Fix focus_follows_mouse switching active window on desktop/space return

When focus_follows_mouse is enabled, returning to a desktop/space fired an
enter event that switched the active window to whichever one was under the
cursor, even though the mouse had not crossed a window boundary.

Distinguish genuine mouse motion into a window from a window reappearing
under a stationary cursor by checking, in cursor_enter_callback, whether the
cursor position actually changed. focus_follows_mouse now switches focus only
when the cursor moved, so motion into a window still switches focus while a
stationary reappearance does not.

docs/changelog.rst

@@ -178,6 +178,8 @@ Detailed list of changes
 
 - macOS: Show a key symbol on the active tab if the macOS Secure Input feature is enabled
 
+- Fix :opt:`focus_follows_mouse` switching the active window when returning to a desktop/space, even though the mouse did not move. Now the window under a stationary cursor is left alone, while moving the mouse across windows still switches focus as before.
+
 0.47.2 [2026-06-07]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kitty/data-types.h

@@ -329,7 +329,7 @@ bool colorprofile_pop_colors(ColorProfile*, unsigned int);
 void colorprofile_report_stack(ColorProfile*, unsigned int*, unsigned int*);
 
 void set_mouse_cursor(MouseShape);
-void enter_event(int modifiers);
+void enter_event(int modifiers, bool cursor_moved);
 void leave_event(int modifiers);
 void mouse_event(const int, int, int);
 void focus_in_event(void);

kitty/glfw.c

@@ -539,12 +539,20 @@ cursor_enter_callback(GLFWwindow *w, int entered) {
     glfwGetCursorPos(w, &x, &y);
     monotonic_t now = monotonic();
     global_state.callback_os_window->last_mouse_activity_at = now;
-    global_state.callback_os_window->mouse_x = x * global_state.callback_os_window->viewport_x_ratio;
-    global_state.callback_os_window->mouse_y = y * global_state.callback_os_window->viewport_y_ratio;
+    double new_mouse_x = x * global_state.callback_os_window->viewport_x_ratio;
+    double new_mouse_y = y * global_state.callback_os_window->viewport_y_ratio;
+    // focus_follows_mouse should react to the mouse moving, not to a window
+    // appearing under a stationary cursor (such as when returning to this
+    // desktop/space). Detect genuine motion by comparing against the last
+    // known cursor position so an enter caused by mouse motion still switches
+    // focus, while a stationary reappearance does not.
+    bool cursor_moved = new_mouse_x != global_state.callback_os_window->mouse_x || new_mouse_y != global_state.callback_os_window->mouse_y;
+    global_state.callback_os_window->mouse_x = new_mouse_x;
+    global_state.callback_os_window->mouse_y = new_mouse_y;
     if (entered) {
         debug_input("Mouse cursor entered window: %llu at %fx%f\n", global_state.callback_os_window->id, x, y);
         cursor_active_callback(now);
-        if (is_window_ready_for_callbacks()) enter_event(global_state.mods_at_last_key_or_button_event);
+        if (is_window_ready_for_callbacks()) enter_event(global_state.mods_at_last_key_or_button_event, cursor_moved);
     } else {
         debug_input("Mouse cursor left window: %llu\n", global_state.callback_os_window->id);
         if (is_window_ready_for_callbacks()) leave_event(global_state.mods_at_last_key_or_button_event);

kitty/mouse.c

@@ -181,7 +181,7 @@ update_scrollbar_hover_state(Window *w, bool hovering) {
 }
 
 static void
-set_currently_hovered_window(id_type window_id, int modifiers) {
+set_currently_hovered_window(id_type window_id, int modifiers, bool focus_follows) {
     if (global_state.mouse_hover_in_window != window_id) {
         Window *left_window = window_for_id(global_state.mouse_hover_in_window);
         global_state.mouse_hover_in_window = window_id;
@@ -196,7 +196,7 @@ set_currently_hovered_window(id_type window_id, int modifiers) {
                 debug("Sent mouse leave event to window: %llu currently hovering: %llu\n", left_window->id, window_id);
             }
         }
-        if (window_id && OPT(focus_follows_mouse).on_cross && global_state.callback_os_window && global_state.callback_os_window->num_tabs) {
+        if (focus_follows && window_id && OPT(focus_follows_mouse).on_cross && global_state.callback_os_window && global_state.callback_os_window->num_tabs) {
             Tab *t = global_state.callback_os_window->tabs + global_state.callback_os_window->active_tab;
             for (unsigned i = 0; i < t->num_windows; i++) {
                 if (t->windows[i].id == window_id) {
@@ -934,7 +934,7 @@ currently_pressed_button(void) {
 HANDLER(handle_event) {
     modifiers &= ~GLFW_LOCK_MASK;
     set_mouse_cursor_for_screen(w->render_data.screen);
-    set_currently_hovered_window(w->id, modifiers);
+    set_currently_hovered_window(w->id, modifiers, true);
     if (button == -1) {
         button = currently_pressed_button();
         handle_move_event(w, button, modifiers, window_idx);
@@ -955,7 +955,7 @@ handle_window_title_bar_mouse(Window *w, int button, int modifiers, int action)
 
 static void
 handle_tab_bar_mouse(int button, int modifiers, int action) {
-    set_currently_hovered_window(0, modifiers);
+    set_currently_hovered_window(0, modifiers, false);
     OSWindow *w = global_state.callback_os_window;
     // dont report motion events, as they are expensive and useless
     if (w && (button > -1 || global_state.tab_being_dragged.id)) {
@@ -1148,11 +1148,11 @@ update_mouse_pointer_shape(void) {
 void
 leave_event(int modifiers) {
     if (global_state.redirect_mouse_handling || global_state.active_drag_in_window || global_state.tracked_drag_in_window) return;
-    set_currently_hovered_window(0, modifiers);
+    set_currently_hovered_window(0, modifiers, false);
 }
 
 void
-enter_event(int modifiers) {
+enter_event(int modifiers, bool cursor_moved) {
 #ifdef __APPLE__
     // On cocoa there is no way to configure the window manager to
     // focus windows on mouse enter, so we do it ourselves
@@ -1170,7 +1170,7 @@ enter_event(int modifiers) {
     if (global_state.redirect_mouse_handling || global_state.active_drag_in_window || global_state.tracked_drag_in_window) return;
     MouseRegion r = mouse_region(false, false);
     Window *w = r.window;
-    set_currently_hovered_window(w ? w->id : 0, modifiers);
+    set_currently_hovered_window(w ? w->id : 0, modifiers, cursor_moved);
     if (!w || r.in_tab_bar || r.in_title_bar) return;
 
     if (handle_scrollbar_mouse(w, -1, MOVE, modifiers)) return;
@@ -1359,7 +1359,7 @@ mouse_event(const int button, int modifiers, int action) {
     }
     MouseRegion r = mouse_region(true, true);
     w = r.window; window_idx = r.window_idx;
-    set_currently_hovered_window(w && !r.window_border && !r.in_title_bar ? w->id : 0, modifiers);
+    set_currently_hovered_window(w && !r.window_border && !r.in_title_bar ? w->id : 0, modifiers, true);
 
     if (r.in_tab_bar || global_state.tab_being_dragged.id) {
         mouse_cursor_shape = POINTER_POINTER;