Bug 759568 - Part 1. Parse background-clip:text; r=dholbert r=heycam

MozReview-Commit-ID: BPuQjWYvAuj
2016-04-14 16:28:06 +08:00 · 2016-04-14 16:28:06 +08:00 · d2552e50a5
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@ -146,6 +146,7 @@ using namespace mozilla::gfx;
 #define DISPLAY_CONTENTS_ENABLED_PREF_NAME "layout.css.display-contents.enabled"
 #define TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME "layout.css.text-align-unsafe-value.enabled"
 #define FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME "layout.css.float-logical-values.enabled"
+#define BG_CLIP_TEXT_ENABLED_PREF_NAME "layout.css.background-clip-text.enabled"

 #ifdef DEBUG
 // TODO: remove, see bug 598468.
@ -392,6 +393,39 @@ FloatLogicalValuesEnabledPrefChangeCallback(const char* aPrefName,
    isFloatLogicalValuesEnabled ? eCSSKeyword_inline_end : eCSSKeyword_UNKNOWN;
 }

+
+// When the pref "layout.css.background-clip-text.enabled" changes, this
+// function is invoked to let us update kBackgroundClipKTable, to selectively
+// disable or restore the entries for "text" in that table.
+static void
+BackgroundClipTextEnabledPrefChangeCallback(const char* aPrefName,
+                                            void* aClosure)
+{
+  NS_ASSERTION(strcmp(aPrefName, BG_CLIP_TEXT_ENABLED_PREF_NAME) == 0,
+               "Did you misspell " BG_CLIP_TEXT_ENABLED_PREF_NAME " ?");
+
+  static bool sIsBGClipKeywordIndexInitialized;
+  static int32_t sIndexOfTextInBGClipTable;
+  bool isBGClipTextEnabled =
+    Preferences::GetBool(BG_CLIP_TEXT_ENABLED_PREF_NAME, false);
+
+  if (!sIsBGClipKeywordIndexInitialized) {
+    // First run: find the position of "text" in kBackgroundClipKTable.
+    sIndexOfTextInBGClipTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_text,
+                                     nsCSSProps::kBackgroundClipKTable);
+
+    sIsBGClipKeywordIndexInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "text" entry in kBackgroundClipKTable,
+  // depending on whether the pref is enabled vs. disabled.
+  if (sIndexOfTextInBGClipTable >= 0) {
+    nsCSSProps::kBackgroundClipKTable[sIndexOfTextInBGClipTable].mKeyword =
+      isBGClipTextEnabled ? eCSSKeyword_text : eCSSKeyword_UNKNOWN;
+  }
+}
+
 template<typename TestType>
 static bool
 HasMatchingCurrentAnimations(const nsIFrame* aFrame, TestType&& aTest)
@ -7647,6 +7681,10 @@ nsLayoutUtils::Initialize()
                                FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME);
  FloatLogicalValuesEnabledPrefChangeCallback(FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME,
                                              nullptr);
+  Preferences::RegisterCallback(BackgroundClipTextEnabledPrefChangeCallback,
+                                BG_CLIP_TEXT_ENABLED_PREF_NAME);
+  BackgroundClipTextEnabledPrefChangeCallback(BG_CLIP_TEXT_ENABLED_PREF_NAME,
+                                              nullptr);

  nsComputedDOMStyle::RegisterPrefChangeCallbacks();
 }
--- a/layout/style/Declaration.cpp
+++ b/layout/style/Declaration.cpp
@ -295,12 +295,16 @@ Declaration::GetImageLayerValue(

