Increase hyphenation penalty for short last line

Tuning for hyphenation parameters. We discourage hyphenation on the
last line, but offset this penalty by also applying a penalty for
each line, which optimizes for minimizing the number of lines. Thus,
when hyphenation can reduce the number of lines, it increases the
chance they're used.

There's probably more tuning and refinement that can be done, but
testing suggests that the tunable parameters are appropriate.

Bug: 20883322

Change-Id: Ida7eaf8aced109e426694f5a386924a842d29c4b

1 files changed, 2 insertions, 7 deletions

diff --git a/include/minikin/LineBreaker.h b/include/minikin/LineBreaker.h
index 36314fb..e031fb3 100644
--- a/include/minikin/LineBreaker.h
+++ b/include/minikin/LineBreaker.h
@@ -200,9 +200,6 @@ class LineBreaker {
 
         float currentLineWidth() const;
 
-        // compute shrink/stretch penalty for line
-        float computeScore(float delta, bool atEnd);
-
         void addWordBreak(size_t offset, ParaWidth preBreak, ParaWidth postBreak, float penalty,
                 uint8_t hyph);
 
@@ -213,10 +210,7 @@ class LineBreaker {
 
         void computeBreaksGreedy();
 
-        void computeBreaksOptimal();
-
-        // special case when LineWidth is constant (layout is rectangle)
-        void computeBreaksOptimalRect();
+        void computeBreaksOptimal(bool isRectangular);
 
         void finishBreaksOptimal();
 
@@ -241,6 +235,7 @@ class LineBreaker {
 
         ParaWidth mWidth = 0;
         std::vector<Candidate> mCandidates;
+        float mLinePenalty = 0.0f;
 
         // the following are state for greedy breaker (updated while adding style runs)
         size_t mLastBreak;