wayland: Add support for high-DPI icons

src/video/wayland/SDL_waylandwindow.c

@@ -2865,28 +2865,56 @@ bool Wayland_SetWindowIcon(SDL_VideoDevice *_this, SDL_Window *window, SDL_Surfa
     struct xdg_toplevel *toplevel = NULL;
 
     if (!_this->internal->xdg_toplevel_icon_manager_v1) {
-        return SDL_SetError("wayland: cannot set icon; xdg_toplevel_icon_v1 protocol not supported");
+        return SDL_SetError("wayland: cannot set icon; required xdg_toplevel_icon_v1 protocol not supported");
     }
 
     if (icon->w != icon->h) {
         return SDL_SetError("wayland: icon width and height must be equal, got %ix%i", icon->w, icon->h);
     }
 
+    int image_count = 0;
+    SDL_Surface **images = SDL_GetSurfaceImages(icon, &image_count);
+    if (!images || !image_count) {
+        return false;
+    }
+
+    // Release the old icon resources.
     if (wind->xdg_toplevel_icon_v1) {
         xdg_toplevel_icon_v1_destroy(wind->xdg_toplevel_icon_v1);
         wind->xdg_toplevel_icon_v1 = NULL;
     }
 
-    // TODO: Add high-DPI icon support
-    Wayland_ReleaseSHMBuffer(&wind->icon);
-    if (!Wayland_AllocSHMBuffer(icon->w, icon->h, &wind->icon)) {
-        return SDL_SetError("wayland: failed to allocate SHM buffer for the icon");
+    for (int i = 0; i < wind->icon_buffer_count; ++i) {
+        Wayland_ReleaseSHMBuffer(&wind->icon_buffers[i]);
     }
-
-    SDL_PremultiplyAlpha(icon->w, icon->h, icon->format, icon->pixels, icon->pitch, SDL_PIXELFORMAT_ARGB8888, wind->icon.shm_data, icon->w * 4, true);
+    SDL_free(wind->icon_buffers);
+    wind->icon_buffer_count = 0;
 
     wind->xdg_toplevel_icon_v1 = xdg_toplevel_icon_manager_v1_create_icon(_this->internal->xdg_toplevel_icon_manager_v1);
-    xdg_toplevel_icon_v1_add_buffer(wind->xdg_toplevel_icon_v1, wind->icon.wl_buffer, 1);
+    wind->icon_buffers = SDL_calloc(image_count, sizeof(struct Wayland_SHMBuffer));
+    if (!wind->icon_buffers) {
+        goto failure_cleanup;
+    }
+
+    for (int i = 0; i < image_count; ++i) {
+        if (images[i]->w == images[i]->h) {
+            struct Wayland_SHMBuffer *buffer = &wind->icon_buffers[wind->icon_buffer_count];
+
+            if (!Wayland_AllocSHMBuffer(images[i]->w, images[i]->h, buffer)) {
+                SDL_SetError("wayland: failed to allocate SHM buffer for the icon");
+                goto failure_cleanup;
+            }
+
+            SDL_PremultiplyAlpha(images[i]->w, images[i]->h, images[i]->format, images[i]->pixels, images[i]->pitch, SDL_PIXELFORMAT_ARGB8888, buffer->shm_data, images[i]->w * 4, true);
+            const int scale = (int)SDL_ceil((double)images[i]->w / (double)icon->w);
+            xdg_toplevel_icon_v1_add_buffer(wind->xdg_toplevel_icon_v1, buffer->wl_buffer, scale);
+            wind->icon_buffer_count++;
+        } else {
+            SDL_LogWarn(SDL_LOG_CATEGORY_VIDEO, "wayland: icon width and height must be equal, got %ix%i for image level %i; skipping", images[i]->w, images[i]->h, i);
+        }
+    }
+
+    SDL_free(images);
 
 #ifdef HAVE_LIBDECOR_H
     if (wind->shell_surface_type == WAYLAND_SHELL_SURFACE_TYPE_LIBDECOR && wind->shell_surface.libdecor.frame) {
@@ -2902,6 +2930,22 @@ bool Wayland_SetWindowIcon(SDL_VideoDevice *_this, SDL_Window *window, SDL_Surfa
     }
 
     return true;
+
+failure_cleanup:
+
+    if (wind->xdg_toplevel_icon_v1) {
+        xdg_toplevel_icon_v1_destroy(wind->xdg_toplevel_icon_v1);
+        wind->xdg_toplevel_icon_v1 = NULL;
+    }
+
+    for (int i = 0; i < wind->icon_buffer_count; ++i) {
+        Wayland_ReleaseSHMBuffer(&wind->icon_buffers[i]);
+    }
+    SDL_free(wind->icon_buffers);
+    wind->icon_buffers = NULL;
+    wind->icon_buffer_count = 0;
+
+    return false;
 }
 
 void *Wayland_GetWindowICCProfile(SDL_VideoDevice *_this, SDL_Window *window, size_t *size)
@@ -3070,7 +3114,11 @@ void Wayland_DestroyWindow(SDL_VideoDevice *_this, SDL_Window *window)
             xdg_toplevel_icon_v1_destroy(wind->xdg_toplevel_icon_v1);
         }
 
-        Wayland_ReleaseSHMBuffer(&wind->icon);
+        for (int i = 0; i < wind->icon_buffer_count; ++i) {
+            Wayland_ReleaseSHMBuffer(&wind->icon_buffers[i]);
+        }
+        SDL_free(wind->icon_buffers);
+        wind->icon_buffer_count = 0;
 
         SDL_free(wind);
         WAYLAND_wl_display_flush(data->display);

src/video/wayland/SDL_waylandwindow.h

@@ -128,7 +128,8 @@ struct SDL_WindowData
     char *app_id;
     double scale_factor;
 
-    struct Wayland_SHMBuffer icon;
+    struct Wayland_SHMBuffer *icon_buffers;
+    int icon_buffer_count;
 
     struct
     {