Added support for six-parameter radial gradients.

The extended radial gradients conform to the radial gradient
specification in HTML 5 canvas.

Task-number: QTBUG-14075
Reviewed-by: Andreas Kling
(cherry picked from commit da55c1ea92474e989e5582b02815936bbf584405)

4 files changed, 25 insertions, 5 deletions

diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
index 8068aa8524..207ab3d07c 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
@@ -495,6 +495,8 @@ GLuint QGLEngineShaderManager::getUniformLocation(Uniform id)
         "fmp",
         "fmp2_m_radius2",
         "inverse_2_fmp2_m_radius2",
+        "sqrfr",
+        "bradius",
         "invertedTextureSize",
         "brushTransform",
         "brushTexture",
diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
index 7cc9dc3bd4..bf2fe429c3 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
@@ -442,6 +442,8 @@ public:
         Fmp,
         Fmp2MRadius2,
         Inverse2Fmp2MRadius2,
+        SqrFr,
+        BRadius,
         InvertedTextureSize,
         BrushTransform,
         BrushTexture,
diff --git a/src/opengl/gl2paintengineex/qglengineshadersource_p.h b/src/opengl/gl2paintengineex/qglengineshadersource_p.h
index fc8b9ef4db..9362c5812b 100644
--- a/src/opengl/gl2paintengineex/qglengineshadersource_p.h
+++ b/src/opengl/gl2paintengineex/qglengineshadersource_p.h
@@ -241,6 +241,7 @@ static const char* const qglslPositionWithRadialGradientBrushVertexShader = "\n\
     uniform   mediump vec2      halfViewportSize; \n\
     uniform   highp   mat3      brushTransform; \n\
     uniform   highp   vec2      fmp; \n\
+    uniform   highp   vec3      bradius; \n\
     varying   highp   float     b; \n\
     varying   highp   vec2      A; \n\
     void setPosition(void) \n\
@@ -253,7 +254,7 @@ static const char* const qglslPositionWithRadialGradientBrushVertexShader = "\n\
         mediump float invertedHTexCoordsZ = 1.0 / hTexCoords.z; \n\
         gl_Position = vec4(gl_Position.xy * invertedHTexCoordsZ, 0.0, invertedHTexCoordsZ); \n\
         A = hTexCoords.xy * invertedHTexCoordsZ; \n\
-        b = 2.0 * dot(A, fmp); \n\
+        b = bradius.x + 2.0 * dot(A, fmp); \n\
     }\n";
 
 static const char* const qglslAffinePositionWithRadialGradientBrushVertexShader
@@ -263,13 +264,22 @@ static const char* const qglslRadialGradientBrushSrcFragmentShader = "\n\
     uniform           sampler2D brushTexture; \n\
     uniform   highp   float     fmp2_m_radius2; \n\
     uniform   highp   float     inverse_2_fmp2_m_radius2; \n\
+    uniform   highp   float     sqrfr; \n\
     varying   highp   float     b; \n\
     varying   highp   vec2      A; \n\
+    uniform   highp   vec3      bradius; \n\
     lowp vec4 srcPixel() \n\
     { \n\
-        highp float c = -dot(A, A); \n\
-        highp vec2 val = vec2((-b + sqrt(b*b - 4.0*fmp2_m_radius2*c)) * inverse_2_fmp2_m_radius2, 0.5); \n\
-        return texture2D(brushTexture, val); \n\
+        highp float c = sqrfr-dot(A, A); \n\
+        highp float det = b*b - 4.0*fmp2_m_radius2*c; \n\
+        lowp vec4 result = vec4(0.0); \n\
+        if (det >= 0.0) { \n\
+            highp float detSqrt = sqrt(det); \n\
+            highp float w = max((-b - detSqrt) * inverse_2_fmp2_m_radius2, (-b + detSqrt) * inverse_2_fmp2_m_radius2); \n\
+            if (bradius.y + w * bradius.z >= 0.0) \n\
+                result = texture2D(brushTexture, vec2(w, 0.5)); \n\
+        } \n\
+        return result; \n\
     }\n";
 
 
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 673f614c0d..38bd58d91c 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -301,7 +301,7 @@ void QGL2PaintEngineExPrivate::updateBrushUniforms()
             const QRadialGradient *g = static_cast<const QRadialGradient *>(currentBrush.gradient());
             QPointF realCenter = g->center();
             QPointF realFocal  = g->focalPoint();
-            qreal   realRadius = g->radius();
+            qreal   realRadius = g->centerRadius() - g->focalRadius();
             translationPoint   = realFocal;
 
             QPointF fmp = realCenter - realFocal;
@@ -311,6 +311,12 @@ void QGL2PaintEngineExPrivate::updateBrushUniforms()
             shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::Fmp2MRadius2), fmp2_m_radius2);
             shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::Inverse2Fmp2MRadius2),
                                                              GLfloat(1.0 / (2.0*fmp2_m_radius2)));
+            shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::SqrFr),
+                                                             GLfloat(g->focalRadius() * g->focalRadius()));
+            shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::BRadius),
+                                                             GLfloat(2 * (g->centerRadius() - g->focalRadius()) * g->focalRadius()),
+                                                             g->focalRadius(),
+                                                             g->centerRadius() - g->focalRadius());
 
             QVector2D halfViewportSize(width*0.5, height*0.5);
             shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::HalfViewportSize), halfViewportSize);