From d2ba81b0a571d63f52507bcaea54ccde4f044613 Mon Sep 17 00:00:00 2001
From: Dongdong Zhou <dzhou121@gmail.com>
Date: Tue, 29 Aug 2023 20:32:35 +0100
Subject: [PATCH] Support rounded scissor rects

---
 src/lib.rs      | 18 ++++++++++++++++++
 src/shader.wgsl |  9 ++++++---
 tests/tests.rs  | 21 +++++++++++++++++++++
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 5ab7c38..9a28215 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -58,6 +58,8 @@ pub(crate) struct Scissor {
     pub xform: WorldToLocal,
     pub origin: [f32; 2],
     pub size: [f32; 2],
+    pub radius: f32,
+    pub padding: f32,
 }
 
 impl Scissor {
@@ -66,6 +68,8 @@ impl Scissor {
             xform: WorldToLocal::identity(),
             origin: [-10000.0, -10000.0],
             size: [20000.0, 20000.0],
+            radius: 0.0,
+            padding: 0.0,
         }
     }
 }
@@ -846,6 +850,20 @@ impl Vger {
                 m.xform = xform;
                 m.origin = rect.origin.to_array();
                 m.size = rect.size.to_array();
+                m.radius = 0.0;
+            }
+        }
+    }
+
+    /// Sets the current scissor to a rounded rect.
+    pub fn rounded_scissor(&mut self, rect: LocalRect, radius: f32) {
+        if let Some(m) = self.scissor_stack.last_mut() {
+            *m = Scissor::new();
+            if let Some(xform) = self.tx_stack.last().unwrap().inverse() {
+                m.xform = xform;
+                m.origin = rect.origin.to_array();
+                m.size = rect.size.to_array();
+                m.radius = radius;
             }
         }
     }
diff --git a/src/shader.wgsl b/src/shader.wgsl
index 12cad64..9bf38ba 100644
--- a/src/shader.wgsl
+++ b/src/shader.wgsl
@@ -576,6 +576,8 @@ struct Scissor {
     xform: PackedMat3x2,
     origin: vec2<f32>,
     size: vec2<f32>,
+    radius: f32,
+    padding: f32,
 };
 
 struct Scissors {
@@ -591,10 +593,11 @@ fn scissor_mask(scissor: Scissor, p: vec2<f32>) -> f32 {
     let pp = (M * vec3<f32>(p, 1.0)).xy;
     let center = scissor.origin + 0.5 * scissor.size;
     let size = scissor.size;
-    if sdBox(pp - center, 0.5 * size, 0.0) < 0.0 {
-        return 1.0;
+    let value = 1.0 - sdBox(pp - center, 0.5 * size, scissor.radius);
+    if scissor.radius > 0.0 {
+        return value;
     } else {
-        return 0.0;
+        return round(value);
     }
 }
 
diff --git a/tests/tests.rs b/tests/tests.rs
index a3a4d2c..d598db0 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -433,6 +433,27 @@ fn test_scissor() {
     assert!(png_not_black(png_name));
 }
 
+#[test]
+fn test_rounded_scissor() {
+    let (device, queue) = setup();
+
+    let mut vger = Vger::new(
+        device.clone(),
+        queue.clone(),
+        wgpu::TextureFormat::Rgba8UnormSrgb,
+    );
+
+    vger.begin(512.0, 512.0, 2.0);
+
+    vger.rounded_scissor(euclid::rect(200.0, 200.0, 100.0, 100.0), 20.0);
+    let cyan = vger.color_paint(Color::WHITE);
+    vger.fill_rect(euclid::rect(100.0, 100.0, 300.0, 300.0), 10.0, cyan);
+
+    let png_name = "rounded_scissor.png";
+    render_test(&mut vger, &device, &queue, png_name, true);
+    assert!(png_not_black(png_name));
+}
+
 #[test]
 fn test_scissor_text() {
     let (device, queue) = setup();