X11: Query actual window depth/visual for 2D framebuffer

misc/x11/min-xlib.h

@@ -216,6 +216,34 @@ typedef struct {
     Cursor cursor;		/* cursor to be displayed (or None) */
 } XSetWindowAttributes;
 
+typedef struct {
+    int x, y;			/* location of window */
+    int width, height;		/* width and height of window */
+    int border_width;		/* border width of window */
+    int depth;          	/* depth of window */
+    Visual *visual;		/* the associated visual structure */
+    Window root;        	/* root of screen containing window */
+#if defined(__cplusplus) || defined(c_plusplus)
+    int c_class;		/* C++ InputOutput, InputOnly*/
+#else
+    int class;			/* InputOutput, InputOnly*/
+#endif
+    int bit_gravity;		/* one of bit gravity values */
+    int win_gravity;		/* one of the window gravity values */
+    int backing_store;		/* NotUseful, WhenMapped, Always */
+    unsigned long backing_planes;/* planes to be preserved if possible */
+    unsigned long backing_pixel;/* value to be used when restoring planes */
+    Bool save_under;		/* boolean, should bits under be saved? */
+    Colormap colormap;		/* color map to be associated with window */
+    Bool map_installed;		/* boolean, is color map currently installed*/
+    int map_state;		/* IsUnmapped, IsUnviewable, IsViewable */
+    long all_event_masks;	/* set of events all people have interest in*/
+    long your_event_mask;	/* my event mask */
+    long do_not_propagate_mask; /* set of events that should not propagate */
+    Bool override_redirect;	/* boolean value for override-redirect */
+    Screen *screen;		/* back pointer to correct screen */
+} XWindowAttributes;
+
 /*
  * Data structure for "image" data, used by image manipulation routines.
  */
@@ -1186,6 +1214,12 @@ extern int XChangeWindowAttributes(
     XSetWindowAttributes* /* attributes */
 );
 
+extern Status XGetWindowAttributes(
+    Display*		/* display */,
+    Window		/* w */,
+    XWindowAttributes*	/* window_attributes_return */
+);
+
 extern Bool XCheckIfEvent(
     Display*		/* display */,
     XEvent*		/* event_return */,

src/Window_X11.c

@@ -1221,11 +1221,15 @@ cc_result Window_SaveFileDialog(const struct SaveFileDialogArgs* args) {
 static GC fb_gc;
 static XImage* fb_image;
 static void* fb_data;
-static int fb_fast;
+static int fb_fast, fb_depth;
 
 void Window_AllocFramebuffer(struct Bitmap* bmp, int width, int height) {
 	Window win = Window_Main.Handle.val;
+	XWindowAttributes attribs = { 0 };
+
 	if (!fb_gc) fb_gc = XCreateGC(win_display, win, 0, NULL);
+	XGetWindowAttributes(win_display, win, &attribs);
+	fb_depth = attribs.depth;
 
 	bmp->scan0  = (BitmapCol*)Mem_Alloc(width * height, BITMAPCOLOR_SIZE, "window pixels");
 	bmp->width  = width;
@@ -1234,11 +1238,11 @@ void Window_AllocFramebuffer(struct Bitmap* bmp, int width, int height) {
 	/* X11 requires that the image to draw has same depth as window */
 	/* Easy for 24/32 bit case, but much trickier with other depths */
 	/*  (have to do a manual and slow second blit for other depths) */
-	fb_fast = win_visual.depth == 24 || win_visual.depth == 32;
+	fb_fast = attribs.depth == 24 || attribs.depth == 32;
 	fb_data = fb_fast ? bmp->scan0 : Mem_Alloc(width * height, BITMAPCOLOR_SIZE, "window blit");
 
-	fb_image = XCreateImage(win_display, win_visual.visual,
+	fb_image = XCreateImage(win_display, attribs.visual,
-		win_visual.depth, ZPixmap, 0, (char*)fb_data,
+		attribs.depth, ZPixmap, 0, (char*)fb_data,
 		width, height, 32, 0);
 }
 
@@ -1261,7 +1265,7 @@ static void BlitFramebuffer(int x1, int y1, int width, int height, struct Bitmap
 			B = BitmapCol_B(src);
 			A = BitmapCol_A(src);
 
-			switch (win_visual.depth)
+			switch (fb_depth)
 			{
 			case 30: /* R10 G10 B10 A2 */
 				pixel = (R << 2) | ((G << 2) << 10) | ((B << 2) << 20) | ((A >> 6) << 30);