Assign non-coverage font runs to base font

When a run has no cmap coverage in any font, use the base font. Most of
the time, this will cause rendering of the .notdef glyph, which is
preferable to displaying nothing. In some cases, Harfbuzz may be able to
decompose the characters (not in the cmap) to ones that are, in which
case we'll render those, as long as they're in the base font.

Bug: 6629748
Bug: 15816880
Change-Id: Ibb1b9242c83626e0c7db363ad65ce44a967a005e

1 files changed, 5 insertions, 3 deletions

diff --git a/libs/minikin/FontCollection.cpp b/libs/minikin/FontCollection.cpp
index 348c5dc..a6977fd 100644
--- a/libs/minikin/FontCollection.cpp
+++ b/libs/minikin/FontCollection.cpp
@@ -48,9 +48,6 @@ FontCollection::FontCollection(const vector<FontFamily*>& typefaces) :
         FontFamily* family = typefaces[i];
         MinikinFont* typeface = family->getClosestMatch(defaultStyle).font;
         if (typeface == NULL) {
-            ALOGE("FontCollection: closest match was null");
-            // TODO: we shouldn't hit this, as there should be more robust
-            // checks upstream to prevent empty/invalid FontFamily objects
             continue;
         }
         family->RefLocked();
@@ -76,6 +73,8 @@ FontCollection::FontCollection(const vector<FontFamily*>& typefaces) :
         lastChar.push_back(instance->mCoverage->nextSetBit(0));
     }
     nTypefaces = mInstances.size();
+    LOG_ALWAYS_FATAL_IF(nTypefaces == 0,
+        "Font collection must have at least one valid typeface");
     size_t nPages = (mMaxChar + kPageMask) >> kLogCharsPerPage;
     size_t offset = 0;
     for (size_t i = 0; i < nPages; i++) {
@@ -144,6 +143,9 @@ const FontCollection::FontInstance* FontCollection::getInstanceForChar(uint32_t
             }
         }
     }
+    if (bestInstance == NULL) {
+        bestInstance = &mInstances[0];
+    }
     return bestInstance;
 }