Multiply radius by 0.5 in calculateBlurStdDev()

Summary: Fix TODO to follow w3.org standard for shadow-blur

Reviewers: #breeze, ngraham

Reviewed By: #breeze, ngraham

Subscribers: ngraham, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D19134

libbreezecommon/breezeboxshadowrenderer.cpp

@@ -45,13 +45,7 @@ static inline int calculateBlurRadius(qreal stdDev)
 
 static inline qreal calculateBlurStdDev(int radius)
 {
-    // https://www.w3.org/TR/css-backgrounds-3/#shadow-blur says that the resulting
-    // shadow must approximate the image that would be generated by applying to the
-    // shadow a Gaussian blur with a standard deviation equal to half the blur radius,
-    // but we had been using a slightly different (non-standard compliant) routine to
-    // derive the standard deviation before, so in order to not break existing shadow
-    // params, we're not following the standard.
-    return radius * 0.43; // TODO: Multiply by 0.5 instead.
+    return radius * 0.5;
 }
 
 static inline QSize calculateBlurExtent(int radius)