Split crates/wayland/src/winit.rs (889 lines) into winit/

Pure reorganization, no behavior change - verified by diffing the
function-name and struct-name sets before/after (both identical) plus
a full cargo test pass. mod.rs keeps the module doc comment, imports,
WaylandPlatform's struct definition, and TARGET_FRAME_TIME, plus mod
declarations. The rest splits by concern:

- connect.rs: connect(), the ~200-line setup/init function.
- run.rs: accept_clients, pump_winit - the small per-poll pair.
- render.rs: render_frame, the per-frame render loop (left as one
  intact ~330-line function, same reasoning as udev's render.rs: its
  structure is deliberate and already documented inline, not a target
  for further decomposition in a pure reorganization pass).
- capture.rs: capture_offscreen, the screencopy path.
- events.rs: handle_winit_event.
- platform.rs: `impl Platform for WaylandPlatform`.

No tests module existed in the original file, so none was split out.

A handful of methods/functions (accept_clients, pump_winit,
render_frame, capture_offscreen, handle_winit_event) went from private
to pub(super): called across what are now sibling submodules, which
Rust's privacy model doesn't let see each other's private items.

1 files changed, 331 insertions, 0 deletions

diff --git a/crates/wayland/src/winit/render.rs b/crates/wayland/src/winit/render.rs
new file mode 100644
index 0000000..3dda278
--- /dev/null
+++ b/crates/wayland/src/winit/render.rs
@@ -0,0 +1,331 @@
+use super::*;
+
+impl WaylandPlatform {
+
+    pub(super) fn render_frame(&mut self) -> PlatformResult<()> {
+        self.state.tick_animations();
+        self.state.tick_dirty_broadcasts();
+        let size = self.backend.window_size();
+        let resized = self.output.current_mode().map(|m| m.size) != Some(size);
+        if resized {
+            // Only push a new output mode - and thus emit `wl_output.mode`/
+            // `done` - when the size actually changed. This used to run
+            // unconditionally every frame; harmless with no Wayland-native
+            // client connected (the only way this was ever exercised before
+            // real layer-shell clients existed), but a real client bound to
+            // `wl_output` would otherwise be flooded with duplicate
+            // mode/done events at the render loop's full frame rate.
+            self.output.change_current_state(Some(OutputMode { size, refresh: 60_000 }), None, None, None);
+            layer_map_for_output(&self.output).arrange();
+        }
+
+        let age = self.backend.buffer_age().unwrap_or(0);
+        let (renderer, mut framebuffer) = self.backend.bind().map_err(err)?;
+
+        // Locked: the lock surface over an opaque black clear, and nothing
+        // else - no windows, no decorations, no layer surfaces.
+        if self.state.lock.locked {
+            let lock_surface = self.state.lock_surface_for(&self.output).cloned();
+            let elements = lock_render_elements(lock_surface.as_ref(), renderer);
+            self.damage_tracker
+                .render_output(renderer, &mut framebuffer, age, &elements, [0.0, 0.0, 0.0, 1.0])
+                .map_err(err)?;
+            drop(framebuffer);
+            self.backend.submit(None).map_err(err)?;
+            send_lock_frame(lock_surface.as_ref(), &self.output, self.state.start_time.elapsed());
+            self.state.confirm_lock_if_presented(&self.output);
+            screencopy::fail_pending(std::mem::take(&mut self.state.screencopy_pending));
+            return Ok(());
+        }
+
+        // `WinitElement`, not `OverlayElement<GlesRenderer>` directly - see
+        // `rounded_corners.rs`'s own doc comment on why content that gets
+        // rounded needs a wider element type than everything else here,
+        // and why that couldn't just be added as a new `OverlayElement`
+        // variant instead. Every existing push below wraps its
+        // `OverlayElement` in `WinitElement::Base`; only the new
+        // rounded-content push (further down) uses `WinitElement::Rounded`
+        // directly.
+        let mut custom_elements: Vec<crate::rounded_corners::WinitElement> = Vec::new();
+        // The right-click titlebar menu, if open - pushed first so it's
+        // topmost over every window (this backend draws no cursor of its
+        // own, see this module's doc comment, so there's no "stay under
+        // the pointer" ordering concern like udev.rs's matching push has).
