Enable anti-aliasing for hw-accelerated lines

Draw anti-aliased lines with OpenGL by constructing a quad with
a border that fades out (to mimic fragment coverage).

Change-Id: Ib81a3e62d663acdf1b46b401ac4aa7ee9855cc7e

1 files changed, 28 insertions, 0 deletions

diff --git a/libs/hwui/Vertex.h b/libs/hwui/Vertex.h
index bbf4d4a..c120428 100644
--- a/libs/hwui/Vertex.h
+++ b/libs/hwui/Vertex.h
@@ -23,6 +23,18 @@ namespace uirenderer {
 /**
  * Simple structure to describe a vertex with a position and a texture.
  */
+struct Vertex {
+    float position[2];
+
+    static inline void set(Vertex* vertex, float x, float y) {
+        vertex[0].position[0] = x;
+        vertex[0].position[1] = y;
+    }
+}; // struct Vertex
+
+/**
+ * Simple structure to describe a vertex with a position and a texture.
+ */
 struct TextureVertex {
     float position[2];
     float texture[2];
@@ -40,6 +52,22 @@ struct TextureVertex {
     }
 }; // struct TextureVertex
 
+/**
+ * Simple structure to describe a vertex with a position and an alpha value.
+ */
+struct AlphaVertex : Vertex {
+    float alpha;
+
+    static inline void set(AlphaVertex* vertex, float x, float y, float alpha) {
+        Vertex::set(vertex, x, y);
+        vertex[0].alpha = alpha;
+    }
+
+    static inline void setColor(AlphaVertex* vertex, float alpha) {
+        vertex[0].alpha = alpha;
+    }
+}; // struct AlphaVertex
+
 }; // namespace uirenderer
 }; // namespace android