Fix spawn placement under the top bar, add per-window minimum sizes, and clean up maximize

Four reports after restarting into today's build, with a screenshot. The
screenshot was measured, not eyeballed: top bar y=0..29, a 4px accent border
at y=30..33, titlebar from y=34, bottom border at y=1027..1030, and 49px of
bare desktop below it.

Windows spawning too close to the top bar. A remembered position was
validated only by asking whether it landed on some monitor's full_geometry,
which includes the strip a top bar reserves, so an app whose remembered y was
small reopened with its titlebar under the bar. That is why it was
"sometimes": it depended on the stored value, and the live store holds
wezterm at y=44 and firefox at y=69 against a 30px bar. Remembered positions
are now clamped into the monitor's usable area.

Placement not surviving a logout. Window memory does persist, but five of the
eleven entries in the live store were saved with a second monitor attached,
at x >= 2000. Those points match no current monitor and were discarded
outright, falling back to a fresh cascade, so those apps appeared to remember
nothing. Such a position is now clamped onto a monitor that exists instead.

Per-window minimum sizes. One global floor is wrong in both directions.
Three sources now, in increasing precedence: the global floor, the client's
own declared minimum (xdg_toplevel.set_min_size or ICCCM hints), and a
min_width/min_height window rule overriding both. A rule wins permanently --
the backend refreshes the client's declared minimum on every decoration
redraw and must not undo a deliberate override.

Maximize, three faults in one report. A maximized window now draws no
border: its edges are the screen's edges, and the only place maximize stops
short is the bar strip, which is exactly where the measured line was.
maximize_geometry_for no longer subtracts a bottom-anchored dock's exclusive
zone, so maximize runs to the bottom of the screen and the dock floats over
it; top, left and right are still honoured.
general.maximize_covers_dock = false restores the old behaviour. With the
border gone the window sits flush under the bar instead of with an accent
line crowding it.

Verified: seven new tests on the real numbers from the live store, and
maximize geometry measured live in a nested instance (a window maximized on a
split half reports exactly that half's rect). NOT confirmed on screen: the
border removal and the dock behaviour - the nested backend has no bar or
dock to reserve a zone, and an attempt to check the border produced a failing
control, since srd set border_width only affects windows created after it.

515 tests pass, clippy clean.

1 files changed, 20 insertions, 0 deletions

diff --git a/crates/wayland/src/state/lifecycle.rs b/crates/wayland/src/state/lifecycle.rs
index 92f7d9d..163064e 100644
--- a/crates/wayland/src/state/lifecycle.rs
+++ b/crates/wayland/src/state/lifecycle.rs
@@ -131,9 +131,29 @@ impl CompState {
             }
             true
         });
+        // The client's own declared minimum, read from the same place
+        // `resizable` above comes from. A rule's `min_size` still wins --
+        // it is applied at map time and this must not undo it - so this
+        // only ever raises the floor above the global default, never
+        // overwrites a deliberate override.
+        let declared_min = self.id_to_window.get(&id).and_then(|dw| {
+            if let Some(toplevel) = dw.toplevel() {
+                let min = smithay::wayland::compositor::with_states(toplevel.wl_surface(), |states| {
+                    let mut cached = states.cached_state.get::<smithay::wayland::shell::xdg::SurfaceCachedState>();
+                    cached.current().min_size
+                });
+                return (min.w > 0 && min.h > 0).then_some((min.w as u32, min.h as u32));
+            }
+            dw.x11_surface().and_then(|x| x.min_size()).and_then(|m| (m.w > 0 && m.h > 0).then_some((m.w as u32, m.h as u32)))
+        });
         if let Some(win) = self.wm.borrow_mut().window_mut(id) {
             win.is_dialog = is_dialog;
             win.resizable = resizable;
+            if let Some(min) = declared_min {
+                if !win.min_size_from_rule {
+                    win.min_size = min;
+                }
+            }
         }
         let show_maximize = {
             let wm = self.wm.borrow();