Bug 914432 - Add support for multiple prefs to enable/disable values in the same property keyword table. r=dbaron

layout/style/nsCSSProps.cpp

@@ -960,9 +960,7 @@ int32_t nsCSSProps::kDisplayKTable[] = {
   eCSSKeyword__moz_popup,         NS_STYLE_DISPLAY_POPUP,
   eCSSKeyword__moz_groupbox,      NS_STYLE_DISPLAY_GROUPBOX,
 #endif
-  // XXXdholbert NOTE: These currently need to be the last entries in the
-  // table, because the "is flexbox enabled" pref that disables these will
-  // disable all the entries after them, too.
+  // The next two entries are controlled by the layout.css.flexbox.enabled pref.
   eCSSKeyword_flex,               NS_STYLE_DISPLAY_FLEX,
   eCSSKeyword_inline_flex,        NS_STYLE_DISPLAY_INLINE_FLEX,
   eCSSKeyword_UNKNOWN,-1
@@ -1380,9 +1378,7 @@ int32_t nsCSSProps::kPositionKTable[] = {
   eCSSKeyword_relative, NS_STYLE_POSITION_RELATIVE,
   eCSSKeyword_absolute, NS_STYLE_POSITION_ABSOLUTE,
   eCSSKeyword_fixed, NS_STYLE_POSITION_FIXED,
-  // NOTE: This currently needs to be the last entry in the table,
-  // because the "layout.css.sticky.enabled" pref that disables
-  // this will disable all the entries after it, too.
+  // The next entry is controlled by the layout.css.sticky.enabled pref.
   eCSSKeyword_sticky, NS_STYLE_POSITION_STICKY,
   eCSSKeyword_UNKNOWN,-1
 };
@@ -1788,15 +1784,33 @@ const int32_t nsCSSProps::kColumnFillKTable[] = {
   eCSSKeyword_UNKNOWN, -1
 };
 
+static bool IsKeyValSentinel(nsCSSKeyword aKey, int32_t aValue)
+{
+  return aKey == eCSSKeyword_UNKNOWN && aValue == -1;
+}
+
 int32_t
 nsCSSProps::FindIndexOfKeyword(nsCSSKeyword aKeyword, const int32_t aTable[])
 {
-  int32_t index = 0;
-  while (eCSSKeyword_UNKNOWN != nsCSSKeyword(aTable[index])) {
-    if (aKeyword == nsCSSKeyword(aTable[index])) {
-      return index;
+  if (eCSSKeyword_UNKNOWN == aKeyword) {
+    // NOTE: we can have keyword tables where eCSSKeyword_UNKNOWN is used
+    // not only for the sentinel, but also in the middle of the table to
+    // knock out values that have been disabled by prefs, e.g. kDisplayKTable.
+    // So we deal with eCSSKeyword_UNKNOWN up front to avoid returning a valid
+    // index in the loop below.
+    return -1;
+  }
+  int32_t i = 0;
+  for (;;) {
+    nsCSSKeyword key = nsCSSKeyword(aTable[i]);
+    int32_t val = aTable[i + 1];
+    if (::IsKeyValSentinel(key, val)) {
+      break;
     }
-    index += 2;
+    if (aKeyword == key) {
+      return i;
+    }
+    i += 2;
   }
   return -1;
 }
@@ -1818,11 +1832,13 @@ nsCSSProps::ValueToKeywordEnum(int32_t aValue, const int32_t aTable[])
 {
   int32_t i = 1;
   for (;;) {
-    if (aTable[i] == -1 && aTable[i-1] == eCSSKeyword_UNKNOWN) {
+    int32_t val = aTable[i];
+    nsCSSKeyword key = nsCSSKeyword(aTable[i - 1]);
+    if (::IsKeyValSentinel(key, val)) {
       break;
     }
-    if (aValue == aTable[i]) {
-      return nsCSSKeyword(aTable[i-1]);
+    if (aValue == val) {
+      return key;
     }
     i += 2;
   }