RenderText API Outline.

ui/gfx/render_text.cc

Index: ui/gfx/render_text.cc
diff --git a/ui/gfx/render_text.cc b/ui/gfx/render_text.cc
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index 0000000000000000000000000000000000000000..c656792cef053a5f6c52db560758e50faf08110d
--- /dev/null
+++ b/ui/gfx/render_text.cc
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+// 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.h"
+
+#include <algorithm>
+
+#include "base/i18n/break_iterator.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/canvas_skia.h"
+
+namespace {
+
+#ifndef NDEBUG
+// Check StyleRanges invariant conditions: sorted and non-overlapping ranges.
+void CheckStyleRanges(const gfx::StyleRanges& style_ranges, size_t length) {
+  if (length == 0) {
+    DCHECK(style_ranges.empty()) << "Style ranges exist for empty text.";
+    return;
+  }
+  for (gfx::StyleRanges::size_type i = 0; i < style_ranges.size() - 1; i++) {
+    const ui::Range& former = style_ranges[i].range;
+    const ui::Range& latter = style_ranges[i + 1].range;
+    DCHECK(!former.is_empty()) << "Empty range at " << i << ":" << former;
+    DCHECK(former.IsValid()) << "Invalid range at " << i << ":" << former;
+    DCHECK(!former.is_reversed()) << "Reversed range at " << i << ":" << former;
+    DCHECK(former.end() == latter.start()) << "Ranges gap/overlap/unsorted." <<
+        "former:" << former << ", latter:" << latter;
+  }
+  const gfx::StyleRange& end_style = *style_ranges.rbegin();
+  DCHECK(!end_style.range.is_empty()) << "Empty range at end.";
+  DCHECK(end_style.range.IsValid()) << "Invalid range at end.";
+  DCHECK(!end_style.range.is_reversed()) << "Reversed range at end.";
+  DCHECK(end_style.range.end() == length) << "Style and text length mismatch.";
+}
+#endif
+
+void ApplyStyleRangeImpl(gfx::StyleRanges& style_ranges,
+                         gfx::StyleRange style_range) {
+  const ui::Range& new_range = style_range.range;
+  // Follow StyleRanges invariant conditions: sorted and non-overlapping ranges.
+  gfx::StyleRanges::iterator i;
+  for (i = style_ranges.begin(); i != style_ranges.end();) {
+    if (i->range.end() < new_range.start()) {
+      i++;
+    } else if (i->range.start() == new_range.end()) {
+      break;
+    } else if (new_range.Contains(i->range)) {
+      i = style_ranges.erase(i);
+      if (i == style_ranges.end())
+        break;
+    } else if (i->range.start() < new_range.start() &&
+               i->range.end() > new_range.end()) {
+      // Split the current style into two styles.
+      gfx::StyleRange split_style = gfx::StyleRange(*i);
+      split_style.range.set_end(new_range.start());
+      i = style_ranges.insert(i, split_style) + 1;
+      i->range.set_start(new_range.end());
+      break;
+    } else if (i->range.start() < new_range.start()) {
+      i->range.set_end(new_range.start());
+      i++;
+    } else if (i->range.end() > new_range.end()) {
+      i->range.set_start(new_range.end());
+      break;
+    } else
+      NOTREACHED();
+  }
+  // Add the new range in its sorted location.
+  style_ranges.insert(i, style_range);
+}
+
+}  // namespace
+
+namespace gfx {
+
+StyleRange::StyleRange()
+    : font(),
+      foreground(SK_ColorBLACK),
+      strike(false),
+      underline(false),
+      range() {
+}
+
+void RenderText::SetText(const string16& text) {
+  size_t old_text_length = text_.length();
+  text_ = text;
+
+  // Update the style ranges as needed.
