Add path to cache GL context on reinit.

If successful, can avoid libretro GL reset context callback being
called.

driver.c

@@ -373,7 +373,7 @@ void init_drivers(void)
    g_extern.frame_count = 0;
    init_video_input();
 
-   if (g_extern.system.hw_render_callback.context_reset)
+   if (!driver.video_cache_context_ack && g_extern.system.hw_render_callback.context_reset)
       g_extern.system.hw_render_callback.context_reset();
 
    init_audio();

driver.h

@@ -419,6 +419,11 @@ typedef struct driver
 
    bool threaded_video;
 
+   // If set during context deinit, the driver should keep
+   // graphics context alive to avoid having to reset all context state.
+   bool video_cache_context;
+   bool video_cache_context_ack; // Set to true by driver if context caching succeeded.
+
    // Set if the respective handles are owned by RetroArch driver core.
    // Consoles upper logic will generally intialize the drivers before
    // the driver core initializes. It will then be up to upper logic

gfx/context/glx_ctx.c

@@ -113,19 +113,23 @@ static void gfx_ctx_check_window(bool *quit,
       switch (event.type)
       {
          case ClientMessage:
-            if ((Atom)event.xclient.data.l[0] == g_quit_atom)
+            if (event.xclient.window == g_win &&
+                  (Atom)event.xclient.data.l[0] == g_quit_atom)
                g_quit = true;
             break;
 
          case DestroyNotify:
+            if (event.xdestroywindow.window == g_win)
                g_quit = true;
             break;
 
          case MapNotify:
+            if (event.xmap.window == g_win)
                g_has_focus = true;
             break;
 
          case UnmapNotify:
+            if (event.xunmap.window == g_win)
                g_has_focus = false;
             break;
 
@@ -210,7 +214,9 @@ static bool gfx_ctx_init(void)
    GLXFBConfig *fbcs = NULL;
    g_quit = 0;
 
+   if (!g_dpy)
       g_dpy = XOpenDisplay(NULL);
+
    if (!g_dpy)
       goto error;
 
@@ -361,6 +367,8 @@ static bool gfx_ctx_set_video_mode(
    XEvent event;
    XIfEvent(g_dpy, &event, glx_wait_notify, NULL);
 
+   if (!g_ctx)
+   {
       if (g_core)
       {
          const int attribs[] = {
@@ -380,6 +388,12 @@ static bool gfx_ctx_set_video_mode(
          RARCH_ERR("[GLX]: Failed to create new context.\n");
          goto error;
       }
+   }
+   else
+   {
+      driver.video_cache_context_ack = true;
+      RARCH_LOG("[GLX]: Using cached GL context.\n");
+   }
 
    glXMakeContextCurrent(g_dpy, g_glx_win, g_glx_win, g_ctx);
    XSync(g_dpy, False);
@@ -445,9 +459,12 @@ static void gfx_ctx_destroy(void)
    if (g_dpy && g_ctx)
    {
       glXMakeContextCurrent(g_dpy, None, None, NULL);
+      if (!driver.video_cache_context)
+      {
          glXDestroyContext(g_dpy, g_ctx);
          g_ctx = NULL;
       }
+   }
 
    if (g_win)
    {
@@ -487,7 +504,7 @@ static void gfx_ctx_destroy(void)
       g_should_reset_mode = false;
    }
 
-   if (g_dpy)
+   if (!driver.video_cache_context && g_dpy)
    {
       XCloseDisplay(g_dpy);
       g_dpy = NULL;

retroarch.c

@@ -1934,8 +1934,11 @@ void rarch_set_fullscreen(bool fullscreen)
 {
    g_settings.video.fullscreen = fullscreen;
 
+   driver.video_cache_context = true;
+   driver.video_cache_context_ack = false;
    uninit_drivers();
    init_drivers();
+   driver.video_cache_context = false;
 
    // Poll input to avoid possibly stale data to corrupt things.
    if (driver.input)