wayland: Restore valid state information when building keymaps

The spec doesn't guarantee that a modifier event won't arrive before a keymap event, or that it will always be sent after a keymap change if the modifiers and layout index haven't changed, so restore any valid state after allocation when building a new keymap.

Author: Kontrabant

src/video/wayland/SDL_waylandevents.c

@@ -1663,6 +1663,11 @@ static void keyboard_handle_keymap(void *data, struct wl_keyboard *keyboard,
         }
 
         WAYLAND_xkb_keymap_key_for_each(seat->keyboard.xkb.keymap, Wayland_KeymapIterator, seat);
+
+        // Restore any previously set modifier/layout information, if valid.
+        WAYLAND_xkb_state_update_mask(seat->keyboard.xkb.state,
+                                      seat->keyboard.xkb.wl_pressed_modifiers, seat->keyboard.xkb.wl_latched_modifiers, seat->keyboard.xkb.wl_locked_modifiers,
+                                      0, 0, seat->keyboard.xkb.current_layout < seat->keyboard.xkb.num_layouts ? seat->keyboard.xkb.current_layout : 0);
         Wayland_SeatSetKeymap(seat);
     }
 
@@ -1806,7 +1811,9 @@ static void Wayland_ReconcileModifiers(SDL_WaylandSeat *seat, bool key_pressed)
      * The modifier will remain active until the latch/lock is released by
      * the system.
      */
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.shift_mask) {
+    const xkb_mod_mask_t xkb_locked_modifiers = seat->keyboard.xkb.wl_latched_modifiers | seat->keyboard.xkb.wl_locked_modifiers;
+
+    if (xkb_locked_modifiers & seat->keyboard.xkb.shift_mask) {
         if (seat->keyboard.pressed_modifiers & SDL_KMOD_SHIFT) {
             seat->keyboard.locked_modifiers &= ~SDL_KMOD_SHIFT;
             seat->keyboard.locked_modifiers |= (seat->keyboard.pressed_modifiers & SDL_KMOD_SHIFT);
@@ -1817,7 +1824,7 @@ static void Wayland_ReconcileModifiers(SDL_WaylandSeat *seat, bool key_pressed)
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_SHIFT;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.ctrl_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.ctrl_mask) {
         if (seat->keyboard.pressed_modifiers & SDL_KMOD_CTRL) {
             seat->keyboard.locked_modifiers &= ~SDL_KMOD_CTRL;
             seat->keyboard.locked_modifiers |= (seat->keyboard.pressed_modifiers & SDL_KMOD_CTRL);
@@ -1828,7 +1835,7 @@ static void Wayland_ReconcileModifiers(SDL_WaylandSeat *seat, bool key_pressed)
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_CTRL;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.alt_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.alt_mask) {
         if (seat->keyboard.pressed_modifiers & SDL_KMOD_ALT) {
             seat->keyboard.locked_modifiers &= ~SDL_KMOD_ALT;
             seat->keyboard.locked_modifiers |= (seat->keyboard.pressed_modifiers & SDL_KMOD_ALT);
@@ -1839,7 +1846,7 @@ static void Wayland_ReconcileModifiers(SDL_WaylandSeat *seat, bool key_pressed)
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_ALT;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.gui_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.gui_mask) {
         if (seat->keyboard.pressed_modifiers & SDL_KMOD_GUI) {
             seat->keyboard.locked_modifiers &= ~SDL_KMOD_GUI;
             seat->keyboard.locked_modifiers |= (seat->keyboard.pressed_modifiers & SDL_KMOD_GUI);
@@ -1850,26 +1857,26 @@ static void Wayland_ReconcileModifiers(SDL_WaylandSeat *seat, bool key_pressed)
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_GUI;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.level3_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.level3_mask) {
         seat->keyboard.locked_modifiers |= SDL_KMOD_MODE;
     } else {
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_MODE;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.level5_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.level5_mask) {
         seat->keyboard.locked_modifiers |= SDL_KMOD_LEVEL5;
     } else {
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_LEVEL5;
     }
 
     // Capslock and Numlock can only be locked, not pressed.
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.caps_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.caps_mask) {
         seat->keyboard.locked_modifiers |= SDL_KMOD_CAPS;
     } else {
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_CAPS;
     }
 
-    if (seat->keyboard.xkb.wl_locked_modifiers & seat->keyboard.xkb.num_mask) {
+    if (xkb_locked_modifiers & seat->keyboard.xkb.num_mask) {
         seat->keyboard.locked_modifiers |= SDL_KMOD_NUM;
     } else {
         seat->keyboard.locked_modifiers &= ~SDL_KMOD_NUM;
@@ -2195,21 +2202,24 @@ static void keyboard_handle_modifiers(void *data, struct wl_keyboard *keyboard,
                                       uint32_t group)
 {
     SDL_WaylandSeat *seat = data;
-
-    if (seat->keyboard.xkb.state == NULL) {
-        /* if we get a modifier notification before the keymap, there's nothing we can do with the information
-        */
-        return;
-    }
-
-    WAYLAND_xkb_state_update_mask(seat->keyboard.xkb.state, mods_depressed, mods_latched,
-                                  mods_locked, 0, 0, group);
+    const uint32_t previous_layout = seat->keyboard.xkb.current_layout;
 
     seat->keyboard.xkb.wl_pressed_modifiers = mods_depressed;
-    seat->keyboard.xkb.wl_locked_modifiers = mods_latched | mods_locked;
+    seat->keyboard.xkb.wl_latched_modifiers = mods_latched;
+    seat->keyboard.xkb.wl_locked_modifiers = mods_locked;
+    seat->keyboard.xkb.current_layout = group;
 
     Wayland_ReconcileModifiers(seat, false);
 
+    // If we get a modifier notification before the keymap, there's no further state to update yet.
+    if (!seat->keyboard.xkb.state) {
+        return;
+    }
+
+    WAYLAND_xkb_state_update_mask(seat->keyboard.xkb.state,
+                                  mods_depressed, mods_latched, mods_locked,
+                                  0, 0, group);
+
     // If a key is repeating, update the text to apply the modifier.
     if (keyboard_repeat_is_set(&seat->keyboard.repeat)) {
         char text[8];
@@ -2220,8 +2230,7 @@ static void keyboard_handle_modifiers(void *data, struct wl_keyboard *keyboard,
         }
     }
 
-    if (group != seat->keyboard.xkb.current_layout) {
-        seat->keyboard.xkb.current_layout = group;
+    if (group != previous_layout) {
         Wayland_SeatSetKeymap(seat);
 
         if (seat->keyboard.xkb.compose_state) {

src/video/wayland/SDL_waylandevents_c.h

@@ -110,6 +110,7 @@ typedef struct SDL_WaylandSeat
 
             // Current system modifier flags
             xkb_mod_mask_t wl_pressed_modifiers;
+            xkb_mod_mask_t wl_latched_modifiers;
             xkb_mod_mask_t wl_locked_modifiers;
         } xkb;
     } keyboard;