ext-layer-shell: fix configure feedback loop; default Super toggles fuzzel

The intermittent "Super needs several presses to open fuzzel" bug was a
layer-shell configure storm, not a keybinding issue. The per-surface commit
handler called arrange() on EVERY wl_surface commit, and arrange()
unconditionally calls wlr_scene_layer_surface_v1_configure, which in wlroots
0.20 emits a fresh configure each call. A client acking + applying its configure
re-entered the commit handler, producing an unbounded
configure -> ack_configure -> commit -> configure loop that overflowed the
client's 4 KiB connection buffer ("Data too big for buffer") and got it killed
mid-handshake. fuzzel therefore only displayed when the burst happened to flush
in time.

Fix: only re-arrange on the initial commit or a commit that changes a
layout-relevant field (current.committed != 0); a plain buffer/frame commit no
longer triggers a configure.

Also:
- ext-keybindings: tap-Super now defaults to a launcher TOGGLE
  ("pkill -x fuzzel || fuzzel") in both default_bindings() and the sample
  unbox.toml — pressing Super while fuzzel is open closes it.
- ext-keybindings: a genuine Super press always re-arms a clean tap, so a
  dropped Super release can no longer eat the next tap (robustness).
- tests: update default-command assertions; add a bounded-configure invariant
  guard to the layer-shell client test.

1 files changed, 16 insertions, 4 deletions

diff --git a/packages/ext-layer-shell/src/ext_layer_shell.cpp b/packages/ext-layer-shell/src/ext_layer_shell.cpp
index 5670c52..3ca013d 100644
--- a/packages/ext-layer-shell/src/ext_layer_shell.cpp
+++ b/packages/ext-layer-shell/src/ext_layer_shell.cpp
@@ -397,11 +397,23 @@ LayerSurface::LayerSurface(LayerShellExt& owner, wlr_layer_surface_v1* surface,
     // RAII handle is a member; it unregisters when this LayerSurface dies.
     host_reg_ = owner_.host().host_surface(surface_->surface, scene_->tree);
 
-    // Re-arrange this surface's output on every commit (covers the mandatory
-    // initial-commit configure and any later anchor/zone/size change), then
-    // re-evaluate keyboard focus.
+    // Re-arrange this surface's output ONLY when the arrangement could have
+    // changed: the mandatory initial-commit configure, or a commit that changed
+    // a layout-relevant field (anchor / desired size / exclusive zone / margin /
+    // layer / exclusive edge — i.e. current.committed != 0). A plain buffer or
+    // frame commit changes none of these (committed == 0, not the initial
+    // commit) and MUST NOT trigger a configure: arrange() unconditionally calls
+    // wlr_scene_layer_surface_v1_configure, and in wlroots 0.20 that emits a
+    // fresh configure event every call. Reconfiguring on every commit created a
+    // configure -> ack_configure -> apply-commit -> configure feedback loop that
+    // flooded the client's 4 KiB connection buffer ("Data too big for buffer")
+    // and got it killed mid-handshake — the intermittent "fuzzel needs several
+    // Super presses to open" bug. Keyboard focus is still re-evaluated every
+    // commit (cheap; it only acts once mapped).
     commit_.connect(surface_->surface->events.commit, [this](void*) {
-        owner_.arrange(surface_->output);
+        if (surface_->initial_commit || surface_->current.committed != 0) {
+            owner_.arrange(surface_->output);
+        }
         update_keyboard_focus();
     });