Fix application of OBB paint-servers when device scale != 1

Source/core/rendering/svg/RenderSVGResourceGradient.cpp

 /*
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 67 matching lines @@
     // Spec: When the geometry of the applicable element has no width or height and objectBoundingBox is specified,
     // then the given effect (e.g. a gradient or a filter) will be ignored.
     FloatRect objectBoundingBox = object->objectBoundingBox();
     if (gradientUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX && objectBoundingBox.isEmpty())
         return false;
 
     OwnPtr<GradientData>& gradientData = m_gradientMap.add(object, nullptr).storedValue->value;
     if (!gradientData)
         gradientData = adoptPtr(new GradientData);
 
-    bool isPaintingText = resourceMode & ApplyToTextMode;
-
     // Create gradient object
     if (!gradientData->gradient) {
         buildGradient(gradientData.get());
 
         // We want the text bounding box applied to the gradient space transform now, so the gradient shader can use it.
         if (gradientUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX && !objectBoundingBox.isEmpty()) {
             gradientData->userspaceTransform.translate(objectBoundingBox.x(), objectBoundingBox.y());
             gradientData->userspaceTransform.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
         }
 
         AffineTransform gradientTransform;
         calculateGradientTransform(gradientTransform);
 
         gradientData->userspaceTransform *= gradientTransform;
-        if (isPaintingText) {
-            // Depending on font scaling factor, we may need to rescale the gradient here since
-            // text painting removes the scale factor from the context.
-            AffineTransform additionalTextTransform;
-            if (shouldTransformOnTextPainting(object, additionalTextTransform))
-                gradientData->userspaceTransform *= additionalTextTransform;
-        }
-        gradientData->gradient->setGradientSpaceTransform(gradientData->userspaceTransform);
     }
 
     if (!gradientData->gradient)
         return false;
 
+    const SVGRenderStyle* svgStyle = style->svgStyle();
+    ASSERT(svgStyle);
+
+    AffineTransform computedGradientSpaceTransform = computeResourceSpaceTransform(object, gradientData->userspaceTransform, svgStyle, resourceMode);

[f(malita), 2014/04/09 16:26:15]

Isn't (resourceMode & ApplyToTextMode) invariant for any given *object (which is
the key for m_gradientMap)? We should be able to include the additional text
transform in the cached based transform, and only adjust the non-scaling stroke
component on applyResource(), no?

[fs, 2014/04/09 16:59:13]

It's not invariant ATM - decorations are not painted with that flag set. I
suppose it would be possible to just pass/set that flag in that case too, and
hence be able to cache it as part of the "base" transform.
It does seem a bit unnecessary to tie in additional dependencies on the CTM if
it can be avoided - or?

[f(malita), 2014/04/09 17:46:51]

Ugh. I find all that SVGInlineTextBox::m_paintingResourceMode shuffling utterly
confusing.
Wouldn't that produce different results though, as we're potentially tweaking
the transform? Maybe that's the correct thing to do for decorations anyway?

[fs, 2014/04/10 08:16:41]

Agreed. (Good that you took care of it! *removes from TODO*)
 
Well, if you start weighing in things like <textPath> it becomes less obvious
surely. In that case the additional per-glyph transform shouldn't affect the
gradient (hmm, need to test that...).
What's to be considered "correct" is just a matter of defining the semantics
though. (It's probably also worth noting that using non-solidcolor fills on
decorations is likely broken ATM for scale!=1 [hint: look at
paintDecorationWithStyle].)
Personally I'd lean towards the side that decouples instance-data as much as
possible (i.e. consider the possibility of moving the bbox-transform out as
well.)

[f(malita), 2014/04/10 12:57:48]

SGTM.

+    gradientData->gradient->setGradientSpaceTransform(computedGradientSpaceTransform);
+
     // Draw gradient
     context->save();
 
-    if (isPaintingText)
+    if (resourceMode & ApplyToTextMode)
         context->setTextDrawingMode(resourceMode & ApplyToFillMode ? TextModeFill : TextModeStroke);
 
-    const SVGRenderStyle* svgStyle = style->svgStyle();
-    ASSERT(svgStyle);
-
     if (resourceMode & ApplyToFillMode) {
         context->setAlphaAsFloat(svgStyle->fillOpacity());
         context->setFillGradient(gradientData->gradient);
         context->setFillRule(svgStyle->fillRule());
     } else if (resourceMode & ApplyToStrokeMode) {
-        if (svgStyle->vectorEffect() == VE_NON_SCALING_STROKE)
-            gradientData->gradient->setGradientSpaceTransform(transformOnNonScalingStroke(object, gradientData->userspaceTransform));
         context->setAlphaAsFloat(svgStyle->strokeOpacity());
         context->setStrokeGradient(gradientData->gradient);
         SVGRenderSupport::applyStrokeStyleToContext(context, style, object);
     }
 
     return true;
 }
 
 void RenderSVGResourceGradient::postApplyResource(RenderObject*, GraphicsContext*& context, unsigned short resourceMode, const Path* path, const RenderSVGShape* shape)
 {
@@ skipping 35 matching lines @@
         return SpreadMethodReflect;
     case SVGSpreadMethodRepeat:
         return SpreadMethodRepeat;
     }
 
     ASSERT_NOT_REACHED();
     return SpreadMethodPad;
 }
 
 }