chromium/ui/views/controls/focus_ring.h

// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_CONTROLS_FOCUS_RING_H_
#define UI_VIEWS_CONTROLS_FOCUS_RING_H_

#include <memory>

#include "base/functional/callback.h"
#include "base/scoped_observation.h"
#include "ui/base/class_property.h"
#include "ui/base/metadata/metadata_types.h"
#include "ui/color/color_id.h"
#include "ui/native_theme/native_theme.h"
#include "ui/views/controls/focusable_border.h"
#include "ui/views/view.h"
#include "ui/views/view_observer.h"
#include "ui/views/views_export.h"

namespace views {

class HighlightPathGenerator;

// FocusRing is a View that is designed to act as an indicator of focus for its
// parent. It is a view that paints to a layer which extends beyond the bounds
// of its parent view.
// If MyView should show a rounded rectangular focus ring when it has focus and
// hide the ring when it loses focus, no other configuration is necessary. In
// other cases, it might be necessary to use the Set*() functions on FocusRing;
// these take care of repainting it when the state changes.
// TODO(tluk): FocusRing should not be a view but instead a new concept which
// only participates in view painting ( https://crbug.com/840796 ).
class VIEWS_EXPORT FocusRing : public View, public ViewObserver { … };

VIEWS_EXPORT SkPath
GetHighlightPath(const View* view,
                 float halo_thickness = FocusRing::kDefaultHaloThickness);

// Set this on the FocusRing host to have the FocusRing paint an outline around
// itself. This ensures that the FocusRing has sufficient contrast with its
// surroundings (this is used for prominent MdTextButtons because they are blue,
// while the background is light/dark, and the FocusRing doesn't contrast well
// with both the interior and exterior of the button). This may need some polish
// (such as blur?) in order to be expandable to all controls. For now it solves
// color contrast on prominent buttons which is an a11y issue. See
// https://crbug.com/1197631.
// TODO(pbos): Consider polishing this well enough that this can be
// unconditional. This may require rolling out `kCascadingBackgroundColor` to
// more surfaces to have an accurate background color.
VIEWS_EXPORT extern const ui::ClassProperty<bool>* const
    kDrawFocusRingBackgroundOutline;

}  // namespace views

#endif  // UI_VIEWS_CONTROLS_FOCUS_RING_H_