wayland: Add multi-seat support

Wayland environments can expose more than one seat for multiple collections of input devices, which can include multiple, simultaneously active, desktop pointers and keyboards with independent layouts. The Wayland input backend previously presumed that only one seat could exist, which caused broken behavior if the compositor exposed more than one, which is possible on wlroots based compositors such as Sway. This introduces support for handling multiple seats, including proper handling of dynamically adding and removing seats and capabilities at run time.

The SDL Wayland input system was accreted over time, and the assumption that only one seat will ever exist resulted in state and related objects not always being tied to their most appropriate owner in a multi-seat scenario, so refactoring was required to manage several bits of state per-seat instead of per-window or globally.

As Wayland keyboards can have per-seat layouts, fast keymap switching is required when multiplexing input from multiple seats to the global SDL keyboard device. A parameter was added to the keymap creation function to specify if the keymap lifetime should be externally managed to facilitte reuse, and some layout info was moved from the global keyboard state to the keymap state to avoid unnecessarily redetermining it whenever a reused keymap is subsequently bound. This reduces the overhead of switching keymaps to setting a single pointer.

Author: Kontrabant

Diff for: src/events/SDL_keyboard.c

@@ -58,9 +58,6 @@ typedef struct SDL_Keyboard
     Uint8 keysource[SDL_SCANCODE_COUNT];
     bool keystate[SDL_SCANCODE_COUNT];
     SDL_Keymap *keymap;
-    bool french_numbers;
-    bool latin_letters;
-    bool thai_keyboard;
     Uint32 keycode_options;
     bool autorelease_pending;
     Uint64 hardware_timestamp;
@@ -175,6 +172,19 @@ void SDL_RemoveKeyboard(SDL_KeyboardID keyboardID, bool send_event)
     }
 }
 
+void SDL_SetKeyboardName(SDL_KeyboardID keyboardID, const char *name)
+{
+    SDL_assert(keyboardID != 0);
+
+    const int keyboard_index = SDL_GetKeyboardIndex(keyboardID);
+
+    if (keyboard_index >= 0) {
+        SDL_KeyboardInstance *instance = &SDL_keyboards[keyboard_index];
+        SDL_free(instance->name);
+        instance->name = SDL_strdup(name ? name : "");
+    }
+}
+
 bool SDL_HasKeyboard(void)
 {
     return (SDL_keyboard_count > 0);
@@ -232,14 +242,15 @@ void SDL_ResetKeyboard(void)
 SDL_Keymap *SDL_GetCurrentKeymap(void)
 {
     SDL_Keyboard *keyboard = &SDL_keyboard;
+    SDL_Keymap *keymap = SDL_keyboard.keymap;
 
-    if (keyboard->thai_keyboard) {
+    if (keymap && keymap->thai_keyboard) {
         // Thai keyboards are QWERTY plus Thai characters, use the default QWERTY keymap
         return NULL;
     }
 
     if ((keyboard->keycode_options & KEYCODE_OPTION_LATIN_LETTERS) &&
-        !keyboard->latin_letters) {
+        keymap && !keymap->latin_letters) {
         // We'll use the default QWERTY keymap
         return NULL;
     }
@@ -251,35 +262,39 @@ void SDL_SetKeymap(SDL_Keymap *keymap, bool send_event)
 {
     SDL_Keyboard *keyboard = &SDL_keyboard;
 
-    if (keyboard->keymap) {
+    if (keyboard->keymap && keyboard->keymap->auto_release) {
         SDL_DestroyKeymap(keyboard->keymap);
     }
 
     keyboard->keymap = keymap;
 
-    // Detect French number row (all symbols)
-    keyboard->french_numbers = true;
-    for (int i = SDL_SCANCODE_1; i <= SDL_SCANCODE_0; ++i) {
-        if (SDL_isdigit(SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_NONE)) ||
-            !SDL_isdigit(SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_SHIFT))) {
-            keyboard->french_numbers = false;
-            break;
-        }
-    }
+    if (keymap && !keymap->layout_determined) {
+        keymap->layout_determined = true;
 
-    // Detect non-Latin keymap
-    keyboard->thai_keyboard = false;
-    keyboard->latin_letters = false;
-    for (int i = SDL_SCANCODE_A; i <= SDL_SCANCODE_D; ++i) {
-        SDL_Keycode key = SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_NONE);
-        if (key <= 0xFF) {
-            keyboard->latin_letters = true;
-            break;
+        // Detect French number row (all symbols)
+        keymap->french_numbers = true;
+        for (int i = SDL_SCANCODE_1; i <= SDL_SCANCODE_0; ++i) {
+            if (SDL_isdigit(SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_NONE)) ||
+                !SDL_isdigit(SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_SHIFT))) {
+                keymap->french_numbers = false;
+                break;
+                }
         }
 
