Implement right-to-left text rendering in Pepper.

ppapi/shared_impl/private/ppb_browser_font_trusted_shared.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/shared_impl/private/ppb_browser_font_trusted_shared.h"
 
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "ppapi/c/dev/ppb_font_dev.h"
 #include "ppapi/shared_impl/ppapi_preferences.h"
 #include "ppapi/shared_impl/var.h"
 #include "ppapi/thunk/enter.h"
 #include "ppapi/thunk/ppb_image_data_api.h"
 #include "ppapi/thunk/thunk.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkRect.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebCanvas.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebFloatPoint.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebFloatRect.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebRect.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFont.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFontDescription.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebTextRun.h"
+#include "unicode/ubidi.h"
 
 using ppapi::StringVar;
 using ppapi::thunk::EnterResourceNoLock;
 using ppapi::thunk::PPB_ImageData_API;
 using WebKit::WebFloatPoint;
 using WebKit::WebFloatRect;
 using WebKit::WebFont;
 using WebKit::WebFontDescription;
 using WebKit::WebRect;
 using WebKit::WebTextRun;
@@ skipping 10 matching lines @@
 string16 GetFontFromMap(
     const webkit_glue::WebPreferences::ScriptFontFamilyMap& map,
     const std::string& script) {
   webkit_glue::WebPreferences::ScriptFontFamilyMap::const_iterator it =
       map.find(script);
   if (it != map.end())
     return it->second;
   return string16();
 }
 
+// Splits a PP_BrowserFont_Trusted_TextRun into a sequence or LTR and RTL
+// WebTextRuns that can be used for WebKit. Normally WebKit does this for us,
+// but the font drawing and measurement routines we call happen after this
+// step. So for correct rendering of RTL content, we need to do it ourselves.
+class TextRunCollection {
+ public:
+  TextRunCollection(const PP_BrowserFont_Trusted_TextRun& run)

[viettrungluu, 2012/06/26 17:59:40]

explicit?

+      : bidi_(NULL),
+        num_runs_(0) {
+    StringVar* text_string = StringVar::FromPPVar(run.text);
+    if (!text_string)
+      return;  // Leave num_runs_ = 0 so we'll do nothing.
+    text_ = UTF8ToUTF16(text_string->value());
+
+    if (run.override_direction) {
+      // Skip autodetection.
+      num_runs_ = 1;
+      override_run_ = WebTextRun(text_, PP_ToBool(run.rtl), true);
+    } else {
+      bidi_ = ubidi_open();
+      UErrorCode uerror = U_ZERO_ERROR;
+      ubidi_setPara(bidi_, text_.c_str(), text_.size(), run.rtl, NULL, &uerror);

[viettrungluu, 2012/06/26 17:59:40]

text_.data() instead .c_str()?

+      if (U_SUCCESS(uerror))
+        num_runs_ = ubidi_countRuns(bidi_, &uerror);
+    }
+  }
+
+  ~TextRunCollection() {
+    if (bidi_)
+      ubidi_close(bidi_);
+  }
+
+  const string16& text() const { return text_; }
+  int num_runs() const { return num_runs_; }
+
+  // Returns a WebTextRun with the info for the run at the given index.
+  // The range covered by the run is in the two output params.
+  WebTextRun GetRunAt(int index, int* run_start, int* run_len) const {
+    if (bidi_) {
+      bool run_rtl = !!ubidi_getVisualRun(bidi_, index, run_start, run_len);

[viettrungluu, 2012/06/26 17:59:40]

If ubidi_setPara() failed, do you really want to do this?
(Also, I suppose you're relying on int = int32_t. That's okay, but I'm not
entirely sure if we want to do that.)

More generally, should you always DCHECK(index < num_runs_) (outside this |if|)?

[brettw, 2012/06/27 17:42:46]

If setPara failed, num_runs will be 0 and we'll never get here.

+      return WebTextRun(string16(&text_[*run_start], *run_len),
+                        run_rtl, true);
+    }
+
+    // Override run, return the single one.
+    DCHECK(index == 0);
+    *run_start = 0;
+    *run_len = static_cast<int>(text_.size());
+    return override_run_;
+  }
+
+ private:
+  // Will be null if we skipped autodetection.
+  UBiDi* bidi_;
+
+  // Text of all the runs.
+  string16 text_;
+
+  int num_runs_;
+
+  // When the content specifies override_direction (bidi_ is null) then this
+  // will contain the single text run for WebKit.
+  WebTextRun override_run_;
+
+  DISALLOW_COPY_AND_ASSIGN(TextRunCollection);
+};
+
 bool PPTextRunToWebTextRun(const PP_BrowserFont_Trusted_TextRun& text,
                            WebTextRun* run) {
   StringVar* text_string = StringVar::FromPPVar(text.text);
   if (!text_string)
     return false;
 
