Conservatively estimate geometry bounds

bug:10761696

Avoids a case where a rect with top coordinate of (e.g.) 0.51f is
assumed to not draw in the first row of pixels, which leads to it not
being clipped. Since rounding can cause it to render in this first
pixel anyway, we very slightly expand geometry bounds.

Now, in ambiguous cases, the geometry bounds are expanded so clipping
is more likely to happen.

Change-Id: I119b7c7720de07bac1634549724ffb63935567fc

1 files changed, 9 insertions, 0 deletions

diff --git a/libs/hwui/Vertex.h b/libs/hwui/Vertex.h
index c06762f7609a..790d4fcb1c61 100644
--- a/libs/hwui/Vertex.h
+++ b/libs/hwui/Vertex.h
@@ -26,6 +26,15 @@ namespace uirenderer {
  * Simple structure to describe a vertex with a position and a texture.
  */
 struct Vertex {
+    /**
+     * Fudge-factor used to disambiguate geometry pixel positioning.
+     *
+     * Used to offset lines and points to avoid ambiguous intersection with pixel centers (see
+     * Program::set()), and used to make geometry damage rect calculation conservative (see
+     * Rect::snapGeometryToPixelBoundaries())
+     */
+    static const float gGeometryFudgeFactor = 0.0656f;
+
     float position[2];
 
     static inline void set(Vertex* vertex, float x, float y) {