Clamp the winit backend's own CSD margin offset to non-negative too

Same fix as the udev backend's matching content-position code: a real
CSD shadow margin (dwindow.geometry().loc) is never negative, but a
live Firefox window was observed reporting loc = (-10, -10) despite
sync_geometry's tiled-state hint telling it to reserve no margin at
all. This path (rounded_content_element, a live GLES shader rendering
the client's own texture directly, not a separate pre-shifted buffer)
doesn't have the udev backend's double-application bug, but it shares
the same single-subtraction call and so needed the same clamp.

1 files changed, 8 insertions, 1 deletions

diff --git a/crates/wayland/src/winit/render.rs b/crates/wayland/src/winit/render.rs
index f4cb7af..6f5f600 100644
--- a/crates/wayland/src/winit/render.rs
+++ b/crates/wayland/src/winit/render.rs
@@ -408,7 +408,14 @@ impl WaylandPlatform {
                     // invisible shadow margin) was never subtracted, so
                     // that margin's worth of gap showed through at this
                     // window's top-left corner.
-                    let content_offset = dwindow.geometry().loc;
+                    //
+                    // Clamped to non-negative, same as that same call site's
+                    // own fix: a real shadow margin is never negative, but a
+                    // live Firefox window was observed reporting
+                    // `loc = (-10, -10)` - subtracting that raw value would
+                    // shift content away from the border instead of into it.
+                    let raw_offset = dwindow.geometry().loc;
+                    let content_offset = smithay::utils::Point::<i32, smithay::utils::Logical>::from((raw_offset.x.max(0), raw_offset.y.max(0)));
                     let pos = (geom.x - content_offset.x, geom.y + band - content_offset.y);
                     let rounded = rounded_corners_enabled.then_some(self.state.rounded_corners_program.as_ref()).flatten().and_then(|program| {
                         let corners = if w.decorated { crate::rounded_corners::RoundedCorners::BOTTOM_ONLY } else { crate::rounded_corners::RoundedCorners::ALL };