Views:: Make Labels support text selection.

ui/views/controls/label.h

 // 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.
 
 #ifndef UI_VIEWS_CONTROLS_LABEL_H_
 #define UI_VIEWS_CONTROLS_LABEL_H_
 
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
+#include "base/optional.h"
 #include "ui/gfx/render_text.h"
+#include "ui/views/selection_controller_delegate.h"
 #include "ui/views/view.h"
 
 namespace views {
+class SelectionController;
 
 // A view subclass that can display a string.
-class VIEWS_EXPORT Label : public View {
+class VIEWS_EXPORT Label : public View, public SelectionControllerDelegate {
  public:
   // Internal class name.
   static const char kViewClassName[];
 
   // The padding for the focus border when rendering focused text.
   static const int kFocusBorderPadding;
 
   Label();
   explicit Label(const base::string16& text);
   Label(const base::string16& text, const gfx::FontList& font_list);
@@ skipping 16 matching lines @@
   // ensure that the foreground colors are readable over the background color.
   void SetAutoColorReadabilityEnabled(bool enabled);
 
   // Sets the color.  This will automatically force the color to be readable
   // over the current background color, if auto color readability is enabled.
   virtual void SetEnabledColor(SkColor color);
   void SetDisabledColor(SkColor color);
 
   SkColor enabled_color() const { return actual_enabled_color_; }
 
-  // Sets the background color.  This won't be explicitly drawn, but the label
+  // Sets the background color. This won't be explicitly drawn, but the label
   // will force the text color to be readable over it.
   void SetBackgroundColor(SkColor color);
   SkColor background_color() const { return background_color_; }
 
+  // Sets the selection text color. This will automatically force the color to
+  // be readable over the selection background color, if auto color readability
+  // is enabled. Initialized with system default.
+  void SetSelectionTextColor(SkColor color);
+  SkColor selection_text_color() const { return actual_selection_text_color_; }
+
+  // Sets the selection background color. Initialized with system default.
+  void SetSelectionBackgroundColor(SkColor color);
+  SkColor selection_background_color() const {
+    return selection_background_color_;
+  }
+
   // Set drop shadows underneath the text.
   void SetShadows(const gfx::ShadowValues& shadows);
   const gfx::ShadowValues& shadows() const { return render_text_->shadows(); }
 
   // Sets whether subpixel rendering is used; the default is true, but this
   // feature also requires an opaque background color.
   // TODO(mukai): rename this as SetSubpixelRenderingSuppressed() to keep the
   // consistency with RenderText field name.
   void SetSubpixelRenderingEnabled(bool subpixel_rendering_enabled);
 
@@ skipping 50 matching lines @@
 
   // Like SizeToFit, but uses a smaller width if possible.
   void SetMaximumWidth(int max_width);
 
   // Sets whether the preferred size is empty when the label is not visible.
   void set_collapse_when_hidden(bool value) { collapse_when_hidden_ = value; }
 
   // Get the text as displayed to the user, respecting the obscured flag.
   base::string16 GetDisplayTextForTesting();
 
+  // Returns true if the label is selectable. Default is false.
+  bool IsSelectable() const;
+
+  // Sets whether the label is selectable. False is returned if the call fails,
+  // i.e. when selection is not supported but |selectable| is true.
+  bool SetSelectable(bool selectable);
+
+  // Returns true if the label has a selection.
+  bool HasSelection() const;
+
+  // Selects the entire text. NO-OP if the label is not selectable.
+  void SelectAll();
+
+  // Clears any active selection.
+  void ClearSelection();
+
+  // Selects the given text range. NO-OP if the label is not selectable or the
+  // |range| endpoints don't lie on grapheme boundaries.
+  void SelectRange(const gfx::Range& range);
+
   // View:
   gfx::Insets GetInsets() const override;
   int GetBaseline() const override;
   gfx::Size GetPreferredSize() const override;
   gfx::Size GetMinimumSize() const override;
   int GetHeightForWidth(int w) const override;
   void Layout() override;
   const char* GetClassName() const override;
   View* GetTooltipHandlerForPoint(const gfx::Point& point) override;
   bool CanProcessEventsWithinSubtree() const override;
   void GetAccessibleState(ui::AXViewState* state) override;
   bool GetTooltipText(const gfx::Point& p,
                       base::string16* tooltip) const override;
   void OnEnabledChanged() override;
 
  protected:
   // Create a single RenderText instance to actually be painted.
   virtual std::unique_ptr<gfx::RenderText> CreateRenderText(
       const base::string16& text,
       gfx::HorizontalAlignment alignment,
       gfx::DirectionalityMode directionality,
-      gfx::ElideBehavior elide_behavior);
+      gfx::ElideBehavior elide_behavior) const;
 
   void PaintText(gfx::Canvas* canvas);
 
   SkColor disabled_color() const { return actual_disabled_color_; }
 
+  // Returns true if the label can be made selectable. For example, links do not
+  // support text selection.
+  // If a subclass stops supporting text selection, it should call

[msw, 2016/10/28 06:30:26]

Since Label [subclass] users can just call SetSelectable(true), shouldn't
subclasses also override this function to return false when they stop supporting
text selection (like how Label itself treats multi-line)? I guess that might be
implied here, but maybe say so explicitly?

[karandeepb, 2016/11/01 11:06:25]

Yeah that is why this is made virtual and is overriden in views::Link. Have
clarified this.