+        if let (Some(menu), Some(buffer)) = (self.state.context_menu.as_ref(), self.state.context_menu_buffer.as_ref()) {
+            let pos = (menu.pos.0 as f64, menu.pos.1 as f64);
+            match MemoryRenderBufferRenderElement::from_buffer(renderer, pos, buffer, None, None, None, Kind::Unspecified) {
+                Ok(elem) => custom_elements.push(crate::rounded_corners::WinitElement::Base(crate::elements::OverlayElement::Memory(elem))),
+                Err(e) => log::warn!("failed to import context menu buffer: {e}"),
+            }
+        }
+        // Content now renders here too, one window at a time, not through
+        // `render_output`'s own `spaces` argument - see this function's
+        // own call to `damage_tracker.render_output` further down for why,
+        // and `elements.rs`'s `surface_content_elements` doc comment for
+        // what it's actually for (per-window opacity, impossible through
+        // `spaces`, which takes one `alpha` for the whole frame).
+        //
+        // An earlier version of this exact change was reverted: with two or
+        // more native Wayland toplevels on screen, whichever was created
+        // *first* always painted in front of later ones regardless of real
+        // focus/stacking order. That bug's real root cause (found by
+        // instrumenting a locally vendored smithay copy directly) turned
+        // out to be `sync_geometry`'s `Space::map_element` call silently
+        // re-stacking windows to the top of `Space`'s *own* internal
+        // order as a side effect of updating position - see `state.rs`'s
+        // `resync_stacking_order` doc comment for the full story and the
+        // fix that landed for it (called after every `map_element` since).
+        // This loop never reads `Space`'s order at all: `ids` below comes
+        // from `WindowManager.order` (`visible_windows_front_to_back`),
+        // srdwm's own stacking model, the same source `hit_test` already
+        // trusts - so the specific bug that sank the earlier attempt
+        // can't recur here regardless of whether `resync_stacking_order`
+        // ever drifts again. `self.state.space` stays mapped and
+        // `resync_stacking_order`-maintained exactly as before; only the
+        // render step stopped reading from it.
+        let ids: Vec<WindowId> = self.wm.borrow().visible_windows_front_to_back().map(|w| w.id).collect();
+        let focused = self.wm.borrow().focused_id();
+        // Popups next: always above every window's own content - see the
+        // matching comment in `udev.rs`'s render loop for why this has to
+        // be pushed ahead of both the bar/dock and every window now that
+        // content shares this same list.
+        let popup_targets = crate::elements::popup_targets(&self.state);
+        custom_elements.extend(crate::elements::popup_render_elements(&popup_targets, renderer, (0, 0)).into_iter().map(crate::rounded_corners::WinitElement::Base));
+        // The bar/dock/launcher, skipped entirely for a fullscreen window --
+        // see `udev.rs`'s matching push for the full reasoning.
+        let hide_top_layers = self.wm.borrow().visible_windows_front_to_back().any(|w| w.fullscreen);
+        // `None` (the user's config never touched `general.rounded_corners`)
+        // defaults to *on* here - this backend has an actual GPU shader
+        // behind the feature (see `rounded_corners.rs`), no untested
+        // per-frame CPU cost to weigh the way the udev backend's own
+        // default has to.
+        let rounded_corners_enabled = self.wm.borrow().rounded_corners_enabled.unwrap_or(true);
+        if !hide_top_layers {
+            custom_elements.extend(
+                crate::elements::output_layer_elements(renderer, &self.output, (0, 0), |layer| matches!(layer, Layer::Top | Layer::Overlay))
+                    .into_iter()
+                    .map(crate::rounded_corners::WinitElement::Base),
+            );
+        }
+        // Windows stacked in front of whichever one border/decoration is
+        // being built right now - `ids` is already front-to-back, so this
+        // only ever needs appending to, not recomputing. A window's own
+        // *content*, pushed inside this same loop below, needs no separate
+        // occlusion test - see the matching comment in `udev.rs`'s render
+        // loop for why ordinary front-to-back push order already occludes
+        // it correctly. The border strips and titlebar bitmap are
+        // different: outside `geometry`, so they still need `occluders`'
+        // explicit clip against whichever window is stacked in front.
