Accumulate wayland-crate additions: capture rendering, focus/Space sync, VT resume, plumbing

Bundles the remaining wayland-crate changes built up here,
touching both backends (udev and winit) and the shared input/rendering
code:
- udev/capture.rs: off-screen Pixman render of an arbitrary (not
  necessarily on-screen) workspace's window content to a PPM file --
  what crates/core's capture-request queue drives, for a workspace
  switcher's thumbnail previews. wlr-screencopy structurally can't do
  this (it can only see what an output is presenting), which is why
  this exists as a separate render path rather than reusing it.
- input::focus_window now also raises the window in smithay's own
  Space, not just core's stacking order - Space is what actually
  renders on top and what pointer hit-testing reads, so any focus path
  that skipped this (an IPC "focus" dispatch, concretely) left a
  window genuinely focused while still rendering, and receiving
  clicks, underneath whatever was already topmost. Both backends'
  poll loops now re-sync this after any IPC mutation.
- udev/session.rs's VT-switch resume fix (drains a stale pending page
  flip before reasserting CRTCs) already has its own earlier, cleanly
  isolated commit - not duplicated here.
- Assorted decoration/cursor/rounded-corners/output-management/
  screencopy/XWayland changes and their cross-backend wiring.

Coarser than the repo's usual one-purpose-per-commit convention,
deliberately - see the core-crate sweep commit's own message for why.

1 files changed, 12 insertions, 0 deletions

diff --git a/crates/wayland/src/rounded_corners.rs b/crates/wayland/src/rounded_corners.rs
index 25fc199..4e02616 100644
--- a/crates/wayland/src/rounded_corners.rs
+++ b/crates/wayland/src/rounded_corners.rs
@@ -176,6 +176,18 @@ pub(crate) fn rounded_content_element(
     radius: f32,
     corners: RoundedCorners,
 ) -> Option<TextureShaderElement> {
+    // This module's doc comment has always said a window with subsurfaces
+    // "won't have them rendered at all through this path" - intended to
+    // mean the caller falls back to `surface_content_elements` (subsurface-
+    // aware) for such a window instead. Nothing here actually enforced that:
+    // without this check, a window whose real content lives in a subsurface
+    // (confirmed live on the udev/Pixman backend's identical bug: Firefox
+    // does this) would round and return just its own root surface - often
+    // blank/background-only - instead of falling back, silently dropping
+    // the window's actual content rather than merely leaving it unrounded.
+    if !smithay::wayland::compositor::get_children(surface).is_empty() {
+        return None;
+    }
     smithay::wayland::compositor::with_states(surface, |states| {
         smithay::backend::renderer::utils::import_surface(renderer, states).ok()?;
         Some(())