Make the X11 SetBordered event tapdancing more robust, restore focus,…

… etc.

src/video/x11/SDL_x11sym.h

@@ -89,6 +89,7 @@ SDL_X11_SYM(int,XSelectInput,(Display* a,Window b,long c),(a,b,c),return)
 SDL_X11_SYM(Status,XSendEvent,(Display* a,Window b,Bool c,long d,XEvent* e),(a,b,c,d,e),return)
 SDL_X11_SYM(XErrorHandler,XSetErrorHandler,(XErrorHandler a),(a),return)
 SDL_X11_SYM(XIOErrorHandler,XSetIOErrorHandler,(XIOErrorHandler a),(a),return)
+SDL_X11_SYM(int,XSetInputFocus,(Display *a,Window b,int c,Time d),(a,b,c,d),return)
 SDL_X11_SYM(int,XSetSelectionOwner,(Display* a,Atom b,Window c,Time d),(a,b,c,d),return)
 SDL_X11_SYM(int,XSetTransientForHint,(Display* a,Window b,Window c),(a,b,c),return)
 SDL_X11_SYM(void,XSetTextProperty,(Display* a,Window b,XTextProperty* c,Atom d),(a,b,c,d),)

src/video/x11/SDL_x11window.c

@@ -734,20 +734,34 @@ static Bool isConfigureNotify(Display *dpy, XEvent *ev, XPointer win)
 void
 X11_SetWindowBordered(_THIS, SDL_Window * window, SDL_bool bordered)
 {
+    const SDL_bool focused = ((window->flags & SDL_WINDOW_INPUT_FOCUS) != 0);
+    const SDL_bool visible = ((window->flags & SDL_WINDOW_HIDDEN) == 0);
     SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
     SDL_DisplayData *displaydata =
         (SDL_DisplayData *) SDL_GetDisplayForWindow(window)->driverdata;
     Display *display = data->videodata->display;
     XEvent event;
 
     SetWindowBordered(display, displaydata->screen, data->xwindow, bordered);
+    XFlush(display);
     XIfEvent(display, &event, &isConfigureNotify, (XPointer)&data->xwindow);
 
-    /* make sure these don't make it to the real event queue if they fired here. */
-    while (XCheckIfEvent(display, &event, &isMapNotify, (XPointer)&data->xwindow)) {}
-    while (XCheckIfEvent(display, &event, &isUnmapNotify, (XPointer)&data->xwindow)) {}
+    if (visible) {
+        XWindowAttributes attr;
+        do {
+            XSync(display, False);
+            XGetWindowAttributes(display, data->xwindow, &attr);
+        } while (attr.map_state != IsViewable);
 
-    XFlush(display);
+        if (focused) {
+            XSetInputFocus(display, data->xwindow, RevertToParent, CurrentTime);
+        }
+    }
+
+    /* make sure these don't make it to the real event queue if they fired here. */
+    XSync(display, False);
+    XCheckIfEvent(display, &event, &isUnmapNotify, (XPointer)&data->xwindow);
+    XCheckIfEvent(display, &event, &isMapNotify, (XPointer)&data->xwindow);
 }
 
 void