Simplify handling of BiDi cursor movement

ui/gfx/render_text.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 "ui/gfx/render_text.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "base/i18n/break_iterator.h"
@@ skipping 320 matching lines @@
     // range ends beyond text_.length, it must be the last one.
     style_ranges_.back().range.set_end(text_.length());
   }
 #ifndef NDEBUG
   CheckStyleRanges(style_ranges_, text_.length());
 #endif
   cached_bounds_and_offset_valid_ = false;
 
   // Reset selection model. SetText should always followed by SetSelectionModel
   // or SetCursorPosition in upper layer.
-  SetSelectionModel(SelectionModel(0, 0, SelectionModel::LEADING));
+  SetSelectionModel(SelectionModel());
 
   UpdateLayout();
 }
 
 void RenderText::SetHorizontalAlignment(HorizontalAlignment alignment) {
   if (horizontal_alignment_ != alignment) {
     horizontal_alignment_ = alignment;
     display_offset_ = Point();
     cached_bounds_and_offset_valid_ = false;
   }
@@ skipping 32 matching lines @@
     UpdateLayout();
   }
 }
 
 void RenderText::SetDisplayRect(const Rect& r) {
   display_rect_ = r;
   cached_bounds_and_offset_valid_ = false;
   UpdateLayout();
 }
 
-size_t RenderText::GetCursorPosition() const {
-  return selection_model_.selection_end();
-}
-
 void RenderText::SetCursorPosition(size_t position) {
   MoveCursorTo(position, false);
 }
 
 void RenderText::MoveCursor(BreakType break_type,
                             VisualCursorDirection direction,
                             bool select) {
-  SelectionModel position(selection_model());
-  position.set_selection_start(GetCursorPosition());
+  SelectionModel position(cursor_position(), selection_model_.caret_affinity());
   // Cancelling a selection moves to the edge of the selection.
-  if (break_type != LINE_BREAK && !EmptySelection() && !select) {
+  if (break_type != LINE_BREAK && !selection().is_empty() && !select) {
     SelectionModel selection_start = GetSelectionModelForSelectionStart();
     int start_x = GetCursorBounds(selection_start, true).x();
     int cursor_x = GetCursorBounds(position, true).x();
     // Use the selection start if it is left (when |direction| is CURSOR_LEFT)
     // or right (when |direction| is CURSOR_RIGHT) of the selection end.
     if (direction == CURSOR_RIGHT ? start_x > cursor_x : start_x < cursor_x)
       position = selection_start;
     // For word breaks, use the nearest word boundary in the appropriate
     // |direction|.
     if (break_type == WORD_BREAK)
       position = GetAdjacentSelectionModel(position, break_type, direction);
   } else {
     position = GetAdjacentSelectionModel(position, break_type, direction);
   }
   if (select)
-    position.set_selection_start(GetSelectionStart());
+    position.set_selection_start(selection().start());
   MoveCursorTo(position);
 }
 
 bool RenderText::MoveCursorTo(const SelectionModel& model) {
-  SelectionModel sel(model);
+  // Enforce valid selection model components.
   size_t text_length = text().length();
-  // Enforce valid selection model components.
-  if (sel.selection_start() > text_length)
-    sel.set_selection_start(text_length);
-  if (sel.selection_end() > text_length)
-    sel.set_selection_end(text_length);
-  // The current model only supports caret positions at valid character indices.
-  if (text_length == 0) {
-    sel.set_caret_pos(0);
-    sel.set_caret_placement(SelectionModel::LEADING);
-  } else if (sel.caret_pos() >= text_length) {
-    SelectionModel end_selection =
-        EdgeSelectionModel(GetVisualDirectionOfLogicalEnd());
-    sel.set_caret_pos(end_selection.caret_pos());
-    sel.set_caret_placement(end_selection.caret_placement());
+  LogicalCursorDirection affinity = model.caret_affinity();
+  if (model.caret_pos() > text_length) {

[msw, 2012/03/08 18:07:19]

When is this true? What tries to move the cursor to a position beyond the text
length, and why do we support it?

[benrg, 2012/03/08 21:22:03]

I think that nobody should, but I'm nervous about changing this because I don't
understand every call site. For example OmniboxViewViews calls it indirectly and
I don't know what's going on with autocompletion, etc. Even if all
SelectionModel constructors were private, a client could accidentally or
deliberately apply a now-invalid saved selection after changing the text.

It might be worth making SelectionModel completely private and force clients to
do everything, including changing the text, through operations like
ReplaceSelection().

[msw, 2012/03/08 21:33:57]

Let's just remove this; in the worst case, a caller with garbage data will wind
up with the wrong affinity.

