SkPDF: Remove some unused glyphs from fallback fonts

src/pdf/SkPDFFont.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkGlyphCache.h"
 #include "SkPaint.h"
@@ skipping 149 matching lines @@
         canon->fTypefaceMetrics.set(id, nullptr);
         return nullptr;
     }
     sk_sp<SkAdvancedTypefaceMetrics> metrics(
             typeface->getAdvancedTypefaceMetrics(
                     SkTypeface::kGlyphNames_PerGlyphInfo | SkTypeface::kToUnicode_PerGlyphInfo,
                     nullptr, 0));
     if (!metrics) {
         metrics = sk_make_sp<SkAdvancedTypefaceMetrics>();
         metrics->fLastGlyphID = SkToU16(count - 1);
-    } 
+    }
     SkASSERT(metrics->fLastGlyphID == SkToU16(count - 1));
     return *canon->fTypefaceMetrics.set(id, metrics.release());
 }
 
 SkAdvancedTypefaceMetrics::FontType font_type(const SkAdvancedTypefaceMetrics& metrics) {
     if (SkToBool(metrics.fFlags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag)) {
         // force Type3 fallback.
         return SkAdvancedTypefaceMetrics::kOther_Font;
     }
     return metrics.fType;
@@ skipping 415 matching lines @@
 }
 
 static void add_type3_font_info(SkPDFCanon* canon,
                                 SkPDFDict* font,
                                 SkTypeface* typeface,
                                 SkScalar emSize,
                                 const SkBitSet& subset,
                                 SkGlyphID firstGlyphID,
                                 SkGlyphID lastGlyphID) {
     SkASSERT(lastGlyphID >= firstGlyphID);
+    // Remove unused glyphs at the end of the range.
+    // Keep the lastGlyphID >= firstGlyphID invariant true.
+    while (lastGlyphID > firstGlyphID && !subset.has(lastGlyphID)) {
+        --lastGlyphID;
+    }
     SkASSERT(emSize > 0.0f);
     SkAutoGlyphCache cache = vector_cache(typeface, emSize);
     font->insertName("Subtype", "Type3");
     // Flip about the x-axis and scale by 1/emSize.
     SkMatrix fontMatrix;
     fontMatrix.setScale(SkScalarInvert(emSize), -SkScalarInvert(emSize));
     font->insertObject("FontMatrix", SkPDFUtils::MatrixToArray(fontMatrix));
 
     auto charProcs = sk_make_sp<SkPDFDict>();
     auto encoding = sk_make_sp<SkPDFDict>("Encoding");
@@ skipping 100 matching lines @@
 
 bool SkPDFFont::CanEmbedTypeface(SkTypeface* typeface, SkPDFCanon* canon) {
     const SkAdvancedTypefaceMetrics* metrics = SkPDFFont::GetMetrics(typeface, canon);
     return metrics && can_embed(*metrics);
 }
 
 void SkPDFFont::drop() {
     fTypeface = nullptr;
     this->SkPDFDict::drop();
 }