    if (clip->mValue.GetIntValue() != NS_STYLE_IMAGELAYER_CLIP_BORDER ||
        origin->mValue.GetIntValue() != NS_STYLE_IMAGELAYER_ORIGIN_PADDING) {
-      MOZ_ASSERT(nsCSSProps::kKeywordTableTable[
-                   aTable[nsStyleImageLayers::origin]] ==
-                 nsCSSProps::kImageLayerOriginKTable);
-      MOZ_ASSERT(nsCSSProps::kKeywordTableTable[
-                   aTable[nsStyleImageLayers::clip]] ==
-                 nsCSSProps::kImageLayerOriginKTable);
+#ifdef DEBUG
+      for (size_t i = 0; nsCSSProps::kImageLayerOriginKTable[i].mValue != -1; i++) {
+        // For each keyword & value in kOriginKTable, ensure that
+        // kBackgroundKTable has a matching entry at the same position.
+        MOZ_ASSERT(nsCSSProps::kImageLayerOriginKTable[i].mKeyword ==
+                   nsCSSProps::kBackgroundClipKTable[i].mKeyword);
+        MOZ_ASSERT(nsCSSProps::kImageLayerOriginKTable[i].mValue ==
+                   nsCSSProps::kBackgroundClipKTable[i].mValue);
+      }
+#endif
      static_assert(NS_STYLE_IMAGELAYER_CLIP_BORDER ==
                    NS_STYLE_IMAGELAYER_ORIGIN_BORDER &&
                    NS_STYLE_IMAGELAYER_CLIP_PADDING ==
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@ -12063,13 +12063,16 @@ CSSParserImpl::ParseImageLayersItem(
        // The spec allows a second box value (for background-clip),
        // immediately following the first one (for background-origin).

-        // 'background-clip' and 'background-origin' use the same keyword table
-        MOZ_ASSERT(nsCSSProps::kKeywordTableTable[
-                     aTable[nsStyleImageLayers::origin]] ==
-                   nsCSSProps::kImageLayerOriginKTable);
-        MOZ_ASSERT(nsCSSProps::kKeywordTableTable[
-                     aTable[nsStyleImageLayers::clip]] ==
-                   nsCSSProps::kImageLayerOriginKTable);
+#ifdef DEBUG
+        for (size_t i = 0; nsCSSProps::kImageLayerOriginKTable[i].mValue != -1; i++) {
+          // For each keyword & value in kOriginKTable, ensure that
+          // kBackgroundKTable has a matching entry at the same position.
+          MOZ_ASSERT(nsCSSProps::kImageLayerOriginKTable[i].mKeyword ==
+                     nsCSSProps::kBackgroundClipKTable[i].mKeyword);
+          MOZ_ASSERT(nsCSSProps::kImageLayerOriginKTable[i].mValue ==
+                     nsCSSProps::kBackgroundClipKTable[i].mValue);
+        }
+#endif
        static_assert(NS_STYLE_IMAGELAYER_CLIP_BORDER ==
                      NS_STYLE_IMAGELAYER_ORIGIN_BORDER &&
                      NS_STYLE_IMAGELAYER_CLIP_PADDING ==
--- a/layout/style/nsCSSPropList.h
+++ b/layout/style/nsCSSPropList.h
@ -522,7 +522,7 @@ CSS_PROP_BACKGROUND(
        CSS_PROPERTY_VALUE_LIST_USES_COMMAS,
    "",
    VARIANT_KEYWORD, // used by list parsing
-    kImageLayerOriginKTable,
+    kBackgroundClipKTable,
    CSS_PROP_NO_OFFSET,
    eStyleAnimType_None)
 CSS_PROP_BACKGROUND(
--- a/layout/style/nsCSSProps.cpp
+++ b/layout/style/nsCSSProps.cpp
@ -890,7 +890,9 @@ const KTableEntry nsCSSProps::kImageLayerAttachmentKTable[] = {
 static_assert(NS_STYLE_IMAGELAYER_CLIP_BORDER == NS_STYLE_IMAGELAYER_ORIGIN_BORDER &&
              NS_STYLE_IMAGELAYER_CLIP_PADDING == NS_STYLE_IMAGELAYER_ORIGIN_PADDING &&
              NS_STYLE_IMAGELAYER_CLIP_CONTENT == NS_STYLE_IMAGELAYER_ORIGIN_CONTENT,
-              "bg-clip and bg-origin style constants must agree");
+              "Except background-clip:text, all {background,mask}-clip and "
+              "{background,mask}-origin style constants must agree");
+
 const KTableEntry nsCSSProps::kImageLayerOriginKTable[] = {
  { eCSSKeyword_border_box, NS_STYLE_IMAGELAYER_ORIGIN_BORDER },
  { eCSSKeyword_padding_box, NS_STYLE_IMAGELAYER_ORIGIN_PADDING },
@ -898,6 +900,21 @@ const KTableEntry nsCSSProps::kImageLayerOriginKTable[] = {
  { eCSSKeyword_UNKNOWN, -1 }
 };

