element: Refactor element acquisition to be push based

src/utils/iced/mod.rs

@@ -35,7 +35,7 @@ use smithay::{
         renderer::{
             ImportMem, Renderer,
             element::{
-                AsRenderElements, Kind,
+                Kind,
                 memory::{MemoryRenderBuffer, MemoryRenderBufferRenderElement},
             },
         },
@@ -910,21 +910,18 @@ impl<P: Program + Send + 'static> SpaceElement for IcedElement<P> {
     }
 }
 
-impl<P, R> AsRenderElements<R> for IcedElement<P>
-where
-    P: Program + Send + 'static,
-    R: Renderer + ImportMem,
-    R::TextureId: Send + Clone + 'static,
-{
-    type RenderElement = MemoryRenderBufferRenderElement<R>;
-
-    fn render_elements<C: From<Self::RenderElement>>(
+impl<P: Program + Send + 'static> IcedElement<P> {
+    pub fn push_render_elements<R>(
         &self,
         renderer: &mut R,
         location: Point<i32, Physical>,
         mut scale: Scale<f64>,
         alpha: f32,
-    ) -> Vec<C> {
+        push: &mut dyn FnMut(MemoryRenderBufferRenderElement<R>),
+    ) where
+        R: Renderer + ImportMem,
+        R::TextureId: Send + Clone + 'static,
+    {
         let mut internal = self.0.lock().unwrap();
         // makes partial borrows easier
         let internal_ref = &mut *internal;
@@ -1055,11 +1052,10 @@ where
                 Kind::Unspecified,
             ) {
                 Ok(buffer) => {
-                    return vec![C::from(buffer)];
+                    push(buffer);
                 }
                 Err(err) => tracing::warn!("What? {:?}", err),
             }
         }
-        Vec::new()
     }
 }

src/utils/screenshot.rs

@@ -14,7 +14,7 @@ use smithay::{
 use tracing::warn;
 
 use crate::{
-    backend::render::{RendererRef, element::AsGlowRenderer, wayland::SurfaceRenderElement},
+    backend::render::{RendererRef, element::AsGlowRenderer},
     shell::element::CosmicSurface,
     state::{State, advertised_node_for_surface},
 };
@@ -27,7 +27,8 @@ pub fn screenshot_window(state: &mut State, surface: &CosmicSurface) {
         R::Error: Send + Sync + 'static,
     {
         let bbox = bbox_from_surface_tree(&window.wl_surface().unwrap(), (0, 0));
-        let elements = window.render_elements::<R, SurfaceRenderElement<R>>(
+        let mut elements = Vec::new();
+        window.push_render_elements(
             renderer,
             (-bbox.loc.x, -bbox.loc.y).into(),
             Scale::from(1.0),
@@ -36,6 +37,8 @@ pub fn screenshot_window(state: &mut State, surface: &CosmicSurface) {
             None,
             false,
             [0; 4],
+            &mut |elem| elements.push(elem),
+            None,
         );
 
         // TODO: 10-bit