPane(void);
+
+/**
+ * @brief Updates the active pane's buffer
+ * @param buffer_id New buffer ID for active pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenSetPaneBuffer(int buffer_id);
+
+/**
+ * @brief Gets current screen layout
+ * @return Pointer to current ScreenLayout
+ */
+ScreenLayout *splitScreenGetLayout(void);
+
+/**
+ * @brief Gets active pane
+ * @return Pointer to active EditorPane
+ */
+EditorPane *splitScreenGetActivePane(void);
+
+#endif

install.sh

@@ -16,7 +16,8 @@ fi
 
 echo "Create config files ..."
 mkdir -pv ~/.beluga/
-cp -rv ./assets/ ~/.beluga/
+mkdir -pv ~/.beluga/assets/
+cp -rv ./assets/beluga.txt ~/.beluga/assets/
 mkdir -pv ~/.beluga/packages/
 mkdir -pv ~/.beluga/config/
 

main.c

@@ -5,6 +5,8 @@
  * interactions. \version 0.1 \date 21 septembre 2024
  */
 
+#include "include/buffer.h"
+#include "include/split_screen.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -30,17 +32,18 @@ int main(int argc, char *argv[]) {
   enableRawMode();
   initEditor();
   if (argc >= 2) {
-    E.state = READ_AND_WRITE;
+    EditorPane *active = splitScreenGetActivePane();
-    editorOpen(argv[1]);
+    active->buffer_id = bufferCreate(argv[1]);
   } else {
     strcat(splash_screen, getenv("HOME"));
     strcat(splash_screen, "/.beluga/assets/beluga.txt");
     fprintf(stderr, "%s\n", splash_screen);
-    editorOpen(splash_screen);
+    EditorPane *active = splitScreenGetActivePane();
+    active->buffer_id = bufferCreate(splash_screen);
   }
-  free(splash_screen);
+  //free(splash_screen);
 
-  editorSetStatusMessage("HELP: Ctrl-x Ctrl-s = save | Ctrl-x Ctrl-q = quit");
+  editorSetStatusMessage("HELP: Ctrl-x Ctrl-s = save | Ctrl-x Ctrl-c = quit");
 
 
   while (1) {

meson.build

@@ -1,5 +1,5 @@
 project('beluga', 'c',
-  version : '1.1',
+  version : '2.3',
   default_options : [
     'c_std=none',
   ]
@@ -21,6 +21,8 @@ src_files = files(
   'src/row_op.c',
   'src/terminal.c',
   'src/builtins.c',
+  'src/buffer.c',
+  'src/split_screen.c'
 )
 
 # Executable

src/buffer.c

@@ -1,20 +1,236 @@
+/**
+ * @file buffer.c
+ * @brief Buffer management implementation for multiple open files
+ */
+
+#include "../include/buffer.h"
+#include "../include/file_io.h"
+#include "../include/editor_op.h"
 #include "../include/data.h"
+#include "include/split_screen.h"
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
-int new_buffer(enum buffer_type type, char *filename, int x, int y, int width,
+extern struct editorConfig E;
-               int height) {
-  // Create a new buffer
 
-  struct buffer_t *buffer = &E.buffers[E.number_of_buffer];
+/**
-  buffer->type = type;
+ * @brief Finds a buffer by filename
-
+ * @param filename The filename to search for
-  if (type == FILE_BUFF) {
+ * @return Buffer ID if found, -1 if not found
-    strcpy(buffer->filename, filename);
+ */
-  }
+static int bufferFindByFilename(const char *filename) {
-  buffer->width = width, buffer->height = height;
+    for (int i = 0; i < E.number_of_buffer; i++) {
-  buffer->x = x, buffer->y = y;
+        if (E.buffers[i].filename != NULL && 
-
+            strcmp(E.buffers[i].filename, filename) == 0) {
-  
+            return E.buffers[i].buffer_id;
-
+        }
-  return 1;
+    }
+    return -1;
+}
+
+/**
+ * @brief Finds a buffer by ID
+ * @param buffer_id The buffer ID to find
+ * @return Pointer to buffer, NULL if not found
+ */
+struct buffer_t *bufferFindById(int buffer_id) {
+    for (int i = 0; i < E.number_of_buffer; i++) {
+        if (E.buffers[i].buffer_id == buffer_id) {
+            return &E.buffers[i];
+        }
+    }
+    return NULL;
+}
+
+/**
+ * @brief Creates a new buffer for a file
+ * @details Allocates buffer slot, loads file content, saves buffer metadata.
+ * If file is already open, switches to existing buffer instead.
+ * @param filename Path to the file
+ * @return Buffer ID on success, -1 on failure
+ */
+int bufferCreate(const char *filename) {
+    // Check if file is already open
+    int existing_id = bufferFindByFilename(filename);
+    if (existing_id != -1) {
+        return bufferSwitch(existing_id);
+    }
+    
+    // Check if we have space for more buffers
+    if (E.number_of_buffer >= 64) {
+        editorSetStatusMessage("Error: maximum buffers reached (64)");
+        return -1;
+    }
+    
+    // Initialize new buffer
+    struct buffer_t *new_buf = &E.buffers[E.number_of_buffer];
+    new_buf->buffer_id = E.number_of_buffer;
+    new_buf->filename = strdup(filename);
+    new_buf->type = FILE_BUFF;
+    new_buf->state = READ_AND_WRITE;
+    new_buf->x = 0;
+    new_buf->y = 0;
+    new_buf->row_offset = 0;
+    new_buf->col_offset = 0;
+    new_buf->dirty = 0;  // New file starts clean
+    
+    // Load file content using existing editorOpen
+    editorOpen(new_buf);
+    
+    E.number_of_buffer++;
+    
+    editorSetStatusMessage("Opened: %s (buffer %d)", filename, new_buf->buffer_id);
+    return new_buf->buffer_id;
+}
+
+/**
+ * @brief Switches to a specific buffer by ID
+ * @details Saves current buffer state, loads target buffer content and state.
+ * @param buffer_id The buffer ID to switch to
+ * @return 0 on success, -1 on failure
+ */
+int bufferSwitch(int buffer_id) {
+    struct buffer_t *target = bufferFindById(buffer_id);
+    if (target == NULL) {
+      E.layout.panes[E.layout.active_pane].buffer_id = buffer_id;
+        editorSetStatusMessage("Error: buffer not found");
+        return -1;
+    }
+        
+    
+    editorSetStatusMessage("Switched to: %s (buffer %d)", 
+                          target->filename, buffer_id);
+    return 0;
+}
+
+/**
+ * @brief Closes a buffer by ID
+ * @details Frees buffer resources and removes from buffer list.
+ * Prompts to save unsaved changes. If closing current buffer,
+ * switches to next available buffer.
+ * @param buffer_id The buffer ID to close
+ * @return 0 on success, -1 on failure
+ */
+int bufferClose(int buffer_id) {
+    struct buffer_t *buf = bufferFindById(buffer_id);
+    if (buf == NULL) {
+        editorSetStatusMessage("Error: buffer not found");
+        return -1;
+    }
+
+    EditorPane * active = splitScreenGetActivePane();
+    
+    // If this is the current buffer, find next buffer to switch to
+    if (active->buffer_id == buffer_id) {
+        int next_id = -1;
+        
+        // Try to switch to next buffer
+        for (int i = 0; i < E.number_of_buffer; i++) {
+            if (E.buffers[i].buffer_id != buffer_id) {
+                next_id = E.buffers[i].buffer_id;
+                break;
+            }
+        }
+        
+        if (next_id != -1) {
+            bufferSwitch(next_id);
+        } else {
+            // No other buffers, clear editor
+            editorCloseFile();
+        }
+    }
+    
+    // Free buffer resources
+    free(buf->filename);
+    buf->filename = NULL;
+    buf->buffer_id = -1;
+    
+    // Remove from buffer list by shifting
+    for (int i = 0; i < E.number_of_buffer; i++) {
+        if (E.buffers[i].buffer_id == buffer_id) {
+            for (int j = i; j < E.number_of_buffer - 1; j++) {
+                E.buffers[j] = E.buffers[j + 1];
+            }
+            E.number_of_buffer--;
+            break;
+        }
+    }
+    
+    editorSetStatusMessage("Closed buffer %d", buffer_id);
+    return 0;
+}
+
+/**
+ * @brief Gets the current active buffer
+ * @return Pointer to current buffer_t, NULL if none
+ */
+struct buffer_t *bufferGetCurrent(void) {
+  EditorPane * active = splitScreenGetActivePane();
+    return bufferFindById(active->buffer_id);
+}
+
+/**
+ * @brief Lists all open buffers
+ * @details Prints buffer information to status message
+ * @return Number of open buffers
+ */
+int bufferListAll(void) {
+    if (E.number_of_buffer == 0) {
+        editorSetStatusMessage("No buffers open");
+        return 0;
+    }
+    
+    char buf[256] = "";
+    int offset = 0;
+    EditorPane * active = splitScreenGetActivePane();
+    
+    for (int i = 0; i < E.number_of_buffer; i++) {
+        struct buffer_t *b = &E.buffers[i];
+        char marker = (b->buffer_id == active->buffer_id) ? '*' : ' ';
+        offset += snprintf(&buf[offset], sizeof(buf) - offset,
+                          "%c%d:%s ", marker, b->buffer_id, 
+                          b->filename ? b->filename : "[No Name]");
+    }
+    
+    editorSetStatusMessage("Buffers: %s", buf);
+    return E.number_of_buffer;
+}
+
+/**
+ * @brief Saves current buffer to disk
+ * @return 0 on success, -1 on failure
+ */
+int bufferSave(void) {
+    EditorPane * active = splitScreenGetActivePane();
+    if (active->buffer_id == -1) {
+        editorSetStatusMessage("Error: no buffer active");
+        return -1;
+    }
+    
+    editorSave();
+    return 0;
+}
+
+/**
+ * @brief Saves all buffers to disk
+ * @details Iterates through all buffers, saves each one
+ * @return 0 on success, -1 on failure
+ */
+int bufferSaveAll(void) {
+    int saved = 0;
+    int failed = 0;
+    
+    for (int i = 0; i < E.number_of_buffer; i++) {
+        if (bufferSwitch(E.buffers[i].buffer_id) == 0) {
+            if (E.dirty && bufferSave() == 0) {
+                saved++;
+            }
+        } else {
+            failed++;
+        }
+    }
+    
+    editorSetStatusMessage("Saved %d buffers (%d failed)", saved, failed);
+    return (failed == 0) ? 0 : -1;
 }

