From 57f45d99419358ee35734b31037de494a4c944cc Mon Sep 17 00:00:00 2001
From: Victor Brekenfeld <github@drakulix.de>
Date: Sat, 27 Nov 2021 20:17:18 +0100
Subject: [PATCH] renderer: Allow clear calls on specific regions

---
 CHANGELOG.md                      | 1 +
 anvil/src/render.rs               | 2 +-
 anvil/src/udev.rs                 | 2 +-
 src/backend/renderer/gles2/mod.rs | 9 ++++++++-
 src/backend/renderer/mod.rs       | 2 +-
 5 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b67e92..81eda76 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@
 - `X11Surface::buffer` now additionally returns the age of the buffer
 - `X11Surface` now has an explicit `submit` function
 - `X11Surface` is now multi-window capable.
+- `Renderer::clear` now expects a second argument to optionally only clear parts of the buffer/surface
 
 ### Additions
 
diff --git a/anvil/src/render.rs b/anvil/src/render.rs
index 4848c45..0d26b30 100644
--- a/anvil/src/render.rs
+++ b/anvil/src/render.rs
@@ -24,7 +24,7 @@ pub fn render_layers_and_windows(
     output_scale: f32,
     logger: &Logger,
 ) -> Result<(), SwapBuffersError> {
-    frame.clear([0.8, 0.8, 0.9, 1.0])?;
+    frame.clear([0.8, 0.8, 0.9, 1.0], None)?;
 
     for layer in [Layer::Background, Layer::Bottom] {
         draw_layers(
diff --git a/anvil/src/udev.rs b/anvil/src/udev.rs
index 957a419..f5a63bc 100644
--- a/anvil/src/udev.rs
+++ b/anvil/src/udev.rs
@@ -873,7 +873,7 @@ fn initial_render(surface: &mut RenderSurface, renderer: &mut Gles2Renderer) ->
     renderer
         .render((1, 1).into(), Transform::Normal, |_, frame| {
             frame
-                .clear([0.8, 0.8, 0.9, 1.0])
+                .clear([0.8, 0.8, 0.9, 1.0], None)
                 .map_err(Into::<SwapBuffersError>::into)
         })
         .map_err(Into::<SwapBuffersError>::into)
diff --git a/src/backend/renderer/gles2/mod.rs b/src/backend/renderer/gles2/mod.rs
index 3a8c49b..5c15b3a 100644
--- a/src/backend/renderer/gles2/mod.rs
+++ b/src/backend/renderer/gles2/mod.rs
@@ -1121,10 +1121,17 @@ impl Frame for Gles2Frame {
     type Error = Gles2Error;
     type TextureId = Gles2Texture;
 
-    fn clear(&mut self, color: [f32; 4]) -> Result<(), Self::Error> {
+    fn clear(&mut self, color: [f32; 4], at: Option<Rectangle<i32, Physical>>) -> Result<(), Self::Error> {
         unsafe {
+            if let Some(rect) = at {
+                self.gl.Enable(ffi::SCISSOR_TEST);
+                self.gl.Scissor(rect.loc.x, rect.loc.y, rect.size.w, rect.size.h);
+            }
             self.gl.ClearColor(color[0], color[1], color[2], color[3]);
             self.gl.Clear(ffi::COLOR_BUFFER_BIT);
+            if at.is_some() {
+                self.gl.Disable(ffi::SCISSOR_TEST);
+            }
         }
 
         Ok(())
diff --git a/src/backend/renderer/mod.rs b/src/backend/renderer/mod.rs
index a975894..f2c8ee6 100644
--- a/src/backend/renderer/mod.rs
+++ b/src/backend/renderer/mod.rs
@@ -171,7 +171,7 @@ pub trait Frame {
     ///
     /// This operation is only valid in between a `begin` and `finish`-call.
     /// If called outside this operation may error-out, do nothing or modify future rendering results in any way.
-    fn clear(&mut self, color: [f32; 4]) -> Result<(), Self::Error>;
+    fn clear(&mut self, color: [f32; 4], at: Option<Rectangle<i32, Physical>>) -> Result<(), Self::Error>;
 
     /// Render a texture to the current target as a flat 2d-plane at a given
     /// position and applying the given transformation with the given alpha value.