Add Lighten and Darken composite ops

Cargo.lock

@@ -219,7 +219,7 @@ dependencies = [
 name = "canvas_metal_minimal"
 version = "0.1.0"
 dependencies = [
- "foreign-types 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "foreign-types 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "gl 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "metal 0.17.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "objc 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)",

canvas/src/lib.rs

@@ -232,6 +232,7 @@ impl CanvasRenderingContext2D {
 
     fn push_path(&mut self, outline: Outline, paint_id: PaintId, fill_rule: FillRule) {
         let clip_path = self.current_state.clip_path;
+        let blend_mode = self.current_state.global_composite_operation.to_blend_mode();
 
         if !self.current_state.shadow_paint.is_fully_transparent() {
             let paint = self.current_state.resolve_paint(&self.current_state.shadow_paint);
@@ -243,7 +244,7 @@ impl CanvasRenderingContext2D {
                                                paint_id,
                                                clip_path,
                                                fill_rule,
-                                               BlendMode::SourceOver,
+                                               blend_mode,
                                                String::new()))
         }
 
@@ -251,7 +252,7 @@ impl CanvasRenderingContext2D {
                                            paint_id,
                                            clip_path,
                                            fill_rule,
-                                           BlendMode::SourceOver,
+                                           blend_mode,
                                            String::new()))
     }
 
@@ -284,6 +285,16 @@ impl CanvasRenderingContext2D {
         self.current_state.global_alpha = new_global_alpha;
     }
 
+    #[inline]
+    pub fn global_composite_operation(&self) -> CompositeOperation {
+        self.current_state.global_composite_operation
+    }
+
+    #[inline]
+    pub fn set_global_composite_operation(&mut self, new_composite_operation: CompositeOperation) {
+        self.current_state.global_composite_operation = new_composite_operation;
+    }
+
     // The canvas state
 
     #[inline]
@@ -316,6 +327,7 @@ struct State {
     shadow_offset: Vector2F,
     text_align: TextAlign,
     global_alpha: f32,
+    global_composite_operation: CompositeOperation,
     clip_path: Option<ClipPathId>,
 }
 
@@ -337,6 +349,7 @@ impl State {
             shadow_offset: Vector2F::default(),
             text_align: TextAlign::Left,
             global_alpha: 1.0,
+            global_composite_operation: CompositeOperation::SourceOver,
             clip_path: None,
         }
     }
@@ -507,3 +520,20 @@ pub enum LineJoin {
     Bevel,
     Round,
 }
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum CompositeOperation {
+    SourceOver,
+    Lighten,
+    Darken,
+}
+
+impl CompositeOperation {
+    fn to_blend_mode(self) -> BlendMode {
+        match self {
+            CompositeOperation::SourceOver => BlendMode::SourceOver,
+            CompositeOperation::Lighten => BlendMode::Lighten,
+            CompositeOperation::Darken => BlendMode::Darken,
+        }
+    }
+}

content/src/effects.rs

@@ -66,6 +66,8 @@ pub enum CompositeOp {
 pub enum BlendMode {
     SourceOver,
     Clear,
+    Lighten,
+    Darken,
 }
 
 #[derive(Clone, Copy, PartialEq, Debug)]
@@ -92,6 +94,7 @@ impl BlendMode {
     pub fn occludes_backdrop(self) -> bool {
         match self {
             BlendMode::SourceOver | BlendMode::Clear => true,
+            BlendMode::Lighten | BlendMode::Darken => false,
         }
     }
 }

examples/canvas_metal_minimal/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Patrick Walton <pcwalton@mimiga.net>"]
 edition = "2018"
 
 [dependencies]
-foreign-types = "0.5"
+foreign-types = "0.3"
 gl = "0.14"
 metal = "0.17"
 objc = "0.2"

gl/src/lib.rs

@@ -965,6 +965,7 @@ impl BlendFactorExt for BlendFactor {
             BlendFactor::One => gl::ONE,
             BlendFactor::SrcAlpha => gl::SRC_ALPHA,
             BlendFactor::OneMinusSrcAlpha => gl::ONE_MINUS_SRC_ALPHA,
+            BlendFactor::DestColor => gl::DST_COLOR,
         }
     }
 }

gpu/src/lib.rs

@@ -226,6 +226,7 @@ pub enum BlendFactor {
     One,
     SrcAlpha,
     OneMinusSrcAlpha,
+    DestColor,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]

metal/src/lib.rs

@@ -1170,6 +1170,7 @@ impl BlendFactorExt for BlendFactor {
             BlendFactor::One => MTLBlendFactor::One,
             BlendFactor::SrcAlpha => MTLBlendFactor::SourceAlpha,
             BlendFactor::OneMinusSrcAlpha => MTLBlendFactor::OneMinusSourceAlpha,
+            BlendFactor::DestColor => MTLBlendFactor::DestinationColor,
         }
     }
 }

renderer/src/gpu/renderer.rs

@@ -1151,6 +1151,24 @@ impl BlendModeExt for BlendMode {
                     ..BlendState::default()
                 }
             }
+            BlendMode::Lighten => {
+                BlendState {
+                    src_rgb_factor: BlendFactor::SrcAlpha,
+                    dest_rgb_factor: BlendFactor::OneMinusSrcAlpha,
+                    src_alpha_factor: BlendFactor::One,
+                    dest_alpha_factor: BlendFactor::One,
+                    op: BlendOp::Max,
+                }
+            }
+            BlendMode::Darken => {
+                BlendState {
+                    src_rgb_factor: BlendFactor::SrcAlpha,
+                    dest_rgb_factor: BlendFactor::OneMinusSrcAlpha,
+                    src_alpha_factor: BlendFactor::One,
+                    dest_alpha_factor: BlendFactor::One,
+                    op: BlendOp::Min,
+                }
+            }
         }
     }
 }