Use fallback blur shader for radius * 2 + 1 != sampleCount.

The faster code path looks a lot worse in this case, so fall back to use the
generic arbitrary large blur size for this case.

Change-Id: I3984b3bf48732a83dd112b7beb0fb4c3f8d38568
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

3 files changed, 14 insertions, 16 deletions

diff --git a/src/effects/GaussianBlur.qml b/src/effects/GaussianBlur.qml
index 82bc290..70943a0 100644
--- a/src/effects/GaussianBlur.qml
+++ b/src/effects/GaussianBlur.qml
@@ -253,9 +253,9 @@ Item {
 
     // private members...
     /*! \internal */
-    property int _paddedTexWidth: transparentBorder ? width + 2 * _kernelRadius: width;
+    property int _paddedTexWidth: transparentBorder ? width + 2 * radius: width;
     /*! \internal */
-    property int _paddedTexHeight: transparentBorder ? height  + 2 * _kernelRadius: height;
+    property int _paddedTexHeight: transparentBorder ? height  + 2 * radius: height;
     /*! \internal */
     property int _kernelRadius: Math.max(0, samples / 2);
     /*! \internal */
@@ -285,14 +285,13 @@ Item {
 
     /*! \internal */
     function _rebuildShaders() {
-        if (samples < 1)
-            return;
-
         var params = {
             radius: _kernelRadius,
-            deviation: deviation,
+            // Limit deviation to something very small avoid getting NaN in the shader.
+            deviation: Math.max(0.00001, deviation),
             alphaOnly: root._alphaOnly,
-            masked: _maskSource != undefined
+            masked: _maskSource != undefined,
+            fallback: root.radius != _kernelRadius
         }
         var shaders = ShaderBuilder.gaussianBlur(params);
         horizontalBlur.fragmentShader = shaders.fragmentShader;
@@ -304,7 +303,7 @@ Item {
         interpolation: SourceProxy.LinearInterpolation
         input: root.source
         sourceRect: root.transparentBorder
-                    ? Qt.rect(-root._kernelRadius, 0, root._paddedTexWidth, parent.height)
+                    ? Qt.rect(-root.radius, 0, root._paddedTexWidth, parent.height)
                     : Qt.rect(0, 0, 0, 0)
     }
 
@@ -320,7 +319,6 @@ Item {
 
         // Used by fallback shader (sampleCount exceeds number of varyings)
         property real deviation: root.deviation
-        property real radius: root._kernelRadius
 
         // Only in use for DropShadow and Glow
         property color color: "white"
@@ -332,7 +330,7 @@ Item {
         layer.enabled: true
         layer.smooth: true
         layer.sourceRect: root.transparentBorder
-                          ? Qt.rect(0, -root._kernelRadius, width, root._paddedTexHeight)
+                          ? Qt.rect(0, -root.radius, width, root._paddedTexHeight)
                           : Qt.rect(0, 0, 0, 0)
         visible: false
         blending: false
@@ -340,7 +338,7 @@ Item {
 
     ShaderEffect {
         id: verticalBlur
-        x: transparentBorder ? -root._kernelRadius : 0
+        x: transparentBorder ? -root.radius : 0
         y: x;
         width: root.transparentBorder ? root._paddedTexWidth: root.width
         height: root.transparentBorder ? root._paddedTexHeight : root.height;
@@ -352,7 +350,6 @@ Item {
         property var dirstep: Qt.vector2d(0, 1 / (root._paddedTexHeight * root._dpr));
 
         property real deviation: horizontalBlur.deviation
-        property real radius: horizontalBlur.radius
 
         property color color: "black"
         property real thickness: horizontalBlur.thickness;
diff --git a/src/effects/private/DropShadowBase.qml b/src/effects/private/DropShadowBase.qml
index 21ef0ea..3660619 100644
--- a/src/effects/private/DropShadowBase.qml
+++ b/src/effects/private/DropShadowBase.qml
@@ -62,7 +62,7 @@ Item {
         x: Math.round(horizontalOffset)
         y: Math.round(verticalOffset)
         source: root.source
-        radius: Math.min(Math.floor(root.samples / 2), root.radius)
+        radius: root.radius
         samples: root.samples
         _thickness: root.spread
         transparentBorder: root.transparentBorder
diff --git a/src/effects/private/qgfxshaderbuilder.cpp b/src/effects/private/qgfxshaderbuilder.cpp
index 81a3c12..fe1d7fe 100644
--- a/src/effects/private/qgfxshaderbuilder.cpp
+++ b/src/effects/private/qgfxshaderbuilder.cpp
@@ -312,10 +312,11 @@ QVariantMap QGfxShaderBuilder::gaussianBlur(const QJSValue &parameters)
     int requestedSamples = requestedRadius * 2 + 1;
     int samples = 1 + requestedSamples / 2;
     int radius = requestedSamples / 4;
+    bool fallback = parameters.property(QStringLiteral("fallback")).toBool();
 
     QVariantMap result;
 
-    if (samples > m_maxBlurSamples || masked) {
+    if (samples > m_maxBlurSamples || masked || fallback) {
         QByteArray fragShader;
         if (masked)
             fragShader += "uniform mediump sampler2D mask;\n";
@@ -354,9 +355,9 @@ QVariantMap QGfxShaderBuilder::gaussianBlur(const QJSValue &parameters)
                 fragShader += ".a";
             fragShader += ";\n";
         }
-        fragShader += "    const mediump float wSum = ";
+        fragShader += "    const mediump float wSum = float(";
         fragShader += QByteArray::number(wSum);
-        fragShader += ";\n"
+        fragShader += ");\n"
             "    gl_FragColor = ";
         if (alphaOnly)
             fragShader += "mix(vec4(0), color, clamp((result / wSum) / thickness, 0.0, 1.0)) * qt_Opacity;\n";