Use correct alpha range for the distance field outlined text.

The alpha treshold values used in the outline shader were hard-coded. It
should use the same logic as in the normal text shader, using the
ThresholdFunc and the AntialiasingSpreadFunc for calculating these
values.

Change-Id: I0e6f38644692cc7a8a4cee1e8e60622fe289d615
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

1 files changed, 14 insertions, 8 deletions

diff --git a/src/quick/scenegraph/qsgdistancefieldglyphnode_p.cpp b/src/quick/scenegraph/qsgdistancefieldglyphnode_p.cpp
index d409cea81a..45fc0f5c6d 100644
--- a/src/quick/scenegraph/qsgdistancefieldglyphnode_p.cpp
+++ b/src/quick/scenegraph/qsgdistancefieldglyphnode_p.cpp
@@ -316,7 +316,7 @@ protected:
     virtual void initialize();
     virtual const char *fragmentShader() const;
 
-    void updateOutlineAlphaRange(int dfRadius);
+    void updateOutlineAlphaRange(ThresholdFunc thresholdFunc, AntialiasingSpreadFunc spreadFunc, int dfRadius);
 
     int m_outlineAlphaMax0_id;
     int m_outlineAlphaMax1_id;
@@ -351,14 +351,18 @@ void DistanceFieldOutlineTextMaterialShader::initialize()
     m_outlineAlphaMax1_id = program()->uniformLocation("outlineAlphaMax1");
 }
 
-void DistanceFieldOutlineTextMaterialShader::updateOutlineAlphaRange(int dfRadius)
+void DistanceFieldOutlineTextMaterialShader::updateOutlineAlphaRange(ThresholdFunc thresholdFunc,
+                                                                     AntialiasingSpreadFunc spreadFunc,
+                                                                     int dfRadius)
 {
-    qreal outlineLimit = qMax(qreal(0.2), qreal(0.5 - 0.5 / dfRadius / m_fontScale));
+    float combinedScale = m_fontScale * m_matrixScale;
+    float base = thresholdFunc(combinedScale);
+    float range = spreadFunc(combinedScale);
+    float outlineLimit = qMax(0.2f, base - 0.5f / dfRadius / m_fontScale);
 
-    qreal combinedScale = m_fontScale * m_matrixScale;
-    qreal alphaMin = qMax(0.0, 0.5 - 0.07 / combinedScale);
-    qreal styleAlphaMin0 = qMax(0.0, outlineLimit - 0.07 / combinedScale);
-    qreal styleAlphaMin1 = qMin(qreal(outlineLimit + 0.07 / combinedScale), alphaMin);
+    float alphaMin = qMax(0.0f, base - range);
+    float styleAlphaMin0 = qMax(0.0f, outlineLimit - range);
+    float styleAlphaMin1 = qMin(outlineLimit + range, alphaMin);
     program()->setUniformValue(m_outlineAlphaMax0_id, GLfloat(styleAlphaMin0));
     program()->setUniformValue(m_outlineAlphaMax1_id, GLfloat(styleAlphaMin1));
 }
@@ -373,7 +377,9 @@ void DistanceFieldOutlineTextMaterialShader::updateState(const RenderState &stat
     if (oldMaterial == 0
             || material->fontScale() != oldMaterial->fontScale()
             || state.isMatrixDirty())
-        updateOutlineAlphaRange(material->glyphCache()->distanceFieldRadius());
+        updateOutlineAlphaRange(material->glyphCache()->manager()->thresholdFunc(),
+                                material->glyphCache()->manager()->antialiasingSpreadFunc(),
+                                material->glyphCache()->distanceFieldRadius());
 }