1 files changed, 32 insertions, 14 deletions

diff --git a/src/Runtime/res/effectlib/distancefieldtext_dropshadow.frag b/src/Runtime/res/effectlib/distancefieldtext_dropshadow.frag
index 94b277cd..fdb68bac 100644
--- a/src/Runtime/res/effectlib/distancefieldtext_dropshadow.frag
+++ b/src/Runtime/res/effectlib/distancefieldtext_dropshadow.frag
@@ -1,29 +1,47 @@
+#ifdef GL_OES_standard_derivatives
+#  extension GL_OES_standard_derivatives : enable
+#else
+#  define use_fallback
+#endif
+
 varying highp vec2 sampleCoord;
-varying highp vec2 alphas;
 varying highp vec2 shadowSampleCoord;
 varying highp vec4 normalizedTextureBounds;
 
+#ifdef use_fallback
+varying highp vec2 alphas;
+#endif
+
 uniform sampler2D _qt_texture;
 uniform highp vec4 color;
 uniform highp vec4 shadowColor;
 
 void main()
 {
-    highp float shadowAlpha = smoothstep(alphas.x,
-                                         alphas.y,
-                                         texture2D(_qt_texture,
-                                                   clamp(shadowSampleCoord,
-                                                         normalizedTextureBounds.xy,
-                                                         normalizedTextureBounds.zw)).a);
+    highp float shadowDistance = texture2D(_qt_texture,
+                                           clamp(shadowSampleCoord,
+                                                 normalizedTextureBounds.xy,
+                                                 normalizedTextureBounds.zw)).a;
+#ifdef use_fallback
+    highp float shadowAlpha = smoothstep(alphas.x, alphas.y, shadowDistance);
+#else
+    highp float shadowDistanceD = fwidth(shadowDistance);
+    highp float shadowAlpha = smoothstep(0.5 - shadowDistanceD, 0.5, shadowDistance);
+#endif
+
     highp vec4 shadowPixel = color * shadowColor * shadowAlpha;
 
-    highp float textAlpha = smoothstep(alphas.x,
-                                       alphas.y,
-                                       texture2D(_qt_texture,
-                                                 clamp(sampleCoord,
-                                                       normalizedTextureBounds.xy,
-                                                       normalizedTextureBounds.zw)).a);
-    highp vec4 textPixel = color * textAlpha;
+    highp float textDistance = texture2D(_qt_texture,
+                                         clamp(sampleCoord,
+                                               normalizedTextureBounds.xy,
+                                               normalizedTextureBounds.zw)).a;
+#ifdef use_fallback
+    highp float textAlpha = smoothstep(alphas.x, alphas.y, textDistance);
+#else
+    highp float textDistanceD = fwidth(textDistance);
+    highp float textAlpha = smoothstep(0.5 - textDistanceD, 0.5, textDistance);
+#endif
 
+    highp vec4 textPixel = color * textAlpha;
     gl_FragColor = mix(shadowPixel, textPixel, textPixel.a);
 }