Bug 1357432 (#750)

* Part 1. Move IsLocalRefURL to nsContentUtils to reuse this function. (port-rewrite)

`IsLocalRefURL` is originally designed to be used by URLValue only.
Since we need this function in SVGUseElement::LookupHref too, move it to nsContentUtils as a util function.

* Revert "Part 1. Move IsLocalRefURL to nsContentUtils to reuse this function. (port-rewrite)"

This reverts commit 19f010c62022e269f99066a8d90e3522fe31adaf.

* Part 1. Duplicate IsLocalRefURL to nsContentUtils to reuse this function.

`IsLocalRefURL` is originally designed to be used by URLValue only.
Since we need this function in SVGUseElement::LookupHref too, duplicate it to nsContentUtils as a util function.
This is a duplication because CSSValue uses stringbuffers and not nsStrings.
While Bug 1356060 - "Just use nsString in URLValueData" converts this use from stringbuffer to nsString, it builds on a bunch of vartype refactoring (nsString vs. nsAString, etc.) which is too much of a headache to deal with just to deduplicate this simple function.

* Part 2. Implement nsSVGEffects::GetBaseURLForLocalRef to export local-ref-url-resolving logic.

ResolveURLUsingLocalRef is designed to be internally used by nsSVGEffects::Get-{SVGEffect}-URI functions.
Since we also need it in SVGUseElement::LookupHref, make it public in nsSVGEffects.

* Part 3. Resolve local-ref in SVGUseElement::LookupHref by nsSVGEffects::GetBaseURLForLocalRef.

* Part 4. Reftest for using local-ref as xlink:href value.

2 files changed, 43 insertions, 17 deletions

diff --git a/layout/svg/nsSVGEffects.cpp b/layout/svg/nsSVGEffects.cpp
index eac094a91..e75c973c8 100644
--- a/layout/svg/nsSVGEffects.cpp
+++ b/layout/svg/nsSVGEffects.cpp
@@ -888,24 +888,13 @@ nsSVGEffects::InvalidateDirectRenderingObservers(nsIFrame* aFrame, uint32_t aFla
   }
 }
 
-static already_AddRefed<nsIURI>
-ResolveURLUsingLocalRef(nsIFrame* aFrame, const css::URLValueData* aURL)
+already_AddRefed<nsIURI>
+nsSVGEffects::GetBaseURLForLocalRef(nsIContent* content, nsIURI* aDocURI)
 {
-  MOZ_ASSERT(aFrame);
-
-  if (!aURL) {
-    return nullptr;
-  }
-
-  // Non-local-reference URL.
-  if (!aURL->IsLocalRef()) {
-    nsCOMPtr<nsIURI> result = aURL->GetURI();
-    return result.forget();
-  }
+  MOZ_ASSERT(content);
 
   // For a local-reference URL, resolve that fragment against the current
   // document that relative URLs are resolved against.
-  nsIContent* content = aFrame->GetContent();
   nsCOMPtr<nsIURI> baseURI = content->OwnerDoc()->GetDocumentURI();
 
   if (content->IsInAnonymousSubtree()) {
@@ -933,12 +922,37 @@ ResolveURLUsingLocalRef(nsIFrame* aFrame, const css::URLValueData* aURL)
         }
       }
 
-      if (originalURI && aURL->EqualsExceptRef(originalURI)) {
-        baseURI = originalURI;
+      if (originalURI) {
+        bool isEqualsExceptRef = false;
+        aDocURI->EqualsExceptRef(originalURI, &isEqualsExceptRef);
+        if (isEqualsExceptRef) {
+          baseURI = originalURI;
+        }
       }
     }
   }
 
+  return baseURI.forget();
+}
+
+static already_AddRefed<nsIURI>
+ResolveURLUsingLocalRef(nsIFrame* aFrame, const css::URLValueData* aURL)
+{
+  MOZ_ASSERT(aFrame);
+
+  if (!aURL) {
+    return nullptr;
+  }
+
+  // Non-local-reference URL.
+  if (!aURL->IsLocalRef()) {
+    nsCOMPtr<nsIURI> result = aURL->GetURI();
+    return result.forget();
+  }
+
+  nsCOMPtr<nsIURI> baseURI =
+    nsSVGEffects::GetBaseURLForLocalRef(aFrame->GetContent(), aURL->GetURI());
+
   return aURL->ResolveLocalRef(baseURI);
 }
 
diff --git a/layout/svg/nsSVGEffects.h b/layout/svg/nsSVGEffects.h
index 9dd92fd31..0cf9b1500 100644
--- a/layout/svg/nsSVGEffects.h
+++ b/layout/svg/nsSVGEffects.h
@@ -626,11 +626,23 @@ public:
   static already_AddRefed<nsIURI>
   GetPaintURI(nsIFrame* aFrame, nsStyleSVGPaint nsStyleSVG::* aPaint);
 
-    /**
+  /**
    * A helper function to resolve SVG mask URL.
    */
   static already_AddRefed<nsIURI>
   GetMaskURI(nsIFrame* aFrame, uint32_t aIndex);
+
+  /**
+   * Return a baseURL for resolving a local-ref URL.
+   *
+   * @param aContent an element which uses a local-ref property. Here are some
+   *                 examples:
+   *                   <rect fill=url(#foo)>
+   *                   <circle clip-path=url(#foo)>
+   *                   <use xlink:href="#foo">
+   */
+  static already_AddRefed<nsIURI>
+  GetBaseURLForLocalRef(nsIContent* aContent, nsIURI* aDocURI);
 };
 
 #endif /*NSSVGEFFECTS_H_*/