+KTableEntry nsCSSProps::kBackgroundClipKTable[] = {
+  { eCSSKeyword_border_box, NS_STYLE_IMAGELAYER_CLIP_BORDER },
+  { eCSSKeyword_padding_box, NS_STYLE_IMAGELAYER_CLIP_PADDING },
+  { eCSSKeyword_content_box, NS_STYLE_IMAGELAYER_CLIP_CONTENT },
+  // The next entry is controlled by the layout.css.background-clip-text.enabled
+  // pref.
+  { eCSSKeyword_text, NS_STYLE_IMAGELAYER_CLIP_TEXT },
+  { eCSSKeyword_UNKNOWN, -1 }
+};
+
+static_assert(ArrayLength(nsCSSProps::kImageLayerOriginKTable) ==
+              ArrayLength(nsCSSProps::kBackgroundClipKTable) - 1,
+              "background-clip has one extra value, which is text, compared"
+              "to {background,mask}-origin");
+
 // Note: Don't change this table unless you update
 // ParseImageLayerPosition!

--- a/layout/style/nsCSSProps.h
+++ b/layout/style/nsCSSProps.h
@ -678,6 +678,9 @@ public:
  static const KTableEntry kImageLayerSizeKTable[];
  static const KTableEntry kImageLayerCompositeKTable[];
  static const KTableEntry kImageLayerModeKTable[];
+  // Not const because we modify its entries when the pref
+  // "layout.css.background-clip.text" changes:
+  static KTableEntry kBackgroundClipKTable[];
  static const KTableEntry kBlendModeKTable[];
  static const KTableEntry kBorderCollapseKTable[];
  static const KTableEntry kBorderColorKTable[];
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@ -1845,7 +1845,7 @@ nsComputedDOMStyle::DoGetBackgroundClip()
  return GetBackgroundList(&nsStyleImageLayers::Layer::mClip,
                           &nsStyleImageLayers::mClipCount,
                           StyleBackground()->mImage,
-                           nsCSSProps::kImageLayerOriginKTable);
+                           nsCSSProps::kBackgroundClipKTable);
 }

 already_AddRefed<CSSValue>
--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@ -267,10 +267,12 @@ enum class FillMode : uint32_t;
 #define NS_STYLE_IMAGELAYER_ATTACHMENT_LOCAL         2

 // See nsStyleImageLayers
-// Code depends on these constants having the same values as BG_ORIGIN_*
+// Code depends on these constants having the same values as IMAGELAYER_ORIGIN_*
 #define NS_STYLE_IMAGELAYER_CLIP_BORDER              0
 #define NS_STYLE_IMAGELAYER_CLIP_PADDING             1
 #define NS_STYLE_IMAGELAYER_CLIP_CONTENT             2
+// One extra constant which does not exist in IMAGELAYER_ORIGIN_*
+#define NS_STYLE_IMAGELAYER_CLIP_TEXT                3

 // A magic value that we use for our "pretend that background-clip is
 // 'padding' when we have a solid border" optimization.  This isn't
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@ -2421,6 +2421,9 @@ pref("layout.css.scope-pseudo.enabled", true);
 // Is support for background-blend-mode enabled?
 pref("layout.css.background-blend-mode.enabled", true);

+// Is support for background-clip:text enabled? (bug 1263516)
+pref("layout.css.background-clip-text.enabled", false);
+
 // Is support for CSS vertical text enabled?
 pref("layout.css.vertical-text.enabled", true);