+        let mut occluders: Vec<srdwm_core::Rect> = Vec::with_capacity(ids.len());
+        for id in ids {
+            let Some(w) = self.wm.borrow().window(id).cloned() else { continue };
+            // `w.geometry` is the animation's target, not necessarily where
+            // the window is actually drawn this frame - see the matching
+            // comment in `udev.rs`'s render loop for the full story
+            // (reported live as the border "not flush" with the window
+            // during an animated maximize/fullscreen/open-slide transition).
+            let geom = self.state.window_anims.get(&id).map(crate::state::WindowAnim::current_rect).unwrap_or(w.geometry);
+            // Same reasoning as udev.rs's matching push: positioned from
+            // `geom`, not `w.geometry`, and not fragment-clipped against
+            // `occluders` - see that comment.
+            if let Some(shadow) = self.state.shadow_buffers.get(&id) {
+                let rect = decoration::shadow_rect(geom);
+                let pos = (rect.x as f64, rect.y as f64);
+                match MemoryRenderBufferRenderElement::from_buffer(renderer, pos, shadow, None, None, None, Kind::Unspecified) {
+                    Ok(elem) => custom_elements.push(crate::rounded_corners::WinitElement::Base(crate::elements::OverlayElement::Memory(elem))),
+                    Err(e) => log::warn!("failed to import shadow buffer for window {id}: {e}"),
+                }
+            }
+            if let Some(deco) = self.state.decorations.get(&id) {
+                // Fragment-clipped, same as udev.rs's matching titlebar
+                // push - see that comment for why all-or-nothing (skip
+                // only once *fully* covered) wasn't enough: a titlebar
+                // only partially covered, the common case for cascaded
+                // windows, still bled through the covered part.
+                let titlebar_rect = srdwm_core::Rect::new(geom.x, geom.y, geom.width, srdwm_core::TITLEBAR_HEIGHT);
+                for fragment in crate::elements::visible_border_fragments(titlebar_rect, &occluders) {
+                    let pos = (fragment.x as f64, fragment.y as f64);
+                    let src = Rectangle::new(
+                        Point::from(((fragment.x - titlebar_rect.x) as f64, (fragment.y - titlebar_rect.y) as f64)),
+                        Size::from((fragment.width as f64, fragment.height as f64)),
+                    );
+                    match MemoryRenderBufferRenderElement::from_buffer(renderer, pos, deco, None, Some(src), None, Kind::Unspecified) {
+                        Ok(elem) => custom_elements.push(crate::rounded_corners::WinitElement::Base(crate::elements::OverlayElement::Memory(elem))),
+                        Err(e) => log::warn!("failed to import titlebar buffer for window {id}: {e}"),
+                    }
+                }
+            }
+            // Border strips sit entirely outside `geometry` (see
+            // `decoration::border_strips`), so they never overlap this same
+            // window's own decoration/content pixels - draw order relative
+            // to those doesn't matter, only relative to other windows'.
+            if w.border_width > 0 {
+                let color = crate::state::effective_border_color(w.border_color, focused == Some(id));
+                let strips = decoration::border_strips(geom, w.border_width);
+                // Strip 0 (top) is rounded to match the titlebar underneath
+                // it - see `render_border_top`'s doc comment - so it's a
+                // cached bitmap (rebuilt only in `redraw_decoration_buffer`,
+                // same as the titlebar itself), not rasterized fresh here
+                // every frame; the other three don't touch a rounded corner
+                // and stay persistent solid-colour buffers instead - see
+                // `elements::border_side_render_element`'s doc comment for
+                // why a per-frame rebuild of either was a real, continuous
+                // cost, not a cosmetic one. Not fragment-clipped like the
+                // other three below - see the matching comment in
+                // `udev.rs` for why the top strip only gets the cheaper
+                // all-or-nothing occlusion check.
