From dd934211af90a914b352b25168fcc9fbacf10809 Mon Sep 17 00:00:00 2001
From: Tristan Hume <tris.hume@gmail.com>
Date: Tue, 5 Dec 2017 21:09:58 -0500
Subject: [PATCH] Fixes #51 by introducing a variable for an early return
 boolean.

This works around a bug in the macOS Nvidia shader compiler
in 2014 rMBPs.
---
 shaders/gles2/common.inc.glsl | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/shaders/gles2/common.inc.glsl b/shaders/gles2/common.inc.glsl
index cec2cd44..41e3cedb 100644
--- a/shaders/gles2/common.inc.glsl
+++ b/shaders/gles2/common.inc.glsl
@@ -358,10 +358,6 @@ vec4 clipLineToPixelRow(vec2 p0, vec2 dP, float pixelCenterY, out float outPixel
     return vec4(p0 + dP * tY.x, dP * (tY.y - tY.x));
 }
 
-bool lineDoesNotPassThroughPixel(vec2 t) {
-    return t.x >= t.y;
-}
-
 /// Computes the area of the polygon covering the pixel with the given boundaries.
 ///
 /// The line must run left-to-right and must already be clipped to the left and right sides of the
@@ -383,7 +379,11 @@ float computeCoverage(vec2 p0X, vec2 dPX, float pixelCenterY, float winding) {
     //
     // This should be worth a branch because it's very common for fragment blocks to all hit this
     // path.
-    if (isNearZero(dP.x) && isNearZero(dP.y))
+    //
+    // The variable is required to work around a bug in the macOS Nvidia drivers.
+    // Without moving the condition in a variable, the early return is ignored. See #51.
+    bool lineDoesNotPassThroughPixel = isNearZero(dP.x) && isNearZero(dP.y);
+    if (lineDoesNotPassThroughPixel)
         return p0X.y < pixelTop ? winding * dPX.x : 0.0;
 
     // Calculate points A0-A2.