Implement font fallback in RenderTextWin, try #2.

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
===================================================================
--- ui/gfx/render_text_win.cc	(revision 110489)
+++ ui/gfx/render_text_win.cc	(working copy)
@@ -5,15 +5,16 @@
 #include "ui/gfx/render_text_win.h"
 
 #include <algorithm>
-#include <map>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/string_util.h"
+#include "base/utf_string_conversions.h"
 #include "base/win/scoped_hdc.h"
 #include "third_party/skia/include/core/SkTypeface.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia.h"
+#include "ui/gfx/platform_font.h"
 
 namespace {
 
@@ -62,6 +63,63 @@
   }
 }
 
+// Callback to |EnumEnhMetaFile()| to intercept font creation.
+int CALLBACK MetaFileEnumProc(HDC hdc,
+                              HANDLETABLE* table,
+                              CONST ENHMETARECORD* record,
+                              int table_entries,
+                              LPARAM log_font) {
+  if (record->iType == EMR_EXTCREATEFONTINDIRECTW) {
+    const EMREXTCREATEFONTINDIRECTW* create_font_record =
+        reinterpret_cast<const EMREXTCREATEFONTINDIRECTW*>(record);
+    *reinterpret_cast<LOGFONT*>(log_font) = create_font_record->elfw.elfLogFont;
+  }
+  return 1;
+}
+
+// Finds a fallback font to use to render the specified |text| with respect to
+// an initial |font|. Returns the resulting font via out param |result|. Returns
+// |true| if a fallback font was found.
+// Adapted from WebKit's |FontCache::GetFontDataForCharacters()|.
+bool ChooseFallbackFont(HDC hdc,
+                        const gfx::Font& font,
+                        const wchar_t* text,
+                        int text_length,
+                        gfx::Font* result) {
+  // Use a meta file to intercept the fallback font chosen by Uniscribe.
+  HDC meta_file_dc = CreateEnhMetaFile(hdc, NULL, NULL, NULL);
+  if (!meta_file_dc)
+    return false;
+
+  SelectObject(meta_file_dc, font.GetNativeFont());
+
+  SCRIPT_STRING_ANALYSIS script_analysis;
+  HRESULT hresult =
+      ScriptStringAnalyse(meta_file_dc, text, text_length, 0, -1,
+                          SSA_METAFILE | SSA_FALLBACK | SSA_GLYPHS | SSA_LINK,
+                          0, NULL, NULL, NULL, NULL, NULL, &script_analysis);
+
+  if (SUCCEEDED(hresult)) {
+    hresult = ScriptStringOut(script_analysis, 0, 0, 0, NULL, 0, 0, FALSE);
+    ScriptStringFree(&script_analysis);
+  }
+
+  bool found_fallback = false;
+  HENHMETAFILE meta_file = CloseEnhMetaFile(meta_file_dc);
+  if (SUCCEEDED(hresult)) {
+    LOGFONT log_font;
+    log_font.lfFaceName[0] = 0;
+    EnumEnhMetaFile(0, meta_file, MetaFileEnumProc, &log_font, NULL);
+    if (log_font.lfFaceName[0]) {
+      *result = gfx::Font(UTF16ToUTF8(log_font.lfFaceName), font.GetFontSize());
+      found_fallback = true;
+    }
+  }
+  DeleteEnhMetaFile(meta_file);
+
+  return found_fallback;
+}
+
 }  // namespace
 
 namespace gfx {
@@ -73,16 +131,20 @@
     underline(false),
     width(0),
     preceding_run_widths(0),
-    glyph_count(0) {
+    glyph_count(0),
+    script_cache(NULL) {
 }
 
+TextRun::~TextRun() {
+  ScriptFreeCache(&script_cache);
+}
+
 }  // namespace internal
 
 RenderTextWin::RenderTextWin()
     : RenderText(),
       script_control_(),
       script_state_(),
-      script_cache_(NULL),
       string_width_(0) {
   // Omitting default constructors for script_* would leave POD uninitialized.
   HRESULT hr = 0;
@@ -102,7 +164,6 @@
 }
 
