wayland: Implement Wayland_AcceptDragAndDrop()

This simply toggles a flag that rejects DnD offers if false. Events were previously dropped silently, but rejecting the offer makes some desktops display a proper icon when the drop will not work.

src/video/wayland/SDL_waylandevents.c

@@ -2798,15 +2798,18 @@ static void data_device_handle_enter(void *data, struct wl_data_device *wl_data_
                                      wl_fixed_t x, wl_fixed_t y, struct wl_data_offer *id)
 {
     SDL_WaylandDataDevice *data_device = data;
+    SDL_WindowData *window = surface ? Wayland_GetWindowDataForOwnedSurface(surface) : NULL;
     data_device->has_mime_file = false;
     data_device->has_mime_text = false;
-    uint32_t dnd_action = WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE;
 
     data_device->drag_serial = serial;
 
+    // Save the drag offer so it can be freed later.
     if (id) {
         data_device->drag_offer = wl_data_offer_get_user_data(id);
+    }
 
+    if (data_device->drag_offer && window && window->accepts_drag_and_drop) {
         // TODO: SDL Support more mime types
 #ifdef SDL_USE_LIBDBUS
         if (Wayland_data_offer_has_mime(data_device->drag_offer, FILE_PORTAL_MIME)) {
@@ -2832,48 +2835,46 @@ static void data_device_handle_enter(void *data, struct wl_data_device *wl_data_
             }
         }
 
-        // SDL only supports "copy" style drag and drop
         if (data_device->has_mime_file || data_device->has_mime_text) {
-            dnd_action = WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY;
+            // SDL only supports "copy" style drag and drop
+            if (wl_data_offer_get_version(data_device->drag_offer->offer) >= WL_DATA_OFFER_SET_ACTIONS_SINCE_VERSION) {
+                wl_data_offer_set_actions(data_device->drag_offer->offer, WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY, WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY);
+            }
+
+            // Set the destination window and send the initial position.
+            data_device->dnd_window = window->sdlwindow;
+            const float dx = (float)(wl_fixed_to_double(x) * data_device->dnd_window->internal->pointer_scale.x);
+            const float dy = (float)(wl_fixed_to_double(y) * data_device->dnd_window->internal->pointer_scale.y);
+            SDL_SendDropPosition(data_device->dnd_window, dx, dy);
+            SDL_LogTrace(SDL_LOG_CATEGORY_INPUT,
+                         ". In wl_data_device_listener . data_device_handle_enter on data_offer 0x%08x at %d x %d into window %d for serial %d",
+                         WAYLAND_wl_proxy_get_id((struct wl_proxy *)id),
+                         wl_fixed_to_int(x), wl_fixed_to_int(y), SDL_GetWindowID(data_device->dnd_window), serial);
         } else {
-            // drag_mime is NULL this will decline the offer
+            // Decline the offer.
             wl_data_offer_accept(id, serial, NULL);
-        }
-        if (wl_data_offer_get_version(data_device->drag_offer->offer) >=
-            WL_DATA_OFFER_SET_ACTIONS_SINCE_VERSION) {
-            wl_data_offer_set_actions(data_device->drag_offer->offer,
-                                      dnd_action, dnd_action);
-        }
-
-        // find the current window
-        if (surface) {
-            SDL_WindowData *window = Wayland_GetWindowDataForOwnedSurface(surface);
-            if (window) {
-                data_device->dnd_window = window->sdlwindow;
-                const float dx = (float)wl_fixed_to_double(x);
-                const float dy = (float)wl_fixed_to_double(y);
-                SDL_SendDropPosition(data_device->dnd_window, dx, dy);
-                SDL_LogTrace(SDL_LOG_CATEGORY_INPUT,
-                             ". In wl_data_device_listener . data_device_handle_enter on data_offer 0x%08x at %d x %d into window %d for serial %d",
-                             WAYLAND_wl_proxy_get_id((struct wl_proxy *)id),
-                             wl_fixed_to_int(x), wl_fixed_to_int(y), SDL_GetWindowID(data_device->dnd_window), serial);
-            } else {
-                data_device->dnd_window = NULL;
-                SDL_LogTrace(SDL_LOG_CATEGORY_INPUT,
-                             ". In wl_data_device_listener . data_device_handle_enter on data_offer 0x%08x at %d x %d for serial %d",
-                             WAYLAND_wl_proxy_get_id((struct wl_proxy *)id),
-                             wl_fixed_to_int(x), wl_fixed_to_int(y), serial);
+            if (wl_data_offer_get_version(data_device->drag_offer->offer) >= WL_DATA_OFFER_SET_ACTIONS_SINCE_VERSION) {
+                wl_data_offer_set_actions(data_device->drag_offer->offer, WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE, WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE);
             }
-        } else {
+
             SDL_LogTrace(SDL_LOG_CATEGORY_INPUT,
                          ". In wl_data_device_listener . data_device_handle_enter on data_offer 0x%08x at %d x %d for serial %d",
-                         WAYLAND_wl_proxy_get_id((struct wl_proxy *)id),
-                         wl_fixed_to_int(x), wl_fixed_to_int(y), serial);
+                         WAYLAND_wl_proxy_get_id((struct wl_proxy *)id), wl_fixed_to_int(x), wl_fixed_to_int(y), serial);
         }
     } else {
+        data_device->dnd_window = NULL;
+
+        // Decline the offer.
+        if (id) {
+            wl_data_offer_accept(id, serial, NULL);
+            if (wl_data_offer_get_version(data_device->drag_offer->offer) >= WL_DATA_OFFER_SET_ACTIONS_SINCE_VERSION) {
+                wl_data_offer_set_actions(data_device->drag_offer->offer, WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE, WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE);
+            }
+        }
         SDL_LogTrace(SDL_LOG_CATEGORY_INPUT,
                      ". In wl_data_device_listener . data_device_handle_enter on data_offer 0x%08x at %d x %d for serial %d",
-                     -1, wl_fixed_to_int(x), wl_fixed_to_int(y), serial);
+                     id ? WAYLAND_wl_proxy_get_id((struct wl_proxy *)id) : -1,
+                     wl_fixed_to_int(x), wl_fixed_to_int(y), serial);
     }
 }
 