[benrg, 2012/03/08 22:06:31]

Done.

+    // Make the cursor appear at the edge of the text, not next to the final
+    // grapheme.
+    affinity = CURSOR_FORWARD;
   }
 
-  if (!IsCursorablePosition(sel.selection_start()) ||
-      !IsCursorablePosition(sel.selection_end()) ||
-      !IsCursorablePosition(sel.caret_pos()))
+  ui::Range range(std::min(model.selection().start(), text_length),
+                  std::min(model.caret_pos(), text_length));
+  // The current model only supports caret positions at valid character indices.
+  if (!IsCursorablePosition(range.start()) ||
+      !IsCursorablePosition(range.end()))
     return false;
-
-  bool changed = !sel.Equals(selection_model_);
+  SelectionModel sel(range, affinity);
+  bool changed = sel != selection_model_;
   SetSelectionModel(sel);
   return changed;
 }
 
 bool RenderText::MoveCursorTo(const Point& point, bool select) {
-  SelectionModel selection = FindCursorPosition(point);
+  SelectionModel position = FindCursorPosition(point);
   if (select)
-    selection.set_selection_start(GetSelectionStart());
-  return MoveCursorTo(selection);
+    position.set_selection_start(selection().start());
+  return MoveCursorTo(position);
 }
 
 bool RenderText::SelectRange(const ui::Range& range) {
-  size_t text_length = text().length();
-  size_t start = std::min(range.start(), text_length);
-  size_t end = std::min(range.end(), text_length);
-
-  if (!IsCursorablePosition(start) || !IsCursorablePosition(end))
+  ui::Range sel(std::min(range.start(), text().length()),
+                std::min(range.end(), text().length()));
+  if (!IsCursorablePosition(sel.start()) || !IsCursorablePosition(sel.end()))
     return false;
-
-  size_t pos = end;
-  SelectionModel::CaretPlacement placement = SelectionModel::LEADING;
-  if (start < end) {
-    pos = IndexOfAdjacentGrapheme(end, CURSOR_BACKWARD);
-    DCHECK_LT(pos, end);
-    placement = SelectionModel::TRAILING;
-  } else if (end == text_length) {
-    SelectionModel end_selection =
-        EdgeSelectionModel(GetVisualDirectionOfLogicalEnd());
-    pos = end_selection.caret_pos();
-    placement = end_selection.caret_placement();
-  }
-  SetSelectionModel(SelectionModel(start, end, pos, placement));
+  LogicalCursorDirection affinity =
+      (sel.is_reversed() || sel.is_empty()) ? CURSOR_FORWARD : CURSOR_BACKWARD;
+  SetSelectionModel(SelectionModel(sel, affinity));
   return true;
 }
 
 bool RenderText::IsPointInSelection(const Point& point) {
-  if (EmptySelection())
+  if (selection().is_empty())
     return false;
-  // TODO(xji): should this check whether the point is inside the visual
-  // selection bounds? In case of "abcFED", if "ED" is selected, |point| points
-  // to the right half of 'c', is the point in selection?
-  size_t pos = FindCursorPosition(point).selection_end();
-  return (pos >= MinOfSelection() && pos < MaxOfSelection());
+  SelectionModel cursor = FindCursorPosition(point);
+  return RangeContainsCaret(
+      selection(), cursor.caret_pos(), cursor.caret_affinity());
 }
 
 void RenderText::ClearSelection() {
-  SelectionModel sel(selection_model());
-  sel.set_selection_start(GetCursorPosition());
-  SetSelectionModel(sel);
+  SetSelectionModel(SelectionModel(cursor_position(),
+                                   selection_model_.caret_affinity()));
 }
 
 void RenderText::SelectAll() {
-  SelectionModel sel = EdgeSelectionModel(CURSOR_RIGHT);
-  sel.set_selection_start(EdgeSelectionModel(CURSOR_LEFT).selection_start());
-  SetSelectionModel(sel);
+  SelectionModel all;
+  if (GetTextDirection() == base::i18n::LEFT_TO_RIGHT)
+    all = SelectionModel(ui::Range(0, text().length()), CURSOR_FORWARD);
+  else
+    all = SelectionModel(ui::Range(text().length(), 0), CURSOR_BACKWARD);
+  SetSelectionModel(all);
 }
 
 void RenderText::SelectWord() {
   if (obscured_) {
     SelectAll();
     return;
   }
 
-  size_t cursor_position = GetCursorPosition();
+  size_t cursor_pos = cursor_position();
 
   base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
   bool success = iter.Init();
   DCHECK(success);
   if (!success)
     return;
 
