Copy distance field shader changes to OpenGL runtime

Also fixes the OpenGL runtime to use alpha channel for the glyph texture
when using ES2.

Task-number: QT3DS-3343
Change-Id: Ia37c341802e504da21ebeaff6f3f1f5b50bd1bfe
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Antti Määttä <antti.maatta@qt.io>
 

1 files changed, 14 insertions, 2 deletions

diff --git a/src/Runtime/res/effectlib/distancefieldtext.vert b/src/Runtime/res/effectlib/distancefieldtext.vert
index 01024c6b..f6b2de41 100644
--- a/src/Runtime/res/effectlib/distancefieldtext.vert
+++ b/src/Runtime/res/effectlib/distancefieldtext.vert
@@ -1,3 +1,9 @@
+#ifdef GL_OES_standard_derivatives
+#  extension GL_OES_standard_derivatives : enable
+#else
+#  define use_fallback
+#endif
+
 uniform highp mat4 mvp;
 uniform highp float fontScale;
 uniform int textureWidth;
@@ -7,6 +13,8 @@ attribute highp vec3 vCoord;
 attribute highp vec2 tCoord;
 
 varying highp vec2 sampleCoord;
+
+#ifdef use_fallback
 varying highp vec2 alphas;
 
 highp float thresholdFunc(highp float scale)
@@ -55,11 +63,15 @@ highp float determinant(highp mat4 m)
     det            -= m[3][0] * determinantOfSubmatrix(m, 0, 1, 2, 1, 2, 3);
     return det;
 }
+#endif
 
 void main()
 {
-    highp float scale = fontScale * sqrt(abs(determinant(mvp)));
+#ifdef use_fallback
+    highp float scale = fontScale * pow(abs(determinant(mvp)), 1.0 / 3.0);
     alphas = alphaRange(scale);
-    sampleCoord = tCoord * vec2(1.0 / highp float(textureWidth), 1.0 / highp float(textureHeight));
+#endif
+
+    sampleCoord = tCoord * vec2(1.0 / float(textureWidth), 1.0 / float(textureHeight));
     gl_Position = mvp * vec4(vCoord, 1.0);
 }