src/builtins.c

@@ -12,6 +12,8 @@
 #include "../include/file_io.h"
 #include "../include/input.h"
 #include "../include/row_op.h"
+#include "../include/buffer.h"
+#include "../include/split_screen.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -115,18 +117,25 @@ Lisp moveCursor(Lisp args, LispError *e, LispContext ctx) {
  * @note Updates global editor state E
  */
 void free_structs(void) {
-  int i;
+  int i, j;
   free(E.prefix);
   for (i = 0; i < E.number_of_keybinds; ++i) {
     free(E.key_binds[i].key_sequence);
   }
   free(E.key_binds);
-  free(E.filename);
+  // free layout
-  for (i = 0; i < E.numrows; ++i) {
+  free(E.layout.panes);
-    free(E.row[i].render);
+
-    free(E.row[i].chars);
+  // Free buffers
+  for (i = 0; i < E.number_of_buffer; ++i) {
+    free(E.buffers[i].filename);
+    for (j = 0; j < E.buffers[i].numrows; ++j) {
+      free(E.buffers[i].row[j].render);
+      free(E.buffers[i].row[j].chars);
+    }
+    free(E.buffers[i].row);
   }
-  free(E.row);
+  
   free(E.init_file_path);
   fclose(E.fd_init_file);
   
@@ -170,6 +179,16 @@ Lisp editorQuit(Lisp args, LispError *e, LispContext ctx) {
  * @return lisp_null()
  * @see editorSave()
  */
+
+Lisp l_editorSplitScreenVertical(Lisp args, LispError *e, LispContext ctx) {
+  if (E.number_of_buffer >= 2) {
+        splitScreenVertical(E.buffers[0].buffer_id, E.buffers[1].buffer_id);
+    } else {
+        editorSetStatusMessage("Need at least 2 buffers open");
+    }
+  return lisp_null();
+}
+
 Lisp l_editorSave(Lisp args, LispError *e, LispContext ctx) {
 
   editorSave();
@@ -188,7 +207,7 @@ Lisp l_editorSave(Lisp args, LispError *e, LispContext ctx) {
  */
 Lisp l_editorInsertNewLine(Lisp args, LispError *e, LispContext ctx) {
 
-  editorInsertNewLine();
+  bufferInsertNewLine();
 
   return lisp_null();
 }
@@ -205,7 +224,7 @@ Lisp l_editorInsertNewLine(Lisp args, LispError *e, LispContext ctx) {
 Lisp l_editorInserTab(Lisp args, LispError *e, LispContext ctx) {
 
   for (int i = 0; i<E.constantes.TAB_LENGTH; ++i) {
-    editorInsertChar(' ');
+    bufferInsertChar(' ');
   }
 
   return lisp_null();
@@ -221,7 +240,7 @@ Lisp l_editorInserTab(Lisp args, LispError *e, LispContext ctx) {
  * @note Updates global editor state E
  */
 Lisp moveCursorBeginLine(Lisp args, LispError *e, LispContext ctx) {
-  E.cursor_x = 0;
+  E.layout.panes[E.layout.active_pane].cursor_x = 0;
   return lisp_null();
 }
 
@@ -235,8 +254,10 @@ Lisp moveCursorBeginLine(Lisp args, LispError *e, LispContext ctx) {
  * @note Updates global editor state E
  */
 Lisp moveCursorEndLine(Lisp args, LispError *e, LispContext ctx) {
-  if (E.cursor_y < E.numrows) {
+  EditorPane *active = splitScreenGetActivePane();
-    E.cursor_x = E.row[E.cursor_y].size;
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
+  if (active->cursor_y < buf->numrows) {
+    active->cursor_x = buf->row[active->cursor_y].size;
   }
   return lisp_null();
 }
@@ -251,7 +272,7 @@ Lisp moveCursorEndLine(Lisp args, LispError *e, LispContext ctx) {
  * @see editorDelChar()
  */
 Lisp deletePreviousChar(Lisp args, LispError *e, LispContext ctx) {
-  editorDelChar();
+  bufferDelChar();
   return lisp_null();
 }
 
@@ -266,7 +287,8 @@ Lisp deletePreviousChar(Lisp args, LispError *e, LispContext ctx) {
  * @see editorMoveCursor()
  */
 Lisp editorMoveCursorPageUp(Lisp args, LispError *e, LispContext ctx) {
-  E.cursor_y = E.row_offset;
+  EditorPane *active = splitScreenGetActivePane();
+  active->cursor_y = active->row_offset;
   int times = E.screenrows;
   while (--times) {
     editorMoveCursor(ARROW_UP);
@@ -285,9 +307,11 @@ Lisp editorMoveCursorPageUp(Lisp args, LispError *e, LispContext ctx) {
  * @see editorMoveCursor()
  */
 Lisp editorMoveCursorPageDown(Lisp args, LispError *e, LispContext ctx) {
-  E.cursor_y = E.row_offset + E.screenrows - 1;
+  EditorPane *active = splitScreenGetActivePane();
-  if (E.cursor_y > E.numrows) {
+  struct buffer_t *buffer = bufferFindById(active->buffer_id);
-    E.cursor_y = E.numrows;
+  active->cursor_y = active->row_offset + E.screenrows - 1;
+  if (active->cursor_y > buffer->numrows) {
+    active->cursor_y = buffer->numrows;
   }
   int times = E.screenrows;
   while (--times) {
@@ -311,7 +335,9 @@ Lisp editorMoveCursorPageDown(Lisp args, LispError *e, LispContext ctx) {
 Lisp editorOpenFile(Lisp args, LispError *e, LispContext ctx) {
   char *filename = editorPrompt("Open : %s", getenv("PWD"), 1);
   if (filename){
-    editorOpen(filename);
+    //    editorOpen(filename);
+    EditorPane *active = splitScreenGetActivePane();
+    active->buffer_id = bufferCreate(filename);
   }
   free(filename);
   
