gecko-dev/dom/svg/SVGFragmentIdentifier.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "SVGFragmentIdentifier.h"

#include "mozilla/dom/SVGSVGElement.h"
#include "mozilla/dom/SVGViewElement.h"
#include "nsContentUtils.h" // for nsCharSeparatedTokenizerTemplate
#include "nsSVGAnimatedTransformList.h"
#include "nsCharSeparatedTokenizer.h"

namespace mozilla {

using namespace dom;

static bool
IsMatchingParameter(const nsAString& aString, const nsAString& aParameterName)
{
  // The first two tests ensure aString.Length() > aParameterName.Length()
  // so it's then safe to do the third test
  return StringBeginsWith(aString, aParameterName) &&
         aString.Last() == ')' &&
         aString.CharAt(aParameterName.Length()) == '(';
}

inline bool
IgnoreWhitespace(char16_t aChar)
{
  return false;
}

static SVGViewElement*
GetViewElement(nsIDocument* aDocument, const nsAString& aId)
{
  Element* element = aDocument->GetElementById(aId);
  return (element && element->IsSVGElement(nsGkAtoms::view)) ?
            static_cast<SVGViewElement*>(element) : nullptr;
}

void
SVGFragmentIdentifier::SaveOldPreserveAspectRatio(SVGSVGElement* root)
{
  if (root->mPreserveAspectRatio.IsExplicitlySet()) {
    root->SetPreserveAspectRatioProperty(root->mPreserveAspectRatio.GetBaseValue());
  }
}

void 
SVGFragmentIdentifier::RestoreOldPreserveAspectRatio(SVGSVGElement* root)
{
  const SVGPreserveAspectRatio* oldPARPtr = root->GetPreserveAspectRatioProperty();
  if (oldPARPtr) {
    root->mPreserveAspectRatio.SetBaseValue(*oldPARPtr, root);
  } else if (root->mPreserveAspectRatio.IsExplicitlySet()) {
    ErrorResult error;
    root->RemoveAttribute(NS_LITERAL_STRING("preserveAspectRatio"), error);
  }
}

void 
SVGFragmentIdentifier::SaveOldViewBox(SVGSVGElement* root)
{
  if (root->mViewBox.IsExplicitlySet()) {
    root->SetViewBoxProperty(root->mViewBox.GetBaseValue());
  }
}

void 
SVGFragmentIdentifier::RestoreOldViewBox(SVGSVGElement* root)
{
  const nsSVGViewBoxRect* oldViewBoxPtr = root->GetViewBoxProperty();
  if (oldViewBoxPtr) {
    root->mViewBox.SetBaseValue(*oldViewBoxPtr, root);
  } else if (root->mViewBox.IsExplicitlySet()) {
    ErrorResult error;
    root->RemoveAttribute(NS_LITERAL_STRING("viewBox"), error);
  }
}

void 
SVGFragmentIdentifier::SaveOldZoomAndPan(SVGSVGElement* root)
{
  if (root->mEnumAttributes[SVGSVGElement::ZOOMANDPAN].IsExplicitlySet()) {
    root->SetZoomAndPanProperty(root->mEnumAttributes[SVGSVGElement::ZOOMANDPAN].GetBaseValue());
  }
}

void
SVGFragmentIdentifier::RestoreOldZoomAndPan(SVGSVGElement* root)
{
  uint16_t oldZoomAndPan = root->GetZoomAndPanProperty();
  if (oldZoomAndPan != SVG_ZOOMANDPAN_UNKNOWN) {
    root->mEnumAttributes[SVGSVGElement::ZOOMANDPAN].SetBaseValue(oldZoomAndPan, root);
  } else if (root->mEnumAttributes[SVGSVGElement::ZOOMANDPAN].IsExplicitlySet()) {
    ErrorResult error;
    root->RemoveAttribute(NS_LITERAL_STRING("zoomAndPan"), error);
  }
}

void 
SVGFragmentIdentifier::SaveOldTransform(SVGSVGElement* root)
{
  nsSVGAnimatedTransformList* transformList = root->GetAnimatedTransformList();

  if (transformList && transformList->IsExplicitlySet()) {
    root->SetTransformProperty(transformList->GetBaseValue());
  }
}

void 
SVGFragmentIdentifier::RestoreOldTransform(SVGSVGElement* root)
{
  const SVGTransformList* oldTransformPtr = root->GetTransformProperty();
  if (oldTransformPtr) {
    root->GetAnimatedTransformList(nsSVGElement::DO_ALLOCATE)->SetBaseValue(*oldTransformPtr);
  } else {
    nsSVGAnimatedTransformList* transformList = root->GetAnimatedTransformList();
    if (transformList && transformList->IsExplicitlySet()) {
      ErrorResult error;
      root->RemoveAttribute(NS_LITERAL_STRING("transform"), error);
    }
  }
}

bool
SVGFragmentIdentifier::ProcessSVGViewSpec(const nsAString& aViewSpec,
                                          SVGSVGElement* root)
{
  if (!IsMatchingParameter(aViewSpec, NS_LITERAL_STRING("svgView"))) {
    return false;
  }

  // SVGViewAttributes may occur in any order, but each type may only occur
  // at most one time in a correctly formed SVGViewSpec.
  // If we encounter any attribute more than once or get any syntax errors
  // we're going to return false and cancel any changes.
  
