Fixed create_cursors_around behaviour.

Now handles starting with multiple cursors.
Now handles being at start of line & being on empty line correctly.

src/editors.jai

@@ -1581,43 +1581,59 @@ create_cursor :: (using editor: *Editor, buffer: Buffer, where: enum { above; be
 }
 
 create_cursors_around :: (using editor: *Editor, buffer: Buffer) {
-    organise_cursors(editor);
+    // (a) If cursor is mid-line, add cursors above-and-below it on all contiguous lines which are at least as long.
+    // (b) If the cursor is at the start of a line, add cursors above-and-below, bounded by empty lines.
+    // (c) If the cursor is on an empty line, add cursors above-and-below on all contiguous empty lines.
 
-    top_cursor    := cursors[0];
-    bottom_cursor := cursors[cursors.count-1];
-    original    := cursors[original_cursor];
-    original_pos_coords := offset_to_coords(editor, buffer, original.pos);
-    original_sel_coords := offset_to_coords(editor, buffer, original.sel);
-
-    add_cursors :: (position: Coords, direction: s32, terminator_line: int) #expand {
-        while position.line != terminator_line {
-            position.line += direction;
-            start := get_line_start_offset(editor, buffer, position.line);
-            end := get_line_end_offset(editor, buffer, position.line);
-            if end - start < original_pos_coords.col
-                break;
+    organise_cursors(editor);
 
-            cursor := add(*cursors);
-            <<cursor = top_cursor;
-            cursor.pos = coords_to_offset(editor, buffer, position);
-            cursor.col_wanted = original_pos_coords.col;
+    from_cursors := NewArray(cursors.count, Cursor, initialized = false,, temp);
+    memcpy(from_cursors.data, cursors.data, cursors.count * size_of(Cursor));
+
+    for from_cursor : from_cursors {
+        from_pos_coords := offset_to_coords(editor, buffer, from_cursor.pos);
+        from_sel_coords := offset_to_coords(editor, buffer, from_cursor.sel);
+        from_cursor_is_at_line_end := from_cursor.pos == get_line_end_offset(editor, buffer, from_pos_coords.line);
+        from_line_is_empty := from_pos_coords.col == 0 && from_cursor_is_at_line_end;
+
+        add_cursors :: (position: Coords, direction: s32, terminator_line: int) #expand {
+            while position.line != terminator_line {
+                position.line += direction;
+                start := get_line_start_offset(editor, buffer, position.line);
+                end := get_line_end_offset(editor, buffer, position.line);
+                if !from_line_is_empty {
+                    if from_pos_coords.col > 0 {
+                        if !from_cursor_is_at_line_end then end -= 1;  // Only expand into line-ends if the original cursor was at the line-end.
+                        if end - start < from_pos_coords.col  break;  // (a)
+                    } else {
+                        if end == start  break;  // (b)
+                    }
+                } else {
+                    if end > start  break;  // (c)
+                }
 
-            if has_selection(original) {
-                sel_coords := position;
-                sel_coords.line += original_sel_coords.line - original_pos_coords.line;
-                sel_coords.col  += original_sel_coords.col  - original_pos_coords.col;
-                cursor.sel = coords_to_offset(editor, buffer, sel_coords);
-            } else {
-                cursor.sel = cursor.pos;
+                cursor := add(*cursors);
+                cursor.* = from_cursor;
+                cursor.pos = coords_to_offset(editor, buffer, position);
+                cursor.col_wanted = from_pos_coords.col;
+
+                if has_selection(from_cursor) {
+                    sel_coords := position;
+                    sel_coords.line += from_sel_coords.line - from_pos_coords.line;
+                    sel_coords.col  += from_sel_coords.col  - from_pos_coords.col;
+                    cursor.sel = coords_to_offset(editor, buffer, sel_coords);
+                    cursor.sel = clamp(cursor.sel, start, end);
+                } else {
+                    cursor.sel = cursor.pos;
+                }
             }
         }
-    }
 
-    add_cursors(offset_to_coords(editor, buffer, top_cursor.pos), -1, 0);
-    add_cursors(offset_to_coords(editor, buffer, top_cursor.pos), +1, buffer.line_starts.count - 1);
+        add_cursors(offset_to_coords(editor, buffer, from_cursor.pos), -1, 0);
+        add_cursors(offset_to_coords(editor, buffer, from_cursor.pos), +1, buffer.line_starts.count - 1);
+    }
 
     main_cursor = cursors.count - 1;
-
     organise_cursors(editor);
 
     cursor_moved = .refresh_only;