Add fallback fonts in pdfium

core/fpdfapi/fpdf_render/fpdf_render_text.cpp

Index: core/fpdfapi/fpdf_render/fpdf_render_text.cpp
diff --git a/core/fpdfapi/fpdf_render/fpdf_render_text.cpp b/core/fpdfapi/fpdf_render/fpdf_render_text.cpp
index 080a7578a77dfa2f7a97a223e7318edfa6e0a23a..759b0fdbf5bbb24ac4899b381e4d5c92984a8011 100644
--- a/core/fpdfapi/fpdf_render/fpdf_render_text.cpp
+++ b/core/fpdfapi/fpdf_render/fpdf_render_text.cpp
@@ -371,6 +371,7 @@ class CPDF_RefType3Cache {
   CPDF_Type3Font* const m_pType3Font;
 };
 
+// TODO(npm) Font fallback for type 3 fonts? (Completely separate code!!)
 FX_BOOL CPDF_RenderStatus::ProcessType3Text(const CPDF_TextObject* textobj,
                                             const CFX_Matrix* pObj2Device) {
   CPDF_Type3Font* pType3Font = textobj->m_TextState.GetFont()->AsType3Font();
@@ -560,6 +561,8 @@ void CPDF_CharPosList::Load(int nChars,
   m_nChars = 0;
   CPDF_CIDFont* pCIDFont = pFont->AsCIDFont();
   FX_BOOL bVertWriting = pCIDFont && pCIDFont->IsVertWriting();
+  if (pFont->m_FontPlusFallbacks.size() == 0)
+    pFont->m_FontPlusFallbacks.push_back(&pFont->m_Font);

[dsinclair, 2016/08/23 19:41:18]

Actually, can you just remove this font from the list and have it strictly a
fallback font list? You're always returning 1 as the index below, so this font
never gets picked up as the fallback font, which is fine. The code to look for
the font would then return >-1 for found fallback font.

[npm, 2016/08/23 20:36:57]

Done.

   for (int iChar = 0; iChar < nChars; iChar++) {
     uint32_t CharCode =
         nChars == 1 ? (uint32_t)(uintptr_t)pCharCodes : pCharCodes[iChar];
@@ -572,6 +575,17 @@ void CPDF_CharPosList::Load(int nChars,
       charpos.m_bFontStyle = true;
     }
     charpos.m_GlyphIndex = pFont->GlyphFromCharCode(CharCode, &bVert);
+    if (charpos.m_GlyphIndex != (uint32_t)-1) {

[dsinclair, 2016/08/23 19:41:18]

static_cast<uint32_t>(-1)

[npm, 2016/08/23 20:36:57]

Done.

+      charpos.m_FallbackFontPosition = 0;
+    } else {
+      charpos.m_FallbackFontPosition =
+          pFont->FallbackFontFromCharcode(CharCode, &bVert);
+      if (charpos.m_FallbackFontPosition > 0) {
+        charpos.m_GlyphIndex = pFont->FallbackGlyphFromCharcode(
+            charpos.m_FallbackFontPosition, CharCode, &bVert);
+      }
+    }
+// TODO(npm) Figure out how this affects m_ExtGID
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_APPLE_
     charpos.m_ExtGID = pFont->GlyphFromCharCodeExt(CharCode);
 #endif
@@ -629,10 +643,27 @@ FX_BOOL CPDF_TextRenderer::DrawTextPath(CFX_RenderDevice* pDevice,
                          : nullptr;
   CPDF_CharPosList CharPosList;
   CharPosList.Load(nChars, pCharCodes, pCharPos, pFont, font_size);
-  return pDevice->DrawTextPathWithFlags(
-      CharPosList.m_nChars, CharPosList.m_pCharPos, &pFont->m_Font, pCache,
-      font_size, pText2User, pUser2Device, pGraphState, fill_argb, stroke_argb,
-      pClippingPath, nFlag);
+  FX_BOOL bDraw = TRUE;
+  uint32_t pFontPosition = CharPosList.m_pCharPos[0].m_FallbackFontPosition;

[dsinclair, 2016/08/23 19:41:18]

This bit would have to become a bit smarter to handle the font that isn't in the
fallback list.

[npm, 2016/08/23 20:36:57]

Done.