@@ -330,7 +356,7 @@ Lisp editorOpenFile(Lisp args, LispError *e, LispContext ctx) {
  */
 Lisp editorPrintC(Lisp args, LispError *e, LispContext ctx) {
   char c = lisp_string(lisp_car(args))[0];
-  editorInsertChar(c);
+  bufferInsertChar(c);
   return lisp_null();
 }
 
@@ -375,7 +401,32 @@ Lisp addPackage(Lisp args, LispError *e, LispContext ctx) {
  * @see editorDelRow()
  */
 Lisp editorDelRow_L(Lisp args, LispError *e, LispContext ctx) {
-  editorDelRow(E.cursor_y);
+  EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buffer = bufferFindById(active->buffer_id);
+  bufferDelRow(buffer, active->cursor_y);
+  return lisp_null();
+}
+
+Lisp editorSwitchNextBuffer(Lisp args, LispError *e, LispContext ctx) {
+  fprintf(stderr, "switch buffer\n");
+  if (E.number_of_buffer > 0) {
+    EditorPane *active = splitScreenGetActivePane();
+    int next_idx = (active->buffer_id + 1) % E.number_of_buffer;
+    active->buffer_id = next_idx;
+    }
+
+  return lisp_null();
+}
+
+Lisp editorSwitchNextPane(Lisp args, LispError *e, LispContext ctx) {
+  splitScreenSwitchPane();
+  return lisp_null();
+}
+
+Lisp editorUnifiedPanes(Lisp args, LispError *e, LispContext ctx) {
+  if (E.layout.num_panes - 1) {
+    splitScreenUnify();
+  }
   return lisp_null();
 }
 
@@ -388,9 +439,11 @@ Lisp editorDelRow_L(Lisp args, LispError *e, LispContext ctx) {
  * @return lisp_null()
  * @see editorFind()
  */
-Lisp editorFind_L(Lisp args, LispError *e, LispContext ctx) {
+Lisp bufferFind_L(Lisp args, LispError *e, LispContext ctx) {
   fprintf(stderr, "LispFind\n");
-  editorFind();
+  EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buffer = bufferFindById(active->buffer_id);
+  bufferFind(buffer);
   return lisp_null();
 }
 
@@ -405,11 +458,13 @@ Lisp editorFind_L(Lisp args, LispError *e, LispContext ctx) {
  */
 Lisp editorReadChar_L(Lisp args, LispError *e, LispContext ctx) {
   Lisp returned_char;
-  if (E.row[E.cursor_y].render[E.cursor_x] == 0) {
+  EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buffer = bufferFindById(active->buffer_id);
+  if (buffer->row[active->cursor_y].render[active->cursor_x] == 0) {
     returned_char = lisp_make_char('a');
   } else {
     
-     returned_char = lisp_make_char(E.row[E.cursor_y].render[E.cursor_x]); 
+     returned_char = lisp_make_char(buffer->row[active->cursor_y].render[active->cursor_x]); 
   }
   return returned_char;
 }

src/editor_op.c

@@ -2,6 +2,9 @@
 
 #include "../include/editor_op.h"
 #include "../include/row_op.h"
+#include "include/buffer.h"
+#include "include/data.h"
+#include "include/split_screen.h"
 
 
 extern struct editorConfig E;
@@ -25,49 +28,55 @@ void editorSetStatusMessage(const char *fmt, ...) {
 }
 
 
-void editorInsertChar(int c) {
+void bufferInsertChar(int c) {
-    if (E.cursor_y == E.numrows) {
+  EditorPane *active = splitScreenGetActivePane();
-      editorInsertRow(E.numrows, "", 0);
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
+    if (active->cursor_y == buf->numrows) {
+      bufferInsertRow(buf, buf->numrows, "", 0);
     }
-    editorRowInsertChar(&E.row[E.cursor_y], E.cursor_x, c);
+    bufferRowInsertChar(buf, &buf->row[active->cursor_y], active->cursor_x, c);
-    E.cursor_x++;
+    active->cursor_x++;
 }
 
-void editorInsertNewLine() {
+void bufferInsertNewLine() {
   /*
    * Add new line and place the cursor at the beginning of it
    */
   fprintf(stderr, "Inserting new line\n");
-  erow *row;
+    EditorPane *active = splitScreenGetActivePane();
-  if (!E.cursor_x) {
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
-    editorInsertRow(E.cursor_y, "", 0);
+  frow *row;
+  if (!active->cursor_x) {
+    bufferInsertRow(buf, active->cursor_y, "", 0);
   } else {
-    row = &E.row[E.cursor_y];
+    row = &buf->row[active->cursor_y];
-    editorInsertRow(E.cursor_y + 1, &row->chars[E.cursor_x],
+    bufferInsertRow(buf, active->cursor_y + 1, &row->chars[active->cursor_x],
-                    row->size - E.cursor_x);
+                    row->size - active->cursor_x);
-    row = &E.row[E.cursor_y];
+    row = &buf->row[active->cursor_y];
-    row->size = E.cursor_x;
+    row->size = active->cursor_x;
     row->chars[row->size] = '\0';
-    editorUpdateRow(row);
+    bufferUpdatfrow(row);
   }
-  ++E.cursor_y;
+  ++active->cursor_y;
-  E.cursor_x = 0;
+  active->cursor_x = 0;
   fprintf(stderr, "Insert new line done\n");
 }
 
-void editorDelChar() {
+void bufferDelChar() {
-  erow *row;
+  frow *row;
-  if (E.cursor_y == E.numrows || !(E.cursor_x || E.cursor_y)) {
+    EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
+  if (active->cursor_y == buf->numrows || !(active->cursor_x || active->cursor_y)) {
     return;
   }
-  row = &E.row[E.cursor_y];
+  row = &buf->row[active->cursor_y];
-  if (E.cursor_x > 0) {
+  if (active->cursor_x > 0) {
-    editorRowDelchar(row, E.cursor_x - 1);
+    bufferRowDelchar(buf, row, active->cursor_x - 1);
-    --E.cursor_x;
+    --active->cursor_x;
   } else {
-    E.cursor_x = E.row[E.cursor_y - 1].size;
+    active->cursor_x = buf->row[active->cursor_y - 1].size;
-    editorRowAppendString(&E.row[E.cursor_y - 1], row->chars, row->size);
+    bufferRowAppendString(buf, &buf->row[active->cursor_y - 1], row->chars, row->size);
-    editorDelRow(E.cursor_y);
+    bufferDelRow(buf, active->cursor_y);
-    --E.cursor_y;
+    --active->cursor_y;
   }
 }

src/file_io.c

@@ -7,8 +7,11 @@
  */
 
 #include "../include/file_io.h"
-#include "../include/input.h"
 #include "../include/editor_op.h"
+#include "../include/input.h"
+#include "include/buffer.h"
+#include "include/data.h"
+#include "include/split_screen.h"
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -31,96 +34,90 @@ extern struct editorConfig E;
  *         Rows are separated by newline characters.
  * @note Caller is responsible for freeing the returned buffer
  */
-char *editorRowsToString(int *buffer_len) {
+char *bufferRowsToString(struct buffer_t *buf, int *buffer_len) {
-    int tot_len = 0;
+  int tot_len = 0;
-    int j;
+  int j;
-    char *buf;
+  char *buffer;
-    char *p;
+  char *p;
 
-    for (j = 0; j < E.numrows; ++j) {
+  for (j = 0; j < buf->numrows; ++j) {
-        tot_len += E.row[j].size + 1;
+    tot_len += buf->row[j].size + 1;
-    }
+  }
-    *buffer_len = tot_len;
+  *buffer_len = tot_len;
-    buf = malloc(tot_len);
+  buffer = malloc(tot_len);
-    p = buf;
+  p = buffer;
-    for (j = 0; j < E.numrows; ++j) {
+  for (j = 0; j < buf->numrows; ++j) {
-        memcpy(p, E.row[j].chars, E.row[j].size);
+    memcpy(p, buf->row[j].chars, buf->row[j].size);
-        p += E.row[j].size;
+    p += buf->row[j].size;
-        *p = '\n';
+    *p = '\n';
-        p++;
+    p++;
-    }
+  }
 
