Fix handling of Ligature when letter-spacing is present.

Blink is applying ligature feature when letter spacing is specified which is not correct as per the CSS specification [1]. With this patch ligature is not applied when letter spacing is specified in CSS. BUG=382381 TEST=fast/text/font-ligature-letter-spacing.html 1: http://dev.w3.org/csswg/css-text-3/#letter-spacing-property Review URL: https://codereview.chromium.org/325673002 git-svn-id: svn://svn.chromium.org/blink/trunk@176539 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Fix handling of Ligature when letter-spacing is present.
Blink is applying ligature feature when letter spacing is specified which is not correct as per the CSS specification [1]. With this patch ligature is not applied when letter spacing is specified in CSS. BUG=382381 TEST=fast/text/font-ligature-letter-spacing.html 1: http://dev.w3.org/csswg/css-text-3/#letter-spacing-property Review URL: https://codereview.chromium.org/325673002 git-svn-id: svn://svn.chromium.org/blink/trunk@176539 bbb929c8-8fbe-4397-9dbb-9b2b20218538
b312644a · h.joshi@samsung.com · a228db4f · b312644a · b312644a · b312644a
Commit b312644a authored Jun 19, 2014 by h.joshi@samsung.com
4 changed files
--- a/third_party/WebKit/LayoutTests/fast/text/font-ligature-letter-spacing-expected.txt
+++ b/third_party/WebKit/LayoutTests/fast/text/font-ligature-letter-spacing-expected.txt
+CACACACA
+CACACACA
+This is a testharness.js-based test.
+PASS Ligature expected not to be applied due to letter spacing. 
+Harness: the test ran to completion.
+
--- a/third_party/WebKit/LayoutTests/fast/text/font-ligature-letter-spacing.html
+++ b/third_party/WebKit/LayoutTests/fast/text/font-ligature-letter-spacing.html
+<!DOCTYPE html>
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
+<title>Letter spacing and Ligature</title>
+
+<style type="text/css">
+@font-face {
+  font-family: megalopolis;
+  src: url(../../third_party/MEgalopolis/MEgalopolisExtra.woff) format("woff");
+}
+
+.dligDiv {
+-moz-font-feature-settings:"frac" 1, "dlig" 1;
+-moz-font-feature-settings:"frac=1, dlig=1";
+-ms-font-feature-settings:"frac" 1, "dlig" 1;
+-o-font-feature-settings:"frac" 1, "dlig" 1;
+-webkit-font-feature-settings:"frac" 1, "dlig" 1;
+font-feature-settings:"frac" 1, "dlig" 1;
+}
+
+.common {
+font-size: 24px;
+line-height: 100%;
+padding: 0px;
+letter-spacing:20px;
+font-family: megalopolis;
+}
+
+p { font-family: serif; font-style: italic; }
+</style>
+
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script>
+    setup({ explicit_done: true });
+    function testLetterSpaceAndLigature() {
+        var elementWidthWithLigatureAndLetterSpacing = document.getElementsByClassName("dligSpan")[0].getBoundingClientRect().width;
+        var elementWidthWithLetterSpacing = document.getElementsByClassName("letterSpace")[0].getBoundingClientRect().width;
+        test(function() {
+            assert_equals(elementWidthWithLigatureAndLetterSpacing, elementWidthWithLetterSpacing, "Ligature not applied due to letter spacing.");
+            }, "Ligature expected not to be applied due to letter spacing.");
+        done();
+    }
+</script>
+</head>
+<body onload="testLetterSpaceAndLigature();">
+<div class="dligDiv common">
+    <span class="dligSpan">CACACACA</span>
+</div>
+
+<div class="common">
+    <span class="letterSpace">CACACACA</span>
+</div>
+</body>
+</html>
--- a/third_party/WebKit/Source/platform/fonts/Font.cpp
+++ b/third_party/WebKit/Source/platform/fonts/Font.cpp
@@ -250,7 +250,7 @@ CodePath Font::codePath(const TextRun& run) const
        return SimplePath;
 #endif

-    if (m_fontDescription.featureSettings() && m_fontDescription.featureSettings()->size() > 0)
+    if (m_fontDescription.featureSettings() && m_fontDescription.featureSettings()->size() > 0 && m_fontDescription.letterSpacing() == 0)
        return ComplexPath;

    if (run.length() > 1 && !WidthIterator::supportsTypesettingFeatures(*this))

--- a/third_party/WebKit/Source/platform/fonts/FontDescription.cpp
+++ b/third_party/WebKit/Source/platform/fonts/FontDescription.cpp
@@ -182,21 +182,27 @@ void FontDescription::updateTypesettingFeatures() const
        break;
    }

-    switch (commonLigaturesState()) {
-    case FontDescription::DisabledLigaturesState:
-        m_typesettingFeatures &= ~Ligatures;
-        break;
-    case FontDescription::EnabledLigaturesState:
-        m_typesettingFeatures |= Ligatures;
-        break;
-    case FontDescription::NormalLigaturesState:
-        break;
-    }
-
-    if (discretionaryLigaturesState() == FontDescription::EnabledLigaturesState
-        || historicalLigaturesState() == FontDescription::EnabledLigaturesState
-        || contextualLigaturesState() == FontDescription::EnabledLigaturesState) {
-        m_typesettingFeatures |= WebCore::Ligatures;
+    // As per CSS (http://dev.w3.org/csswg/css-text-3/#letter-spacing-property),
+    // When the effective letter-spacing between two characters is not zero (due to
+    // either justification or non-zero computed letter-spacing), user agents should
+    // not apply optional ligatures.
+    if (m_letterSpacing == 0) {
+        switch (commonLigaturesState()) {
+        case FontDescription::DisabledLigaturesState:
+            m_typesettingFeatures &= ~Ligatures;
+            break;
+        case FontDescription::EnabledLigaturesState:
+            m_typesettingFeatures |= Ligatures;
+            break;
+        case FontDescription::NormalLigaturesState:
+            break;
+        }
+
+        if (discretionaryLigaturesState() == FontDescription::EnabledLigaturesState
+            || historicalLigaturesState() == FontDescription::EnabledLigaturesState
+            || contextualLigaturesState() == FontDescription::EnabledLigaturesState) {
+            m_typesettingFeatures |= WebCore::Ligatures;
+        }
    }
 }