+  if (text_.empty()) {
+    style_ranges_.clear();
+  } else if (style_ranges_.empty()) {
+    ApplyDefaultStyle();
+  } else if (text_.length() > old_text_length) {
+    style_ranges_.back().range.set_end(text_.length());
+  } else if (text_.length() < old_text_length) {
+    StyleRanges::iterator i;
+    for (i = style_ranges_.begin(); i != style_ranges_.end(); i++) {
+      if (i->range.start() >= text_.length()) {
+        i = style_ranges_.erase(i);
+        if (i == style_ranges_.end())
+          break;
+      } else if (i->range.end() > text_.length()) {
+        i->range.set_end(text_.length());
+      }
+    }
+    style_ranges_.back().range.set_end(text_.length());
+  }
+#ifndef NDEBUG
+  CheckStyleRanges(style_ranges_, text_.length());
+#endif
+}
+
+size_t RenderText::GetCursorPosition() const {
+  return GetSelection().end();
+}
+
+void RenderText::SetCursorPosition(const size_t position) {
+  SetSelection(ui::Range(position, position));
+}
+
+void RenderText::MoveCursorLeft(BreakType break_type, bool select) {
+  if (break_type == LINE_BREAK) {
+    MoveCursorTo(0, select);
+    return;
+  }
+  size_t position = GetCursorPosition();
+  // Cancelling a selection moves to the edge of the selection.
+  if (!GetSelection().is_empty() && !select) {
+    // Use the selection start if it is left of the selection end.
+    if (GetCursorBounds(GetSelection().start(), false).x() <
+        GetCursorBounds(position, false).x())
+      position = GetSelection().start();
+    // If |move_by_word|, use the nearest word boundary left of the selection.
+    if (break_type == WORD_BREAK)
+      position = GetLeftCursorPosition(position, true);
+  } else {
+    position = GetLeftCursorPosition(position, break_type == WORD_BREAK);
+  }
+  MoveCursorTo(position, select);
+}
+
+void RenderText::MoveCursorRight(BreakType break_type, bool select) {
+  if (break_type == LINE_BREAK) {
+    MoveCursorTo(text().length(), select);
+    return;
+  }
+  size_t position = GetCursorPosition();
+  // Cancelling a selection moves to the edge of the selection.
+  if (!GetSelection().is_empty() && !select) {
+    // Use the selection start if it is right of the selection end.
+    if (GetCursorBounds(GetSelection().start(), false).x() >
+        GetCursorBounds(position, false).x())
+      position = GetSelection().start();
+    // If |move_by_word|, use the nearest word boundary right of the selection.
+    if (break_type == WORD_BREAK)
+      position = GetRightCursorPosition(position, true);
+  } else {
+    position = GetRightCursorPosition(position, break_type == WORD_BREAK);
+  }
+  MoveCursorTo(position, select);
+}
+
+bool RenderText::MoveCursorTo(size_t position, bool select) {
+  bool changed = GetCursorPosition() != position ||
+                 select == GetSelection().is_empty();
+  if (select)
+    SetSelection(ui::Range(GetSelection().start(), position));
+  else
+    SetSelection(ui::Range(position, position));
+  return changed;
+}
+
+bool RenderText::MoveCursorTo(const gfx::Point& point, bool select) {
+  // TODO(msw): Make this function support cursor placement via mouse near BiDi
+  //  level changes. The visual cursor appearance will depend on the location
+  //  clicked, not solely the resulting logical cursor position. See the TODO
+  //  note pertaining to selection_range_ for more information.
+  return MoveCursorTo(FindCursorPosition(point), select);
+}
+
+const ui::Range& RenderText::GetSelection() const {
+  return selection_range_;
+}
+
+void RenderText::SetSelection(const ui::Range& range) {
+  selection_range_.set_end(std::min(range.end(), text().length()));
+  selection_range_.set_start(std::min(range.start(), text().length()));
+
+  // Update |display_offset_| to ensure the current cursor is visible.
+  gfx::Rect cursor_bounds(GetCursorBounds(GetCursorPosition(), insert_mode()));
+  int display_width = display_rect_.width();
+  int string_width = GetStringWidth();
+  if (string_width < display_width) {
+    // Show all text whenever the text fits to the size.
+    display_offset_.set_x(0);
+  } else if ((display_offset_.x() + cursor_bounds.right()) > display_width) {
+    // Pan to show the cursor when it overflows to the right,
+     display_offset_.set_x(display_width - cursor_bounds.right());
+  } else if ((display_offset_.x() + cursor_bounds.x()) < 0) {
+    // Pan to show the cursor when it overflows to the left.
+    display_offset_.set_x(-cursor_bounds.x());
+  }
+}
+
+bool RenderText::IsPointInSelection(const gfx::Point& point) const {
+  size_t pos = FindCursorPosition(point);
+  return (pos >= GetSelection().GetMin() && pos < GetSelection().GetMax());
+}
+
+void RenderText::ClearSelection() {
+  SetCursorPosition(GetCursorPosition());
+}
+
+void RenderText::SelectAll() {
+  SetSelection(ui::Range(0, text().length()));
+}
+
+void RenderText::SelectWord() {
+  size_t selection_start = GetSelection().start();
+  size_t cursor_position = GetCursorPosition();
+  // First we setup selection_start_ and cursor_pos_. There are so many cases
+  // because we try to emulate what select-word looks like in a gtk textfield.