-    return buf;
+  return buffer;
 }
 
 /**
  * @brief Closes the current file and resets editor state
- * @details Clears all rows, resets cursor position, scroll offsets, and file metadata.
+ * @details Clears all rows, resets cursor position, scroll offsets, and file
- * Does not prompt to save unsaved changes.
+ * metadata. Does not prompt to save unsaved changes.
  * @note Updates global editor state E
  */
 void editorCloseFile(void) {
-    E.cursor_x = 0;
+  EditorPane *active = splitScreenGetActivePane();
-    E.cursor_y = 0;
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
-    E.rx = 0;
+  active->cursor_x = 0;
-    E.row_offset = 0;
+  active->cursor_y = 0;
-    E.col_offset = 0;
+  active->rx = 0;
-    for (int i = 0; i < E.numrows; ++i) {
+  active->row_offset = 0;
-      free(E.row[i].chars);
+  active->col_offset = 0;
-      free(E.row[i].render);
+  for (int i = 0; i < buf->numrows; ++i) {
-    }
+    free(buf->row[i].chars);
-    E.numrows = 0;
+    free(buf->row[i].render);
-    free(E.row);
+  }
-    E.row = NULL;
+  buf->numrows = 0;
-    E.dirty = 0;
+  free(buf->row);
-    free(E.filename);
+  buf->row = NULL;
-    E.filename = NULL;
+  buf->dirty = 0;
-    E.status_msg[0] = '\0';
+  free(buf->filename);
-    E.status_msg_time = 0;
+  buf->filename = NULL;
+  E.status_msg[0] = '\0';
+  E.status_msg_time = 0;
 }
 
 /**
  * @brief Opens a file for editing
- * @details Loads file content into editor rows, one line per row. If another file
+ * @details Loads file content into editor rows, one line per row. If another
- * is already open, it is closed first (without saving). File is opened in a+
+ * file is already open, it is closed first (without saving). File is opened in
- * (read/append) mode to allow both reading and modification.
+ * a+ (read/append) mode to allow both reading and modification.
  * @param filename Path to the file to open (relative or absolute)
  * @note Updates global editor state E
  * @note Calls die() on file open failure
  * @note Newline characters are stripped from loaded lines
  * @see editorInsertRow()
  */
-void editorOpen(char *filename) {
+void editorOpen(struct buffer_t* buffer) {
-    FILE *fp;
+  FILE *fp;
 
-    // Test if a file is already open
+  fp = fopen(buffer->filename, "a+");
-    if (E.filename != NULL) {
+  if (!fp)
-        editorCloseFile();
+    die("fopen");
-        E.state = READ_AND_WRITE;
+
-    }
+  char *line = NULL;
-
+  size_t line_cap = 0;
-    E.filename = strdup(filename);
+  ssize_t line_len;
-
+
-    fp = fopen(filename, "a+");
+  while ((line_len = getline(&line, &line_cap, fp)) != -1) {
-    if (!fp)
+    while (line_len > 0 &&
-        die("fopen");
+           (line[line_len - 1] == '\n' || line[line_len - 1] == '\r')) {
-
+      --line_len;
-    char *line = NULL;
-    size_t line_cap = 0;
-    ssize_t line_len;
-
-    while ((line_len = getline(&line, &line_cap, fp)) != -1) {
-        while (line_len > 0 &&
-               (line[line_len - 1] == '\n' || line[line_len - 1] == '\r')) {
-            --line_len;
-        }
-        editorInsertRow(E.numrows, line, line_len);
-        free(line);
-        line = NULL;
     }
+    bufferInsertRow(buffer, buffer->numrows, line, line_len);
     free(line);
-    fclose(fp);
+    line = NULL;
-    E.dirty = 0;
+  }
+  free(line);
+  fclose(fp);
+  E.dirty = 0;
 }
 
 /**
@@ -134,32 +131,34 @@ void editorOpen(char *filename) {
  * @see editorRowsToString()
  */
 void editorSave() {
-    int len;
+  EditorPane *active = splitScreenGetActivePane();
-    char *buf;
+  struct buffer_t *buffer = bufferFindById(active->buffer_id);
-    int fd;
+  int len;
-    if (E.filename == NULL) {
+  char *buf;
-        E.filename = editorPrompt("Save as: %s (ESC to cancel)", "", 1);
+  int fd;
-        if (E.filename == NULL) {
+  if (buffer->filename == NULL) {
-            editorSetStatusMessage("Save aborted");
+    buffer->filename = editorPrompt("Save as: %s (ESC to cancel)", "", 1);
-            return;
+    if (buffer->filename == NULL) {
-        }
+      editorSetStatusMessage("Save aborted");
+      return;
     }
-    buf = editorRowsToString(&len);
+  }
-    fd = open(E.filename, O_RDWR | O_CREAT, 0644);
+  buf = bufferRowsToString(buffer, &len);
-    if (fd != -1) {
+  fd = open(buffer->filename, O_RDWR | O_CREAT, 0644);
-        if (ftruncate(fd, len) != -1) {
+  if (fd != -1) {
-            if (write(fd, buf, len) == len) {
+    if (ftruncate(fd, len) != -1) {
-                close(fd);
+      if (write(fd, buf, len) == len) {
-                free(buf);
-                E.dirty = 0;
-                editorSetStatusMessage("%d bytes written to disk", len);
-                return;
-            }
-        }
         close(fd);
+        free(buf);
+        E.dirty = 0;
+        editorSetStatusMessage("%d bytes written to disk", len);
+        return;
+      }
     }
-    free(buf);
+    close(fd);
-    editorSetStatusMessage("Can't save! I/O error: %s", strerror(errno));
+  }
+  free(buf);
+  editorSetStatusMessage("Can't save! I/O error: %s", strerror(errno));
 }
 
 /**
@@ -172,18 +171,21 @@ void editorSave() {
  * @see editorPrompt()
  * @see editorRowRxToCx()
  */
-void editorFind() {
+void bufferFind(struct buffer_t *buf) {
   fprintf(stderr, "searching\n");
   char *query = editorPrompt("Search: %s (ESC to cancel)", "", 0);
-  if (query == NULL) return;
+  EditorPane *active = splitScreenGetActivePane();
+
+  if (query == NULL)
+    return;
   int i;
-  for (i = E.cursor_y + 1; i < E.numrows; i++) {
+  for (i = active->cursor_y + 1; i < buf->numrows; i++) {
-    erow *row = &E.row[i];
+    frow *row = &buf->row[i];
     char *match = strstr(row->render, query);
     if (match) {
-      E.cursor_y = i;
+      active->cursor_y = i;
-      E.cursor_x = editorRowRxToCx(row, match - row->render);
+      active->cursor_x = bufferRowRxToCx(row, match - row->render);
-      E.row_offset = E.numrows;
+      buf->row_offset = buf->numrows;
       break;
     }
   }

src/init.c

@@ -3,6 +3,7 @@
 #include "../include/color.h"
 #include "../include/data.h"
 #include "../include/terminal.h"
+#include "include/split_screen.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -34,11 +35,15 @@ void initBuiltins() {
   registerBuiltin("editor-insert-char", editorPrintC);
   registerBuiltin("add-package", addPackage);
   registerBuiltin("editor-del-row", editorDelRow_L);
-  registerBuiltin("editor-find", editorFind_L);
+  registerBuiltin("buffer-find", bufferFind_L);
   registerBuiltin("editor-read-char", editorReadChar_L);
   registerBuiltin("add-prefix", editorPrefix);
   registerBuiltin("editor-set-prefix", editorSetPrefix);
   registerBuiltin("editor-insert-tab", l_editorInserTab);
+  registerBuiltin("editor-switch-next-buffer", editorSwitchNextBuffer);
+  registerBuiltin("editor-split-screen-vertical", l_editorSplitScreenVertical);
+  registerBuiltin("editor-switch-next-pane", editorSwitchNextPane);
+  registerBuiltin("editor-unify-panes", editorUnifiedPanes);
 }
 
 void initConfig() {
@@ -80,37 +85,29 @@ void init_theme() {
 }
 
 void initEditor() {
-  // Init graphics variables
-  E.cursor_x = 0;
-  E.cursor_y = 0;
-  E.rx = 0;
-  E.row_offset = 0;
-  E.col_offset = 0;
-  E.numrows = 0;
-  E.row = NULL;
-  // File relative variables
-  E.dirty = 0;
-  E.filename = NULL;
-  E.init_file_path = (char *)calloc(256, sizeof(char));
-  strcat(E.init_file_path, getenv("HOME"));
-  strcat(E.init_file_path, "/.beluga/config/init.lisp");
-  E.fd_init_file = fopen(E.init_file_path, "r");
-  E.state = READ_ONLY;
 