+                if strips[0].width > 0 && strips[0].height > 0 && !strips[0].subtract_all(&occluders).is_empty() {
+                    if let Some(buffer) = self.state.border_top_decorations.get(&id) {
+                        match MemoryRenderBufferRenderElement::from_buffer(renderer, (strips[0].x as f64, strips[0].y as f64), buffer, None, None, None, Kind::Unspecified) {
+                            Ok(elem) => custom_elements.push(crate::rounded_corners::WinitElement::Base(crate::elements::OverlayElement::Memory(elem))),
+                            Err(e) => log::warn!("failed to import top border buffer for window {id}: {e}"),
+                        }
+                    }
+                }
+                let pool = self.state.border_side_buffers.entry(id).or_default();
+                let mut buf_index = 0;
+                for strip in &strips[1..] {
+                    if strip.width == 0 || strip.height == 0 {
+                        continue;
+                    }
+                    for fragment in crate::elements::visible_border_fragments(*strip, &occluders) {
+                        let buf = crate::elements::border_fragment_buffer(pool, buf_index);
+                        buf_index += 1;
+                        custom_elements.push(crate::rounded_corners::WinitElement::Base(crate::elements::OverlayElement::Solid(crate::elements::border_side_render_element(buf, fragment, color, (0, 0)))));
+                    }
+                }
+            }
+            // The window's own content, at its own `opacity` - see the
+            // matching push in `udev.rs`'s render loop for why. Single
+            // output at the global origin, so no offset to subtract (see
+            // `elements.rs`'s doc comment on why `udev.rs`'s per-head call
+            // does). Rounded via `rounded_corners::rounded_content_element`
+            // when the feature's on and the shader compiled - a decorated
+            // window only rounds its bottom two corners (the top two are
+            // already rounded, on the titlebar's own bitmap, by
+            // `decoration.rs`), an undecorated/CSD one rounds all four,
+            // since its content *is* the window's whole visible extent.
+            // Falls back to the plain, unrounded `surface_content_elements`
+            // on any failure - no committed buffer yet, a single-pixel
+            // solid-colour buffer, or the feature simply being off - same
+            // "always show something over a prettier maybe-nothing"
+            // reasoning `cursor.rs`'s built-in-arrow fallback already uses.
+            if let Some(dwindow) = self.state.id_to_window.get(&id) {
+                if let Some(surface) = crate::elements::window_wl_surface(dwindow) {
+                    let band = if w.decorated { srdwm_core::TITLEBAR_HEIGHT as i32 } else { 0 };
+                    let pos = (geom.x, geom.y + band);
+                    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 };
+                        crate::rounded_corners::rounded_content_element(renderer, program, &surface, pos, w.opacity, crate::decoration::CORNER_RADIUS as f32, corners)
+                    });
+                    match rounded {
+                        Some(elem) => custom_elements.push(crate::rounded_corners::WinitElement::Rounded(elem)),
+                        None => custom_elements.extend(crate::elements::surface_content_elements(renderer, &surface, pos, w.opacity).into_iter().map(crate::rounded_corners::WinitElement::Base)),
+                    }
+                }
+            }
+            occluders.push(geom);
+        }
+        // Background/bottom layer-shell (wallpaper engines) last --
+        // bottommost, matching smithay's own `space_render_elements`
+        // ordering, which this whole custom loop now replaces.
+        custom_elements.extend(
+            crate::elements::output_layer_elements(renderer, &self.output, (0, 0), |layer| matches!(layer, Layer::Background | Layer::Bottom))
+                .into_iter()
+                .map(crate::rounded_corners::WinitElement::Base),
+        );
+
+        // Not `smithay::desktop::space::render_output`: see `udev.rs`'s
+        // matching call site for why (per-window opacity, fullscreen-aware
+        // layer-shell inclusion - `custom_elements` above already carries
+        // everything that wrapper would have built).
+        let result = self
+            .damage_tracker
+            .render_output(renderer, &mut framebuffer, age, &custom_elements, [0.05, 0.05, 0.08, 1.0])
+            .map_err(err)?;
+        let damage_rects: Vec<Rectangle<i32, Physical>> = result.damage.cloned().unwrap_or_default();
+        let has_damage = !damage_rects.is_empty();
+        drop(framebuffer);
+        // Both the buffer swap and the frame-callback notification are
+        // conditional on real damage now - this used to run
+        // unconditionally on every call to this function (every ~16ms
+        // regardless of activity), which told every window it could render
+        // its next frame whether or not the screen had actually changed.
