[unseasoned-pdf] Implement Blink-based Linux font mapping.

Talk directly to FontService, instead of proxying the request through
PPAPI.

Bug: 1139079
Change-Id: I42627fc7ebdab74884cfd593ca1208cdbe78c754
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2853614
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#894358}

pdf/BUILD.gn

@@ -209,7 +209,10 @@ if (enable_pdf) {
         "pdfium/pdfium_font_linux.h",
       ]
 
-      deps += [ ":font_table_linux" ]
+      deps += [
+        ":font_table_linux",
+        "//components/services/font/public/cpp",
+      ]
     }
   }
 

pdf/pdfium/DEPS

@@ -1,4 +1,5 @@
 include_rules = [
+  "+components/services/font/public/cpp",
   "+third_party/pdfium/public",
   "+ui/gfx/codec",
   "+v8/include/cppgc/platform.h",

pdf/pdfium/pdfium_font_linux.cc

@@ -4,15 +4,19 @@
 
 #include "pdf/pdfium/pdfium_font_linux.h"
 
-#include <algorithm>
+#include <memory>
 #include <string>
 
+#include "base/files/file.h"
 #include "base/i18n/encoding_detection.h"
 #include "base/i18n/icu_string_conversions.h"
-#include "base/notreached.h"
+#include "base/no_destructor.h"
 #include "base/numerics/ranges.h"
+#include "base/sequence_checker.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
+#include "components/services/font/public/cpp/font_loader.h"
+#include "pdf/font_table_linux.h"
 #include "pdf/pdfium/pdfium_engine.h"
 #include "pdf/ppapi_migration/pdfium_font_linux.h"
 #include "third_party/blink/public/platform/web_font_description.h"
@@ -22,6 +26,85 @@ namespace chrome_pdf {
 
 namespace {
 
+// Maps font description and charset to `FontId` as requested by PDFium, with
+// `FontId` as an opaque type that PDFium works with. Based on the `FontId`,
+// PDFium can read from the font files using GetFontData(). Properly frees the
+// underlying resource type when PDFium is done with the mapped font.
+class BlinkFontMapper {
+ public:
+  // Defined as the type most convenient for use with PDFium's
+  // `FPDF_SYSFONTINFO` functions.
+  using FontId = void*;
+
+  BlinkFontMapper() = default;
+  ~BlinkFontMapper() = delete;
+
+  // Returns a handle to the font mapped based on `desc` and `charset`, for use
+  // as the `font_id` in GetFontData() and DeleteFont() below. Returns nullptr
+  // on failure.
+  // TODO(thestig): Document how this handles TTC files.
+  FontId MapFont(const blink::WebFontDescription& desc, int charset) {
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+    auto font_file = std::make_unique<base::File>();
+    // In RendererBlinkPlatform, SkFontConfigInterface::SetGlobal() only ever
+    // sets the global to a FontLoader. Thus it is safe to assume the returned
+    // result is just that.
+    auto* font_loader = reinterpret_cast<font_service::FontLoader*>(
+        SkFontConfigInterface::RefGlobal().get());
+    font_loader->MatchFontWithFallback(
+        desc.family.Utf8(),
+        desc.weight >= blink::WebFontDescription::kWeightBold, desc.italic,
+        charset, blink::WebFontDescription::kGenericFamilyStandard,
+        font_file.get());
+    if (!font_file->IsValid())
+      return nullptr;
+
+    // Release to PDFium. PDFium will free `font_file` in DeleteFont() below.
+    return font_file.release();
+  }
+
+  // Releases the font file that `font_id` points to.
+  void DeleteFont(FontId font_id) {
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+    delete FileFromFontId(font_id);
+  }
+
+  // Reads data from the `font_id` handle for `table` into a `buffer` of
+  // `buf_size`. Returns the amount of data read on success, or 0 on failure.
+  // If `buffer` is null, then just return the required size for the buffer.
+  // See content::GetFontTable() for information on the `table_tag` parameter.
+  unsigned long GetFontData(FontId font_id,
+                            unsigned int table_tag,
+                            unsigned char* buffer,
+                            unsigned long buf_size) const {
+    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+    // TODO(thestig): cache?
+    base::PlatformFile platform_file =
+        FileFromFontId(font_id)->GetPlatformFile();
+    size_t size = buf_size;
+    if (!pdf::GetFontTable(platform_file, table_tag, /*offset=*/0, buffer,
+                           &size)) {
+      return 0;
+    }
+    return size;
+  }
+
+ private:
+  static base::File* FileFromFontId(FontId font_id) {
+    return reinterpret_cast<base::File*>(font_id);
+  }
+
+  SEQUENCE_CHECKER(sequence_checker_);
+};
+
+BlinkFontMapper& GetBlinkFontMapper() {
+  static base::NoDestructor<BlinkFontMapper> mapper;
+  return *mapper;
+}
+
 bool UsePepperMapping() {
   return PDFiumEngine::GetFontMappingMode() != FontMappingMode::kBlink;
 }
@@ -153,8 +236,7 @@ void* MapFont(FPDF_SYSFONTINFO*,
   if (UsePepperMapping())
     return MapPepperFont(desc, charset);
 
-  NOTIMPLEMENTED();
+  return GetBlinkFontMapper().MapFont(desc, charset);
-  return nullptr;
 }
 
 unsigned long GetFontData(FPDF_SYSFONTINFO*,
@@ -165,8 +247,7 @@ unsigned long GetFontData(FPDF_SYSFONTINFO*,
   if (UsePepperMapping())
     return GetPepperFontData(font_id, table, buffer, buf_size);
 
-  NOTIMPLEMENTED();
+  return GetBlinkFontMapper().GetFontData(font_id, table, buffer, buf_size);
-  return 0;
 }
 
 void DeleteFont(FPDF_SYSFONTINFO*, void* font_id) {
@@ -175,7 +256,7 @@ void DeleteFont(FPDF_SYSFONTINFO*, void* font_id) {
     return;
   }
 
-  NOTIMPLEMENTED();
+  GetBlinkFontMapper().DeleteFont(font_id);
 }
 
 FPDF_SYSFONTINFO g_font_info = {1,           0, EnumFonts, MapFont,   0,