   *run = WebTextRun(UTF8ToUTF16(text_string->value()),
                     PP_ToBool(text.rtl),
                     PP_ToBool(text.override_direction));
   return true;
@@ skipping 209 matching lines @@
     const PP_BrowserFont_Trusted_TextRun* text) {
   WebTextRun run;
   if (!PPTextRunToWebTextRun(*text, &run))
     return -1;
   return font_->calculateWidth(run);
 }
 
 uint32_t PPB_BrowserFont_Trusted_Shared::CharacterOffsetForPixel(
     const PP_BrowserFont_Trusted_TextRun* text,
     int32_t pixel_position) {
-  WebTextRun run;
-  if (!PPTextRunToWebTextRun(*text, &run))
-    return -1;
-  return static_cast<uint32_t>(font_->offsetForPosition(
-      run, static_cast<float>(pixel_position)));
+  TextRunCollection runs(*text);
+  int32_t cur_pixel_offset = 0;
+  for (int i = 0; i < runs.num_runs(); i++) {
+    int run_begin = 0, run_len = 0;

[viettrungluu, 2012/06/26 17:59:40]

Does our style guide really allow this?

+    WebTextRun run = runs.GetRunAt(i, &run_begin, &run_len);
+    int cur_width = font_->calculateWidth(run);

[viettrungluu, 2012/06/26 17:59:40]

I think "run_width" would be a better name for this variable.

+    if (pixel_position < cur_pixel_offset + cur_width) {
+      // Offset is in this run.
+      return static_cast<uint32_t>(font_->offsetForPosition(
+              run, static_cast<float>(pixel_position - cur_pixel_offset))) +
+          run_begin;
+    }
+    cur_pixel_offset += cur_width;
+  }
+  return runs.text().size();
 }
 
 int32_t PPB_BrowserFont_Trusted_Shared::PixelOffsetForCharacter(
     const PP_BrowserFont_Trusted_TextRun* text,
     uint32_t char_offset) {
-  WebTextRun run;
-  if (!PPTextRunToWebTextRun(*text, &run))
-    return -1;
-  if (char_offset >= run.text.length())
-    return -1;
-
-  WebFloatRect rect = font_->selectionRectForText(
-      run, WebFloatPoint(0.0f, 0.0f), font_->height(), 0, char_offset);
-  return static_cast<int>(rect.width);
+  TextRunCollection runs(*text);
+  int32_t cur_pixel_offset = 0;
+  for (int i = 0; i < runs.num_runs(); i++) {
+    int run_begin = 0, run_len = 0;

[viettrungluu, 2012/06/26 17:59:40]

...

+    WebTextRun run = runs.GetRunAt(i, &run_begin, &run_len);
+    if (char_offset >= static_cast<uint32_t>(run_begin) &&
+        char_offset < static_cast<uint32_t>(run_begin + run_len)) {
+      // Character we're looking for is in this run.
+      WebFloatRect rect = font_->selectionRectForText(
+          run, WebFloatPoint(0.0f, 0.0f), font_->height(), 0,
+          char_offset - run_begin);
+      return cur_pixel_offset + static_cast<int>(rect.width);
+    } else {
+      // Character is past this run, account for the pixels and continue
+      // looking.
+      cur_pixel_offset += font_->calculateWidth(run);
+    }
+  }
+  return -1;  // Requested a char beyond the end.
 }
 
 void PPB_BrowserFont_Trusted_Shared::DrawTextToCanvas(
     skia::PlatformCanvas* destination,
     const PP_BrowserFont_Trusted_TextRun& text,
     const PP_Point* position,
     uint32_t color,
     const PP_Rect* clip,
     PP_Bool image_data_is_opaque) {
-  WebTextRun run;
-  if (!PPTextRunToWebTextRun(text, &run))
-    return;
-
   // Convert position and clip.
   WebFloatPoint web_position(static_cast<float>(position->x),
                              static_cast<float>(position->y));
   WebRect web_clip;
   if (!clip) {
     // Use entire canvas. SkCanvas doesn't have a size on it, so we just use
     // the current clip bounds.
     SkRect skclip;
     destination->getClipBounds(&skclip);
     web_clip = WebRect(skclip.fLeft, skclip.fTop, skclip.fRight - skclip.fLeft,
                        skclip.fBottom - skclip.fTop);
   } else {
     web_clip = WebRect(clip->point.x, clip->point.y,
                        clip->size.width, clip->size.height);
   }
 
-  font_->drawText(destination, run, web_position, color, web_clip,
-                  PP_ToBool(image_data_is_opaque));
+  TextRunCollection runs(text);
+  for (int i = 0; i < runs.num_runs(); i++) {
+    int run_begin = 0, run_len = 0;

[viettrungluu, 2012/06/26 17:59:40]

...

+    WebTextRun run = runs.GetRunAt(i, &run_begin, &run_len);
+    font_->drawText(destination, run, web_position, color, web_clip,
+                    PP_ToBool(image_data_is_opaque));
+
+    // Advance to the next run. Note that we avoid doing this for the last run
+    // since it's unnecessary, measuring text is slow, and most of the time
+    // there will be only one run anyway.
+    if (i != runs.num_runs() - 1)
+      web_position.x += font_->calculateWidth(run);
+  }
 }
 
 }  // namespace ppapi