Create a separate X11 Display object for libva

Sharing these directly is fraught with concurrency issues that
require extreme care on both sides to avoid spurious X11 errors,
hangs, and other nasty stuff. We can't necessarily depend on SDL,
libva, or the underlying VA drivers to do the right thing here.

Using a new Display (as FFmpeg does for VAAPI and VDPAU) avoids
all these problems.

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

@@ -34,6 +34,11 @@ VAAPIRenderer::VAAPIRenderer(int decoderSelectionPass)
     SDL_zero(m_PrimeDescriptor);
 #endif
 
+#ifdef HAVE_LIBVA_X11
+    m_XDisplay = nullptr;
+    m_XWindow = None;
+#endif
+
 #ifdef HAVE_LIBVA_DRM
     m_DrmFd = -1;
 #endif
@@ -74,6 +79,12 @@ VAAPIRenderer::~VAAPIRenderer()
     }
 #endif
 
+#ifdef HAVE_LIBVA_X11
+    if (m_XDisplay != nullptr) {
+        XCloseDisplay(m_XDisplay);
+    }
+#endif
+
     if (m_OverlayMutex != nullptr) {
         SDL_DestroyMutex(m_OverlayMutex);
     }
@@ -98,7 +109,19 @@ VAAPIRenderer::openDisplay(SDL_Window* window)
     if (info.subsystem == SDL_SYSWM_X11) {
 #ifdef HAVE_LIBVA_X11
         m_XWindow = info.info.x11.window;
-        display = vaGetDisplay(info.info.x11.display);
+
+        // It's possible to enter this function several times as we're probing VA drivers.
+        // Only open the new Display object the first time through.
+        if (m_XDisplay == nullptr) {
+            m_XDisplay = XOpenDisplay(XDisplayString(info.info.x11.display));
+            if (m_XDisplay == nullptr) {
+                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                             "Unable to clone SDL X11 display for VAAPI");
+                return nullptr;
+            }
+        }
+
+        display = vaGetDisplay(m_XDisplay);
         if (display == nullptr) {
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                          "Unable to open X11 display for VAAPI");

app/streaming/video/ffmpeg-renderers/vaapi.h

@@ -106,6 +106,7 @@ private:
     SDL_Rect m_OverlayRect[Overlay::OverlayMax];
 
 #ifdef HAVE_LIBVA_X11
+    Display* m_XDisplay;
     Window m_XWindow;
 #endif