window-x11: Use any focusable window as fallback delayed focus window

As per commit f71151a5 we focus an input window if no take-focus-window accepts
it. This might lead to an infinite loop if there are various focusable but
non-input windows in the stack.

When the current focus window is unmanaging and we're trying to focus a
WM_TAKE_FOCUS window, we intent to give the focus to the first focusable input
window in the stack.

However, if an application (such as the Java ones) only uses non-input
WM_TAKE_FOCUS windows, are not requesting these ones to get the focus. This
might lead to a state where no window is focused, or a wrong one is.

So, instead of only focus the first eventually input window available, try to
request to all the take-focus windows that are in the stack between the
destroyed one and the first input one to acquire the input focus.
Use a queue to keep track of those windows, that is passed around stealing
ownership, while we protect for unmanaged queued windows.

Also, reduce the default timeout value, as the previous one might lead to an
excessive long wait.

Added metatests verifying these situations.

Closes: https://gitlab.gnome.org/GNOME/mutter/issues/660
https://gitlab.gnome.org/GNOME/mutter/merge_requests/669

4 files changed, 81 insertions, 4 deletions

diff --git a/src/tests/stacking/closed-transient-no-input-parent.metatest b/src/tests/stacking/closed-transient-no-input-parent.metatest
index e0f1dc1e2..d0f3228d5 100644
--- a/src/tests/stacking/closed-transient-no-input-parent.metatest
+++ b/src/tests/stacking/closed-transient-no-input-parent.metatest
@@ -25,6 +25,6 @@ dispatch
 assert_focused none
 assert_stacking 2/1 1/1 1/2
 
-sleep 250
+sleep 150
 assert_focused 1/1
 assert_stacking 2/1 1/1 1/2
diff --git a/src/tests/stacking/closed-transient-no-input-parents-queued-default-focus-destroyed.metatest b/src/tests/stacking/closed-transient-no-input-parents-queued-default-focus-destroyed.metatest
new file mode 100644
index 000000000..49ecc510f
--- /dev/null
+++ b/src/tests/stacking/closed-transient-no-input-parents-queued-default-focus-destroyed.metatest
@@ -0,0 +1,43 @@
+new_client 0 x11
+create 0/1
+show 0/1
+
+new_client 1 x11
+create 1/1
+show 1/1
+
+create 1/2 csd
+set_parent 1/2 1
+accept_focus 1/2 false
+show 1/2
+
+create 1/3 csd
+set_parent 1/3 2
+accept_focus 1/3 false
+show 1/3
+
+create 1/4 csd
+set_parent 1/4 3
+accept_focus 1/4 false
+show 1/4
+
+create 1/5 csd
+set_parent 1/5 3
+show 1/5
+
+wait
+assert_focused 1/5
+assert_stacking 0/1 1/1 1/2 1/3 1/4 1/5
+
+destroy 1/5
+dispatch
+
+assert_focused none
+assert_stacking 0/1 1/1 1/2 1/3 1/4
+
+destroy 1/2
+dispatch
+
+sleep 450
+assert_focused 1/1
+assert_stacking 0/1 1/1 1/3 1/4
diff --git a/src/tests/stacking/closed-transient-no-input-parents.metatest b/src/tests/stacking/closed-transient-no-input-parents.metatest
index e3ec2e84a..ee9984192 100644
--- a/src/tests/stacking/closed-transient-no-input-parents.metatest
+++ b/src/tests/stacking/closed-transient-no-input-parents.metatest
@@ -35,12 +35,12 @@ dispatch
 assert_focused none
 assert_stacking 0/1 1/1 1/2 1/3 1/4
 
-sleep 250
-assert_focused none
+sleep 600
+assert_focused 1/1
 assert_stacking 0/1 1/1 1/2 1/3 1/4
 
 destroy 1/3
 wait
 
-assert_focused none
+assert_focused 1/1
 assert_stacking 0/1 1/1 1/2 1/4
diff --git a/src/tests/stacking/closed-transient-only-take-focus-parents.metatest b/src/tests/stacking/closed-transient-only-take-focus-parents.metatest
new file mode 100644
index 000000000..8aa86700f
--- /dev/null
+++ b/src/tests/stacking/closed-transient-only-take-focus-parents.metatest
@@ -0,0 +1,34 @@
+new_client 0 x11
+create 0/1
+show 0/1
+
+new_client 1 x11
+create 1/1
+accept_focus 1/1 false
+can_take_focus 1/1 true
+accept_take_focus 1/1 true
+show 1/1
+
+create 1/2 csd
+set_parent 1/2 1
+accept_focus 1/2 false
+can_take_focus 1/2 true
+accept_take_focus 1/2 true
+show 1/2
+
+create 1/3
+set_parent 1/3 2
+show 1/3
+
+assert_focused 1/3
+assert_stacking 0/1 1/1 1/2 1/3
+
+destroy 1/3
+wait
+
+assert_focused 1/2
+assert_stacking 0/1 1/1 1/2
+
+sleep 150
+assert_focused 1/2
+assert_stacking 0/1 1/1 1/2