+  // See associated testcase for different cases.
+  if (cursor_position > 0 && cursor_position < text().length()) {
+    if (isalnum(text()[cursor_position])) {
+      selection_start = cursor_position;
+      cursor_position++;
+    } else
+      selection_start = cursor_position - 1;
+  } else if (cursor_position == 0) {
+    selection_start = cursor_position;
+    if (text().length() > 0)
+      cursor_position++;
+  } else {
+    selection_start = cursor_position - 1;
+  }
+
+  // Now we move selection_start_ to beginning of selection. Selection boundary
+  // is defined as the position where we have alpha-num character on one side
+  // and non-alpha-num char on the other side.
+  for (; selection_start > 0; selection_start--) {
+    if (IsPositionAtWordSelectionBoundary(selection_start))
+      break;
+  }
+
+  // Now we move cursor_pos_ to end of selection. Selection boundary
+  // is defined as the position where we have alpha-num character on one side
+  // and non-alpha-num char on the other side.
+  for (; cursor_position < text().length(); cursor_position++) {
+    if (IsPositionAtWordSelectionBoundary(cursor_position))
+      break;
+  }
+
+  SetSelection(ui::Range(selection_start, cursor_position));
+}
+
+const ui::Range& RenderText::GetCompositionRange() const {
+  return composition_range_;
+}
+
+void RenderText::SetCompositionRange(const ui::Range& composition_range) {
+  CHECK(!composition_range.IsValid() ||
+        ui::Range(0, text_.length()).Contains(composition_range));
+  composition_range_.set_end(composition_range.end());
+  composition_range_.set_start(composition_range.start());
+}
+
+void RenderText::ApplyStyleRange(StyleRange style_range) {
+  const ui::Range& new_range = style_range.range;
+  if (!new_range.IsValid() || new_range.is_empty())
+    return;
+  CHECK(!new_range.is_reversed());
+  CHECK(ui::Range(0, text_.length()).Contains(new_range));
+  ApplyStyleRangeImpl(style_ranges_, style_range);
+#ifndef NDEBUG
+  CheckStyleRanges(style_ranges_, text_.length());
+#endif
+}
+
+void RenderText::ApplyDefaultStyle() {
+  style_ranges_.clear();
+  StyleRange style = StyleRange(default_style_);
+  style.range.set_end(text_.length());
+  style_ranges_.push_back(style);
+}
+
+base::i18n::TextDirection RenderText::GetTextDirection() const {
+  // TODO(msw): Bidi implementation, intended to replace the functionality added
+  //  in crrev.com/91881 (discussed in codereview.chromium.org/7324011).
+  return base::i18n::LEFT_TO_RIGHT;
+}
+
+int RenderText::GetStringWidth() const {
+  return GetSubstringBounds(ui::Range(0, text_.length()))[0].width();
+}
+
+void RenderText::Draw(gfx::Canvas* canvas) {
+  // Clip the canvas to the text display area.
+  canvas->ClipRectInt(display_rect_.x(), display_rect_.y(),
+                      display_rect_.width(), display_rect_.height());
+
+  // Draw the selection.
+  std::vector<gfx::Rect> selection(GetSubstringBounds(GetSelection()));
+  SkColor selection_color =
+      focused() ? kFocusedSelectionColor : kUnfocusedSelectionColor;
+  for (std::vector<gfx::Rect>::const_iterator i = selection.begin();
+       i < selection.end(); ++i) {
+    gfx::Rect r(*i);
+    r.Offset(display_offset_);
+    canvas->FillRectInt(selection_color, r.x(), r.y(), r.width(), r.height());
+  }
+
+  // Create a temporary copy of the style ranges for composition and selection.
+  // TODO(msw): This pattern ought to be reconsidered; what about composition
+  //            and selection overlaps, retain existing local style features?
+  StyleRanges style_ranges(style_ranges_);
+  // Apply a composition style override to a copy of the style ranges.
