fix crash in FontCollection::init() when FontFamily is empty (flutter#23019)

Author: liguisheng

third_party/txt/src/minikin/FontCollection.cpp

@@ -51,21 +51,20 @@ std::string GetFontLocale(uint32_t langListId) {
   return langs.size() ? langs[0].getString() : "";
 }
 
-FontCollection::FontCollection(std::shared_ptr<FontFamily>&& typeface)
-    : mMaxChar(0) {
-  std::vector<std::shared_ptr<FontFamily>> typefaces;
-  typefaces.push_back(typeface);
-  init(typefaces);
+std::shared_ptr<minikin::FontCollection> FontCollection::Create(
+    const std::vector<std::shared_ptr<FontFamily>>& typefaces) {
+  std::shared_ptr<minikin::FontCollection> font_collection(
+      new minikin::FontCollection());
+  if (!font_collection || !font_collection->init(typefaces)) {
+    return nullptr;
+  }
+  return font_collection;
 }
 
-FontCollection::FontCollection(
-    const vector<std::shared_ptr<FontFamily>>& typefaces)
-    : mMaxChar(0) {
-  init(typefaces);
-}
+FontCollection::FontCollection() : mMaxChar(0) {}
 
-void FontCollection::init(
-    const vector<std::shared_ptr<FontFamily>>& typefaces) {
+bool FontCollection::init(
+    const std::vector<std::shared_ptr<FontFamily>>& typefaces) {
   std::scoped_lock _l(gMinikinLock);
   mId = sNextId++;
   vector<uint32_t> lastChar;
@@ -91,10 +90,14 @@ void FontCollection::init(
     mSupportedAxes.insert(supportedAxes.begin(), supportedAxes.end());
   }
   nTypefaces = mFamilies.size();
-  LOG_ALWAYS_FATAL_IF(nTypefaces == 0,
-                      "Font collection must have at least one valid typeface");
-  LOG_ALWAYS_FATAL_IF(nTypefaces > 254,
-                      "Font collection may only have up to 254 font families.");
+  if (nTypefaces == 0) {
+    ALOGE("Font collection must have at least one valid typeface.");
+    return false;
+  }
+  if (nTypefaces > 254) {
+    ALOGE("Font collection may only have up to 254 font families.");
+    return false;
+  }
   size_t nPages = (mMaxChar + kPageMask) >> kLogCharsPerPage;
   // TODO: Use variation selector map for mRanges construction.
   // A font can have a glyph for a base code point and variation selector pair
@@ -122,9 +125,12 @@ void FontCollection::init(
     }
     range->end = mFamilyVec.size();
   }
-  // See the comment in Range for more details.
-  LOG_ALWAYS_FATAL_IF(mFamilyVec.size() >= 0xFFFF,
-                      "Exceeded the maximum indexable cmap coverage.");
+
+  if (mFamilyVec.size() >= 0xFFFF) {
+    ALOGE("Exceeded the maximum indexable cmap coverage.");
+    return false;
+  }
+  return true;
 }
 
 // Special scores for the font fallback.
@@ -566,7 +572,7 @@ std::shared_ptr<FontCollection> FontCollection::createCollectionWithVariation(
     }
   }
 
-  return std::shared_ptr<FontCollection>(new FontCollection(families));
+  return FontCollection::Create(std::move(families));
 }
 
 uint32_t FontCollection::getId() const {

third_party/txt/src/minikin/FontCollection.h

@@ -28,10 +28,12 @@
 namespace minikin {
 
 class FontCollection {
+ private:
+  explicit FontCollection();
+
  public:
-  explicit FontCollection(
+  static std::shared_ptr<minikin::FontCollection> Create(
       const std::vector<std::shared_ptr<FontFamily>>& typefaces);
-  explicit FontCollection(std::shared_ptr<FontFamily>&& typeface);
 
   // libtxt extension: an interface for looking up fallback fonts for characters
   // that do not match this collection's font families.
@@ -94,7 +96,7 @@ class FontCollection {
   };
 
   // Initialize the FontCollection.
-  void init(const std::vector<std::shared_ptr<FontFamily>>& typefaces);
+  bool init(const std::vector<std::shared_ptr<FontFamily>>& typefaces);
 
   const std::shared_ptr<FontFamily>& getFamilyForChar(uint32_t ch,
                                                       uint32_t vs,

third_party/txt/src/txt/font_collection.cc

@@ -207,7 +207,11 @@ FontCollection::GetMinikinFontCollectionForFamilies(
   }
   // Create the minikin font collection.
   auto font_collection =
-      std::make_shared<minikin::FontCollection>(std::move(minikin_families));
+      minikin::FontCollection::Create(std::move(minikin_families));
+  if (!font_collection) {
+    font_collections_cache_[family_key] = nullptr;
+    return nullptr;
+  }
   if (enable_font_fallback_) {
     font_collection->set_fallback_font_provider(
         std::make_unique<TxtFallbackFontProvider>(shared_from_this()));

third_party/txt/src/txt/paragraph_txt.cc

@@ -807,6 +807,9 @@ void ParagraphTxt::Layout(double width) {
 
       std::shared_ptr<minikin::FontCollection> minikin_font_collection =
           GetMinikinFontCollectionForStyle(run.style());
+      if (!minikin_font_collection) {
+        return;
+      }
 
       // Lay out this run.
       uint16_t* text_ptr = text_.data();