Add support for multiple break strategies to better support edge case situations.

Change-Id: I61fc4d95a57b34f59073e99ad834c9a0d7ec7c76

engine/src/flutter/src/paragraph.cc

@@ -177,8 +177,16 @@ void Paragraph::Layout(double width, bool force) {
       collection_map;
 
   breaker_.setLineWidths(0.0f, 0, width_);
+  // TODO(garyq): Get hyphenator working. Hyphenator should be created with
+  // a pattern binary dataset. Should be something along these lines:
+  //
+  //   minikin::Hyphenator* hyph =
+  //   minikin::Hyphenator::loadBinary(<paramsgohere>);
+  //      breaker_.setLocale(icu::Locale::getRoot(), &hyph);
+  //
   AddRunsToLineBreaker(collection_map);
   breaker_.setJustified(paragraph_style_.text_align == TextAlign::justify);
+  breaker_.setStrategy(paragraph_style_.break_strategy);
   size_t breaks_count = breaker_.computeBreaks();
   const int* breaks = breaker_.getBreaks();
 

engine/src/flutter/src/paragraph.h

@@ -117,6 +117,7 @@ class Paragraph {
   FRIEND_TEST(RenderTest, ChineseParagraph);
   FRIEND_TEST(RenderTest, DISABLED_ArabicParagraph);
   FRIEND_TEST(RenderTest, SpacingParagraph);
+  FRIEND_TEST(RenderTest, LongWordParagraph);
 
   std::vector<uint16_t> text_;
   StyledRuns runs_;

engine/src/flutter/src/paragraph_style.h

@@ -20,6 +20,7 @@
 #include <climits>
 #include <string>
 
+#include "lib/txt/include/minikin/LineBreaker.h"
 #include "lib/txt/src/font_style.h"
 #include "lib/txt/src/font_weight.h"
 #include "lib/txt/src/text_align.h"
@@ -36,6 +37,12 @@ class ParagraphStyle {
   size_t max_lines = UINT_MAX;
   double line_height = 1.0;
   std::string ellipsis = "...";
+  // Default strategy is kBreakStrategy_Greedy. Sometimes,
+  // kBreakStrategy_HighQuality will produce more desireable layouts (eg, very
+  // long words are more likely to be reasonably placed).
+  // kBreakStrategy_Balanced will balance between the two.
+  minikin::BreakStrategy break_strategy =
+      minikin::BreakStrategy::kBreakStrategy_Greedy;
   // TODO(garyq): Implement right to left.
   // Right to left (Arabic, Hebrew, etc).
   bool rtl = false;

engine/src/flutter/src/styled_runs.h

@@ -70,6 +70,7 @@ class StyledRuns {
   FRIEND_TEST(RenderTest, ItalicsParagraph);
   FRIEND_TEST(RenderTest, ChineseParagraph);
   FRIEND_TEST(RenderTest, DISABLED_ArabicParagraph);
+  FRIEND_TEST(RenderTest, LongWordParagraph);
 
   struct IndexedRun {
     size_t style_index = 0;

engine/src/flutter/tests/txt/paragraph_unittests.cc

@@ -1200,7 +1200,49 @@ TEST_F(RenderTest, SpacingParagraph) {
   ASSERT_EQ(paragraph->records_[4].style().word_spacing, 20);
   ASSERT_EQ(paragraph->records_[5].style().word_spacing, 0);
   ASSERT_EQ(paragraph->records_[6].style().word_spacing, 20);
+}
 
+TEST_F(RenderTest, LongWordParagraph) {
+  const char* text =
+      "A "
+      "veryverylongwordtoseewherethiswillwraporifitwillatallandifitdoesthenthat"
+      "wouldbeagoodthingbecausethebreakingisworking.";
+  auto icu_text = icu::UnicodeString::fromUTF8(text);
+  std::u16string u16_text(icu_text.getBuffer(),
+                          icu_text.getBuffer() + icu_text.length());
+
+  txt::ParagraphStyle paragraph_style;
+  paragraph_style.break_strategy = minikin::kBreakStrategy_HighQuality;
+  auto font_collection = FontCollection::GetFontCollection(txt::GetFontDir());
+  txt::ParagraphBuilder builder(paragraph_style, &font_collection);
+
+  txt::TextStyle text_style;
+  text_style.font_size = 30;
+  text_style.letter_spacing = 0;
+  text_style.word_spacing = 0;
+  text_style.color = SK_ColorBLACK;
+  text_style.height = 1;
+  builder.PushStyle(text_style);
+  builder.AddText(u16_text);
+
+  builder.Pop();
+
+  auto paragraph = builder.Build();
+  paragraph->Layout(GetTestCanvasWidth() / 2);
+
+  paragraph->Paint(GetCanvas(), 0, 0);
+
+  ASSERT_TRUE(Snapshot());
+  ASSERT_EQ(paragraph->text_.size(), std::string{text}.length());
+  for (size_t i = 0; i < u16_text.length(); i++) {
+    ASSERT_EQ(paragraph->text_[i], u16_text[i]);
+  }
+  ASSERT_EQ(paragraph->runs_.runs_.size(), 1ull);
+  ASSERT_EQ(paragraph->runs_.styles_.size(), 1ull);
+  ASSERT_TRUE(paragraph->runs_.styles_[0].equals(text_style));
+  ASSERT_EQ(paragraph->records_[0].style().color, text_style.color);
+  ASSERT_EQ(paragraph->GetLineCount(), 4);
+  ASSERT_TRUE(Snapshot());
 }
 
 }  // namespace txt