Source/platform/Theme.h

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef Theme_h
#define Theme_h

#include "platform/LengthBox.h"
#include "platform/LengthSize.h"
#include "platform/PlatformExport.h"
#include "platform/ThemeTypes.h"
#include "platform/fonts/FontDescription.h"
#include "platform/geometry/IntRect.h"
#include "platform/graphics/Color.h"
#include "wtf/Forward.h"

namespace blink {

class GraphicsContext;
class ScrollableArea;

// Unlike other platform classes, Theme does extensively use virtual functions.  This design allows a platform to switch between multiple themes at runtime.
class PLATFORM_EXPORT Theme {
public:
    Theme() { }
    virtual ~Theme() { }

    // A method to obtain the baseline position adjustment for a "leaf" control.  This will only be used if a baseline
    // position cannot be determined by examining child content. Checkboxes and radio buttons are examples of
    // controls that need to do this.  The adjustment is an offset that adds to the baseline, e.g., marginTop() + height() + |offset|.
    // The offset is not zoomed.
    virtual int baselinePositionAdjustment(ControlPart) const { return 0; }

    // A method asking if the control changes its appearance when the window is inactive.
    virtual bool controlHasInactiveAppearance(ControlPart) const { return false; }

    // General methods for whether or not any of the controls in the theme change appearance when the window is inactive or
    // when hovered over.
    virtual bool controlsCanHaveInactiveAppearance() const { return false; }
    virtual bool controlsCanHaveHoveredAppearance() const { return false; }

    // Used by LayoutTheme::isControlStyled to figure out if the native look and feel should be turned off.
    virtual bool controlDrawsBorder(ControlPart) const { return true; }
    virtual bool controlDrawsBackground(ControlPart) const { return true; }
    virtual bool controlDrawsFocusOutline(ControlPart) const { return true; }

    // Methods for obtaining platform-specific colors.
    virtual Color selectionColor(ControlPart, ControlState, SelectionPart) const { return Color(); }
    virtual Color textSearchHighlightColor() const { return Color(); }

    // CSS system colors and fonts
    virtual Color systemColor(ThemeColor) const { return Color(); }

    // How fast the caret blinks in text fields.
    virtual double caretBlinkInterval() const { return 0.5; }

    // Methods used to adjust the ComputedStyles of controls.

    // The font description result should have a zoomed font size.
    virtual FontDescription controlFont(ControlPart, const FontDescription& fontDescription, float /*zoomFactor*/) const { return fontDescription; }

    // The size here is in zoomed coordinates already.  If a new size is returned, it also needs to be in zoomed coordinates.
    virtual LengthSize controlSize(ControlPart, const FontDescription&, const LengthSize& zoomedSize, float /*zoomFactor*/) const { return zoomedSize; }

    // Returns the minimum size for a control in zoomed coordinates.
    virtual LengthSize minimumControlSize(ControlPart, const FontDescription&, float /*zoomFactor*/) const { return LengthSize(Length(0, Fixed), Length(0, Fixed)); }

    // Allows the theme to modify the existing padding/border.
    virtual LengthBox controlPadding(ControlPart, const FontDescription&, const LengthBox& zoomedBox, float zoomFactor) const;
    virtual LengthBox controlBorder(ControlPart, const FontDescription&, const LengthBox& zoomedBox, float zoomFactor) const;

    // Whether or not whitespace: pre should be forced on always.
    virtual bool controlRequiresPreWhiteSpace(ControlPart) const { return false; }

    // Method for painting a control. The rect is in zoomed coordinates.
    virtual void paint(ControlPart, ControlStates, GraphicsContext*, const IntRect& /*zoomedRect*/, float /*zoomFactor*/, ScrollableArea*) const { }

    // Add visual overflow (e.g., the check on an OS X checkbox). The rect passed in is in zoomed coordinates so
    // the inflation should take that into account and make sure the inflation amount is also scaled by the zoomFactor.
    virtual void addVisualOverflow(ControlPart, ControlStates, float zoomFactor, IntRect& borderBox) const { }

private:
    mutable Color m_activeSelectionColor;
    mutable Color m_inactiveSelectionColor;
};

PLATFORM_EXPORT Theme* platformTheme();

} // namespace blink

#endif // Theme_h