Add some comments in drawTQPixmapToWindow()

Signed-off-by: rjb330 <122177540+rjb330@users.noreply.github.com>

src/qt_qt_wrapper.cpp

@@ -655,10 +655,13 @@ TQColor gdkColorToTQColor(GdkColor* c)
 	return TQColor(c->red / 256, c->green / 256, c->blue / 256);
 }
 
-void drawTQPixmapToWindow(GdkWindow* window, GdkGC* gc, TQPixmap* pixmap, int x, int y, int w, int h) {
-	static GdkGC* igc = gdk_gc_new(window);
+void drawTQPixmapToWindow(GdkWindow* window, GdkGC* gc, TQPixmap* pixmap, int x, int y, int w, int h)
+{
+	static GdkGC* imggc = gdk_gc_new(window);
 	GdkPixmap* pix;
 
+	// gdk_drawable_get_image crashes if requested region is outside of the window.
+	// Bitmap masks cause artifacts with Domino and Baghira.
 	int width, height;
 	gdk_drawable_get_size(window, &width, &height);
 	if (!pixmap->hasAlpha() || isDomino || isBaghira ||
@@ -669,10 +672,12 @@ void drawTQPixmapToWindow(GdkWindow* window, GdkGC* gc, TQPixmap* pixmap, int x,
 		return;
 	}
 
+	// Gdk isn't aware of the TQPixmap mask,
+	// so instead we create a new pixmap from the window region and bitBlt over it.
 	TQPixmap gpixmap(w, h);
 	pix = gdk_pixmap_foreign_new(gpixmap.handle());
 	GdkImage* img = gdk_drawable_get_image(window, x, y, w, h);
-	gdk_draw_image(pix, igc, img, 0, 0, 0, 0, w, h);
+	gdk_draw_image(pix, imggc, img, 0, 0, 0, 0, w, h);
 	bitBlt(&gpixmap, 0, 0, pixmap, 0, 0, w, h, TQt::CopyROP);
 
 	gdk_draw_drawable(window, gc, pix, 0, 0, x, y, w, h);