x11: Use XcursorLibraryLoadCursor to load system cursors when available.

Apparently this is necessary on the latest Gnome to get properly themed
cursors, vs ancient X11 standard cursors, as Gnome has dropped the old
theme names that XCreateFontCursor eventually expected to find.

Fixes #8939.

src/video/x11/SDL_x11mouse.c

@@ -214,8 +214,9 @@ static SDL_Cursor *X11_CreateCursor(SDL_Surface *surface, int hot_x, int hot_y)
 
 static SDL_Cursor *X11_CreateSystemCursor(SDL_SystemCursor id)
 {
-    SDL_Cursor *cursor;
-    unsigned int shape;
+    SDL_Cursor *cursor = NULL;
+    unsigned int shape = 0;
+    const char *xcursorname = NULL;
 
     switch (id) {
     default:
@@ -225,71 +226,101 @@ static SDL_Cursor *X11_CreateSystemCursor(SDL_SystemCursor id)
     /*   http://tronche.com/gui/x/xlib/appendix/b/ */
     case SDL_SYSTEM_CURSOR_ARROW:
         shape = XC_left_ptr;
+        xcursorname = "default";
         break;
     case SDL_SYSTEM_CURSOR_IBEAM:
         shape = XC_xterm;
+        xcursorname = "text";
         break;
     case SDL_SYSTEM_CURSOR_WAIT:
         shape = XC_watch;
+        xcursorname = "wait";
         break;
     case SDL_SYSTEM_CURSOR_CROSSHAIR:
         shape = XC_tcross;
+        xcursorname = "crosshair";
         break;
     case SDL_SYSTEM_CURSOR_WAITARROW:
         shape = XC_watch;
+        xcursorname = "progress";
         break;
     case SDL_SYSTEM_CURSOR_SIZENWSE:
         shape = XC_top_left_corner;
+        xcursorname = "nwse-resize";
         break;
     case SDL_SYSTEM_CURSOR_SIZENESW:
         shape = XC_top_right_corner;
+        xcursorname = "nesw-resize";
         break;
     case SDL_SYSTEM_CURSOR_SIZEWE:
         shape = XC_sb_h_double_arrow;
+        xcursorname = "ew-resize";
         break;
     case SDL_SYSTEM_CURSOR_SIZENS:
         shape = XC_sb_v_double_arrow;
+        xcursorname = "ns-resize";
         break;
     case SDL_SYSTEM_CURSOR_SIZEALL:
         shape = XC_fleur;
+        xcursorname = "move";
         break;
     case SDL_SYSTEM_CURSOR_NO:
         shape = XC_pirate;
+        xcursorname = "not-allowed";
         break;
     case SDL_SYSTEM_CURSOR_HAND:
         shape = XC_hand2;
+        xcursorname = "pointer";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_TOPLEFT:
         shape = XC_top_left_corner;
+        xcursorname = "nw-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_TOP:
         shape = XC_top_side;
+        xcursorname = "n-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_TOPRIGHT:
         shape = XC_top_right_corner;
+        xcursorname = "ne-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_RIGHT:
         shape = XC_right_side;
+        xcursorname = "e-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_BOTTOMRIGHT:
         shape = XC_bottom_right_corner;
+        xcursorname = "se-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_BOTTOM:
         shape = XC_bottom_side;
+        xcursorname = "s-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_BOTTOMLEFT:
         shape = XC_bottom_left_corner;
+        xcursorname = "sw-resize";
         break;
     case SDL_SYSTEM_CURSOR_WINDOW_LEFT:
         shape = XC_left_side;
+        xcursorname = "w-resize";
         break;
     }
 
     cursor = SDL_calloc(1, sizeof(*cursor));
     if (cursor) {
-        Cursor x11_cursor;
+        Display *dpy = GetDisplay();
+        Cursor x11_cursor = None;
+
+#ifdef SDL_VIDEO_DRIVER_X11_XCURSOR
+        SDL_assert(xcursorname != NULL);
+        if (SDL_X11_HAVE_XCURSOR) {
+            x11_cursor = X11_XcursorLibraryLoadCursor(dpy, xcursorname);
+        }
+#endif
 
-        x11_cursor = X11_XCreateFontCursor(GetDisplay(), shape);
+        if (x11_cursor == None) {
+            x11_cursor = X11_XCreateFontCursor(dpy, shape);
+        }
 
         cursor->driverdata = (void *)(uintptr_t)x11_cursor;
     }

src/video/x11/SDL_x11sym.h

@@ -262,6 +262,7 @@ SDL_X11_MODULE(XCURSOR)
 SDL_X11_SYM(XcursorImage*,XcursorImageCreate,(int a,int b),(a,b),return)
 SDL_X11_SYM(void,XcursorImageDestroy,(XcursorImage *a),(a),)
 SDL_X11_SYM(Cursor,XcursorImageLoadCursor,(Display *a,const XcursorImage *b),(a,b),return)
+SDL_X11_SYM(Cursor,XcursorLibraryLoadCursor,(Display *a, const char *b),(a,b),return)
 #endif
 
 /* Xdbe support */