Convert first letter into a pseudo element.

Source/core/dom/FirstLetterHelper.cpp

+/*
+ * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
+ *           (C) 1999 Antti Koivisto (koivisto@kde.org)
+ *           (C) 2007 David Smith (catfish.man@gmail.com)
+ * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
+ * Copyright (C) Research In Motion Limited 2010. All rights reserved.
+ *
+ * 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.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "config.h"
+#include "core/dom/FirstLetterHelper.h"
+
+#include "core/dom/Element.h"
+#include "core/rendering/RenderObject.h"
+#include "core/rendering/RenderText.h"
+#include "wtf/text/WTFString.h"
+#include "wtf/unicode/icu/UnicodeIcu.h"
+
+namespace blink {
+
+using namespace WTF;
+using namespace Unicode;
+
+// CSS 2.1 http://www.w3.org/TR/CSS21/selector.html#first-letter
+// "Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
+// "initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows the first letter should be included"
+static inline bool isPunctuationForFirstLetter(UChar c)
+{
+    CharCategory charCategory = category(c);
+    return charCategory == Punctuation_Open
+        || charCategory == Punctuation_Close
+        || charCategory == Punctuation_InitialQuote
+        || charCategory == Punctuation_FinalQuote
+        || charCategory == Punctuation_Other;
+}
+
+static inline bool isSpaceOrNewline(UChar c)
+{
+    // Use isASCIISpace() for basic Latin-1.
+    // This will include newlines, which aren't included in Unicode DirWS.
+    return c <= 0x7F ? WTF::isASCIISpace(c) : WTF::Unicode::direction(c) == WTF::Unicode::WhiteSpaceNeutral;
+}
+
+static inline bool isSpaceForFirstLetter(UChar c)
+{
+    return isSpaceOrNewline(c) || c == noBreakSpace;
+}
+
+unsigned FirstLetterHelper::firstLetterLength(const String& text)
+{
+    unsigned length = 0;
+    unsigned textLength = text.length();
+
+    // Account for leading spaces first.
+    while (length < textLength && isSpaceForFirstLetter(text[length]))
+        length++;
+
+    // Now account for leading punctuation.
+    while (length < textLength && isPunctuationForFirstLetter(text[length]))
+        length++;
+
+    // Bail if we didn't find a letter before the end of the text or before a space.
+    if (isSpaceForFirstLetter(text[length]) || (textLength && length == textLength))
+        return 0;
+
+    // Account the next character for first letter.
+    length++;
+
+    // Keep looking allowed punctuation for the :first-letter.

[Julien - ping for review, 2014/10/01 21:14:47]

Keep looking *for* allowed punctuation?

[dsinclair, 2014/10/04 02:01:34]

Done.

+    for (unsigned scanLength = length; scanLength < textLength; ++scanLength) {
+        UChar c = text[scanLength];
+
+        if (!isPunctuationForFirstLetter(c))
+            break;
+
+        length = scanLength + 1;

[Julien - ping for review, 2014/10/01 21:14:47]

It seems wasteful to do this update in the loop instead of just outside when we
have bailed out.

This is just copied from the old code so we will just want to add a FIXME.

[dsinclair, 2014/10/04 02:01:34]

Fixed the code. We don't need scanLength at all as we can just increment length
as we iterate the loop instead.

+    }
+
+    // FIXME: If textLength is 0, length may still be 1!
+    return length;
+}
+
+
+RenderObject* FirstLetterHelper::firstLetterTextRenderer(const Element& element)
+{
+    RenderObject* parentRenderer;
+
+    // If we are looking at a first letter element then we need to find the
+    // first letter text renderer from the parent node, and not ourselves.
+    if (element.isFirstLetterPseudoElement())
+        parentRenderer = element.parentOrShadowHostElement()->renderer();
+    else
+        parentRenderer = element.renderer();
+
+    if (!parentRenderer
+        || !parentRenderer->style()->hasPseudoStyle(FIRST_LETTER)
+        || !parentRenderer->canHaveGeneratedChildren()
+        || !(parentRenderer->isRenderBlockFlow() || parentRenderer->isRenderButton()))
+        return nullptr;
+
+    // Drill down into our children and look for our first text child.
+    RenderObject* firstLetterTextRenderer = parentRenderer->slowFirstChild();
+    while (firstLetterTextRenderer) {
+
+        // This can be called when the first letter renderer is already in the tree. We do not
+        // want to consider that renderer for our text renderer so we go the sibling.
+        if (firstLetterTextRenderer->style() && firstLetterTextRenderer->style()->styleType() == FIRST_LETTER) {
+            firstLetterTextRenderer = firstLetterTextRenderer->nextSibling();
+

[Julien - ping for review, 2014/10/01 21:14:47]

While helpful, those extra spaces are not consistent with the rest of the Blink
code so I would drop them off.

[dsinclair, 2014/10/04 02:01:34]

Done.

+        } else if (firstLetterTextRenderer->isText()) {
+            // FIXME: If there is leading punctuation in a different RenderText than
+            // the first letter, we'll not apply the correct style to it.

[Julien - ping for review, 2014/10/01 21:14:47]

Could you give an example of when this would happen?

[Julien - ping for review, 2014/10/01 21:14:47]

Could you give an example of when this would happen (ideally in the comment)?

[dsinclair, 2014/10/04 02:01:34]

I don't know. This is from the original code. I'll see if I can figure out an
example where this is an issue.

+            if (firstLetterLength(toRenderText(firstLetterTextRenderer)->originalText()))
+                break;
+            firstLetterTextRenderer = firstLetterTextRenderer->nextSibling();
+
+        } else if (firstLetterTextRenderer->isListMarker()) {
+            firstLetterTextRenderer = firstLetterTextRenderer->nextSibling();
+
+        } else if (firstLetterTextRenderer->isFloatingOrOutOfFlowPositioned()) {
+            if (firstLetterTextRenderer->style()->styleType() == FIRST_LETTER) {
+                firstLetterTextRenderer = firstLetterTextRenderer->slowFirstChild();
+                break;
+            }
+            firstLetterTextRenderer = firstLetterTextRenderer->nextSibling();
+
+        } else if (firstLetterTextRenderer->isReplaced() || firstLetterTextRenderer->isRenderButton()
+            || firstLetterTextRenderer->isMenuList()) {
+            return nullptr;
+
+        } else if (firstLetterTextRenderer->style()->hasPseudoStyle(FIRST_LETTER)
+            && firstLetterTextRenderer->canHaveGeneratedChildren())  {
+            // Let the child handle it when it's attached.
+            return nullptr;
+
+        } else {
+            firstLetterTextRenderer = firstLetterTextRenderer->slowFirstChild();
+        }
+    }
+
+    // No first letter text to display, we're done.
+    // FIXME: This black-list of disallowed RenderText subclasses is fragile.
+    // Should counter be on this list? What about RenderTextFragment?
+    if (!firstLetterTextRenderer || !firstLetterTextRenderer->isText()
+        || firstLetterTextRenderer->isBR() || toRenderText(firstLetterTextRenderer)->isWordBreak())
+        return nullptr;
+
+    return firstLetterTextRenderer;
+}
+
+} // namespace blink