@@ -2911,8 +2912,8 @@ static void data_device_handle_motion(void *data, struct wl_data_device *wl_data
     SDL_WaylandDataDevice *data_device = data;
 
     if (data_device->drag_offer && data_device->dnd_window && (data_device->has_mime_file || data_device->has_mime_text)) {
-        const float dx = (float)wl_fixed_to_double(x);
-        const float dy = (float)wl_fixed_to_double(y);
+        const float dx = (float)(wl_fixed_to_double(x) * data_device->dnd_window->internal->pointer_scale.x);
+        const float dy = (float)(wl_fixed_to_double(y) * data_device->dnd_window->internal->pointer_scale.y);
 
         /* XXX: Send the filename here if the event system ever starts passing it though.
          *      Any future implementation should cache the filenames, as otherwise this could

src/video/wayland/SDL_waylandvideo.c

@@ -732,6 +732,7 @@ static SDL_VideoDevice *Wayland_CreateDevice(bool require_preferred_protocols)
     device->SyncWindow = Wayland_SyncWindow;
     device->SetWindowFocusable = Wayland_SetWindowFocusable;
     device->ReconfigureWindow = Wayland_ReconfigureWindow;
+    device->AcceptDragAndDrop = Wayland_AcceptDragAndDrop;
 
 #ifdef SDL_USE_LIBDBUS
     if (SDL_SystemTheme_Init())

src/video/wayland/SDL_waylandwindow.c

@@ -3426,6 +3426,11 @@ bool Wayland_SyncWindow(SDL_VideoDevice *_this, SDL_Window *window)
     return true;
 }
 
+void Wayland_AcceptDragAndDrop(SDL_Window *window, bool accept)
+{
+    window->internal->accepts_drag_and_drop = accept;
+}
+
 bool Wayland_SetWindowFocusable(SDL_VideoDevice *_this, SDL_Window *window, bool focusable)
 {
     if (window->flags & SDL_WINDOW_POPUP_MENU) {

src/video/wayland/SDL_waylandwindow.h

@@ -234,6 +234,7 @@ struct SDL_WindowData
     bool scale_to_display;
     bool reparenting_required;
     bool double_buffer;
+    bool accepts_drag_and_drop;
 
     SDL_HitTestResult hit_test_result;
 
@@ -271,6 +272,7 @@ extern bool Wayland_SetWindowIcon(SDL_VideoDevice *_this, SDL_Window *window, SD
 extern bool Wayland_SetWindowFocusable(SDL_VideoDevice *_this, SDL_Window *window, bool focusable);
 extern float Wayland_GetWindowContentScale(SDL_VideoDevice *_this, SDL_Window *window);
 extern void *Wayland_GetWindowICCProfile(SDL_VideoDevice *_this, SDL_Window *window, size_t *size);
+extern void Wayland_AcceptDragAndDrop(SDL_Window *window, bool accept);
 
 extern bool Wayland_SetWindowHitTest(SDL_Window *window, bool enabled);
 extern bool Wayland_FlashWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_FlashOperation operation);