Optimised hwui rounded corners shader

This is a ~2x performance increase for the rounded corners shader which
was previously shader limited even on many high-end GPUs. It simplifies
the calculations by pre-dividing by the radius, which also allows to
maintain mediump/FP16 precision (this improves performance and might
improve image quality on GPUs that don't support highp e.g. Mali-400).
It also uses a conditional in the shader to save much of the work on
the vast majority of pixels which are not close to the corners.

Test: manual - visual inspection on fugu (nexus player)

Change-Id: I38f491cfb006e2991ef0b9d6b3d67d2c4d328d44

1 files changed, 11 insertions, 5 deletions

diff --git a/libs/hwui/renderstate/RenderState.cpp b/libs/hwui/renderstate/RenderState.cpp
index c4e8e4f2df6e..2a3a9f3635ca 100644
--- a/libs/hwui/renderstate/RenderState.cpp
+++ b/libs/hwui/renderstate/RenderState.cpp
@@ -274,14 +274,20 @@ void RenderState::render(const Glop& glop, const Matrix4& orthoMatrix) {
         // TODO: avoid query, and cache values (or RRCS ptr) in program
         const RoundRectClipState* state = glop.roundRectClipState;
         const Rect& innerRect = state->innerRect;
-        glUniform4f(fill.program->getUniform("roundRectInnerRectLTRB"),
-                innerRect.left, innerRect.top,
-                innerRect.right, innerRect.bottom);
-        glUniformMatrix4fv(fill.program->getUniform("roundRectInvTransform"),
-                1, GL_FALSE, &state->matrix.data[0]);
 
         // add half pixel to round out integer rect space to cover pixel centers
         float roundedOutRadius = state->radius + 0.5f;
+
+        // Divide by the radius to simplify the calculations in the fragment shader
+        // roundRectPos is also passed from vertex shader relative to top/left & radius
+        glUniform4f(fill.program->getUniform("roundRectInnerRectLTWH"),
+                innerRect.left / roundedOutRadius, innerRect.top / roundedOutRadius,
+                (innerRect.right - innerRect.left) / roundedOutRadius,
+                (innerRect.bottom - innerRect.top) / roundedOutRadius);
+
+        glUniformMatrix4fv(fill.program->getUniform("roundRectInvTransform"),
+                1, GL_FALSE, &state->matrix.data[0]);
+
         glUniform1f(fill.program->getUniform("roundRectRadius"),
                 roundedOutRadius);
     }