Fix modesetting for non-EGL HEVC streams

app/streaming/video/ffmpeg-renderers/drm.cpp

@@ -206,6 +206,23 @@ bool DrmRenderer::initialize(PDECODER_PARAMETERS params)
         return DIRECT_RENDERING_INIT_FAILED;
     }
 
+    // Create a dummy renderer to force SDL to complete the modesetting
+    // operation that the KMSDRM backend keeps pending until the next
+    // time we swap buffers. We have to do this before we enumerate
+    // CRTC modes below.
+    SDL_Renderer* renderer = SDL_CreateRenderer(params->window, -1, SDL_RENDERER_SOFTWARE);
+    if (renderer != nullptr) {
+        SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
+        SDL_RenderClear(renderer);
+        SDL_RenderPresent(renderer);
+        SDL_DestroyRenderer(renderer);
+    }
+    else {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                    "SDL_CreateRenderer() failed: %s",
+                    SDL_GetError());
+    }
+
     drmModeRes* resources = drmModeGetResources(m_DrmFd);
     if (resources == nullptr) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,