Let a new window pick its own size instead of forcing a guessed placeholder

Root-caused "windows spawn small and square, not remembering placement or
size": new_managed_window hardcoded a fresh toplevel's geometry to 800x632
before the client had said anything about its own preferred size, and
sync_geometry forced that guess onto the client's very first
xdg_toplevel::configure unconditionally. Per xdg-shell, size: None on that
first configure is how every mainstream compositor lets a client pick its
own natural size instead; this one never did, so every app converged on
the same placeholder rectangle regardless of what it would have chosen.

Window::size_is_provisional marks a size that really was just the guess
(not a remembered geometry, a rule's explicit geometry action, or a
maximize/phone-mode fill, none of which are guesses). sync_geometry sends
size: None for such a window's first configure; a new adopt_provisional_size,
called from the commit handler, adopts the client's own real first size
into Window::geometry the moment it commits one, clamping only position so
a bigger-than-guessed window can't hang off its monitor's edge.

Live-verified in a nested compositor: a zenity dialog now renders at its
own compact natural size instead of being stretched to the old guess.

1 files changed, 8 insertions, 0 deletions

diff --git a/crates/wayland/src/state/mod.rs b/crates/wayland/src/state/mod.rs
index 629b58c..f39edcc 100644
--- a/crates/wayland/src/state/mod.rs
+++ b/crates/wayland/src/state/mod.rs
@@ -586,6 +586,14 @@ pub(crate) struct CompState {
     /// motion event of every drag, which is what made moving a window
     /// stutter. Only a real size change now does either.
     pub(crate) last_synced_size: HashMap<WindowId, (i32, i32)>,
+    /// Windows whose `Window::size_is_provisional` was `true` at creation
+    /// and whose client hasn't sent a real, non-empty content commit yet --
+    /// see that field's own doc comment. `sync_geometry` sends `size: None`
+    /// (let the client pick) instead of forcing this guessed size for the
+    /// one configure sent while a window is in this set; `commit()` removes
+    /// it and adopts the client's own real first size into `Window::
+    /// geometry` the moment one arrives.
+    pub(crate) provisional_size: HashSet<WindowId>,
     /// A size-changing `xdg_toplevel.configure` that's been sent but not
     /// yet reflected in the client's own real committed content size --
     /// `(size requested, when it was sent)`. `sync_geometry` won't send