[PATCH] UI/GTK: full-screen after wait for hiding of tabs and menu_bar

[Edmund Raile via <qemu-devel@nongnu.org>]

Wait for hiding of GTK notebook tabs and GTK menu_bar before entering
full-screen due to asynchronous nature of GTK.

prevent:
 * full-screen window overlap onto monitor below
 * black bar on top of full-screen guest display
 * misallignment of host-drawn guest cursor and invisible guest cursor

Signed-off-by: Edmund Raile <edmund.raile@proton.me>
---
I'd like to report an issue with GTK UI and suggest a solution for it.
When entering full-screen, the tabs and menu_bar need to be hidden.

Currently, gd_menu_full_screen() does all of this in-line but since
GTK operates asynchronously, this results in:
 * a full-screen window that overlaps onto the monitor below
 * a full-screen guest display that has a black bar above it
 * a guest cursor that is misalligned to the
   host cursor the GTK UI draws in-style of the guest cursor (QXL vga)

My solution is to wait for GTK to hide tabs and menu_bar,
and only then enter full screen.
I've implemented this with a callback on a simple 10ms timer.

It has been tested to work reliably under heavy CPU load, when
GTK may take longer to respond to requests.

Since gtk.c currently has no maintainer, I am uncertain who to submit
this patch to.

Kind regards,
Edmund Raile.
 ui/gtk.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/ui/gtk.c b/ui/gtk.c
index bf9d3dd679..2f6aac6386 100644
--- a/ui/gtk.c
+++ b/ui/gtk.c
@@ -1463,6 +1463,32 @@ static void gd_accel_show_menubar(void *opaque)
     gtk_menu_item_activate(GTK_MENU_ITEM(s->show_menubar_item));
 }
 
+static gboolean full_screen_enter_callback(gpointer user_data)
+{
+    GtkDisplayState *s = user_data;
+    VirtualConsole *vc = gd_vc_find_current(s);
+
+    gboolean tabs_visible = gtk_notebook_get_show_tabs(
+                                GTK_NOTEBOOK(s->notebook));
+    gboolean menu_bar_visible = gtk_widget_get_visible(s->menu_bar);
+
+    if (!tabs_visible && !menu_bar_visible) {
+        gtk_window_fullscreen(GTK_WINDOW(s->window));
+        s->full_screen = TRUE;
+
+        gd_update_windowsize(vc);
+
+        /** deactivate callback **/
+        return FALSE;
+    } else {
+        /*
+         * re-schedule callback if GTK _still_
+         * did not manage to hide tabs and menu_bar
+         */
+        return TRUE;
+    }
+}
+
 static void gd_menu_full_screen(GtkMenuItem *item, void *opaque)
 {
     GtkDisplayState *s = opaque;
@@ -1474,8 +1500,11 @@ static void gd_menu_full_screen(GtkMenuItem
*item, void *opaque)
         if (vc->type == GD_VC_GFX) {
             gtk_widget_set_size_request(vc->gfx.drawing_area, -1, -1);
         }
-        gtk_window_fullscreen(GTK_WINDOW(s->window));
-        s->full_screen = TRUE;
+
+        gd_update_windowsize(vc);
+
+        /** give GTK 10ms to perform the resize **/
+        g_timeout_add(10, full_screen_enter_callback, s);
     } else {
         gtk_window_unfullscreen(GTK_WINDOW(s->window));
         gd_menu_show_tabs(GTK_MENU_ITEM(s->show_tabs_item), s);
-- 
2.47.0