+  if (composition_range_.IsValid() && !composition_range_.is_empty()) {
+    StyleRange composition_style(default_style_);
+    composition_style.underline = true;
+    composition_style.range.set_start(composition_range_.start());
+    composition_style.range.set_end(composition_range_.end());
+    ApplyStyleRangeImpl(style_ranges, composition_style);
+  }
+  // Apply a selection style override to a copy of the style ranges.
+  if (selection_range_.IsValid() && !selection_range_.is_empty()) {
+    StyleRange selection_style(default_style_);
+    selection_style.foreground = kSelectedTextColor;
+    selection_style.range.set_start(selection_range_.GetMin());
+    selection_style.range.set_end(selection_range_.GetMax());
+    ApplyStyleRangeImpl(style_ranges, selection_style);
+  }
+
+  // Draw the text.
+  gfx::Rect bounds(display_rect_);
+  bounds.Offset(display_offset_);
+  for (StyleRanges::const_iterator i = style_ranges.begin();
+       i < style_ranges.end(); ++i) {
+    Font font = !i->underline ? i->font :
+        i->font.DeriveFont(0, i->font.GetStyle() | Font::UNDERLINED);
+    string16 text = text_.substr(i->range.start(), i->range.length());
+    bounds.set_width(font.GetStringWidth(text));
+    canvas->DrawStringInt(text, font, i->foreground, bounds);
+
+    // Draw the strikethrough.
+    if (i->strike) {
+      SkPaint paint;
+      paint.setAntiAlias(true);
+      paint.setStyle(SkPaint::kFill_Style);
+      paint.setColor(i->foreground);
+      paint.setStrokeWidth(kStrikeWidth);
+      canvas->AsCanvasSkia()->drawLine(SkIntToScalar(bounds.x()),
+                                       SkIntToScalar(bounds.bottom()),
+                                       SkIntToScalar(bounds.right()),
+                                       SkIntToScalar(bounds.y()),
+                                       paint);
+    }
+
+    bounds.set_x(bounds.x() + bounds.width());
+  }
+
+  // Paint cursor. Replace cursor is drawn as rectangle for now.
+  if (cursor_visible() && focused()) {
+    bounds = GetCursorBounds(GetCursorPosition(), insert_mode());
+    bounds.Offset(display_offset_);
+    if (!bounds.IsEmpty())
+      canvas->DrawRectInt(kCursorColor,
+                          bounds.x(),
+                          bounds.y(),
+                          bounds.width(),
+                          bounds.height());
+  }
+}
+
+size_t RenderText::FindCursorPosition(const gfx::Point& point) const {
+  const gfx::Font& font = Font();
+  int left = 0;
+  int left_pos = 0;
+  int right = font.GetStringWidth(text());
+  int right_pos = text().length();
+
+  int x = point.x();
+  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> RenderText::GetSubstringBounds(
+    const ui::Range& range) const {
+  size_t start = range.GetMin();
+  size_t end = range.GetMax();
+  gfx::Font 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;
+}
+
+gfx::Rect RenderText::GetCursorBounds(size_t cursor_pos,
+                                      bool insert_mode) const {
+  gfx::Font font;
+  int x = font.GetStringWidth(text_.substr(0U, cursor_pos));
+  DCHECK_GE(x, 0);
+  int h = std::min(display_rect_.height(), font.GetHeight());
+  gfx::Rect bounds(x, (display_rect_.height() - h) / 2, 1, h);
+  if (!insert_mode && text_.length() != cursor_pos)
+    bounds.set_width(font.GetStringWidth(text_.substr(0, cursor_pos + 1)) - x);
+  return bounds;
+}
+
+size_t RenderText::GetLeftCursorPosition(size_t position,
+                                         bool move_by_word) const {
+  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 RenderText::GetRightCursorPosition(size_t position,
+                                          bool move_by_word) const {
+  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;
+}
+
+RenderText::RenderText()
+    : text_(),
+      selection_range_(),
+      cursor_visible_(false),
+      insert_mode_(true),
+      composition_range_(),
+      style_ranges_(),
+      default_style_(),
+      display_rect_(),
+      display_offset_() {
+}
+
+RenderText::~RenderText() {
+}
+
+bool RenderText::IsPositionAtWordSelectionBoundary(size_t pos) {
+  return pos == 0 || (isalnum(text()[pos - 1]) && !isalnum(text()[pos])) ||
+      (!isalnum(text()[pos - 1]) && isalnum(text()[pos]));
+}
+
+}  // namespace gfx