Add penalty for breaks in URLs and email addresses

Recent changes have added special cases for line breaks within URLs
and email addresses. Such breaks are undesirable when they can be
avoided, but at other times are needed to avoid huge gaps, or indeed
to make the line fit at all.

This patch assigns a penalty for such breaks, equal to the hyphenation
penalty. The mechanism is currently very simple, but would be easy to
fine-tune based on more detailed information about break quality.

Bug: 20126487
Bug: 20566159
Change-Id: I0d3323897737a2850f1e734fa17b96b065eabd9c

4 files changed, 52 insertions, 1 deletions

diff --git a/include/minikin/WordBreaker.h b/include/minikin/WordBreaker.h
index c4aa151..4eff9d1 100644
--- a/include/minikin/WordBreaker.h
+++ b/include/minikin/WordBreaker.h
@@ -50,6 +50,8 @@ public:
 
     ssize_t wordEnd() const;
 
+    int breakBadness() const;
+
     void finish();
 
 private:
diff --git a/libs/minikin/LineBreaker.cpp b/libs/minikin/LineBreaker.cpp
index 214f195..9cf07d5 100644
--- a/libs/minikin/LineBreaker.cpp
+++ b/libs/minikin/LineBreaker.cpp
@@ -207,7 +207,8 @@ float LineBreaker::addStyleRun(MinikinPaint* paint, const FontCollection* typefa
 
             // Skip break for zero-width characters inside replacement span
             if (paint != nullptr || current == end || mCharWidths[current] > 0) {
-                addWordBreak(current, mWidth, postBreak, 0.0, 0);
+                float penalty = hyphenPenalty * mWordBreaker.breakBadness();
+                addWordBreak(current, mWidth, postBreak, penalty, 0);
             }
             lastBreak = current;
             lastBreakWidth = mWidth;
diff --git a/libs/minikin/WordBreaker.cpp b/libs/minikin/WordBreaker.cpp
index edac993..ca69a50 100644
--- a/libs/minikin/WordBreaker.cpp
+++ b/libs/minikin/WordBreaker.cpp
@@ -193,6 +193,10 @@ ssize_t WordBreaker::wordEnd() const {
     return result;
 }
 
+int WordBreaker::breakBadness() const {
+    return (mInEmailOrUrl && mCurrent < mScanOffset) ? 1 : 0;
+}
+
 void WordBreaker::finish() {
     mText = nullptr;
     // Note: calling utext_close multiply is safe
diff --git a/tests/WordBreakerTests.cpp b/tests/WordBreakerTests.cpp
index 284b02c..9662b2f 100644
--- a/tests/WordBreakerTests.cpp
+++ b/tests/WordBreakerTests.cpp
@@ -42,10 +42,12 @@ TEST_F(WordBreakerTest, basic) {
     EXPECT_EQ(6, breaker.next());  // after "hello "
     EXPECT_EQ(0, breaker.wordStart());  // "hello"
     EXPECT_EQ(5, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ(6, breaker.current());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(6, breaker.wordStart());  // "world"
     EXPECT_EQ(11, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ(11, breaker.current());
 }
 
@@ -58,9 +60,11 @@ TEST_F(WordBreakerTest, softHyphen) {
     EXPECT_EQ(7, breaker.next());  // after "hel{SOFT HYPHEN}lo "
     EXPECT_EQ(0, breaker.wordStart());  // "hel{SOFT HYPHEN}lo"
     EXPECT_EQ(6, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(7, breaker.wordStart());  // "world"
     EXPECT_EQ(12, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, punct) {
@@ -73,9 +77,11 @@ TEST_F(WordBreakerTest, punct) {
     EXPECT_EQ(9, breaker.next());  // after "¡¡hello, "
     EXPECT_EQ(2, breaker.wordStart());  // "hello"
     EXPECT_EQ(7, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(9, breaker.wordStart());  // "world"
     EXPECT_EQ(14, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, email) {
@@ -87,11 +93,14 @@ TEST_F(WordBreakerTest, email) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(11, breaker.next());  // after "foo@example"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(16, breaker.next());  // after ".com "
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(16, breaker.wordStart());  // "x"
     EXPECT_EQ(17, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, mailto) {
@@ -103,13 +112,17 @@ TEST_F(WordBreakerTest, mailto) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(7, breaker.next());  // after "mailto:"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(18, breaker.next());  // after "foo@example"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(23, breaker.next());  // after ".com "
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(23, breaker.wordStart());  // "x"
     EXPECT_EQ(24, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 // The current logic always places a line break after a detected email address or URL
@@ -123,11 +136,14 @@ TEST_F(WordBreakerTest, emailNonAscii) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(11, breaker.next());  // after "foo@example"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(15, breaker.next());  // after ".com"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(15, breaker.wordStart());  // "一"
     EXPECT_EQ(16, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, emailCombining) {
@@ -139,11 +155,14 @@ TEST_F(WordBreakerTest, emailCombining) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(11, breaker.next());  // after "foo@example"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(17, breaker.next());  // after ".com̃ "
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(17, breaker.wordStart());  // "x"
     EXPECT_EQ(18, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, lonelyAt) {
@@ -155,11 +174,14 @@ TEST_F(WordBreakerTest, lonelyAt) {
     EXPECT_EQ(2, breaker.next());  // after "a "
     EXPECT_EQ(0, breaker.wordStart());  // "a"
     EXPECT_EQ(1, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ(4, breaker.next());  // after "@ "
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(4, breaker.wordStart());  // "b"
     EXPECT_EQ(5, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, url) {
@@ -171,15 +193,20 @@ TEST_F(WordBreakerTest, url) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(5, breaker.next());  // after "http:"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(7, breaker.next());  // after "//"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(14, breaker.next());  // after "example"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(19, breaker.next());  // after ".com "
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_EQ(19, breaker.wordStart());  // "x"
     EXPECT_EQ(20, breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 // Breaks according to section 14.12 of Chicago Manual of Style, *URLs or DOIs and line breaks*
@@ -192,38 +219,55 @@ TEST_F(WordBreakerTest, urlBreakChars) {
     EXPECT_EQ(0, breaker.current());
     EXPECT_EQ(5, breaker.next());  // after "http:"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(7, breaker.next());  // after "//"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(8, breaker.next());  // after "a"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(10, breaker.next());  // after ".b"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(11, breaker.next());  // after "/"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(13, breaker.next());  // after "~c"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(15, breaker.next());  // after ",d"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(17, breaker.next());  // after "-e"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(19, breaker.next());  // after "?f"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(20, breaker.next());  // after "="
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(21, breaker.next());  // after "g"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(22, breaker.next());  // after "&"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(23, breaker.next());  // after "h"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(25, breaker.next());  // after "#i"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(27, breaker.next());  // after "%j"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ(29, breaker.next());  // after "_k"
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(1, breaker.breakBadness());
     EXPECT_EQ((ssize_t)NELEM(buf), breaker.next());  // end
     EXPECT_TRUE(breaker.wordStart() >= breaker.wordEnd());
+    EXPECT_EQ(0, breaker.breakBadness());
 }
 
 TEST_F(WordBreakerTest, urlNoHyphenBreak) {