-        if (key >= 0x0E00 && key <= 0x0E7F) {
-            keyboard->thai_keyboard = true;
-            break;
+        // Detect non-Latin keymap
+        keymap->thai_keyboard = false;
+        keymap->latin_letters = false;
+        for (int i = SDL_SCANCODE_A; i <= SDL_SCANCODE_D; ++i) {
+            SDL_Keycode key = SDL_GetKeymapKeycode(keymap, (SDL_Scancode)i, SDL_KMOD_NONE);
+            if (key <= 0xFF) {
+                keymap->latin_letters = true;
+                break;
+            }
+
+            if (key >= 0x0E00 && key <= 0x0E7F) {
+                keymap->thai_keyboard = true;
+                break;
+            }
         }
     }
 
@@ -308,7 +323,7 @@ static void SetKeymapEntry(SDL_Scancode scancode, SDL_Keymod modstate, SDL_Keyco
     SDL_Keyboard *keyboard = &SDL_keyboard;
 
     if (!keyboard->keymap) {
-        keyboard->keymap = SDL_CreateKeymap();
+        keyboard->keymap = SDL_CreateKeymap(true);
     }
 
     SDL_SetKeymapEntry(keyboard->keymap, scancode, modstate, keycode);
@@ -483,7 +498,7 @@ SDL_Keycode SDL_GetKeyFromScancode(SDL_Scancode scancode, SDL_Keymod modstate, b
         modstate = SDL_KMOD_NONE;
 
         if ((keyboard->keycode_options & KEYCODE_OPTION_FRENCH_NUMBERS) &&
-            keyboard->french_numbers &&
+            keymap && keymap->french_numbers &&
             (scancode >= SDL_SCANCODE_1 && scancode <= SDL_SCANCODE_0)) {
             // Add the shift state to generate a numeric keycode
             modstate |= SDL_KMOD_SHIFT;
@@ -876,7 +891,7 @@ void SDL_QuitKeyboard(void)
     SDL_free(SDL_keyboards);
     SDL_keyboards = NULL;
 
-    if (SDL_keyboard.keymap) {
+    if (SDL_keyboard.keymap && SDL_keyboard.keymap->auto_release) {
         SDL_DestroyKeymap(SDL_keyboard.keymap);
         SDL_keyboard.keymap = NULL;
     }

Diff for: src/events/SDL_keyboard_c.h

@@ -43,6 +43,9 @@ extern void SDL_AddKeyboard(SDL_KeyboardID keyboardID, const char *name, bool se
 // A keyboard has been removed from the system
 extern void SDL_RemoveKeyboard(SDL_KeyboardID keyboardID, bool send_event);
 
+// Set or update the name of a keyboard instance.
+extern void SDL_SetKeyboardName(SDL_KeyboardID keyboardID, const char *name);
+
 // Set the mapping of scancode to key codes
 extern void SDL_SetKeymap(SDL_Keymap *keymap, bool send_event);
 

Diff for: src/events/SDL_keymap.c

@@ -23,22 +23,17 @@
 #include "SDL_keymap_c.h"
 #include "SDL_keyboard_c.h"
 
-struct SDL_Keymap
-{
-    SDL_HashTable *scancode_to_keycode;
-    SDL_HashTable *keycode_to_scancode;
-};
-
 static SDL_Keycode SDL_GetDefaultKeyFromScancode(SDL_Scancode scancode, SDL_Keymod modstate);
 static SDL_Scancode SDL_GetDefaultScancodeFromKey(SDL_Keycode key, SDL_Keymod *modstate);
 
-SDL_Keymap *SDL_CreateKeymap(void)
+SDL_Keymap *SDL_CreateKeymap(bool auto_release)
 {
-    SDL_Keymap *keymap = (SDL_Keymap *)SDL_malloc(sizeof(*keymap));
+    SDL_Keymap *keymap = (SDL_Keymap *)SDL_calloc(1, sizeof(*keymap));
     if (!keymap) {
         return NULL;
     }
 
+    keymap->auto_release = auto_release;
     keymap->scancode_to_keycode = SDL_CreateHashTable(256, false, SDL_HashID, SDL_KeyMatchID, NULL, NULL);
     keymap->keycode_to_scancode = SDL_CreateHashTable(256, false, SDL_HashID, SDL_KeyMatchID, NULL, NULL);
     if (!keymap->scancode_to_keycode || !keymap->keycode_to_scancode) {

Diff for: src/events/SDL_keymap_c.h

@@ -23,10 +23,19 @@
 #ifndef SDL_keymap_c_h_
 #define SDL_keymap_c_h_
 
-typedef struct SDL_Keymap SDL_Keymap;
+typedef struct SDL_Keymap
+{
+  SDL_HashTable *scancode_to_keycode;
+  SDL_HashTable *keycode_to_scancode;
+  bool auto_release;
+  bool layout_determined;
+  bool french_numbers;
+  bool latin_letters;
+  bool thai_keyboard;
+} SDL_Keymap;
 