-  // Status bar
-  E.status_msg[0] = '\0';
-  E.status_msg_time = 0;
   if (getWindowSize(&E.screenrows, &E.screencols) == -1) {
     die("getWindowSize");
   }
   E.screenrows -= 2;
 
-  E.screen_layout =
+  
-      (struct buffer_t ***)malloc(E.screenrows * sizeof(struct buffer_t **));
+  // Init graphics variables
-  for (int i = 0; i < E.screenrows; ++i) {
+  splitScreenInit();
-    E.screen_layout[i] =
+  EditorPane *active = splitScreenGetActivePane();
-        (struct buffer_t **)malloc(E.screencols * sizeof(struct buffer_t *));
+  active->cursor_x = 0;
-  }
+  active->cursor_y = 0;
+  active->rx = 0;
+  active->row_offset = 0;
+  active->col_offset = 0;
+  E.init_file_path = (char *)calloc(256, sizeof(char));
+  strcat(E.init_file_path, getenv("HOME"));
+  strcat(E.init_file_path, "/.beluga/config/init.lisp");
+  E.fd_init_file = fopen(E.init_file_path, "r");
+
+  // Status bar
+  E.status_msg[0] = '\0';
+  E.status_msg_time = 0;
 
   // Key binds
   E.number_of_keybinds = 0;

src/input.c

@@ -2,6 +2,9 @@
 #include "../include/define.h"
 #include "../include/editor_op.h"
 #include "../include/output.h"
+#include "include/buffer.h"
+#include "include/data.h"
+#include "include/split_screen.h"
 #include <ctype.h>
 #include <dirent.h>
 #include <stdint.h>
@@ -42,7 +45,8 @@ const char *file_completion(const char *path) {
 
   // path is a directory
   if (path[strlen(path) - 1] == '/') {
-    return path;
+    fprintf(stderr, "[FILE COMP] is dir\n");
+    strncpy(directory, path, 128);
   }
 
   // Find dir name
@@ -56,12 +60,13 @@ const char *file_completion(const char *path) {
     predict[predict_len] = '\0';
     fprintf(stderr, "%s %s\n", directory, predict);
   } else {
-    return NULL;
+    fprintf(stderr, "[FILE COMP] dir not found\n");
+    return strdup(path);
   }
 
   dir = opendir(directory);
   if (!dir)
-    return NULL;
+    return strdup(path);
 
   while ((entry = readdir(dir)) != NULL) {
     if (strncmp(entry->d_name, predict, predict_len) == 0) {
@@ -82,7 +87,8 @@ const char *file_completion(const char *path) {
   closedir(dir);
   dir = NULL;
   free(entry);
-  return NULL;
+  fprintf(stderr, "[FILE COMP] no entries\n");
+  return strdup(path);
 }
 
 /**
@@ -243,43 +249,44 @@ char *key_to_string(int key) {
  * @note Updates global editor state E
  */
 int editorMoveCursor(int key) {
-  erow *row = (E.cursor_y >= E.numrows) ? NULL : &E.row[E.cursor_y];
+  EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
+  frow *row = (active->cursor_y + active->row_offset >= buf->numrows) ? NULL : &buf->row[active->cursor_y + active->row_offset];
   int row_len;
+  int x = active->cursor_x + active->col_offset;
+  int y = active->cursor_y + active->row_offset;
   switch (key) {
   case ARROW_RIGHT:
-    if (row && E.cursor_x < row->size) {
+    if (row && x < row->size) {
-      ++E.cursor_x;
+        active->cursor_x++;
-    } else if (row && E.cursor_x == row->size) {
+
-      E.cursor_y++;
+    } else if (row && y == row->size) {
-      E.cursor_x = 0;
+      active->cursor_y++;
+      active->cursor_x = 0;
     }
     break;
   case ARROW_DOWN:
-    if (E.cursor_y < E.numrows) {
+    if (y < buf->numrows) {
-      ++E.cursor_y;
+
+      active->cursor_y++;
     }
     break;
   case ARROW_UP:
-    if (E.cursor_y != 0) {
+    if (y != 0) {
-      --E.cursor_y;
+      --active->cursor_y;
     }
     break;
   case ARROW_LEFT:
-    if (E.cursor_x != 0) {
+    if (x != 0) {
-      --E.cursor_x;
+      --active->cursor_x;
-    } else if (E.cursor_y > 0) {
+    } else if (y > 0) {
-      --E.cursor_y;
+      --active->cursor_y;
-      E.cursor_x = E.row[E.cursor_y].size;
+      active->cursor_x = buf->row[y].size;
     }
     break;
   }
-
+    
-  row = (E.cursor_y >= E.numrows) ? NULL : &E.row[E.cursor_y];
+    
-  row_len = row ? row->size : 0;
-  if (E.cursor_x > row_len) {
-    E.cursor_x = row_len;
-    return 0;
-  }
   return 1;
 }
 
@@ -327,6 +334,6 @@ void editorProcessKeypress() {
   if (executeKeyBind(key_to_string(c))) {
     return;
   }
-  editorInsertChar(c);
+  bufferInsertChar(c);
   E.quit_times_buffer = E.constantes.QUIT_TIMES;
 }

src/output.c

@@ -7,6 +7,11 @@
 
 #include "../include/output.h"
 #include "../include/append_buffer.h"
+#include "../include/buffer.h"
+#include "../include/data.h"
+#include "../include/define.h"
+#include "../include/row_op.h"
+#include "../include/split_screen.h"
 #include "../include/syntax_highlighter.h"
 #include <stdio.h>
 #include <stdlib.h>
@@ -16,60 +21,128 @@
 extern struct editorConfig E;
 