  bool viewBoxFound = false;
  bool preserveAspectRatioFound = false;
  bool transformFound = false;
  bool zoomAndPanFound = false;

  // Each token is a SVGViewAttribute
  int32_t bracketPos = aViewSpec.FindChar('(');
  uint32_t lengthOfViewSpec = aViewSpec.Length() - bracketPos - 2;
  nsCharSeparatedTokenizerTemplate<IgnoreWhitespace> tokenizer(
    Substring(aViewSpec, bracketPos + 1, lengthOfViewSpec), ';');

  if (!tokenizer.hasMoreTokens()) {
    return false;
  }
  do {

    nsAutoString token(tokenizer.nextToken());

    bracketPos = token.FindChar('(');
    if (bracketPos < 1 || token.Last() != ')') {
      // invalid SVGViewAttribute syntax
      return false;
    }

    const nsAString &params =
      Substring(token, bracketPos + 1, token.Length() - bracketPos - 2);

    if (IsMatchingParameter(token, NS_LITERAL_STRING("viewBox"))) {
      if (viewBoxFound ||
          NS_FAILED(root->mViewBox.SetBaseValueString(
                      params, root, true))) {
        return false;
      }
      viewBoxFound = true;
    } else if (IsMatchingParameter(token, NS_LITERAL_STRING("preserveAspectRatio"))) {
      if (preserveAspectRatioFound ||
          NS_FAILED(root->mPreserveAspectRatio.SetBaseValueString(
                      params, root, true))) {
        return false;
      }
      preserveAspectRatioFound = true;
    } else if (IsMatchingParameter(token, NS_LITERAL_STRING("transform"))) {
      if (transformFound ||
          NS_FAILED(root->GetAnimatedTransformList(nsSVGElement::DO_ALLOCATE)->
                      SetBaseValueString(params))) {
        return false;
      }
      transformFound = true;
    } else if (IsMatchingParameter(token, NS_LITERAL_STRING("zoomAndPan"))) {
      if (zoomAndPanFound) {
        return false;
      }
      nsIAtom* valAtom = NS_GetStaticAtom(params);
      if (!valAtom) {
        return false;
      }
      const nsSVGEnumMapping* mapping = SVGSVGElement::sZoomAndPanMap;
      while (mapping->mKey) {
        if (valAtom == *(mapping->mKey)) {
          // If we've got a valid zoomAndPan value, then set it on our root element.
          if (NS_FAILED(root->mEnumAttributes[SVGSVGElement::ZOOMANDPAN].SetBaseValue(
                          mapping->mVal, root))) {
            return false;
          }
          break;
        }
        mapping++;
      }
      if (!mapping->mKey) {
          // Unrecognised zoomAndPan value
          return false;
      }
      zoomAndPanFound = true;
    } else {
      // We don't support viewTarget currently
      return false;
    }
  } while (tokenizer.hasMoreTokens());

  if (root->mUseCurrentView) {
    // A previous SVGViewSpec may have overridden some attributes.
    // If they are no longer overridden we need to restore the old values.
    if (!transformFound) {
      RestoreOldTransform(root);
    }
    if (!viewBoxFound) {
      RestoreOldViewBox(root);
    }
    if (!preserveAspectRatioFound) {
      RestoreOldPreserveAspectRatio(root);
    }
    if (!zoomAndPanFound) {
      RestoreOldZoomAndPan(root);
    }
  }

  return true;
}

bool
SVGFragmentIdentifier::ProcessFragmentIdentifier(nsIDocument* aDocument,
                                                 const nsAString& aAnchorName)
{
  MOZ_ASSERT(aDocument->GetRootElement()->IsSVGElement(nsGkAtoms::svg),
             "expecting an SVG root element");

  SVGSVGElement* rootElement =
    static_cast<SVGSVGElement*>(aDocument->GetRootElement());

  if (!rootElement->mUseCurrentView) {
    SaveOldViewBox(rootElement);
    SaveOldPreserveAspectRatio(rootElement);
    SaveOldZoomAndPan(rootElement);
  }

  const SVGViewElement* viewElement = GetViewElement(aDocument, aAnchorName);

  if (viewElement) {
    if (!rootElement->mCurrentViewID) {
      rootElement->mCurrentViewID = new nsString();
    }
    *rootElement->mCurrentViewID = aAnchorName;
    rootElement->mUseCurrentView = true;
    rootElement->InvalidateTransformNotifyFrame();
    // not an svgView()-style fragment identifier, return false so the caller
    // continues processing to match any :target pseudo elements
    return false;
  }

  bool wasOverridden = !!rootElement->mCurrentViewID;
  rootElement->mCurrentViewID = nullptr;

  rootElement->mUseCurrentView = ProcessSVGViewSpec(aAnchorName, rootElement);
  if (rootElement->mUseCurrentView) {
    return true;
  }
  RestoreOldViewBox(rootElement);
  rootElement->ClearViewBoxProperty();
  RestoreOldPreserveAspectRatio(rootElement);
  rootElement->ClearPreserveAspectRatioProperty();
  RestoreOldZoomAndPan(rootElement);
  rootElement->ClearZoomAndPanProperty();
  RestoreOldTransform(rootElement);
  rootElement->ClearTransformProperty();
  if (wasOverridden) {
    rootElement->InvalidateTransformNotifyFrame();
  }
  return false;
}

} // namespace mozilla