CE edit moving cursor up and down

ce/edit.c

@@ -15,6 +15,7 @@
 #include <string.h>
 #include <system.h>
 #include <tcursor.h>
+#include <terminal.h>
 #include <tgraphics.h>
 #include <tscreen.h>
 
@@ -32,6 +33,8 @@ struct editor {
   struct list_node_link* lines;
   struct edit_line* current_line;
   struct cursor cursor;
+  size_t col_offset;
+  size_t row_offset;
 };
 
 static struct editor editor;
@@ -58,34 +61,93 @@ static bool prepare_lines_cb (void* ctx, const char* start, size_t len) {
 
 static void prepare_lines (const char* text) { strtokenize (text, '\n', NULL, &prepare_lines_cb); }
 
+static void update_horz_scroll (size_t screen_cols) {
+  if (editor.cursor.col < editor.col_offset)
+    editor.col_offset = editor.cursor.col;
+
+  if (editor.cursor.col >= editor.col_offset + screen_cols)
+    editor.col_offset = editor.cursor.col - screen_cols + 1;
+}
+
+static void update_vert_scroll (size_t screen_rows) {
+  if (editor.cursor.line < editor.row_offset)
+    editor.row_offset = editor.cursor.line;
+
+  if (editor.cursor.line >= editor.row_offset + (screen_rows - 1))
+    editor.row_offset = editor.cursor.line - (screen_rows - 1) + 1;
+}
+
 void edit_start (const char* text) {
   prepare_lines (text);
   struct arena temp_arena;
+  size_t cols, rows;
+
+  terminal_dimensions (&cols, &rows);
 
   mprintf (ANSIQ_SCR_SAVE ANSIQ_SCR_CLR_ALL ANSIQ_CUR_INVISIBLE);
 
   for (;;) {
+    update_horz_scroll (cols);
+    update_vert_scroll (rows);
+
+    int w;
     const size_t backbuffer_max = 128 * 1024;
+    size_t bb_remaining = backbuffer_max;
     char* backbuffer = arena_malloc (&temp_arena, backbuffer_max);
     memset (backbuffer, 0, backbuffer_max);
+    char* bbptr = backbuffer;
 
-    strncat (backbuffer, ANSIQ_CUR_HOME ANSIQ_SCR_CLR_ALL, backbuffer_max);
+    w = snprintf (bbptr, bb_remaining, ANSIQ_CUR_HOME);
+    bbptr += w;
+    bb_remaining -= w;
+
+    size_t lines_drawn = 0;
+    size_t current_idx = 0;
 
     struct list_node_link *line_link, *tmp_line_link;
     list_foreach (editor.lines, line_link, tmp_line_link) {
+      if (current_idx < editor.row_offset) {
+        current_idx++;
+        continue;
+      }
+
+      if (lines_drawn >= rows - 1)
+        break;
+
       struct edit_line* line = list_entry (line_link, struct edit_line, lines_link);
 
-      strncat (backbuffer, ANSIQ_SCR_CLR_LINE, backbuffer_max);
+      w = snprintf (bbptr, bb_remaining, ANSIQ_SCR_CLR_LINE);
+      bbptr += w;
+      bb_remaining -= w;
 
       char* render = gapbuffer_get_string (&warena_malloc, &temp_arena, &line->gb);
-      strncat (backbuffer, render, backbuffer_max);
-      strncat (backbuffer, "\n", backbuffer_max);
+      size_t len = strlen (render);
+
+      if (len > editor.col_offset) {
+        char* visible = render + editor.col_offset;
+        size_t visible_len = len - editor.col_offset;
+
+        if (visible_len > cols)
+          visible_len = cols;
+
+        w = snprintf (bbptr, bb_remaining, "%.*s", (int)visible_len, visible);
+        bbptr += w;
+        bb_remaining -= w;
+      }
+
+      w = snprintf (bbptr, bb_remaining, ANSIQ_SCR_CLR2LEND "\n");
+      bbptr += w;
+      bb_remaining -= w;
+
+      lines_drawn++;
+      current_idx++;
     }
 
-    char tmp[128];
-    snprintf (tmp, sizeof (tmp), ANSIQ_DYN_CUR_SET ANSIQ_CUR_VISIBLE, (int)editor.cursor.line + 1,
-              (int)editor.cursor.col + 1);
-    strncat (backbuffer, tmp, backbuffer_max);
+    w = snprintf (bbptr, bb_remaining, ANSIQ_DYN_CUR_SET ANSIQ_CUR_VISIBLE,
+                  (int)(editor.cursor.line - editor.row_offset) + 1,
+                  (int)(editor.cursor.col - editor.col_offset) + 1);
+    bbptr += w;
+    bb_remaining -= w;
 
     mail_send (e_pgid, backbuffer, strlen (backbuffer));
 
@@ -102,20 +164,37 @@ void edit_start (const char* text) {
       }
       break;
     case KB_DELETE:
-      if (editor.cursor.col < gapbuffer_length (&editor.current_line->gb)) {
+      if (editor.cursor.col < gapbuffer_length (&editor.current_line->gb))
         editor.current_line->gb.gap_end++;
-      }
       break;
     case KB_LEFT:
-      if (editor.cursor.col > 0) {
+      if (editor.cursor.col > 0)
         editor.cursor.col--;
-      }
       break;
     case KB_RIGHT:
-      if (editor.cursor.col < gapbuffer_length (&editor.current_line->gb)) {
+      if (editor.cursor.col < gapbuffer_length (&editor.current_line->gb))
         editor.cursor.col++;
-      }
       break;
+    case KB_UP: {
+      if (editor.cursor.line > 0) {
+        editor.cursor.line--;
+        editor.current_line =
+            list_entry (editor.current_line->lines_link.prev, struct edit_line, lines_link);
+        size_t len = gapbuffer_length (&editor.current_line->gb);
+        if (editor.cursor.col > len)
+          editor.cursor.col = len;
+      }
+    } break;
+    case KB_DOWN: {
+      if (editor.current_line->lines_link.next != NULL) {
+        editor.cursor.line++;
+        editor.current_line =
+            list_entry (editor.current_line->lines_link.next, struct edit_line, lines_link);
+        size_t len = gapbuffer_length (&editor.current_line->gb);
+        if (editor.cursor.col > len)
+          editor.cursor.col = len;
+      }
+    } break;
     default:
       if (isprint (ch)) {
         gapbuffer_insert (&wrealloc, NULL, &editor.current_line->gb, ch);