RenderText API Outline.

ui/gfx/render_text_win.cc

+// Copyright (c) 2011 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 "ui/gfx/render_text_win.h"
+
+// TODO(msw): Remove headers we're not using after Uniscribe impl...
+#include "base/i18n/break_iterator.h"
+#include "base/i18n/rtl.h"
+#include "base/logging.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/canvas_skia.h"
+
+namespace {
+
+// TODO(msw): Remove this and use Uniscribe rendering.
+// Compute the windows flags necessary to implement the provided text Canvas
+// flags.
+int ComputeFormatFlags(int flags, const string16& text) {
+  // Setting the text alignment explicitly in case it hasn't already been set.
+  // This will make sure that we don't align text to the left on RTL locales
+  // just because no alignment flag was passed to DrawStringInt().
+  if (!(flags & (gfx::Canvas::TEXT_ALIGN_CENTER |
+                 gfx::Canvas::TEXT_ALIGN_RIGHT |
+                 gfx::Canvas::TEXT_ALIGN_LEFT))) {
+    flags |= gfx::CanvasSkia::DefaultCanvasTextAlignment();
+  }
+
+  // horizontal alignment
+  int f = 0;
+  if (flags & gfx::Canvas::TEXT_ALIGN_CENTER)
+    f |= DT_CENTER;
+  else if (flags & gfx::Canvas::TEXT_ALIGN_RIGHT)
+    f |= DT_RIGHT;
+  else
+    f |= DT_LEFT;
+
+  // vertical alignment
+  if (flags & gfx::Canvas::TEXT_VALIGN_TOP)
+    f |= DT_TOP;
+  else if (flags & gfx::Canvas::TEXT_VALIGN_BOTTOM)
+    f |= DT_BOTTOM;
+  else
+    f |= DT_VCENTER;
+
+  if (flags & gfx::Canvas::MULTI_LINE) {
+    f |= DT_WORDBREAK;
+    if (flags & gfx::Canvas::CHARACTER_BREAK)
+      f |= DT_EDITCONTROL;  // Turns on character breaking (not documented)
+    else if (!(flags & gfx::Canvas::NO_ELLIPSIS))
+      f |= DT_WORD_ELLIPSIS;
+  } else {
+    f |= DT_SINGLELINE;
+  }
+
+  if (flags & gfx::Canvas::HIDE_PREFIX)
+    f |= DT_HIDEPREFIX;
+  else if ((flags & gfx::Canvas::SHOW_PREFIX) == 0)
+    f |= DT_NOPREFIX;
+
+  if (!(flags & gfx::Canvas::NO_ELLIPSIS))
+    f |= DT_END_ELLIPSIS;
+
+  // In order to make sure RTL/BiDi strings are rendered correctly, we must
+  // pass the flag DT_RTLREADING to DrawText (when the locale's language is
+  // a right-to-left language) so that Windows does the right thing.
+  //
+  // In addition to correctly displaying text containing both RTL and LTR
+  // elements (for example, a string containing a telephone number within a
+  // sentence in Hebrew, or a sentence in Hebrew that contains a word in
+  // English) this flag also makes sure that if there is not enough space to
+  // display the entire string, the ellipsis is displayed on the left hand side
+  // of the truncated string and not on the right hand side.
+  //
+  // We make a distinction between Chrome UI strings and text coming from a web
+  // page.
+  //
+  // For text coming from a web page we determine the alignment based on the
+  // first character with strong directionality. If the directionality of the
+  // first character with strong directionality in the text is LTR, the
+  // alignment is set to DT_LEFT, and the directionality should not be set as
+  // DT_RTLREADING.
+  //
+  // This heuristic doesn't work for Chrome UI strings since even in RTL
+  // locales, some of those might start with English text but we know they're
+  // localized so we always want them to be right aligned, and their
+  // directionality should be set as DT_RTLREADING.
+  //
+  // Caveat: If the string is purely LTR, don't set DTL_RTLREADING since when
+  // the flag is set, LRE-PDF don't have the desired effect of rendering
+  // multiline English-only text as LTR.
+  //
+  // Note that if the caller is explicitly requesting displaying the text
+  // using RTL directionality then we respect that and pass DT_RTLREADING to
+  // ::DrawText even if the locale is LTR.
+  if ((flags & gfx::Canvas::FORCE_RTL_DIRECTIONALITY) ||
+      (base::i18n::IsRTL() &&
+       (f & DT_RIGHT) && base::i18n::StringContainsStrongRTLChars(text))) {
+    f |= DT_RTLREADING;
+  }
+
+  return f;
+}
+
+// TODO(msw): Use Uniscribe.
+// We make sure that LTR text we draw in an RTL context is modified
+// appropriately to make sure it maintains it LTR orientation.
+void DoDrawText(HDC hdc,
+                const string16& text,
+                RECT* text_bounds,
+                int flags) {
+  // Only adjust string directionality if both of the following are true:
+  // 1. The current locale is RTL.
+  // 2. The string itself has RTL directionality.