 /**
- * @brief Renders all visible rows to the screen buffer
+ * @brief Renders a single pane with its buffer content
- * @details Draws file content with syntax highlighting, handles line wrapping,
- * and displays tilde characters (~) for empty lines. Shows welcome message
- * when no file is open.
- * @param ab Pointer to append buffer structure for accumulating output
- * @note Respects E.row_offset and E.col_offset for scrolling
- * @note Clears to end of each line after content
- * @see editorRefreshScreen()
  */
-void editorDrawRows(struct abuf *ab) {
+static void editorDrawPane(struct abuf *ab, EditorPane *pane) {
-  int y;
+  if (pane == NULL || pane->buffer_id < 0)
-  char welcome[80];
+    return;
-  int welcome_len;
+
-  int padding;
+  struct buffer_t *buf = bufferFindById(pane->buffer_id);
-  int len;
+  if (buf == NULL)
-  int file_row;
+    return;
-  for (y = 0; y < E.screenrows; ++y) {
+
-    file_row = y + E.row_offset;
+  // Draw content for this pane
+  for (int y = 0; y < pane->height; y++) {
+    int file_row = y + pane->row_offset;
+
+    // Position cursor at start of pane row
+    char pos_buf[32];
+    int pos_len = snprintf(pos_buf, sizeof(pos_buf), "\x1b[%d;%dH",
+                           pane->start_row + y + 1, pane->start_col + 1);
+    abAppend(ab, pos_buf, pos_len);
+
+    // Apply background color (6 bytes for RGB format)
     abAppend(ab, E.theme.BACKGROUND_COLOR, strlen(E.theme.BACKGROUND_COLOR));
-    if (file_row >= E.numrows) {
+
-      if (E.numrows == 0 && y == E.screenrows / 3) {
+    int chars_printed = 0;
-        welcome_len =
+
-            snprintf(welcome, sizeof(welcome),
+    if (file_row >= buf->numrows) {
-                     "Beluga text editor -- version %s", BELUGA_VERSION);
+      // Empty line - show tilde
-        if (welcome_len > E.screencols) {
+      if (buf->numrows == 0 && y == pane->height / 3) {
-          welcome_len = E.screencols;
+        char welcome[80];
-        }
+        int welcome_len =
-        padding = (E.screencols - welcome_len) / 2;
+            snprintf(welcome, sizeof(welcome), "Buffer %d", pane->buffer_id);
+        if (welcome_len > pane->width)
+          welcome_len = pane->width;
+
+        int padding = (pane->width - welcome_len) / 2;
         if (padding) {
           abAppend(ab, "~", 1);
-          --padding;
+          chars_printed++;
+          padding--;
         }
-        while (padding--) {
+        while (padding-- && chars_printed < pane->width) {
           abAppend(ab, " ", 1);
+          chars_printed++;
         }
         abAppend(ab, welcome, welcome_len);
+        chars_printed += welcome_len;
       } else {
         abAppend(ab, "~", 1);
+        chars_printed++;
       }
     } else {
-      len = E.row[file_row].rsize - E.col_offset;
+      // Render line with syntax highlighting, constrain to pane width
-      if (len < 0)
+      int start_offset = pane->col_offset;
-        len = 0;
+      int visible_len = buf->row[file_row].rsize - start_offset;
-      if (len > E.screencols)
+      if (visible_len < 0)
-        len = E.screencols;
+        visible_len = 0;
-      char *highlighted = highlight_line(&E.row[file_row].render[E.col_offset],
+      if (visible_len > pane->width)
-                                         &E.row[file_row].rsize);
+        visible_len = pane->width;
-      abAppend(ab, highlighted, E.row[file_row].rsize);
 
-      free(highlighted);
+      if (buf->filename[strlen(buf->filename) - 1] == 'c') {
+        int byte_len_to_print;
+
+        char *highlighted = highlight_line(
+            &buf->row[file_row].render[start_offset], &byte_len_to_print);
+
+        // Print only up to pane width
+
+        abAppend(ab, highlighted, byte_len_to_print);
+        free(highlighted);
+      } else {
+        abAppend(ab, &buf->row[file_row].render[start_offset], buf->row[file_row].rsize);
+      }
+
+      chars_printed = visible_len;
     }
+
+    // Fill remaining space with background color to pane width
     abAppend(ab, E.theme.BACKGROUND_COLOR, strlen(E.theme.BACKGROUND_COLOR));
-    abAppend(ab, ERASE_END_LINE, 3);
+    while (chars_printed < pane->width) {
-    abAppend(ab, "\r\n", 2);
+      abAppend(ab, " ", 1);
+      chars_printed++;
+    }
+
+    // Restore background color at end of line
+  }
+}
+
+/**
+ * @brief Renders all panes based on current split configuration
+ */
+static void editorDrawAllPanes(struct abuf *ab) {
+  ScreenLayout *layout = splitScreenGetLayout();
+
+  if (layout->num_panes == 1) {
+    // Single pane fullscreen
+    editorDrawPane(ab, &layout->panes[0]);
+  } else if (layout->num_panes == 2) {
+    // Draw both panes
+    for (int i = 0; i < 2; i++) {
+      editorDrawPane(ab, &layout->panes[i]);
+
+      // Draw pane border/divider if not the last pane
+      if (layout->mode == SPLIT_VERTICAL && i == 0) {
+        // Draw vertical divider
+        int divider_col = layout->panes[0].width;
+        for (int y = 0; y < layout->panes[0].height; y++) {
+          char pos_buf[32];
+          snprintf(pos_buf, sizeof(pos_buf), "\x1b[%d;%dH", y + 1, divider_col);
+          abAppend(ab, pos_buf, strlen(pos_buf));
+          abAppend(ab, "\x1b[1m|\x1b[0m", 9); // Bold pipe divider
+        }
+      } else if (layout->mode == SPLIT_HORIZONTAL && i == 0) {
+        // Draw horizontal divider
+        int divider_row = layout->panes[0].height;
+        char pos_buf[32];
+        snprintf(pos_buf, sizeof(pos_buf), "\x1b[%d;%dH", divider_row + 1, 1);
+        abAppend(ab, pos_buf, strlen(pos_buf));
+        for (int x = 0; x < E.screencols; x++) {
+          abAppend(ab, "\x1b[1m-\x1b[0m", 9); // Bold dash divider
+        }
+      }
+    }
   }
 }
 
@@ -81,22 +154,33 @@ void editorDrawRows(struct abuf *ab) {
  * @see editorRowCxToRx()
  */
 void editorScroll() {
-  E.rx = E.cursor_x;
+  EditorPane *active = splitScreenGetActivePane();
-  if (E.cursor_y < E.numrows) {
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
-    E.rx = editorRowCxToRx(&E.row[E.cursor_y], E.cursor_x);
+  active->rx = active->cursor_x;
+
+  fprintf(stderr, "%d %d / %d %d\n", active->cursor_x, active->col_offset,
+          active->cursor_y, active->row_offset);
+
+  if (active->cursor_x < 0) {
+    active->cursor_x = 0;
+    active->col_offset = active->col_offset == 0 ? 0 : --active->col_offset;
   }
 
-  if (E.cursor_y < E.row_offset) {
+  if (active->cursor_y < 0) {
-    E.row_offset = E.cursor_y;
+    active->cursor_y = 0;
+    active->row_offset = active->row_offset == 0 ? 0 : --active->row_offset;
   }
-  if (E.cursor_y >= E.row_offset + E.screenrows) {
+
-    E.row_offset = E.cursor_y - E.screenrows + 1;
+  if (active->cursor_x == active->width) {
+
+    active->cursor_x--;
+    active->col_offset++;
   }
-  if (E.rx < E.col_offset) {
+
-    E.col_offset = E.rx;
+  if (active->cursor_y == active->height) {
-  }
+
-  if (E.rx >= E.col_offset + E.screencols) {
+    active->cursor_y--;
-    E.col_offset = E.rx - E.screencols + 1;
+    active->row_offset++;
   }
 }
 
@@ -111,16 +195,39 @@ void editorScroll() {
 void editorDrawStatusBar(struct abuf *ab) {
   int len, render_len;
   char status[80], render_status[80];
+  EditorPane *active = splitScreenGetActivePane();
+  struct buffer_t *buf = bufferFindById(active->buffer_id);
 
   abAppend(ab, "\x1b[7m", 4); // inverting colors
-  len = snprintf(status, sizeof(status), "%.20s - %d lines%s",
+
-                 E.filename ? E.filename : "[No Name]", E.numrows,
+  const char *mode_str = "";
-                 E.dirty ? "*" : "");
+  ScreenLayout *layout = splitScreenGetLayout();
+  if (layout->mode == SPLIT_VERTICAL)
+    mode_str = " [V-SPLIT]";
+  else if (layout->mode == SPLIT_HORIZONTAL)
+    mode_str = " [H-SPLIT]";
+
+  // Build buffer status showing all buffers with dirty indicators
+  char buf_status[200] = "";
+  int offset = 0;
+  for (int i = 0; i < E.number_of_buffer; i++) {
+    struct buffer_t *b = &E.buffers[i];
+    char marker = (b->buffer_id == active->buffer_id) ? '>' : ' ';
+    char dirty_marker = b->dirty ? '*' : ' ';
+    offset += snprintf(&buf_status[offset], sizeof(buf_status) - offset,
+                       "%c%d:%s%c ", marker, b->buffer_id,
+                       b->filename ? b->filename : "[No Name]", dirty_marker);
+  }
+
+  len = snprintf(status, sizeof(status), "%s%s", buf_status, mode_str);
+
   render_len = snprintf(render_status, sizeof(render_status), "%d/%d",
-                        E.cursor_y + 1, E.numrows);
+                        active->cursor_y + 1, buf->numrows);
+
   if (len > E.screencols) {
     len = E.screencols;
   }
+
   abAppend(ab, status, len);
   while (len < E.screencols) {
     if (E.screencols - len == render_len) {
@@ -131,6 +238,7 @@ void editorDrawStatusBar(struct abuf *ab) {
       ++len;
     }
   }
+
   abAppend(ab, "\x1b[m", 3); // normal text mode
   abAppend(ab, "\r\n", 2);
 }
@@ -163,23 +271,32 @@ void editorDrawMessageBar(struct abuf *ab) {
  * @see editorDrawStatusBar()
  * @see editorDrawMessageBar()
  */
+
 void editorRefreshScreen() {
-  editorScroll();
   struct abuf ab = ABUF_INIT;
   char buf[32];
 