+  // SetSelectable(false).
+  virtual bool IsSelectionSupported() const;
+
   // View:
   void OnBoundsChanged(const gfx::Rect& previous_bounds) override;
   void VisibilityChanged(View* starting_from, bool is_visible) override;
   void OnPaint(gfx::Canvas* canvas) override;
   void OnDeviceScaleFactorChanged(float device_scale_factor) override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
+  gfx::NativeCursor GetCursor(const ui::MouseEvent& event) override;
+  void OnFocus() override;
+  void OnBlur() override;
+  bool OnMousePressed(const ui::MouseEvent& event) override;
+  bool OnMouseDragged(const ui::MouseEvent& event) override;
+  void OnMouseReleased(const ui::MouseEvent& event) override;
+  void OnMouseCaptureLost() override;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(LabelTest, ResetRenderTextData);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, MultilineSupportedRenderText);
   FRIEND_TEST_ALL_PREFIXES(LabelTest, TextChangeWithoutLayout);
   FRIEND_TEST_ALL_PREFIXES(LabelFocusTest, FocusBounds);
   FRIEND_TEST_ALL_PREFIXES(LabelFocusTest, EmptyLabel);
 
+  // SelectionControllerDelegate overrides:
+  gfx::RenderText* GetRenderTextForSelectionController() override;
+  bool IsReadOnly() const override;
+  bool SupportsDrag() const override;
+  bool HasTextBeingDragged() const override;
+  void SetTextBeingDragged(bool value) override;
+  int GetViewHeight() const override;
+  int GetViewWidth() const override;
+  int GetDragSelectionDelay() const override;
+  void OnBeforePointerAction() override;
+  void OnAfterPointerAction(bool text_changed, bool selection_changed) override;
+  bool PasteSelectionClipboard() override;
+  void UpdateSelectionClipboard() override;
+
+  const gfx::RenderText* GetRenderTextForSelectionController() const;
+
   void Init(const base::string16& text, const gfx::FontList& font_list);
 
   void ResetLayout();
 
   // Set up |lines_| to actually be painted.
-  void MaybeBuildRenderTextLines();
+  void MaybeBuildRenderTextLines() const;
 
-  gfx::Rect GetFocusBounds();
+  gfx::Rect GetFocusBounds() const;
 
   // Get the text broken into lines as needed to fit the given |width|.
   std::vector<base::string16> GetLinesForWidth(int width) const;
 
   // Get the text size for the current layout.
   gfx::Size GetTextSize() const;
 
   // Updates |actual_{enabled,disabled}_color_| from requested colors.
   void RecalculateColors();
 
   // Applies |actual_{enabled,disabled}_color_| to |lines_|.
-  void ApplyTextColors();
+  void ApplyTextColors() const;
 
   // Updates any colors that have not been explicitly set from the theme.
   void UpdateColorsFromTheme(const ui::NativeTheme* theme);
 
   bool ShouldShowDefaultTooltip() const;
 
+  // Empties |lines_| and updates |last_selection_range_|.
+  void ClearRenderTextLines() const;
+
   // An un-elided and single-line RenderText object used for preferred sizing.
   std::unique_ptr<gfx::RenderText> render_text_;
 
   // The RenderText instances used to display elided and multi-line text.
-  std::vector<std::unique_ptr<gfx::RenderText>> lines_;
+  mutable std::vector<std::unique_ptr<gfx::RenderText>> lines_;
+
+  // Persists the current selection range between the calls to
+  // ClearRenderTextLines() and MaybeBuildRenderTextLines().
+  mutable base::Optional<gfx::Range> last_selection_range_;

[msw, 2016/10/28 06:30:26]

Nice explanatory comment. Some questions/comments here:
1) How bad is it to just clear the selection on layout and other
ClearRenderTextLines() callers? Is it really common/annoying?
2) Can we just use the selection range from the render_text_ instance?
3) Can we avoid optional and set the range invalid instead?
4) And maybe name this |stored_selection_range_|?

[karandeepb, 2016/11/01 11:06:25]

That would cause the selection to erase every time we resize the Label. Don't
think we'd want that.
This seems clearer to me.
It would be confusing to have render_text_->selection() not always be in sync
with the actual selection (like last_selection_range_ is currently). To keep
them in sync, would require some more code.
Done.
Done.

 
   SkColor requested_enabled_color_ = SK_ColorRED;
   SkColor actual_enabled_color_ = SK_ColorRED;
   SkColor requested_disabled_color_ = SK_ColorRED;
   SkColor actual_disabled_color_ = SK_ColorRED;
   SkColor background_color_ = SK_ColorRED;
+  SkColor requested_selection_text_color_ = SK_ColorRED;
+  SkColor actual_selection_text_color_ = SK_ColorRED;
+  SkColor selection_background_color_ = SK_ColorRED;
 
   // Set to true once the corresponding setter is invoked.
   bool enabled_color_set_;
   bool disabled_color_set_;
   bool background_color_set_;
+  bool selection_text_color_set_;
+  bool selection_background_color_set_;
 
   gfx::ElideBehavior elide_behavior_;
 
   bool subpixel_rendering_enabled_;
   bool auto_color_readability_;
   // TODO(mukai): remove |multi_line_| when all RenderText can render multiline.
   bool multi_line_;
   base::string16 tooltip_text_;
   bool handles_tooltips_;
   // Whether to collapse the label when it's not visible.
   bool collapse_when_hidden_;
   int fixed_width_;
   int max_width_;
 
   // TODO(ckocagil): Remove is_first_paint_text_ before crbug.com/441028 is
   // closed.
   bool is_first_paint_text_;
 
+  std::unique_ptr<SelectionController> selection_controller_;
+
   DISALLOW_COPY_AND_ASSIGN(Label);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_LABEL_H_