Add low memory setting on FontCollection. Only remove trailing whitespace at end of line, and do not justify last line.

Change-Id: Iee32003624862b3c7f5f2d0e999ef72719302551

engine/src/flutter/src/font_collection.cc

@@ -100,13 +100,31 @@ bool FontCollection::HasFamily(const std::string family) const {
 
 void FontCollection::FlushCache() {
   minikin_font_collection_map_.clear();
+  lru_tracker_.clear();
 }
 
 void FontCollection::SetCacheCapacity(const size_t cap) {
   cache_capacity_ = cap;
 }
 
-// TODO(garyq): Rework this to use font fallback system.
+void FontCollection::SetLowMemoryMode(bool mode, size_t cap) {
+  cache_capacity_ = cap;
+  if (mode) {
+    cache_method_ = CacheMethod::kLRU;
+    TrimCache();
+  } else {
+    cache_method_ = CacheMethod::kUnlimited;
+  }
+}
+
+void FontCollection::TrimCache() {
+  while (minikin_font_collection_map_.size() > cache_capacity_) {
+    std::string family_to_evict = lru_tracker_.back();
+    lru_tracker_.pop_back();
+    minikin_font_collection_map_.erase(family_to_evict);
+  }
+}
+
 const std::string FontCollection::ProcessFamilyName(const std::string& family) {
 #ifdef DIRECTORY_FONT_MANAGER_AVAILABLE
   return family.length() == 0 ? DEFAULT_FAMILY_NAME : family;
@@ -178,15 +196,13 @@ FontCollection::GetMinikinFontCollectionForFamily(const std::string& family) {
   }
 
   // Maintain LRU and evict old fonts no longer used.
+
+  lru_tracker_.remove(processed_family_name);
+  lru_tracker_.push_front(processed_family_name);
   if (cache_method_ == CacheMethod::kLRU) {
-    lru_tracker_.remove(processed_family_name);
-    lru_tracker_.push_front(processed_family_name);
-    if (lru_tracker_.size() > cache_capacity_) {
-      std::string family_to_evict = lru_tracker_.back();
-      lru_tracker_.pop_back();
-      minikin_font_collection_map_.erase(family_to_evict);
-    }
+    TrimCache();
   }
+
   return minikin_font_collection_map_[processed_family_name];
 }
 

engine/src/flutter/src/font_collection.h

@@ -18,6 +18,7 @@
 #define LIB_TXT_SRC_FONT_COLLECTION_H_
 
 #define DEFAULT_FAMILY_NAME "Roboto"
+#define DEFAULT_CACHE_CAPACITY 20
 
 #include <list>
 #include <memory>
@@ -75,13 +76,17 @@ class FontCollection {
 
   void SetCacheCapacity(const size_t cap);
 
+  // Call this to limit memory usage by cached fonts. SetLowMemoryMode() will
+  // enable default LRU policy and flush fonts beyond capacity.
+  void SetLowMemoryMode(bool mode = true, size_t cap = DEFAULT_CACHE_CAPACITY);
+
  private:
   std::vector<sk_sp<SkFontMgr>> skia_font_managers_;
   // Cache the names because GetFamilyNames() can be frequently called.
   std::set<std::string> family_names_;
   CacheMethod cache_method_ = CacheMethod::kUnlimited;
   std::list<std::string> lru_tracker_;
-  size_t cache_capacity_ = 20;
+  size_t cache_capacity_ = DEFAULT_CACHE_CAPACITY;
 
   // Cache minikin font collections to prevent slow disk reads.
   // TODO(garyq): Implement optional low-memory optimized system to prevent
@@ -95,6 +100,8 @@ class FontCollection {
 
   const std::string ProcessFamilyName(const std::string& family);
 
+  void TrimCache();
+
   static const std::string GetDefaultFamilyName() {
     return DEFAULT_FAMILY_NAME;
   };

engine/src/flutter/src/paragraph.cc

@@ -252,8 +252,10 @@ void Paragraph::Layout(double width, bool force) {
 
         // Check if we should remove trailing whitespace of blobs.
         size_t trailing_length = 0;
-        while (minikin::isWordSpace(
-            text_[character_index + blob_length - trailing_length - 1])) {
+        while (
+            minikin::isWordSpace(
+                text_[character_index + blob_length - trailing_length - 1]) &&
+            layout_end == next_break) {
           ++trailing_length;
         }
 
@@ -307,7 +309,7 @@ void Paragraph::Layout(double width, bool force) {
       paint.getFontMetrics(&metrics);
       // Apply additional word spacing if the text is justified.
       if (paragraph_style_.text_align == TextAlign::justify &&
-          buffer_sizes.size() > 0) {
+          buffer_sizes.size() > 0 && character_index != text_.size()) {
         JustifyLine(buffers, buffer_sizes, word_count, character_index);
       }
       records_.push_back(

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

@@ -567,9 +567,7 @@ TEST_F(RenderTest, JustifyAlignParagraph) {
       "tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim "
       "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
       "commodo consequat. Duis aute irure dolor in reprehenderit in voluptate "
-      "velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint "
-      "occaecat cupidatat non proident, sunt in culpa qui officia deserunt "
-      "mollit anim id est laborum.";
+      "velit esse cillum dolore eu fugiat.";
   auto icu_text = icu::UnicodeString::fromUTF8(text);
   std::u16string u16_text(icu_text.getBuffer(),
                           icu_text.getBuffer() + icu_text.length());