+  uint32_t pStartIndex = 0;
+  for (uint32_t i = 0; i < CharPosList.m_nChars; i++) {
+    uint32_t pCurFontPosition =
+        CharPosList.m_pCharPos[i].m_FallbackFontPosition;
+    if (pFontPosition != pCurFontPosition) {
+      bDraw &= pDevice->DrawTextPathWithFlags(
+          i - pStartIndex, CharPosList.m_pCharPos + pStartIndex,
+          pFont->m_FontPlusFallbacks[pFontPosition], pCache, font_size,
+          pText2User, pUser2Device, pGraphState, fill_argb, stroke_argb,
+          pClippingPath, nFlag);
+      pFontPosition = pCurFontPosition;
+      pStartIndex = i;
+    }
+  }
+  bDraw &= pDevice->DrawTextPathWithFlags(
+      CharPosList.m_nChars - pStartIndex, CharPosList.m_pCharPos + pStartIndex,
+      pFont->m_FontPlusFallbacks[pFontPosition], pCache, font_size, pText2User,
+      pUser2Device, pGraphState, fill_argb, stroke_argb, pClippingPath, nFlag);
+  return bDraw;
 }
 
 // static
@@ -735,9 +766,26 @@ FX_BOOL CPDF_TextRenderer::DrawNormalText(CFX_RenderDevice* pDevice,
   if (pFont->IsCIDFont()) {
     FXGE_flags |= FXFONT_CIDFONT;
   }
-  return pDevice->DrawNormalText(CharPosList.m_nChars, CharPosList.m_pCharPos,
-                                 &pFont->m_Font, pCache, font_size,
-                                 pText2Device, fill_argb, FXGE_flags);
+  FX_BOOL bDraw = TRUE;
+  uint32_t pFontPosition = CharPosList.m_pCharPos[0].m_FallbackFontPosition;
+  uint32_t pStartIndex = 0;
+  for (uint32_t i = 0; i < CharPosList.m_nChars; i++) {
+    uint32_t pCurFontPosition =
+        CharPosList.m_pCharPos[i].m_FallbackFontPosition;
+    if (pFontPosition != pCurFontPosition) {
+      bDraw &= pDevice->DrawNormalText(
+          i - pStartIndex, CharPosList.m_pCharPos + pStartIndex,
+          pFont->m_FontPlusFallbacks[pFontPosition], pCache, font_size,
+          pText2Device, fill_argb, FXGE_flags);
+      pFontPosition = pCurFontPosition;
+      pStartIndex = i;
+    }
+  }
+  bDraw &= pDevice->DrawNormalText(
+      CharPosList.m_nChars - pStartIndex, CharPosList.m_pCharPos + pStartIndex,
+      pFont->m_FontPlusFallbacks[pFontPosition], pCache, font_size,
+      pText2Device, fill_argb, FXGE_flags);
+  return bDraw;
 }
 
 void CPDF_RenderStatus::DrawTextPathWithPattern(const CPDF_TextObject* textobj,
@@ -770,15 +818,21 @@ void CPDF_RenderStatus::DrawTextPathWithPattern(const CPDF_TextObject* textobj,
   } else {
     pCache = CFX_GEModule::Get()->GetFontCache();
   }
-  CFX_FaceCache* pFaceCache = pCache->GetCachedFace(&pFont->m_Font);
-  CFX_AutoFontCache autoFontCache(pCache, &pFont->m_Font);
   CPDF_CharPosList CharPosList;
   CharPosList.Load(textobj->m_nChars, textobj->m_pCharCodes,
                    textobj->m_pCharPos, pFont, font_size);
+  std::vector<CFX_FaceCache*> pFaceCaches;
+  std::vector<CFX_AutoFontCache> autoFontCaches;
+  for (auto& font : pFont->m_FontPlusFallbacks) {
+    pFaceCaches.push_back(pCache->GetCachedFace(font));
+    autoFontCaches.push_back(CFX_AutoFontCache(pCache, font));
+  }
   for (uint32_t i = 0; i < CharPosList.m_nChars; i++) {
     FXTEXT_CHARPOS& charpos = CharPosList.m_pCharPos[i];
-    const CFX_PathData* pPath = pFaceCache->LoadGlyphPath(
-        &pFont->m_Font, charpos.m_GlyphIndex, charpos.m_FontCharWidth);
+    const CFX_PathData* pPath =
+        pFaceCaches[charpos.m_FallbackFontPosition]->LoadGlyphPath(
+            pFont->m_FontPlusFallbacks[charpos.m_FallbackFontPosition],
+            charpos.m_GlyphIndex, charpos.m_FontCharWidth);
     if (!pPath) {
       continue;
     }