 SDL_Keymap *SDL_GetCurrentKeymap(void);
-SDL_Keymap *SDL_CreateKeymap(void);
+SDL_Keymap *SDL_CreateKeymap(bool auto_release);
 void SDL_SetKeymapEntry(SDL_Keymap *keymap, SDL_Scancode scancode, SDL_Keymod modstate, SDL_Keycode keycode);
 SDL_Keycode SDL_GetKeymapKeycode(SDL_Keymap *keymap, SDL_Scancode scancode, SDL_Keymod modstate);
 SDL_Scancode SDL_GetKeymapScancode(SDL_Keymap *keymap, SDL_Keycode keycode, SDL_Keymod *modstate);

Diff for: src/events/SDL_mouse.c

@@ -409,6 +409,19 @@ void SDL_RemoveMouse(SDL_MouseID mouseID, bool send_event)
     }
 }
 
+void SDL_SetMouseName(SDL_MouseID mouseID, const char *name)
+{
+    SDL_assert(mouseID != 0);
+
+    const int mouse_index = SDL_GetMouseIndex(mouseID);
+
+    if (mouse_index >= 0) {
+        SDL_MouseInstance *instance = &SDL_mice[mouse_index];
+        SDL_free(instance->name);
+        instance->name = SDL_strdup(name ? name : "");
+    }
+}
+
 bool SDL_HasMouse(void)
 {
     return (SDL_mouse_count > 0);

Diff for: src/events/SDL_mouse_c.h

@@ -169,6 +169,9 @@ extern void SDL_AddMouse(SDL_MouseID mouseID, const char *name, bool send_event)
 // A mouse has been removed from the system
 extern void SDL_RemoveMouse(SDL_MouseID mouseID, bool send_event);
 
+// Set or update the name of a mouse instance.
+extern void SDL_SetMouseName(SDL_MouseID mouseID, const char *name);
+
 // Get the mouse state structure
 extern SDL_Mouse *SDL_GetMouse(void);
 

Diff for: src/events/SDL_touch.c

@@ -203,6 +203,16 @@ int SDL_AddTouch(SDL_TouchID touchID, SDL_TouchDeviceType type, const char *name
     return index;
 }
 
+// Set or update the name of a touch.
+void SDL_SetTouchName(SDL_TouchID id, const char *name)
+{
+    SDL_Touch *touch = SDL_GetTouch(id);
+    if (touch) {
+        SDL_free(touch->name);
+        touch->name = SDL_strdup(name ? name : "");
+    }
+}
+
 static bool SDL_AddFinger(SDL_Touch *touch, SDL_FingerID fingerid, float x, float y, float pressure)
 {
     SDL_Finger *finger;

Diff for: src/events/SDL_touch_c.h

@@ -42,6 +42,9 @@ extern bool SDL_TouchDevicesAvailable(void);
 // Add a touch, returning the index of the touch, or -1 if there was an error.
 extern int SDL_AddTouch(SDL_TouchID id, SDL_TouchDeviceType type, const char *name);
 
+// Set or update the name of a touch.
+extern void SDL_SetTouchName(SDL_TouchID id, const char *name);
+
 // Get the touch with a given id
 extern SDL_Touch *SDL_GetTouch(SDL_TouchID id);
 

Diff for: src/video/cocoa/SDL_cocoakeyboard.m

@@ -327,7 +327,7 @@ static void UpdateKeymap(SDL_CocoaVideoData *data, bool send_event)
 
     UInt32 keyboard_type = LMGetKbdType();
 
-    SDL_Keymap *keymap = SDL_CreateKeymap();
+    SDL_Keymap *keymap = SDL_CreateKeymap(true);
     for (int m = 0; m < SDL_arraysize(mods); ++m) {
         for (int i = 0; i < SDL_arraysize(darwin_scancode_table); i++) {
             OSStatus err;

Diff for: src/video/wayland/SDL_waylandclipboard.c

@@ -32,11 +32,16 @@
 bool Wayland_SetClipboardData(SDL_VideoDevice *_this)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandDataDevice *data_device = NULL;
-    bool result = true;
+    SDL_WaylandSeat *seat = video_data->last_implicit_grab_seat;
+    bool result = false;
+
+    // If no implicit grab is available yet, just attach it to the first available seat.
+    if (!seat && !WAYLAND_wl_list_empty(&video_data->seat_list)) {
+        seat = wl_container_of(video_data->seat_list.next, seat, link);
+    }
 