+        // Any client using the standard wait-for-frame-callback render
+        // pattern (most of them) had no reason not to redraw at whatever
+        // rate this loop cycled, forever - confirmed live on the udev
+        // backend: wezterm-gui pinned at 140%+ CPU sitting on a fully idle,
+        // unchanged terminal, from the identical bug there.
+        //
+        // That output-wide gate wasn't enough on its own: cursor motion
+        // alone damages the small region around the pointer, which still
+        // marked the *whole output* damaged and sent every mapped window a
+        // callback regardless of whether the cursor was anywhere near it.
+        // `windows_touched_by_damage` narrows this to windows the actual
+        // damage rectangles overlap - see its doc comment in elements.rs.
+        if has_damage {
+            self.backend.submit(None).map_err(err)?;
+            let scale = Scale::from(self.output.current_scale().fractional_scale());
+            let now = self.state.start_time.elapsed();
+            for w in crate::elements::windows_touched_by_damage(&self.state.space, &damage_rects, scale) {
+                w.send_frame(&self.output, now, None, |_, _| Some(self.output.clone()));
+            }
+        }
+        // Deliberately outside `if has_damage`: the whole point of
+        // `always_notify` is covering the case where the output has *no*
+        // damage at all (a fully idle desktop, cursor not moving) but the
+        // focused/hovered window still has a pending callback it needs
+        // answered to unblock an input-driven redraw. Nesting this inside
+        // `if has_damage` (the first version of this fix) meant it only
+        // ever ran on a tick that already had damage from something else
+        // happening - i.e. never in the exact scenario it exists for.
+        // Reported live as clicks in Firefox still doing nothing at all,
+        // not just intermittently, after the first version of this fix.
+        {
+            let pointer_pos = last_pointer_pos(&self.state);
+            let now = self.state.start_time.elapsed();
+            let wm = self.wm.borrow();
+            let always_notify = [wm.focused_id(), wm.window_at(pointer_pos.x as i32, pointer_pos.y as i32)];
+            drop(wm);
+            for w in always_notify.into_iter().flatten().filter_map(|id| self.state.id_to_window.get(&id)) {
+                w.send_frame(&self.output, now, None, |_, _| Some(self.output.clone()));
+            }
+        }
+        // Layer-shell surfaces get their callback every pass, unconditionally
+        // - NOT folded into the `has_damage` gate above. See the matching
+        // (much longer) comment in udev.rs's `render_udev_frame`: many
+        // layer-shell clients (GTK4/AGS among them) drive their entire
+        // repaint loop off frame callbacks with no independent timer
+        // fallback, so withholding the callback until *something* on the
+        // desktop happens to produce damage deadlocks them permanently
+        // after their first frame - confirmed live, AGS and waybar both
+        // froze exactly this way. Toplevel windows keep the damage gate
+        // (that's what fixed the wezterm-gui CPU-burn bug); layer surfaces
+        // are few, cheap to redraw, and are exactly the periodic-UI-chrome
+        // case frame callbacks exist to pace.
+        for layer in layer_map_for_output(&self.output).layers() {
+            layer.send_frame(&self.output, self.state.start_time.elapsed(), None, |_, _| Some(self.output.clone()));
+        }
+
+        // Screencopy is serviced *after* the on-screen frame is submitted,
+        // into its own offscreen buffer - never by reading back the window
+        // surface. Reading the winit backend's EGL window surface (what an
+        // earlier version did) reliably killed the GL context: the first
+        // `grim` capture produced `eglSwapBuffers: BAD_SURFACE` followed by
+        // `BAD_ALLOC` and "context has been lost", confirmed by A/B-ing the
+        // same build with only the readback call removed. The offscreen
+        // detour costs a second scene render, but only on frames where a
+        // capture was actually requested.
+        //
+        // Deliberately placed after the locked-session early return above,
+        // so a capture requested while the screen is locked can never see
+        // client content.
+        let captures = std::mem::take(&mut self.state.screencopy_pending);
+        if !captures.is_empty() {
+            if let Err(e) = self.capture_offscreen(captures) {
+                log::warn!("screencopy: offscreen capture pass failed: {e}");
+            }
+        }
+        Ok(())
+    }
+}