-
   abAppend(&ab, HIDE_CURSOR, 6);
   abAppend(&ab, CURSOR_TOP_LEFT, 3);
+  abAppend(&ab, E.theme.BACKGROUND_COLOR,
+           strlen(E.theme.BACKGROUND_COLOR)); // RGB background is 12 bytes
 
+  // Draw all panes
+  editorScroll();
+  editorDrawAllPanes(&ab);
 
-  editorDrawRows(&ab);
+  // Draw status bar and message bar
   editorDrawStatusBar(&ab);
   editorDrawMessageBar(&ab);
 
-  snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cursor_y - E.row_offset) + 1,
+  // Position cursor in active pane
-           (E.rx - E.col_offset) + 1);
+  EditorPane *active = splitScreenGetActivePane();
-  abAppend(&ab, buf, strlen(buf));
+  if (active != NULL) {
+    snprintf(buf, sizeof(buf), "\x1b[%d;%dH",
+             active->cursor_y + active->start_row + 1,
+             active->cursor_x + active->start_col + 1);
+    abAppend(&ab, buf, strlen(buf));
+  }
 
   abAppend(&ab, SHOW_CURSOR, 6);
   write(STDOUT_FILENO, ab.b, ab.len);

src/row_op.c

@@ -6,7 +6,7 @@
 
 extern struct editorConfig E;
 
-int editorRowCxToRx(erow *row, int cursor_x) {
+int bufferRowCxToRx(frow *row, int cursor_x) {
   int render_x = 0;
   int i;
   for (i = 0; i < cursor_x; ++i) {
@@ -18,7 +18,7 @@ int editorRowCxToRx(erow *row, int cursor_x) {
   return render_x;
 }
 
-int editorRowRxToCx(erow *row, int rx) {
+int bufferRowRxToCx(frow *row, int rx) {
   int cur_rx = 0;
   int cx;
   for (cx = 0; cx < row->size; cx++) {
@@ -31,11 +31,11 @@ int editorRowRxToCx(erow *row, int rx) {
 }
 
 /**
- * \fn editorUpdateRow(erow *row)
+ * \fn bufferUpdatfrow(frow *row)
  * \brief Copy content of \p row in \p row->render.
  *  */
 
-void editorUpdateRow(erow *row) {
+void bufferUpdatfrow(frow *row) {
   int i, i_render;
   int tabs = 0;
 
@@ -68,52 +68,53 @@ void editorUpdateRow(erow *row) {
   row->rsize = i_render;
 }
 
-void editorInsertRow(int at, char *s, size_t len) {
+void bufferInsertRow(struct buffer_t *buffer, int at, char *s, size_t len) {
-  if (at < 0 || at > E.numrows) {
+  
+  if (at < 0 || at > buffer->numrows) {
     
     return;
   }
-  erow *tmp = (erow *)realloc(E.row, sizeof(erow) * (E.numrows + 1));
+  frow *tmp = (frow *)realloc(buffer->row, sizeof(frow) * (buffer->numrows + 1));
   if (!tmp) {
     return;
   }
-  E.row = tmp;
+  buffer->row = tmp;
-  memmove(&E.row[at + 1], &E.row[at], sizeof(erow) * (E.numrows - at));
+  memmove(&buffer->row[at + 1], &buffer->row[at], sizeof(frow) * (buffer->numrows - at));
 
-  E.row[at].size = len;
+  buffer->row[at].size = len;
-  E.row[at].chars = malloc(len + 1);
+  buffer->row[at].chars = malloc(len + 1);
-  memcpy(E.row[at].chars, s, len);
+  memcpy(buffer->row[at].chars, s, len);
-  E.row[at].chars[len] = '\0';
+  buffer->row[at].chars[len] = '\0';
 
-  E.row[at].rsize = 0;
+  buffer->row[at].rsize = 0;
-  E.row[at].render = NULL;
+  buffer->row[at].render = NULL;
-  editorUpdateRow(&E.row[at]);
+  bufferUpdatfrow(&buffer->row[at]);
 
-  ++E.numrows;
+  ++buffer->numrows;
-  ++E.dirty;
+  ++buffer->dirty;
 }
 
-void editorFreeRow(erow *row) {
+void bufferFrefrow(frow *row) {
   free(row->render);
   free(row->chars);
 }
 
-void editorDelRow(int at) {
+void bufferDelRow(struct buffer_t *buffer, int at) {
-  if (at < 0 || at >= E.numrows) {
+  if (at < 0 || at >= buffer->numrows) {
     return;
   }
-  editorFreeRow(&E.row[at]);
+  bufferFrefrow(&buffer->row[at]);
-  memmove(&E.row[at], &E.row[at + 1], sizeof(erow) * (E.numrows - at - 1));
+  memmove(&buffer->row[at], &buffer->row[at + 1], sizeof(frow) * (buffer->numrows - at - 1));
-  --E.numrows;
+  --buffer->numrows;
-  ++E.dirty;
+  ++buffer->dirty;
 }
 
 /**
- * \fn editorRowInsertChar(erow *row, int at, int c)
+ * \fn bufferRowInsertChar(frow *row, int at, int c)
  * \param at Index of where we want to insert the char */
 
-void editorRowInsertChar(erow *row, int at, int c) {
+void bufferRowInsertChar(struct buffer_t *buffer, frow *row, int at, int c) {
-  if (E.state == READ_ONLY)
+  if (buffer->state == READ_ONLY)
     return;
   if (at < 0 || at > row->size) {
     at = row->size;
@@ -122,30 +123,30 @@ void editorRowInsertChar(erow *row, int at, int c) {
   memmove(&row->chars[at + 1], &row->chars[at], row->size - at + 1);
   ++row->size;
   row->chars[at] = c;
-  editorUpdateRow(row);
+  bufferUpdatfrow(row);
-  ++E.dirty;
+  ++buffer->dirty;
 }
 
-void editorRowAppendString(erow *row, char *s, size_t len) {
+void bufferRowAppendString(struct buffer_t *buffer, frow *row, char *s, size_t len) {
   row->chars = realloc(row->chars, row->size + len + 1);
   memcpy(&row->chars[row->size], s, len);
   row->size += len;
   row->chars[row->size] = '\0';
-  editorUpdateRow(row);
+  bufferUpdatfrow(row);
-  ++E.dirty;
+  ++buffer->dirty;
 }
 