-    if (video_data->input && video_data->input->data_device) {
-        data_device = video_data->input->data_device;
+    if (seat && seat->data_device) {
+        SDL_WaylandDataDevice *data_device = seat->data_device;
 
         if (_this->clipboard_callback && _this->clipboard_mime_types) {
             SDL_WaylandDataSource *source = Wayland_data_source_create(_this);
@@ -57,11 +62,11 @@ bool Wayland_SetClipboardData(SDL_VideoDevice *_this)
 void *Wayland_GetClipboardData(SDL_VideoDevice *_this, const char *mime_type, size_t *length)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandDataDevice *data_device = NULL;
+    SDL_WaylandSeat *seat = video_data->last_incoming_data_offer_seat;
     void *buffer = NULL;
 
-    if (video_data->input && video_data->input->data_device) {
-        data_device = video_data->input->data_device;
+    if (seat && seat->data_device) {
+        SDL_WaylandDataDevice *data_device = seat->data_device;
         if (data_device->selection_source) {
             buffer = SDL_GetInternalClipboardData(_this, mime_type, length);
         } else if (Wayland_data_offer_has_mime(data_device->selection_offer, mime_type)) {
@@ -75,11 +80,11 @@ void *Wayland_GetClipboardData(SDL_VideoDevice *_this, const char *mime_type, si
 bool Wayland_HasClipboardData(SDL_VideoDevice *_this, const char *mime_type)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandDataDevice *data_device = NULL;
+    SDL_WaylandSeat *seat = video_data->last_incoming_data_offer_seat;
     bool result = false;
 
-    if (video_data->input && video_data->input->data_device) {
-        data_device = video_data->input->data_device;
+    if (seat && seat->data_device) {
+        SDL_WaylandDataDevice *data_device = seat->data_device;
         if (data_device->selection_source) {
             result = SDL_HasInternalClipboardData(_this, mime_type);
         } else {
@@ -106,11 +111,16 @@ const char **Wayland_GetTextMimeTypes(SDL_VideoDevice *_this, size_t *num_mime_t
 bool Wayland_SetPrimarySelectionText(SDL_VideoDevice *_this, const char *text)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandPrimarySelectionDevice *primary_selection_device = NULL;
+    SDL_WaylandSeat *seat = video_data->last_implicit_grab_seat;
     bool result;
 
-    if (video_data->input && video_data->input->primary_selection_device) {
-        primary_selection_device = video_data->input->primary_selection_device;
+    // If no implicit grab is available yet, just attach it to the first available seat.
+    if (!seat && !WAYLAND_wl_list_empty(&video_data->seat_list)) {
+        seat = wl_container_of(video_data->seat_list.next, seat, link);
+    }
+
+    if (seat && seat->primary_selection_device) {
+        SDL_WaylandPrimarySelectionDevice *primary_selection_device = seat->primary_selection_device;
         if (text[0] != '\0') {
             SDL_WaylandPrimarySelectionSource *source = Wayland_primary_selection_source_create(_this);
             Wayland_primary_selection_source_set_callback(source, SDL_ClipboardTextCallback, SDL_strdup(text));
@@ -134,12 +144,12 @@ bool Wayland_SetPrimarySelectionText(SDL_VideoDevice *_this, const char *text)
 char *Wayland_GetPrimarySelectionText(SDL_VideoDevice *_this)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandPrimarySelectionDevice *primary_selection_device = NULL;
+    SDL_WaylandSeat *seat = video_data->last_incoming_primary_selection_seat;
     char *text = NULL;
     size_t length = 0;
 
-    if (video_data->input && video_data->input->primary_selection_device) {
-        primary_selection_device = video_data->input->primary_selection_device;
+    if (seat && seat->primary_selection_device) {
+        SDL_WaylandPrimarySelectionDevice *primary_selection_device = seat->primary_selection_device;
         if (primary_selection_device->selection_source) {
             text = Wayland_primary_selection_source_get_data(primary_selection_device->selection_source, TEXT_MIME, &length);
         } else {
@@ -162,11 +172,11 @@ char *Wayland_GetPrimarySelectionText(SDL_VideoDevice *_this)
 bool Wayland_HasPrimarySelectionText(SDL_VideoDevice *_this)
 {
     SDL_VideoData *video_data = _this->internal;
-    SDL_WaylandPrimarySelectionDevice *primary_selection_device = NULL;
+    SDL_WaylandSeat *seat = video_data->last_incoming_primary_selection_seat;
     bool result = false;
 
-    if (video_data->input && video_data->input->primary_selection_device) {
-        primary_selection_device = video_data->input->primary_selection_device;
+    if (seat && seat->primary_selection_device) {
+        SDL_WaylandPrimarySelectionDevice *primary_selection_device = seat->primary_selection_device;
         if (primary_selection_device->selection_source) {
             result = true;
         } else {