From 7c79e2fc9eb531879142ba243846099ef6cd434f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 20 Mar 2026 02:21:50 +0000
Subject: [PATCH] Fix text selection via click-and-drag in unfocused splits

The regression was introduced by commit b277a016b which added an early
`return` in handle_button_event that prevented kitty's internal text
selection from starting on focus-transfer clicks to unfocused splits.

Changes:
- In handle_button_event: replace the early return with a local
  suppress_child_forwarding flag that prevents PRESS from being forwarded
  to child processes in mouse-tracking mode, while still allowing
  dispatch_mouse_event to run (which starts text selection)
- In mouse_event's active_drag_in_window release path: clear
  suppress_left_mouse_release to prevent stale flags after drags

Fixes #9713
Fixes #9715
---
 kitty/mouse.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kitty/mouse.c b/kitty/mouse.c
index 65d331e75..9a72d2de9 100644
--- a/kitty/mouse.c
+++ b/kitty/mouse.c
@@ -839,13 +839,16 @@ HANDLER(handle_button_event) {
 
     if (handle_scrollbar_mouse(w, button, is_release ? RELEASE : PRESS, modifiers)) return;
 
+    bool suppress_child_forwarding = false;
     if (osw->is_focused && window_idx != t->active_window && !is_release) {
         call_boss(switch_focus_to_in_active_tab, "K", t->windows[window_idx].id);
         if (button == GLFW_MOUSE_BUTTON_LEFT) {
-            // Treat split-focus transfer clicks as focus-only and suppress
-            // the matching release to avoid release-without-press reports.
+            // Treat split-focus transfer clicks as focus-only for child processes:
+            // suppress forwarding the left press and matching release to the child
+            // to avoid release-without-press reports. Still allow kitty to process
+            // the event internally (e.g., start text selection via click-and-drag).
             osw->suppress_left_mouse_release = true;
-            return;
+            suppress_child_forwarding = true;
         }
     }
 
@@ -856,7 +859,7 @@ HANDLER(handle_button_event) {
     if (!set_mouse_position(w, &a, &b)) return;
     id_type wid = w->id;
     if (!dispatch_mouse_event(w, button, is_release ? -1 : 1, modifiers, screen->modes.mouse_tracking_mode != 0)) {
-        if (screen->modes.mouse_tracking_mode != 0) {
+        if (!suppress_child_forwarding && screen->modes.mouse_tracking_mode != 0) {
             int sz = encode_mouse_button(w, button, is_release ? RELEASE : PRESS, modifiers);
             if (sz > 0) { mouse_event_buf[sz] = 0; write_escape_code_to_child(screen, ESC_CSI, mouse_event_buf); }
         }
@@ -1211,6 +1214,10 @@ mouse_event(const int button, int modifiers, int action) {
             w = window_for_id(global_state.active_drag_in_window);
             if (w) {
                 end_drag(w);
+                // Clear any stale suppress flag that was set during a focus-transfer
+                // press, since the drag release bypasses handle_button_event where
+                // it would normally be cleared.
+                if (osw) osw->suppress_left_mouse_release = false;
                 debug("handled as drag end\n");
                 dispatch_possible_click(w, button, modifiers);
                 return;