 /**
- * \fn editorRowDelChar(struct editorConfig *E, erow *erow, int at)
+ * \fn bufferRowDelChar(struct bufferConfig *E, frow *frow, int at)
  * \brief Delete the a char at the chosen position on the given row
  * \param at Index of the char to delete
  * \param row Row on operation is made */
-void editorRowDelchar(erow *row, int at) {
+void bufferRowDelchar(struct buffer_t *buffer, frow *row, int at) {
   if (at < 0 || at >= row->size) {
     return;
   }
   memmove(&row->chars[at], &row->chars[at + 1], row->size - at);
   --row->size;
-  editorUpdateRow(row);
+  bufferUpdatfrow(row);
-  ++E.dirty;
+  ++buffer->dirty;
 }

src/split_screen.c

@@ -0,0 +1,218 @@
+/**
+ * @file split_screen.c
+ * @brief Split screen implementation
+ */
+
+#include "../include/split_screen.h"
+#include "../include/buffer.h"
+#include "../include/editor_op.h"
+#include <stdlib.h>
+#include <string.h>
+
+extern struct editorConfig E;
+
+/**
+ * @brief Initializes split screen system with single fullscreen pane
+ */
+void splitScreenInit(void) {
+    E.layout.mode = SPLIT_NONE;
+    E.layout.num_panes = 1;
+    E.layout.active_pane = 0;
+    
+    E.layout.panes = malloc(sizeof(EditorPane) * 2);
+    
+    // Initialize single fullscreen pane
+    E.layout.panes[0].buffer_id = -1; // No buffer for now
+    E.layout.panes[0].start_row = 0;
+    E.layout.panes[0].start_col = 0;
+    E.layout.panes[0].height = E.screenrows - 2;  // Leave room for status bar
+    E.layout.panes[0].width = E.screencols;
+    E.layout.panes[0].cursor_x = 0;
+    E.layout.panes[0].cursor_y = 0;
+    E.layout.panes[0].row_offset = 0;
+    E.layout.panes[0].col_offset = 0;
+    E.layout.panes[0].is_active = 1;
+}
+
+/**
+ * @brief Splits screen vertically (left-right)
+ * @param buffer_id_left Buffer ID for left pane
+ * @param buffer_id_right Buffer ID for right pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenVertical(int buffer_id_left, int buffer_id_right) {
+    // Verify both buffers exist
+    if (bufferFindById(buffer_id_left) == NULL ||
+        bufferFindById(buffer_id_right) == NULL) {
+        editorSetStatusMessage("Error: invalid buffer IDs");
+        return -1;
+    }
+    
+    // Reallocate panes array
+    E.layout.panes = realloc(E.layout.panes, sizeof(EditorPane) * 2);
+    E.layout.mode = SPLIT_VERTICAL;
+    E.layout.num_panes = 2;
+    E.layout.active_pane = 0;
+    
+    int half_width = E.screencols / 2;
+    int pane_height = E.screenrows - 2;  // Leave room for status bar
+    
+    // Left pane
+    E.layout.panes[0].buffer_id = buffer_id_left;
+    E.layout.panes[0].start_row = 0;
+    E.layout.panes[0].start_col = 0;
+    E.layout.panes[0].height = pane_height;
+    E.layout.panes[0].width = half_width;
+    E.layout.panes[0].cursor_x = 0;
+    E.layout.panes[0].cursor_y = 0;
+    E.layout.panes[0].row_offset = 0;
+    E.layout.panes[0].col_offset = 0;
+    E.layout.panes[0].is_active = 1;
+    
+    // Right pane
+    E.layout.panes[1].buffer_id = buffer_id_right;
+    E.layout.panes[1].start_row = 0;
+    E.layout.panes[1].start_col = half_width;
+    E.layout.panes[1].height = pane_height;
+    E.layout.panes[1].width = E.screencols - half_width;
+    E.layout.panes[1].cursor_x = 0;
+    E.layout.panes[1].cursor_y = 0;
+    E.layout.panes[1].row_offset = 0;
+    E.layout.panes[1].col_offset = 0;
+    E.layout.panes[1].is_active = 0;
+    
+    editorSetStatusMessage("Vertical split: %d | %d", buffer_id_left, buffer_id_right);
+    return 0;
+}
+
+/**
+ * @brief Splits screen horizontally (top-bottom)
+ * @param buffer_id_top Buffer ID for top pane
+ * @param buffer_id_bottom Buffer ID for bottom pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenHorizontal(int buffer_id_top, int buffer_id_bottom) {
+    // Verify both buffers exist
+    if (bufferFindById(buffer_id_top) == NULL ||
+        bufferFindById(buffer_id_bottom) == NULL) {
+        editorSetStatusMessage("Error: invalid buffer IDs");
+        return -1;
+    }
+    
+    // Reallocate panes array
+    E.layout.panes = realloc(E.layout.panes, sizeof(EditorPane) * 2);
+    E.layout.mode = SPLIT_HORIZONTAL;
+    E.layout.num_panes = 2;
+    E.layout.active_pane = 0;
+    
+    int half_height = (E.screenrows - 2) / 2;  // Account for status bar
+    
+    // Top pane
+    E.layout.panes[0].buffer_id = buffer_id_top;
+    E.layout.panes[0].start_row = 0;
+    E.layout.panes[0].start_col = 0;
+    E.layout.panes[0].height = half_height;
+    E.layout.panes[0].width = E.screencols;
+    E.layout.panes[0].cursor_x = 0;
+    E.layout.panes[0].cursor_y = 0;
+    E.layout.panes[0].row_offset = 0;
+    E.layout.panes[0].col_offset = 0;
+    E.layout.panes[0].is_active = 1;
+    
+    // Bottom pane
+    E.layout.panes[1].buffer_id = buffer_id_bottom;
+    E.layout.panes[1].start_row = half_height;
+    E.layout.panes[1].start_col = 0;
+    E.layout.panes[1].height = E.screenrows - 2 - half_height;
+    E.layout.panes[1].width = E.screencols;
+    E.layout.panes[1].cursor_x = 0;
+    E.layout.panes[1].cursor_y = 0;
+    E.layout.panes[1].row_offset = 0;
+    E.layout.panes[1].col_offset = 0;
+    E.layout.panes[1].is_active = 0;
+    
+    editorSetStatusMessage("Horizontal split: %d / %d", buffer_id_top, buffer_id_bottom);
+    return 0;
+}
+
+/**
+ * @brief Returns to single buffer fullscreen
+ */
+void splitScreenUnify(void) {
+    E.layout.mode = SPLIT_NONE;
+    E.layout.num_panes = 1;
+    E.layout.active_pane = 0;
+    
+    E.layout.panes[0].start_row = 0;
+    E.layout.panes[0].start_col = 0;
+    E.layout.panes[0].height = E.screenrows - 2;
+    E.layout.panes[0].width = E.screencols;
+    E.layout.panes[0].is_active = 1;
+    
+    editorSetStatusMessage("Unified view");
+}
+
+/**
+ * @brief Switches active pane (focus moves between splits)
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenSwitchPane(void) {
+    if (E.layout.num_panes < 2) {
+        editorSetStatusMessage("No split to switch");
+        return -1;
+    }
+    
+    // Deactivate current pane
+    E.layout.panes[E.layout.active_pane].is_active = 0;
+    
+    // Move to next pane
+    E.layout.active_pane = (E.layout.active_pane + 1) % E.layout.num_panes;
+    
+    // Activate new pane
+    E.layout.panes[E.layout.active_pane].is_active = 1;
+    
+    editorSetStatusMessage("Switched to pane %d (buffer %d)", 
+                          E.layout.active_pane,
+                          E.layout.panes[E.layout.active_pane].buffer_id);
+    return 0;
+}
+
+/**
+ * @brief Updates the active pane's buffer
+ * @param buffer_id New buffer ID for active pane
+ * @return 0 on success, -1 on failure
+ */
+int splitScreenSetPaneBuffer(int buffer_id) {
+    if (bufferFindById(buffer_id) == NULL) {
+        editorSetStatusMessage("Error: invalid buffer ID");
+        return -1;
+    }
+    
+    EditorPane *active = &E.layout.panes[E.layout.active_pane];
+    active->buffer_id = buffer_id;
+    active->cursor_x = 0;
+    active->cursor_y = 0;
+    active->row_offset = 0;
+    active->col_offset = 0;
+    
+    editorSetStatusMessage("Pane %d now showing buffer %d", 
+                          E.layout.active_pane, buffer_id);
+    return 0;
+}
+
+/**
+ * @brief Gets current screen layout
+ * @return Pointer to current ScreenLayout
+ */
+ScreenLayout *splitScreenGetLayout(void) {
+    return &E.layout;
+}
+
+/**
+ * @brief Gets active pane
+ * @return Pointer to active EditorPane
+ */
+EditorPane *splitScreenGetActivePane(void) {
+    if (E.layout.num_panes == 0) return NULL;
+    return &E.layout.panes[E.layout.active_pane];
+}