 RenderTextWin::~RenderTextWin() {
-  ScriptFreeCache(&script_cache_);
   STLDeleteContainerPointers(runs_.begin(), runs_.end());
 }
 
@@ -341,7 +402,6 @@
 }
 
 void RenderTextWin::ItemizeLogicalText() {
-  text_is_dirty_ = false;
   STLDeleteContainerPointers(runs_.begin(), runs_.end());
   runs_.clear();
   if (text().empty())
@@ -352,18 +412,18 @@
 
   HRESULT hr = E_OUTOFMEMORY;
   int script_items_count = 0;
-  scoped_array<SCRIPT_ITEM> script_items;
+  std::vector<SCRIPT_ITEM> script_items;
   for (size_t n = kGuessItems; hr == E_OUTOFMEMORY && n < kMaxItems; n *= 2) {
     // Derive the array of Uniscribe script items from the logical text.
     // ScriptItemize always adds a terminal array item so that the length of the
     // last item can be derived from the terminal SCRIPT_ITEM::iCharPos.
-    script_items.reset(new SCRIPT_ITEM[n]);
+    script_items.resize(n);
     hr = ScriptItemize(raw_text,
                        text_length,
                        n - 1,
                        &script_control_,
                        &script_state_,
-                       script_items.get(),
+                       &script_items[0],
                        &script_items_count);
   }
   DCHECK(SUCCEEDED(hr));
@@ -375,7 +435,7 @@
   // TODO(msw): Only break for font changes, not color etc. See TextRun comment.
   // TODO(msw): Apply the overriding selection and composition styles.
   StyleRanges::const_iterator style = style_ranges().begin();
-  SCRIPT_ITEM* script_item = script_items.get();
+  SCRIPT_ITEM* script_item = &script_items[0];
   for (int run_break = 0; run_break < text_length;) {
     internal::TextRun* run = new internal::TextRun();
     run->range.set_start(run_break);
@@ -418,7 +478,7 @@
       run->glyphs.reset(new WORD[max_glyphs]);
       run->visible_attributes.reset(new SCRIPT_VISATTR[max_glyphs]);
       hr = ScriptShape(hdc,
-                       &script_cache_,
+                       &run->script_cache,
                        run_text,
                        run_length,
                        max_glyphs,
@@ -430,12 +490,20 @@
       if (hr == E_OUTOFMEMORY) {
         max_glyphs *= 2;
       } else if (hr == USP_E_SCRIPT_NOT_IN_FONT) {
-        // The run's font doesn't contain the required glyphs, use an alternate.
-        // TODO(msw): Font fallback... Don't use SCRIPT_UNDEFINED.
+        // TODO(msw): Don't use SCRIPT_UNDEFINED. Apparently Uniscribe can crash
+        //            on certain surrogate pairs with SCRIPT_UNDEFINED.
         //            See https://bugzilla.mozilla.org/show_bug.cgi?id=341500
         //            And http://maxradi.us/documents/uniscribe/
         if (run->script_analysis.eScript == SCRIPT_UNDEFINED)
           break;
+
+        // The run's font doesn't contain the required glyphs, use an alternate.
+        if (ChooseFallbackFont(hdc, run->font, run_text, run_length,
+                               &run->font)) {
+          ScriptFreeCache(&run->script_cache);
+          SelectObject(hdc, run->font.GetNativeFont());
+        }
+
         run->script_analysis.eScript = SCRIPT_UNDEFINED;
       } else {
         break;
@@ -447,7 +515,7 @@
       run->advance_widths.reset(new int[run->glyph_count]);
       run->offsets.reset(new GOFFSET[run->glyph_count]);
       hr = ScriptPlace(hdc,
-                       &script_cache_,
+                       &run->script_cache,
                        run->glyphs.get(),
                        run->glyph_count,
                        run->visible_attributes.get(),
@@ -507,7 +575,6 @@
   return run;
 }
 
-
 SelectionModel RenderTextWin::FirstSelectionModelInsideRun(
     internal::TextRun* run) {
   size_t caret = run->range.start();