Read, write and draw with a document's own fonts

core/fpdfapi/parser/cpdf_document.h

@@ -139,6 +139,24 @@ class CPDF_Document : public Observable,
     epdf_attachment_ = std::move(attachment);
   }
 
+  // EmbedPDF(fonts): the document's font index (CPDF_DocumentFonts in
+  // core/fpdfdoc), made on first use: what each embedded font program is,
+  // and the session's font state. Destroyed before the parser.
+  class FontIndex {
+   public:
+    virtual ~FontIndex() = default;
+    // A layer's transaction ended, committed or aborted: |objnums| are every
+    // object number it wrote, created or hid, and the overlay epoch was
+    // |epoch_at_begin| when it began and is |epoch| now.
+    virtual void TransactionEnded(const std::set<uint32_t>& objnums,
+                                  uint64_t epoch_at_begin,
+                                  uint64_t epoch) {}
+  };
+  FontIndex* font_index() const { return font_index_.get(); }
+  void SetFontIndex(std::unique_ptr<FontIndex> index) {
+    font_index_ = std::move(index);
+  }
+
   // EmbedPDF(fonts): session-scoped provenance for a resource name this
   // document instance handed out for a registered runtime font (a /DA font
   // alias reserved before its /DR entry exists). Never written to the file; a
@@ -438,6 +456,8 @@ class CPDF_Document : public Observable,
   // EmbedPDF(signatures): destroyed before everything declared above it (the
   // parser included), after the extension and the stock font clearer.
   std::unique_ptr<Attachment> epdf_attachment_;
+  // EmbedPDF(fonts): see font_index(); destroyed before the attachment.
+  std::unique_ptr<FontIndex> font_index_;
 
   // Must be second to last.
   StockFontClearer stock_font_clearer_;

core/fpdfapi/parser/cpdf_layer_document.cpp

@@ -504,6 +504,7 @@ bool CPDF_LayerDocument::BeginTransaction() {
   CPDF_WriteGeneration::SetCurrent(transaction_->generation);
   transaction_->root_before = GetCachedRootDict();
   transaction_->info_before = GetCachedInfoDict();
+  transaction_->epoch_at_begin = overlay_epoch_;
   return true;
 }
 
@@ -541,6 +542,9 @@ bool CPDF_LayerDocument::CommitTransaction() {
   }
   last_transaction_stats_ = tx->stats;
   ++overlay_epoch_;
+  if (FontIndex* index = font_index()) {
+    index->TransactionEnded(tx->touched, tx->epoch_at_begin, overlay_epoch_);
+  }
   return true;
 }
 
@@ -569,6 +573,9 @@ bool CPDF_LayerDocument::AbortTransaction() {
   ForgetDerivedDataOf(unreachable);
   last_transaction_stats_ = tx->stats;
   ++overlay_epoch_;
+  if (FontIndex* index = font_index()) {
+    index->TransactionEnded(tx->touched, tx->epoch_at_begin, overlay_epoch_);
+  }
   // tx->written and tx->hidden are dropped with tx. Nothing is undone.
   return true;
 }

core/fpdfapi/parser/cpdf_layer_document.h

@@ -52,6 +52,11 @@ class CPDF_LayerDocument final : public CPDF_Document {
   bool CommitTransaction();
   bool AbortTransaction();
   bool InTransaction() const { return !!transaction_; }
+  // EmbedPDF(fonts): the open transaction, for a derived cache that reads
+  // mid-write (what it has touched so far); null outside one.
+  const CPDF_LayerTransaction* open_transaction() const {
+    return transaction_.get();
+  }
   // What the last ended (or the open) transaction cost.
   const CPDF_LayerTransactionStats& GetTransactionStats() const {
     return transaction_ ? transaction_->stats : last_transaction_stats_;

core/fpdfapi/parser/cpdf_layer_transaction.h

@@ -75,6 +75,10 @@ struct CPDF_LayerTransaction {
   RetainPtr<CPDF_Dictionary> root_before;
   RetainPtr<CPDF_Dictionary> info_before;
 
+  // EmbedPDF(fonts): the overlay epoch at begin, for the font index to tell
+  // what changed outside any transaction.
+  uint64_t epoch_at_begin = 0;
+
   CPDF_LayerTransactionStats stats;
 };
 

core/fpdfdoc/BUILD.gn

@@ -26,6 +26,15 @@ source_set("fpdfdoc") {
     # EmbedPDF: a font as a face (family, weight, italic), one reader for all.
     "cpdf_fontface.cpp",
     "cpdf_fontface.h",
+    # EmbedPDF: the fonts a document uses and what each program is, a
+    # document font as a browser can draw it, and the fonts a write would
+    # draw text with (a resolver read).
+    "cpdf_displayprogram.cpp",
+    "cpdf_displayprogram.h",
+    "cpdf_documentfonts.cpp",
+    "cpdf_documentfonts.h",
+    "cpdf_fontresolver.cpp",
+    "cpdf_fontresolver.h",
     "cpdf_richtext.h",
     "cpdf_richtextjson.cpp",
     "cpdf_richtextjson.h",