Deprecate currentView, useCurrentView properties of SVGSVGElement and SVGViewSpec interface

third_party/WebKit/Source/core/svg/SVGSVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Google, Inc.
  *
  * 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 618 matching lines @@
 
     SVGLengthContext lengthContext(this);
     return height()->currentValue()->value(lengthContext);
 }
 
 AffineTransform SVGSVGElement::viewBoxToViewTransform(float viewWidth, float viewHeight) const
 {
     if (!m_useCurrentView || !m_viewSpec)
         return SVGFitToViewBox::viewBoxToViewTransform(currentViewBoxRect(), preserveAspectRatio()->currentValue(), viewWidth, viewHeight);
 
-    AffineTransform ctm = SVGFitToViewBox::viewBoxToViewTransform(currentViewBoxRect(), m_viewSpec->preserveAspectRatio()->currentValue(), viewWidth, viewHeight);
-    SVGTransformList* transformList = m_viewSpec->transform();
-    if (transformList->isEmpty())
-        return ctm;
-
-    AffineTransform transform;
-    if (transformList->concatenate(transform))
-        ctm *= transform;
-
-    return ctm;
+    return SVGFitToViewBox::viewBoxToViewTransform(currentViewBoxRect(), m_viewSpec->preserveAspectRatio()->currentValue(), viewWidth, viewHeight);;
 }
 
 void SVGSVGElement::setupInitialView(const String& fragmentIdentifier, Element* anchorNode)
 {
     LayoutObject* layoutObject = this->layoutObject();
     SVGViewSpec* view = m_viewSpec.get();
     if (view)
         view->reset();
 
     bool hadUseCurrentView = m_useCurrentView;
     m_useCurrentView = false;
 
-    if (fragmentIdentifier.startsWith("svgView(")) {

[fs, 2016/07/21 13:08:27]

This is still in the spec AFAIK. the only thing that should be removed here is:

 * the SVGViewSpec interface
 * the SVGSVGElement.useCurrentView and SVGSVGElement.currentView

i.e the DOM exposed bits. Any cleanup that isn't obvious "JS only" (like
removing the ScriptWrappable and related bits; *FromJavascript methods;
obviously dead code) is best done as a follow-up (and the removal here would not
be subject to that.)

[foolip, 2016/07/22 04:44:39]

Hmm, so this gets at the same thing I'm wondering about on blink-dev. To remove
only the web-exposed bits of this but keeping all the internals, has any
meaningful simplification been achieved?

I looked around in cs.chromium.org but am not really familiar with any of the
history, so what would happen if SVGViewSpec and SVGViewElement were removed
entirely?

(I added davve@ and pdr@ in case they have thoughts on the matter.)

[fs, 2016/07/22 08:31:38]

Just of the top of my head, some simplifications we could do:

 * Simpler types. Since we no longer need to expose the "exact" semantics of
SVGTransformList et.c, we could use a more efficient (and thus simpler) internal
representation.

 * Slightly simpler lifetimes. Oilpan fixed this quite a bit already (and there
are bits that are dead already from that - like
SVGViewSpec::detachContextElement.)

 * Removing SVGViewElement probably means we can simplify the setup of the (now
internal-only) SVGViewSpec (less need for things like
inheritViewAttributesFromElement, although removing the SVGViewSpec interface is
likely the bigger help there.)

 * With both gone we'd only have a single user of SVGZoomAndPan, and it's
possible we do something with that. (I'd be a bit surprised if anyone actually
used the functionality that is exposes though...)

When you start pulling the strings, it's quite possible more things fall off as
well.

-        if (!view)
-            view = currentView(); // Create the SVGViewSpec.
-
-        view->inheritViewAttributesFromElement(this);
-
-        if (view->parseViewSpec(fragmentIdentifier)) {
-            UseCounter::count(document(), UseCounter::SVGSVGElementFragmentSVGView);
-            m_useCurrentView = true;
-        } else {
-            view->reset();
-        }
-
-        if (layoutObject && (hadUseCurrentView || m_useCurrentView))
-            markForLayoutAndParentResourceInvalidation(layoutObject);
-        return;
-    }
-
     // Spec: If the SVG fragment identifier addresses a 'view' element within an SVG document (e.g., MyDrawing.svg#MyView
     // or MyDrawing.svg#xpointer(id('MyView'))) then the closest ancestor 'svg' element is displayed in the viewport.
     // Any view specification attributes included on the given 'view' element override the corresponding view specification
     // attributes on the closest ancestor 'svg' element.
     // TODO(ed): The spec text above is a bit unclear.
     // Should the transform from outermost svg to nested svg be applied to "display"
     // the inner svg in the viewport, then let the view element override the inner
     // svg's view specification attributes. Should it fill/override the outer viewport?
     if (isSVGViewElement(anchorNode)) {
         SVGViewElement& viewElement = toSVGViewElement(*anchorNode);
@@ skipping 47 matching lines @@
     visitor->trace(m_width);
     visitor->trace(m_height);
     visitor->trace(m_translation);
     visitor->trace(m_timeContainer);
     visitor->trace(m_viewSpec);
     SVGGraphicsElement::trace(visitor);
     SVGFitToViewBox::trace(visitor);
 }
 
 } // namespace blink