Fix BeforeEdit cursor removal, add multicursor deletion

src/basic/basic.h

@@ -183,16 +183,47 @@ for (int i = 0; i < array.len; i += 1) {
     }
 }
 
+// Simple delete
+
 IterRemove(arr) {
     IterRemovePrepare(arr);
 
     remove_item = true;
 }
 
+//
+// Deleting backwards
+//
+
 For(arr.reverse_iter()) {
     defer{ arr.unordered_remove(it); };
 }
 
+//
+// When double looping and deleting
+//
+
+Array<Cursor *> deleted_cursors = {scratch};
+ForItem(cursor, window->cursors) {
+    For(deleted_cursors) if (it == &cursor) goto end_of_cursor_loop;
+
+    For(window->cursors) {
+        if (&it == &cursor) break;
+        bool a = cursor.range.max >= it.range.min && cursor.range.max <= it.range.max;
+        bool b = cursor.range.min >= it.range.min && cursor.range.min <= it.range.max;
+        if (a || b) {
+            deleted_cursors.add(&it);
+            cursor.range.max = Max(cursor.range.max, it.range.max);
+            cursor.range.min = Min(cursor.range.min, it.range.min);
+            break;
+        }
+    }
+end_of_cursor_loop:;
+}
+
+For(deleted_cursors) window->cursors.ordered_remove(*it);
+
+
 */
 #define IterRemove(a) for (int i = 0; i < (a).len; i += 1)
 #define IterRemovePrepare(a)        \