-  size_t selection_start = cursor_position;
+  size_t selection_start = cursor_pos;
   for (; selection_start != 0; --selection_start) {
     if (iter.IsStartOfWord(selection_start) ||
         iter.IsEndOfWord(selection_start))
       break;
   }
 
-  if (selection_start == cursor_position)
-    ++cursor_position;
+  if (selection_start == cursor_pos)
+    ++cursor_pos;
 
-  for (; cursor_position < text().length(); ++cursor_position) {
-    if (iter.IsEndOfWord(cursor_position) ||
-        iter.IsStartOfWord(cursor_position))
+  for (; cursor_pos < text().length(); ++cursor_pos)
+    if (iter.IsEndOfWord(cursor_pos) || iter.IsStartOfWord(cursor_pos))
       break;
-  }
 
   MoveCursorTo(selection_start, false);
-  MoveCursorTo(cursor_position, true);
+  MoveCursorTo(cursor_pos, true);
 }
 
 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());
@@ skipping 45 matching lines @@
 
   DrawCursor(canvas);
 
   if (!text().empty()) {
     TRACE_EVENT0("gfx", "RenderText::Draw draw text");
     DrawVisualText(canvas);
   }
   canvas->Restore();
 }
 
+Rect RenderText::GetCursorBounds(const SelectionModel& caret,
+                                 bool insert_mode) {
+  EnsureLayout();
+
+  size_t caret_pos = caret.caret_pos();
+  // In overtype mode, ignore the affinity and always indicate that we will
+  // overtype the next character.
+  LogicalCursorDirection caret_affinity =
+      insert_mode ? caret.caret_affinity() : CURSOR_FORWARD;
+  int x = 0, width = 0, height = 0;
+  if (caret_pos == (caret_affinity == CURSOR_BACKWARD ? 0 : text().length())) {
+    // The caret is attached to the boundary. Always return a zero-width caret,
+    // since there is nothing to overtype.
+    Size size = GetStringSize();
+    if ((GetTextDirection() == base::i18n::RIGHT_TO_LEFT) == (caret_pos == 0))
+      x = size.width();
+    height = size.height();
+  } else {
+    size_t grapheme_start = (caret_affinity == CURSOR_FORWARD) ?
+        caret_pos : IndexOfAdjacentGrapheme(caret_pos, CURSOR_BACKWARD);
+    ui::Range xspan;
+    GetGlyphBounds(grapheme_start, &xspan, &height);
+    if (insert_mode) {
+      x = (caret_affinity == CURSOR_BACKWARD) ? xspan.end() : xspan.start();
+    } else {  // overtype mode
+      x = xspan.GetMin();
+      width = xspan.length();
+    }
+  }
+  height = std::min(height, display_rect().height());
+  int y = (display_rect().height() - height) / 2;
+  return Rect(ToViewPoint(Point(x, y)), Size(width, height));
+}
+
 const Rect& RenderText::GetUpdatedCursorBounds() {
   UpdateCachedBoundsAndOffset();
   return cursor_bounds_;
 }
 
 SelectionModel RenderText::GetSelectionModelForSelectionStart() {
-  size_t selection_start = GetSelectionStart();
-  size_t selection_end = GetCursorPosition();
-  if (selection_start < selection_end)
-    return SelectionModel(selection_start,
-                          selection_start,
-                          SelectionModel::LEADING);
-  else if (selection_start > selection_end)
-    return SelectionModel(
-        selection_start,
-        IndexOfAdjacentGrapheme(selection_start, CURSOR_BACKWARD),
-        SelectionModel::TRAILING);
-  return selection_model_;
+  const ui::Range& sel = selection();
+  if (sel.is_empty())
+    return selection_model_;
+  return SelectionModel(sel.start(),
+                        sel.is_reversed() ? CURSOR_BACKWARD : CURSOR_FORWARD);
 }
 
 RenderText::RenderText()
     : horizontal_alignment_(base::i18n::IsRTL() ? ALIGN_RIGHT : ALIGN_LEFT),
       cursor_enabled_(true),
       cursor_visible_(false),
       insert_mode_(true),
       cursor_color_(kDefaultCursorColor),
       focused_(false),
       composition_range_(ui::Range::InvalidRange()),
@@ skipping 16 matching lines @@
   EnsureLayout();
 
   if (break_type == LINE_BREAK || text().empty())
     return EdgeSelectionModel(direction);
   if (break_type == CHARACTER_BREAK)
     return AdjacentCharSelectionModel(current, direction);
   DCHECK(break_type == WORD_BREAK);
   return AdjacentWordSelectionModel(current, direction);
 }
 
