Rounded corners on udev/Pixman backend, opt-in and off by default

CPU-side rounded corners for the software-only udev/Pixman renderer,
which has no shader stage to hook the existing GLES version into.
Reads a window's own committed wl_shm buffer, punches premultiplied-
alpha holes into the four corner regions, and hands the masked copy
to MemoryRenderBuffer - the same path already used for titlebar/
border/shadow bitmaps, so it composites through the ordinary unmasked
path and the corners genuinely disappear rather than being painted
over.

Cached per window, invalidated by a per-commit content_epoch counter
rather than rebuilt every frame, so an idle window costs nothing once
masked. general.rounded_corners now defaults per backend instead of
one global true: on for GLES/winit (a real GPU shader, no measurable
cost), off for udev/Pixman (an untested-on-real-hardware CPU cost for
constantly-repainting clients) - WindowManager.rounded_corners_enabled
is Option<bool> so the backend can tell "unset" from "explicitly off".

1 files changed, 1 insertions, 0 deletions

diff --git a/crates/wayland/src/lib.rs b/crates/wayland/src/lib.rs
index 7687812..711006d 100644
--- a/crates/wayland/src/lib.rs
+++ b/crates/wayland/src/lib.rs
@@ -50,6 +50,7 @@ mod output_management;
 mod output_power;
 mod protocols;
 mod rounded_corners;
+mod rounded_corners_pixman;
 mod screencopy;
 mod state;
 mod udev;