ime: track IME focus independently from keyboard focus

Replace the seat->ime.focused boolean with a terminal instace pointer,
seat->ime_focus.

Set and reset this on ime::enter() and ime::leave() events, and use
this instead of seat->kbd_focus on all other IME events.

This fixes two issues:

a) buggy compositors that sometimes sends an IME enter event without
  first having sent a keyboard enter event.

b) seats may be IME capable while still lacking the keyboard
  capability. Such seats will *always* see IME enter events without a
  corresponding keyboard enter event.

CHANGELOG.md

@@ -72,6 +72,7 @@
 * Graphical corruption when viewport is at the top of the scrollback,
   and the output is scrolling.
 * Improved text reflow of logical lines with trailing empty cells ([#1055][1055])
+* IME focus is now tracked independently from keyboard focus.
 
 [1055]: https://codeberg.org/dnkl/foot/issues/1055
 

ime.c

@@ -56,12 +56,18 @@ enter(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
       struct wl_surface *surface)
 {
     struct seat *seat = data;
+    struct wl_window *win = wl_surface_get_user_data(surface);
+    struct terminal *term = win->term;
 
-    LOG_DBG("enter: seat=%s", seat->name);
+    LOG_DBG("enter: seat=%s, term=%p", seat->name, (const void *)term);
+
+    if (seat->kbd_focus != term) {
+        LOG_WARN("compositor sent ime::enter() event before the "
+                 "corresponding keyboard_enter() event");
+    }
 
     /* The main grid is the *only* input-receiving surface we have */
-    xassert(seat->kbd_focus != NULL);
-    seat->ime.focused = true;
+    seat->ime_focus = term;
     ime_enable(seat);
 }
 
@@ -73,7 +79,7 @@ leave(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
     LOG_DBG("leave: seat=%s", seat->name);
 
     ime_disable(seat);
-    seat->ime.focused = false;
+    seat->ime_focus = NULL;
 }
 
 static void
@@ -138,7 +144,7 @@ done(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
 
     LOG_DBG("done: serial=%u", serial);
     struct seat *seat = data;
-    struct terminal *term = seat->kbd_focus;
+    struct terminal *term = seat->ime_focus;
 
     if (seat->ime.serial != serial) {
         LOG_DBG("IME serial mismatch: expected=0x%08x, got 0x%08x",
@@ -364,10 +370,10 @@ ime_send_cursor_rect(struct seat *seat)
     if (unlikely(seat->wayl->text_input_manager == NULL))
         return;
 
-    if (!seat->ime.focused)
+    if (seat->ime_focus == NULL)
         return;
 
-    struct terminal *term = seat->kbd_focus;
+    struct terminal *term = seat->ime_focus;
 
     if (!term->ime_enabled)
         return;
@@ -399,10 +405,10 @@ ime_enable(struct seat *seat)
     if (unlikely(seat->wayl->text_input_manager == NULL))
         return;
 
-    if (!seat->ime.focused)
+    if (seat->ime_focus == NULL)
         return;
 
-    struct terminal *term = seat->kbd_focus;
+    struct terminal *term = seat->ime_focus;
     if (term == NULL)
         return;
 
@@ -437,7 +443,7 @@ ime_disable(struct seat *seat)
     if (unlikely(seat->wayl->text_input_manager == NULL))
         return;
 
-    if (!seat->ime.focused)
+    if (seat->ime_focus == NULL)
         return;
 
     ime_reset_pending(seat);
@@ -451,7 +457,7 @@ ime_disable(struct seat *seat)
 void
 ime_update_cursor_rect(struct seat *seat)
 {
-    struct terminal *term = seat->kbd_focus;
+    struct terminal *term = seat->ime_focus;
 
     /* Set in render_ime_preedit() */
     if (seat->ime.preedit.cells != NULL)

render.c

@@ -3576,7 +3576,7 @@ frame_callback(void *data, struct wl_callback *wl_callback, uint32_t callback_da
         grid_render(term);
 
     tll_foreach(term->wl->seats, it) {
-        if (it->item.kbd_focus == term)
+        if (it->item.ime_focus == term)
             ime_update_cursor_rect(&it->item);
     }
 
@@ -4058,7 +4058,7 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
                 grid_render(term);
 
             tll_foreach(term->wl->seats, it) {
-                if (it->item.kbd_focus == term)
+                if (it->item.ime_focus == term)
                     ime_update_cursor_rect(&it->item);
             }
 

wayland.h

@@ -81,6 +81,7 @@ struct seat {
     /* Focused terminals */
     struct terminal *kbd_focus;
     struct terminal *mouse_focus;
+    struct terminal *ime_focus;
 
     /* Keyboard state */
     struct wl_keyboard *wl_keyboard;
@@ -202,7 +203,6 @@ struct seat {
             } pending;
         } surrounding;
 
-        bool focused;
         uint32_t serial;
     } ime;
 #endif