From 6ba476b3bdcd709574750f56fe7c002b9a55bfba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Fri, 28 Feb 2020 18:43:33 +0100
Subject: [PATCH] wayland: configure: work around GNOME/mutter weirdness

When resizing the window under mutter, mutter seems to expect a
configure ack *and* a surface commit *right* away, or things get out
of sync.

Unlike kwin, which is requires a commit for each configure ack, but is
fine with having the commit arrive later (after we've rendered it),
mutter is not.

I even tried delaying the configure ack until just before the commit,
but still no go.

So for now, detect when we're running under mutter and always do a
surface commit right away.

This can *not* be done on any other compositor as it breaks the CSD
and main surface synchronization; we've resized the CSDs, but not the
main surface.

I.e. this *should* not work, but for some reason is the *only* way to
make things work on mutter.

Interestingly, doing it any other way on mutter causes visual
glitches; window jumping around when resizing, or de-synchronized
CSDs/main surface.
---
 wayland.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/wayland.c b/wayland.c
index 979c3bd7..9b8cb258 100644
--- a/wayland.c
+++ b/wayland.c
@@ -595,11 +595,41 @@ xdg_surface_configure(void *data, struct xdg_surface *xdg_surface,
     else
         term_visual_focus_out(term);
 
-    if (!resized) {
+    static bool desktop_is_gnome = false;
+    static bool desktop_is_initialized = false;
+
+    if (!desktop_is_initialized) {
+        const char *current_desktop = getenv("XDG_CURRENT_DESKTOP");
+
+        desktop_is_gnome = current_desktop != NULL &&
+            strcasestr(current_desktop, "gnome") != NULL;
+
+        if (desktop_is_gnome)
+            LOG_WARN("applying wl_surface_commit() workaround for mutter");
+
+        desktop_is_initialized = true;
+    }
+
+    if (desktop_is_gnome) {
         /*
-         * kwin seems to need a commit for each configure ack, or it
-         * will get stuck. Since we'll get a "real" commit soon if we
-         * resized, only commit here if size did *not* change
+         * Resizing the window under mutter causes the "other" side to
+         * jump back and forth, *even* if we re-render and commit a
+         * properly resized frame immediately.
+         *
+         * For that reason, the code path below also does not work,
+         * since in case we *did* resize, it appears the commit
+         * happens "too late" after the ack.
+         *
+         * Finally, doing this on any other compositor breaks the CSD
+         * synchronization with the main surface. Hence we only do
+         * this when running under mutter.
+         */
+        wl_surface_commit(win->surface);
+    } else if (!resized) {
+        /*
+         * If we didn't resize, we won't be commit a new surface
+         * anytime soon. Some compositors require a commit in
+         * combination with an ack - make them happy.
          */
         wl_surface_commit(win->surface);
     }