Implement wl_subsurface.place_{above,below}.

src/compositor/handlers.rs

@@ -1,7 +1,7 @@
 use super::{CompositorHandler, Damage, Handler as UserHandler, Rectangle, RectangleKind,
             SubsurfaceAttributes};
 use super::region::RegionData;
-use super::tree::SurfaceData;
+use super::tree::{Location, SurfaceData};
 use wayland_server::{Client, Destroy, EventLoopHandle, Resource};
 use wayland_server::protocol::{wl_buffer, wl_callback, wl_compositor, wl_output, wl_region,
                                wl_subcompositor, wl_subsurface, wl_surface};
@@ -227,31 +227,43 @@ unsafe fn with_subsurface_attributes<U, F>(subsurface: &wl_subsurface::WlSubsurf
 }
 
 impl<U, H> wl_subsurface::Handler for CompositorHandler<U, H> {
-    fn set_position(&mut self, _: &mut EventLoopHandle, _: &Client, resource: &wl_subsurface::WlSubsurface,
-                    x: i32, y: i32) {
+    fn set_position(&mut self, _: &mut EventLoopHandle, _: &Client,
+                    subsurface: &wl_subsurface::WlSubsurface, x: i32, y: i32) {
         unsafe {
-            with_subsurface_attributes::<U, _>(resource, |attrs| {
+            with_subsurface_attributes::<U, _>(subsurface, |attrs| {
                 attrs.x = x;
                 attrs.y = y;
             });
         }
     }
-    fn place_above(&mut self, _: &mut EventLoopHandle, _: &Client, resource: &wl_subsurface::WlSubsurface,
-                   sibling: &wl_surface::WlSurface) {
-        unimplemented!()
-    }
-    fn place_below(&mut self, _: &mut EventLoopHandle, _: &Client, resource: &wl_subsurface::WlSubsurface,
-                   sibling: &wl_surface::WlSurface) {
-        unimplemented!()
-    }
-    fn set_sync(&mut self, _: &mut EventLoopHandle, _: &Client, resource: &wl_subsurface::WlSubsurface) {
+    fn place_above(&mut self, _: &mut EventLoopHandle, _: &Client,
+                   subsurface: &wl_subsurface::WlSubsurface, sibling: &wl_surface::WlSurface) {
         unsafe {
-            with_subsurface_attributes::<U, _>(resource, |attrs| { attrs.sync = true; });
+            let ptr = subsurface.get_user_data();
+            let surface = &*(ptr as *mut wl_surface::WlSurface);
+            if let Err(()) = SurfaceData::<U>::reorder(surface, Location::After, sibling) {
+                subsurface.post_error(wl_subsurface::Error::BadSurface as u32, "Provided surface is not a sibling or parent.".into());
             }
         }
-    fn set_desync(&mut self, _: &mut EventLoopHandle, _: &Client, resource: &wl_subsurface::WlSubsurface) {
+    }
+    fn place_below(&mut self, _: &mut EventLoopHandle, _: &Client,
+                   subsurface: &wl_subsurface::WlSubsurface, sibling: &wl_surface::WlSurface) {
         unsafe {
-            with_subsurface_attributes::<U, _>(resource, |attrs| { attrs.sync = false; });
+            let ptr = subsurface.get_user_data();
+            let surface = &*(ptr as *mut wl_surface::WlSurface);
+            if let Err(()) = SurfaceData::<U>::reorder(surface, Location::Before, sibling) {
+                subsurface.post_error(wl_subsurface::Error::BadSurface as u32, "Provided surface is not a sibling or parent.".into());
+            }
+        }
+    }
+    fn set_sync(&mut self, _: &mut EventLoopHandle, _: &Client, subsurface: &wl_subsurface::WlSubsurface) {
+        unsafe {
+            with_subsurface_attributes::<U, _>(subsurface, |attrs| { attrs.sync = true; });
+        }
+    }
+    fn set_desync(&mut self, _: &mut EventLoopHandle, _: &Client, subsurface: &wl_subsurface::WlSubsurface) {
+        unsafe {
+            with_subsurface_attributes::<U, _>(subsurface, |attrs| { attrs.sync = false; });
         }
     }
 }

src/compositor/mod.rs

@@ -192,7 +192,8 @@ impl<U: Send + 'static, H: Handler + Send + 'static> CompositorToken<U, H> {
     /// Access the data of a surface tree
     ///
     /// The provided closure is called successively on the surface and all its child subsurfaces,
-    /// in a depth-first order.
+    /// in a depth-first order. This matches the order in which the surfaces are supposed to be
+    /// drawn: top-most last.
     ///
     /// If the surface is not managed by the CompositorGlobal that provided this token, this
     /// will panic (having more than one compositor is not supported).

src/compositor/tree.rs

@@ -43,6 +43,11 @@ pub enum RoleStatus {
     HasRole,
 }
 
+pub enum Location {
+    Before,
+    After,
+}
+
 impl<U: Default> SurfaceData<U> {
     fn new() -> SurfaceData<U> {
         SurfaceData {
@@ -191,6 +196,54 @@ impl<U> SurfaceData<U> {
         child_guard.parent.as_ref().map(|p| p.clone_unchecked())
     }
 
+    /// Reorders a surface relative to one of its sibling
+    ///
+    /// Fails if `relative_to` is not a sibling or parent of `surface`.
+    pub unsafe fn reorder(surface: &wl_surface::WlSurface, to: Location,
+                          relative_to: &wl_surface::WlSurface)
+                          -> Result<(), ()> {
+        let parent = {
+            let data_mutex = Self::get_data(surface);
+            let data_guard = data_mutex.lock().unwrap();
+            data_guard
+                .parent
+                .as_ref()
+                .map(|p| p.clone_unchecked())
+                .unwrap()
+        };
+        if parent.equals(relative_to) {
+            // TODO: handle positioning relative to parent
+            return Ok(());
+        }
+
+        fn index_of(surface: &wl_surface::WlSurface, slice: &[wl_surface::WlSurface]) -> Option<usize> {
+            for (i, s) in slice.iter().enumerate() {
+                if s.equals(surface) {
+                    return Some(i);
+                }
+            }
+            None
+        }
+
+        let parent_mutex = Self::get_data(&parent);
+        let mut parent_guard = parent_mutex.lock().unwrap();
+        let my_index = index_of(surface, &parent_guard.children).unwrap();
+        let mut other_index = match index_of(surface, &parent_guard.children) {
+            Some(idx) => idx,
+            None => return Err(()),
+        };
+        let me = parent_guard.children.remove(my_index);
+        if my_index < other_index {
+            other_index -= 1;
+        }
+        let new_index = match to {
+            Location::Before => other_index,
+            Location::After => other_index + 1,
+        };
+        parent_guard.children.insert(new_index, me);
+        Ok(())
+    }
+
     /// Access the attributes associated with a surface
     ///
     /// Note that an internal lock is taken during access of this data,