From b201e19cc7a3536c184014456e79b14af307d4c3 Mon Sep 17 00:00:00 2001
From: Nathan Adams <dinnerbone@dinnerbone.com>
Date: Thu, 20 Jul 2023 01:23:31 +0200
Subject: [PATCH] wgpu: Don't create an extra fresh texture for applying
 filters to a CAB

---
 core/src/display_object.rs           |  1 +
 render/src/filters.rs                | 11 +++++++++++
 render/wgpu/src/backend.rs           | 19 +++++++++++++------
 swf/src/types/blur_filter.rs         |  4 ++++
 swf/src/types/color_matrix_filter.rs |  6 ++++++
 5 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/core/src/display_object.rs b/core/src/display_object.rs
index cb3173a1c..a23fd0310 100644
--- a/core/src/display_object.rs
+++ b/core/src/display_object.rs
@@ -747,6 +747,7 @@ pub fn render_base<'gc>(this: DisplayObject<'gc>, context: &mut RenderContext<'_
         let bounds: Rectangle<Twips> = this.bounds_with_transform(&base_transform.matrix);
         let name = this.name();
         let mut filters: Vec<Filter> = this.filters();
+        filters.retain(|f| !f.impotent());
 
         if let Some(cache) = this.base_mut(context.gc_context).bitmap_cache_mut() {
             let width = bounds.width().to_pixels().ceil().max(0.0);
diff --git a/render/src/filters.rs b/render/src/filters.rs
index 352a6c807..bee7c4fc8 100644
--- a/render/src/filters.rs
+++ b/render/src/filters.rs
@@ -59,6 +59,17 @@ impl Filter {
             _ => {}
         }
     }
+
+    /// Checks if this filter is impotent.
+    /// Impotent filters will have no effect if applied, and can safely be skipped.
+    pub fn impotent(&self) -> bool {
+        // TODO: There's more cases here, find them!
+        match self {
+            Filter::BlurFilter(filter) => filter.impotent(),
+            Filter::ColorMatrixFilter(filter) => filter.impotent(),
+            _ => false,
+        }
+    }
 }
 
 impl From<&swf::Filter> for Filter {
diff --git a/render/wgpu/src/backend.rs b/render/wgpu/src/backend.rs
index f11b1d4c1..ff0d1e755 100644
--- a/render/wgpu/src/backend.rs
+++ b/render/wgpu/src/backend.rs
@@ -548,13 +548,20 @@ impl<T: RenderTarget + 'static> RenderBackend for WgpuRenderBackend<T> {
                     &mut self.offscreen_texture_pool,
                 );
             } else {
+                // We're relying on there being no impotent filters here,
+                // so that we can safely start by using the actual CAB texture.
+                // It's guaranteed that at least one filter would have used it and moved the target to something else,
+                // letting us safely copy back to it later.
                 let mut target = surface.draw_commands(
-                    RenderTargetMode::FreshWithColor(wgpu::Color {
-                        r: f64::from(entry.clear.r) / 255.0,
-                        g: f64::from(entry.clear.g) / 255.0,
-                        b: f64::from(entry.clear.b) / 255.0,
-                        a: f64::from(entry.clear.a) / 255.0,
-                    }),
+                    RenderTargetMode::ExistingWithColor(
+                        texture.texture.clone(),
+                        wgpu::Color {
+                            r: f64::from(entry.clear.r) / 255.0,
+                            g: f64::from(entry.clear.g) / 255.0,
+                            b: f64::from(entry.clear.b) / 255.0,
+                            a: f64::from(entry.clear.a) / 255.0,
+                        },
+                    ),
                     &self.descriptors,
                     &self.meshes,
                     entry.commands,
diff --git a/swf/src/types/blur_filter.rs b/swf/src/types/blur_filter.rs
index 3a1e2ed30..e5392c877 100644
--- a/swf/src/types/blur_filter.rs
+++ b/swf/src/types/blur_filter.rs
@@ -18,6 +18,10 @@ impl BlurFilter {
         self.blur_x *= Fixed16::from_f32(x);
         self.blur_y *= Fixed16::from_f32(y);
     }
+
+    pub fn impotent(&self) -> bool {
+        self.blur_x == Fixed16::ZERO && self.blur_y == Fixed16::ZERO
+    }
 }
 
 bitflags! {
diff --git a/swf/src/types/color_matrix_filter.rs b/swf/src/types/color_matrix_filter.rs
index b0345fbd1..4a543596f 100644
--- a/swf/src/types/color_matrix_filter.rs
+++ b/swf/src/types/color_matrix_filter.rs
@@ -15,3 +15,9 @@ impl Default for ColorMatrixFilter {
         }
     }
 }
+
+impl ColorMatrixFilter {
+    pub fn impotent(&self) -> bool {
+        self == &Default::default()
+    }
+}