Added SDL_HINT_VIDEO_X11_VISUALID

include/SDL3/SDL_hints.h

@@ -3311,6 +3311,15 @@ extern "C" {
  */
 #define SDL_HINT_VIDEO_X11_SCALING_FACTOR      "SDL_VIDEO_X11_SCALING_FACTOR"
 
+/**
+ * A variable forcing the visual ID used for X11 display modes.
+ *
+ * This hint should be set before initializing the video subsystem.
+ *
+ * \since This hint is available since SDL 3.0.0.
+ */
+#define SDL_HINT_VIDEO_X11_VISUALID "SDL_VIDEO_X11_VISUALID"
+
 /**
  * A variable forcing the visual ID chosen for new X11 windows.
  *

src/video/x11/SDL_x11modes.c

@@ -265,11 +265,11 @@ static float GetGlobalContentScale(SDL_VideoDevice *_this)
 
 static int get_visualinfo(Display *display, int screen, XVisualInfo *vinfo)
 {
-    const char *visual_id = SDL_getenv("SDL_VIDEO_X11_VISUALID");
+    const char *visual_id = SDL_GetHint(SDL_HINT_VIDEO_X11_VISUALID);
     int depth;
 
     /* Look for an exact visual, if requested */
-    if (visual_id) {
+    if (visual_id && *visual_id) {
         XVisualInfo *vi, template;
         int nvis;
 

src/video/x11/SDL_x11window.c

@@ -531,8 +531,9 @@ int X11_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_PropertiesI
 #if defined(SDL_VIDEO_OPENGL_GLX) || defined(SDL_VIDEO_OPENGL_EGL)
     const int transparent = (window->flags & SDL_WINDOW_TRANSPARENT) ? SDL_TRUE : SDL_FALSE;
     const char *forced_visual_id = SDL_GetHint(SDL_HINT_VIDEO_X11_WINDOW_VISUALID);
+    const char *display_visual_id = SDL_GetHint(SDL_HINT_VIDEO_X11_VISUALID);
 
-    if (forced_visual_id && forced_visual_id[0] != '\0') {
+    if (forced_visual_id && *forced_visual_id) {
         XVisualInfo *vi, template;
         int nvis;
 
@@ -547,7 +548,7 @@ int X11_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_PropertiesI
             return -1;
         }
     } else if ((window->flags & SDL_WINDOW_OPENGL) &&
-               !SDL_getenv("SDL_VIDEO_X11_VISUALID")) {
+               (!display_visual_id || !*display_visual_id)) {
         XVisualInfo *vinfo = NULL;
 
 #ifdef SDL_VIDEO_OPENGL_EGL