Add real desktop icons plus right-click desktop/icon context menus

Closes "right-click on bare desktop" - previously a true no-op, nothing
rendered above the wallpaper at all. Requested directly: a real desktop
"just like windows does" - Home/Computer/Trash plus one icon per real
~/Desktop entry, individually draggable with persisted grid positions,
double-click to open, right-click menus (per-icon "Open" plus "Set as
Wallpaper" for image files when general.wallpaper_command is set; bare
desktop "New Folder"/"Refresh").

Architecture mirrors the existing context_menu.rs/snap_flyout.rs
"compositor-owned floating UI" pattern: desktop_icons.rs (data model, grid
layout, filesystem scan, hit-test), desktop_icons_state.rs (JSON
persistence, same shape as monitor_layout.rs), desktop_menu.rs (the new
right-click menu, reusing decoration::render_context_menu's existing
rasterizer), state/desktop_icons.rs (CompState glue: rescan/select/drag/
open/persist), and a new decoration::render_desktop_icon rasterizer --
hand-drawn glyphs, since no PNG/SVG decoding capability exists anywhere in
this workspace. Wired into both render loops (udev and winit) above the
wallpaper and below every window, and into input/pointer.rs's button/
motion handlers for selection, drag, double-click, and both menus.

Four new config keys: general.desktop_icons (default true - a directly
requested, purely visual feature, unlike the opt-in-while-experimental
general.gpu), general.file_manager, general.desktop_icon_single_click,
general.wallpaper_command (all default off/empty).

Deliberately out of scope for this pass, stated up front: move-to-trash
and "Empty Trash" (destructive, no confirmation-dialog primitive to gate
them on yet), filesystem watching, multi-select, per-mimetype icon art,
icons on any monitor but the primary one.

124 wayland-crate tests (up from 106), full workspace build and clippy
clean.

2 files changed, 34 insertions, 0 deletions

diff --git a/crates/wayland/src/udev/platform.rs b/crates/wayland/src/udev/platform.rs
index a4a72a0..2633f16 100644
--- a/crates/wayland/src/udev/platform.rs
+++ b/crates/wayland/src/udev/platform.rs
@@ -230,6 +230,12 @@ impl UdevPlatform {
             context_menu_buffer: None,
             snap_flyout: None,
             snap_flyout_buffer: None,
+            desktop_icons: None,
+            desktop_icon_buffers: HashMap::new(),
+            desktop_icon_drag: None,
+            desktop_menu: None,
+            desktop_menu_buffer: None,
+            last_icon_click: None,
             wm: wm.clone(),
             surface_to_id: HashMap::new(),
             id_to_window: HashMap::new(),
diff --git a/crates/wayland/src/udev/render.rs b/crates/wayland/src/udev/render.rs
index 802428f..73aaa82 100644
--- a/crates/wayland/src/udev/render.rs
+++ b/crates/wayland/src/udev/render.rs
@@ -21,6 +21,12 @@ impl CompState {
         // Same reason again: a native lock's capture step (below) needs
         // this, and `self.wm` can't be borrowed once `self.udev` is.
         let lock_blur_radius = self.wm.borrow().lock.blur_radius;
+        // Same "capture before `self.udev`'s borrow starts" reason as
+        // `cursor_status`/`cursor_buffers` above: global-space, so computed
+        // once here rather than per head, each head's own per-frame push
+        // below just re-offsets these same positions by its own `origin`.
+        self.ensure_desktop_icons();
+        let desktop_icon_render_list = self.desktop_icon_render_list();
         // Captured-and-blurred backgrounds collected during the per-head
         // loop below, applied via `self.capture_output` only after it
         // ends - `self.udev`'s mutable borrow is held for the whole loop
@@ -323,6 +329,15 @@ impl CompState {
                         Err(e) => log::warn!("udev: failed to import snap flyout buffer: {e}"),
                     }
                 }
+                // The desktop-icon/bare-desktop right-click menu, if open --
+                // same "topmost but never hides the cursor" placement.
+                if let (Some(menu), Some(buffer)) = (self.desktop_menu.as_ref(), self.desktop_menu_buffer.as_ref()) {
+                    let pos = ((menu.pos.0 - origin.x) as f64, (menu.pos.1 - origin.y) as f64);
+                    match MemoryRenderBufferRenderElement::from_buffer(&mut udev.renderer, pos, buffer, None, None, None, Kind::Unspecified) {
+                        Ok(elem) => custom_elements.push(crate::elements::OverlayElement::Memory(elem)),
+                        Err(e) => log::warn!("udev: failed to import desktop menu buffer: {e}"),
+                    }
+                }
                 // Popups next: always above every window's own content,
                 // matching this codebase's long-standing behavior from
                 // before content moved into this same `custom_elements`
@@ -903,6 +918,19 @@ impl CompState {
                     }
                     occluders.push(frame);
                 }
+                // Real desktop icons - above the wallpaper, below every
+                // window: pushed after the windows loop above (so nothing
+                // here can occlude a real window) but before the
+                // background-layer push just below (so the wallpaper still
+                // shows through everywhere an icon doesn't draw). See
+                // `desktop_icons.rs`'s own module doc comment.
+                for (pos, buffer) in &desktop_icon_render_list {
+                    let pos = ((pos.0 - origin.x) as f64, (pos.1 - origin.y) as f64);
+                    match MemoryRenderBufferRenderElement::from_buffer(&mut udev.renderer, pos, buffer, None, None, None, Kind::Unspecified) {
+                        Ok(elem) => custom_elements.push(crate::elements::OverlayElement::Memory(elem)),
+                        Err(e) => log::warn!("udev: failed to import desktop icon buffer: {e}"),
+                    }
+                }
                 // Background/bottom layer-shell (wallpaper engines) last --
                 // bottommost, matching smithay's own `space_render_elements`
                 // ordering, which this whole custom loop now replaces.