Add fallback fonts in pdfium

core/fpdfapi/fpdf_font/cpdf_font.cpp

Index: core/fpdfapi/fpdf_font/cpdf_font.cpp
diff --git a/core/fpdfapi/fpdf_font/cpdf_font.cpp b/core/fpdfapi/fpdf_font/cpdf_font.cpp
index 8101bd49a65eab2364ec6cd611466b9eac8e87bc..69fd72032b01934f727656d995d707094ba7242c 100644
--- a/core/fpdfapi/fpdf_font/cpdf_font.cpp
+++ b/core/fpdfapi/fpdf_font/cpdf_font.cpp
@@ -451,3 +451,24 @@ const FX_CHAR* CPDF_Font::GetAdobeCharName(
     name = PDF_CharNameFromPredefinedCharSet(iBaseEncoding, charcode);
   return name && name[0] ? name : nullptr;
 }
+
+uint32_t CPDF_Font::FallbackFontFromCharcode(uint32_t charcode,
+                                             bool* pVertGlyph) {
+  if (m_FontFallbacks.size() < 1) {

[Lei Zhang, 2016/08/24 04:43:10]

m_FontFallbacks.empty()

[npm, 2016/08/24 14:39:22]

Done.

+    m_FontFallbacks.push_back(std::unique_ptr<CFX_Font>(new CFX_Font()));

[Lei Zhang, 2016/08/24 04:43:10]

We have our own WrapUnique() if you don't want to write out CFX_Font 2x.

[npm, 2016/08/24 14:39:22]

Done.

+    m_FontFallbacks[0]->LoadSubst("Arial", IsTrueTypeFont(), m_Flags,
+                                  m_StemV * 5, m_ItalicAngle, 0,
+                                  IsVertWriting());
+  }
+  return 0;

[Lei Zhang, 2016/08/24 04:43:10]

So always return 0?

[npm, 2016/08/24 14:39:22]

For now, just having a single fallback font

+}
+
+int CPDF_Font::FallbackGlyphFromCharcode(int fallbackFont,
+                                         uint32_t charcode,
+                                         bool* pVertGlyph) {

[Lei Zhang, 2016/08/24 04:43:10]

not used?

[npm, 2016/08/24 14:39:22]

The vert parameter is in GlyphFromCharcode so it might be needed later on. But
for now I see no use for it. Should I delete then?

+  int glyph =
+      FXFT_Get_Char_Index(m_FontFallbacks[fallbackFont]->GetFace(), charcode);

[Lei Zhang, 2016/08/24 04:43:10]

Can |fallbackFont| go out of bound?

[npm, 2016/08/24 14:39:22]

This should not happen if the two methods are implemented properly, but I've
added a check

+  if (glyph == 0 || glyph == 0xffff)
+    return -1;
+  return glyph;
+}