+SelectionModel RenderText::EdgeSelectionModel(
+    VisualCursorDirection direction) {
+  if (direction == GetVisualDirectionOfLogicalEnd())
+    return SelectionModel(text().length(), CURSOR_FORWARD);
+  return SelectionModel(0, CURSOR_BACKWARD);
+}
+
 void RenderText::SetSelectionModel(const SelectionModel& model) {
-  DCHECK_LE(model.selection_start(), text().length());
-  selection_model_.set_selection_start(model.selection_start());
-  DCHECK_LE(model.selection_end(), text().length());
-  selection_model_.set_selection_end(model.selection_end());
-  DCHECK_LT(model.caret_pos(), std::max<size_t>(text().length(), 1));
-  selection_model_.set_caret_pos(model.caret_pos());
-  selection_model_.set_caret_placement(model.caret_placement());
-
+  DCHECK_LE(model.selection().GetMax(), text().length());
+  selection_model_ = model;
   cached_bounds_and_offset_valid_ = false;
 }
 
 string16 RenderText::GetDisplayText() const {
   if (!obscured_)
     return text_;
   size_t obscured_text_length =
       static_cast<size_t>(ui::UTF16IndexToOffset(text_, 0, text_.length()));
   return string16(obscured_text_length, kPasswordReplacementChar);
 }
 
 void RenderText::ApplyCompositionAndSelectionStyles(
     StyleRanges* style_ranges) {
   // TODO(msw): This pattern ought to be reconsidered; what about composition
   //            and selection overlaps, retain existing local style features?
   // 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());
+    composition_style.range = composition_range_;
     ApplyStyleRangeImpl(style_ranges, composition_style);
   }
   // Apply a selection style override to a copy of the style ranges.
-  if (!EmptySelection()) {
+  if (!selection().is_empty()) {
     StyleRange selection_style(default_style_);
     selection_style.foreground = NativeTheme::instance()->GetSystemColor(
         NativeTheme::kColorId_TextfieldSelectionColor);
-    selection_style.range.set_start(MinOfSelection());
-    selection_style.range.set_end(MaxOfSelection());
+    selection_style.range = ui::Range(selection().GetMin(),
+                                      selection().GetMax());
     ApplyStyleRangeImpl(style_ranges, selection_style);
   }
   // Apply replacement-mode style override to a copy of the style ranges.
   //
   // TODO(xji): NEED TO FIX FOR WINDOWS ASAP. Windows call this function (to
   // apply styles) in ItemizeLogicalText(). In order for the cursor's underline
   // character to be drawn correctly, we will need to re-layout the text. It's
   // not practical to do layout on every cursor blink. We need to fix Windows
   // port to apply styles during drawing phase like Linux port does.
   // http://crbug.com/110109
   if (!insert_mode_ && cursor_visible() && focused()) {
     StyleRange replacement_mode_style(default_style_);
     replacement_mode_style.foreground = NativeTheme::instance()->GetSystemColor(
         NativeTheme::kColorId_TextfieldSelectionColor);
-    size_t cursor = GetCursorPosition();
+    size_t cursor = cursor_position();
     replacement_mode_style.range.set_start(cursor);
     replacement_mode_style.range.set_end(
         IndexOfAdjacentGrapheme(cursor, CURSOR_FORWARD));
     ApplyStyleRangeImpl(style_ranges, replacement_mode_style);
   }
 }
 
 Point RenderText::GetTextOrigin() {
   Point origin = display_rect().origin();
   origin = origin.Add(GetUpdatedDisplayOffset());
   origin = origin.Add(GetAlignmentOffset());
   return origin;
 }
 
 Point RenderText::ToTextPoint(const Point& point) {
   return point.Subtract(GetTextOrigin());
 }
 
 Point RenderText::ToViewPoint(const Point& point) {
   return point.Add(GetTextOrigin());
 }
 
 int RenderText::GetContentWidth() {
-  return GetStringWidth() + (cursor_enabled_ ? 1 : 0);
+  return GetStringSize().width() + (cursor_enabled_ ? 1 : 0);
 }
 
 Point RenderText::GetAlignmentOffset() {
   if (horizontal_alignment() != ALIGN_LEFT) {
     int x_offset = display_rect().width() - GetContentWidth();
     if (horizontal_alignment() == ALIGN_CENTER)
       x_offset /= 2;
     return Point(x_offset, 0);
   }
   return Point();
 }
 