+  const wchar_t* string_ptr = text.c_str();
+  int string_size = static_cast<int>(text.length());
+
+  string16 localized_text;
+  if (flags & DT_RTLREADING) {
+    localized_text = text;
+    base::i18n::AdjustStringForLocaleDirection(&localized_text);
+    string_ptr = localized_text.c_str();
+    string_size = static_cast<int>(localized_text.length());
+  }
+
+  DrawText(hdc, string_ptr, string_size, text_bounds, flags);
+}
+
+}  // namespace
+
+namespace gfx {
+
+RenderTextWin::RenderTextWin()
+    : RenderText() {
+}
+
+RenderTextWin::RenderTextWin(const string16& text,
+                             const gfx::Font& font,
+                             const SkColor& color,
+                             const gfx::Rect display_rect,
+                             int flags)
+    : RenderText(text, font, color, display_rect, flags) {
+}
+
+RenderTextWin::~RenderTextWin() {
+}
+
+void RenderTextWin::Draw(HDC drawing_context) const {
+  // TODO(msw): Use Uniscribe.
+  gfx::Rect r = get_display_rect();
+  RECT text_bounds = { r.x(), r.y(), r.x() + r.width(), r.y() + r.height() };
+  int flags = ComputeFormatFlags(get_flags(), text());
+  DoDrawText(drawing_context, text(), &text_bounds, flags);
+}
+
+size_t RenderTextWin::FindCursorPosition(const gfx::Point& point) const {
+  // TODO(msw): Use Uniscribe.
+  const gfx::Font& font = GetStyleRanges()[0]->font;
+  // TODO(msw): gfx::Insets insets = GetInsets();
+  int left = 0;
+  int left_pos = 0;
+  int right = font.GetStringWidth(text());
+  int right_pos = text().length();
+
+  int x = point.x(); // TODO(msw): - insets.left() - text_offset_;
+  if (x <= left) return left_pos;
+  if (x >= right) return right_pos;
+  // binary searching the cursor position.
+  // TODO(oshima): use the center of character instead of edge.
+  // Binary search may not work for language like arabic.
+  while (std::abs(static_cast<long>(right_pos - left_pos) > 1)) {
+    int pivot_pos = left_pos + (right_pos - left_pos) / 2;
+    int pivot = font.GetStringWidth(text().substr(0, pivot_pos));
+    if (pivot < x) {
+      left = pivot;
+      left_pos = pivot_pos;
+    } else if (pivot == x) {
+      return pivot_pos;
+    } else {
+      right = pivot;
+      right_pos = pivot_pos;
+    }
+  }
+  return left_pos;
+}
+
+std::vector<gfx::Rect> RenderTextWin::GetSubstringBounds(
+    const ui::Range& range) const {
+  // TODO(msw): Use Uniscribe.
+  size_t start = range.GetMin();
+  size_t end = range.GetMax();
+  const gfx::Font& font = GetStyleRanges()[0]->font;
+  int start_x = font.GetStringWidth(text().substr(0, start));
+  int end_x = font.GetStringWidth(text().substr(0, end));
+  std::vector<gfx::Rect> bounds;
+  bounds.push_back(gfx::Rect(start_x, 0, end_x - start_x, font.GetHeight()));
+  return bounds;
+}
+
+size_t RenderTextWin::GetLeftCursorPosition(size_t position,
+                                            bool move_by_word) const {
+  // TODO(msw): Use Uniscribe.
+  if (!move_by_word)
+    return position == 0? position : position - 1;
+  // Notes: We always iterate words from the begining.
+  // This is probably fast enough for our usage, but we may
+  // want to modify WordIterator so that it can start from the
+  // middle of string and advance backwards.
+  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
+  bool success = iter.Init();
+  DCHECK(success);
+  if (!success)
+    return position;
+  int last = 0;
+  while (iter.Advance()) {
+    if (iter.IsWord()) {
+      size_t begin = iter.pos() - iter.GetString().length();
+      if (begin == position) {
+        // The cursor is at the beginning of a word.
+        // Move to previous word.
+        break;
+      } else if(iter.pos() >= position) {
+        // The cursor is in the middle or at the end of a word.
+        // Move to the top of current word.
+        last = begin;
+        break;
+      } else {
+        last = iter.pos() - iter.GetString().length();
+      }
+    }
+  }
+
+  return last;
+}
+
+size_t RenderTextWin::GetRightCursorPosition(size_t position,
+                                             bool move_by_word) const {
+  // TODO(msw): Use Uniscribe.
+  if (!move_by_word)
+    return std::min(position + 1, text().length());
+  base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
+  bool success = iter.Init();
+  DCHECK(success);
+  if (!success)
+    return position;
+  size_t pos = 0;
+  while (iter.Advance()) {
+    pos = iter.pos();
+    if (iter.IsWord() && pos > position) {
+      break;
+    }
+  }
+  return pos;
+}
+
+gfx::Rect RenderTextWin::GetCursorBounds(size_t position,
+                                         bool insert_mode) const {
+  // TODO(msw): Use Uniscribe.
+  NOTIMPLEMENTED();
+  return gfx::Rect();
+}
+
+RenderText* RenderText::CreateRenderText() {
+  return new RenderTextWin;
+}
+
+RenderText* RenderText::CreateRenderText(const string16& text,
+                                         const gfx::Font& font,
+                                         const SkColor& color,
+                                         const gfx::Rect& display_rect,
+                                         int flags) {
+  return new RenderTextWin(text, font, color, display_rect, flags);
+}
+
+}  // namespace gfx