Draw decorations on commit, skip drawing if params unchanged

src/deco.rs

@@ -8,7 +8,6 @@ use wl_proxy::{
             WpCursorShapeDeviceV1, WpCursorShapeDeviceV1Shape,
         },
         wayland::{
-            wl_buffer::WlBuffer,
             wl_pointer::WlPointerButtonState,
             wl_seat::WlSeat,
             wl_subsurface::WlSubsurface,
@@ -20,8 +19,14 @@ use wl_proxy::{
 
 use crate::{buffer::SimpleBufferPool, globals::Globals, util::Bounds};
 
+#[derive(Default, Debug, Clone, PartialEq)]
+struct DecoParams {
+    bounds: Bounds,
+}
+
 pub struct Deco {
-    bounds: RefCell<Bounds>,
+    last_params: RefCell<DecoParams>,
+    next_params: RefCell<DecoParams>,
     top_size: i32,
     border_size: i32,
 
@@ -34,10 +39,11 @@ pub struct Deco {
 
 impl Deco {
     fn resize_anchor(&self, x: i32, y: i32) -> XdgToplevelResizeEdge {
+        let bounds = &self.last_params.borrow().bounds;
         let n = y < self.border_size;
-        let e = x >= self.bounds.borrow().width + self.border_size;
+        let e = x >= bounds.width + self.border_size;
         let w = x < self.border_size;
-        let s = y >= self.bounds.borrow().height + self.border_size;
+        let s = y >= bounds.height + self.border_size;
         if n && e {
             XdgToplevelResizeEdge::TOP_RIGHT
         } else if n && w {
@@ -126,6 +132,7 @@ impl Deco {
         globals: &Rc<Globals>,
     ) -> Rc<Deco> {
         let wl_surface = globals.wl_compositor.new_send_create_surface();
+        log::debug!("creating deco for surface {host_surface:?} -> {wl_surface:?}");
         wl_surface.set_forward_to_client(false);
         let subsurface = globals
             .wl_subcompositor
@@ -135,12 +142,8 @@ impl Deco {
         let pool = SimpleBufferPool::new(globals, 1, 1).unwrap();
         let args = crate::ARGS.get().unwrap();
         let deco = Rc::new(Deco {
-            bounds: RefCell::new(Bounds {
-                x: 0,
-                y: 0,
-                width: 10,
-                height: 10,
-            }),
+            last_params: RefCell::new(Default::default()),
+            next_params: RefCell::new(Default::default()),
             top_size: args.thickness as i32, // TODO: title
             border_size: args.thickness as i32,
             wl_surface: wl_surface.clone(),
@@ -159,17 +162,24 @@ impl Deco {
         y: i32,
         width: i32,
         height: i32,
-    ) -> eyre::Result<(i32, i32, i32, i32)> {
-        self.bounds.replace(Bounds {
+    ) -> (i32, i32, i32, i32) {
+        log::debug!(
+            "decoration {:?} handling geometry {width}x{height} @ {x},{y}",
+            self.wl_surface
+        );
+        self.next_params.borrow_mut().bounds = Bounds {
             x,
             y,
             width,
             height,
-        });
-        self.draw()?;
+        };
         let width = width + self.border_size * 2;
         let height = height + self.top_size + self.border_size;
-        Ok((x - self.border_size, y - self.top_size, width, height))
+        (x - self.border_size, y - self.top_size, width, height)
+    }
+
+    pub fn handle_commit(&self) -> eyre::Result<()> {
+        self.draw()
     }
 
     pub fn transform_configure(&self, width: i32, height: i32) -> (i32, i32) {
@@ -190,8 +200,18 @@ impl Deco {
         (x + self.border_size, y + self.top_size)
     }
 
-    fn draw(&self) -> eyre::Result<Rc<WlBuffer>> {
-        let bounds = self.bounds.borrow();
+    fn draw(&self) -> eyre::Result<()> {
+        let params = self.next_params.borrow();
+        if *params == *self.last_params.borrow() {
+            log::debug!("decoration {:?} unchanged", self.wl_surface);
+            return Ok(());
+        }
+        log::debug!(
+            "decoration {:?} changed to {params:?}, drawing",
+            self.wl_surface
+        );
+        self.last_params.replace(params.clone());
+        let bounds = &params.bounds;
         let (width, height) = self.transform_size(bounds.width, bounds.height);
 
         let mut pool = self.pool.borrow_mut();
@@ -224,6 +244,6 @@ impl Deco {
             .send_set_position(bounds.x - self.border_size, bounds.y - self.top_size);
         self.wl_surface.send_commit();
         // let _ = self.globals.wl_display.new_send_sync();
-        Ok(buf)
+        Ok(())
     }
 }