 Point RenderText::GetOriginForSkiaDrawing() {
   Point origin(GetTextOrigin());
   // TODO(msw): Establish a vertical baseline for strings of mixed font heights.
   const Font& font = GetFont();
   int height = font.GetHeight();
   DCHECK_LE(height, display_rect().height());
   // Center the text vertically in the display area.
   origin.Offset(0, (display_rect().height() - height) / 2);
   // Offset by the font size to account for Skia expecting y to be the bottom.
   origin.Offset(0, font.GetFontSize());
   return origin;
 }
 
 void RenderText::ApplyFadeEffects(internal::SkiaTextRenderer* renderer) {
   if (!fade_head() && !fade_tail())
     return;
 
-  const int text_width = GetStringWidth();
+  const int text_width = GetStringSize().width();
   const int display_width = display_rect().width();
 
   // If the text fits as-is, no need to fade.
   if (text_width <= display_width)
     return;
 
   int gradient_width = CalculateFadeGradientWidth(GetFont(), display_width);
   if (gradient_width == 0)
     return;
 
@@ skipping 22 matching lines @@
 
   const SkColor color = default_style().foreground;
   SkAutoTUnref<SkShader> shader(
       CreateFadeShader(text_rect, left_part, right_part, color));
   if (shader.get()) {
     // |renderer| adds its own ref. So don't |release()| it from the ref ptr.
     renderer->SetShader(shader.get());
   }
 }
 
+// static
+bool RenderText::RangeContainsCaret(const ui::Range& range,
+                                    size_t caret_pos,
+                                    LogicalCursorDirection caret_affinity) {
+  // NB: exploits unsigned wraparound (WG14/N1124 section 6.2.5 paragraph 9).
+  size_t adjacent = (caret_affinity == CURSOR_BACKWARD) ?
+      caret_pos - 1 : caret_pos + 1;
+  return range.Contains(ui::Range(caret_pos, adjacent));
+}
+
 void RenderText::MoveCursorTo(size_t position, bool select) {
   size_t cursor = std::min(position, text().length());
-  size_t caret_pos = IndexOfAdjacentGrapheme(cursor, CURSOR_BACKWARD);
-  SelectionModel::CaretPlacement placement = (caret_pos == cursor) ?
-      SelectionModel::LEADING : SelectionModel::TRAILING;
-  size_t selection_start = select ? GetSelectionStart() : cursor;
-  if (IsCursorablePosition(cursor)) {
-    SelectionModel sel(selection_start, cursor, caret_pos, placement);
-    SetSelectionModel(sel);
-  }
+  if (IsCursorablePosition(cursor))
+    SetSelectionModel(SelectionModel(
+        ui::Range(select ? selection().start() : cursor, cursor),
+        (cursor == 0) ? CURSOR_FORWARD : CURSOR_BACKWARD));
 }
 
 void RenderText::UpdateCachedBoundsAndOffset() {
   if (cached_bounds_and_offset_valid_)
     return;
 
   // First, set the valid flag true to calculate the current cursor bounds using
   // the stale |display_offset_|. Applying |delta_offset| at the end of this
   // function will set |cursor_bounds_| and |display_offset_| to correct values.
   cached_bounds_and_offset_valid_ = true;
@@ skipping 28 matching lines @@
     const int offset = negate_rtl * display_offset_.x();
     if (display_width > (content_width + offset))
       delta_offset = negate_rtl * (display_width - (content_width + offset));
   }
 
   display_offset_.Offset(delta_offset, 0);
   cursor_bounds_.Offset(delta_offset, 0);
 }
 
 void RenderText::DrawSelection(Canvas* canvas) {
-  std::vector<Rect> sel = GetSubstringBounds(
-      GetSelectionStart(), GetCursorPosition());
+  std::vector<Rect> sel = GetSubstringBounds(selection());
   NativeTheme::ColorId color_id = focused() ?
       NativeTheme::kColorId_TextfieldSelectionBackgroundFocused :
       NativeTheme::kColorId_TextfieldSelectionBackgroundUnfocused;
   SkColor color = NativeTheme::instance()->GetSystemColor(color_id);
   for (std::vector<Rect>::const_iterator i = sel.begin(); i < sel.end(); ++i)
     canvas->FillRect(*i, color);
 }
 
 void RenderText::DrawCursor(Canvas* canvas) {
   // Paint cursor. Replace cursor is drawn as rectangle for now.
   // TODO(msw): Draw a better cursor with a better indication of association.
   if (cursor_enabled() && cursor_visible() && focused()) {
     const Rect& bounds = GetUpdatedCursorBounds();
     if (bounds.width() != 0)
       canvas->FillRect(bounds, cursor_color_);
     else
       canvas->DrawRect(bounds, cursor_color_);
   }
 }
 
 }  // namespace gfx