gecko/gfx/public/nsITheme.h

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/* service providing platform-specific native rendering for widgets */

#ifndef nsITheme_h_
#define nsITheme_h_

#include "nsISupports.h"
#include "nsCOMPtr.h"
#include "nsColor.h"

struct nsRect;
struct nsSize;
struct nsFont;
struct nsMargin;
class nsPresContext;
class nsIRenderingContext;
class nsIDeviceContext;
class nsIFrame;
class nsIContent;
class nsIAtom;

// IID for the nsITheme interface
// {df8baf21-5ea7-49eb-a2bc-f2fd4a9fd896}
#define NS_ITHEME_IID     \
{ 0xdf8baf21, 0x5ea7, 0x49eb, { 0xa2, 0xbc, 0xf2, 0xfd, 0x4a, 0x9f, 0xd8, 0x96 } }

// {D930E29B-6909-44e5-AB4B-AF10D6923705}
#define NS_THEMERENDERER_CID \
{ 0xd930e29b, 0x6909, 0x44e5, { 0xab, 0x4b, 0xaf, 0x10, 0xd6, 0x92, 0x37, 0x5 } }

/**
 * nsITheme is a service that provides platform-specific native
 * rendering for widgets.  In other words, it provides the necessary
 * operations to draw a rendering object (an nsIFrame) as a native
 * widget.
 *
 * All the methods on nsITheme take a rendering context or device
 * context, a frame (the rendering object), and a widget type (one of
 * the constants in nsThemeConstants.h).
 */
class nsITheme: public nsISupports {
public:
  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ITHEME_IID)
  
  NS_IMETHOD DrawWidgetBackground(nsIRenderingContext* aContext,
                                  nsIFrame* aFrame,
                                  PRUint8 aWidgetType,
                                  const nsRect& aRect,
                                  const nsRect& aClipRect)=0;

  /**
   * Get the computed CSS border for the widget, in pixels.
   */
  NS_IMETHOD GetWidgetBorder(nsIDeviceContext* aContext, 
                             nsIFrame* aFrame,
                             PRUint8 aWidgetType,
                             nsMargin* aResult)=0;

  /**
   * This method can return PR_FALSE to indicate that the CSS padding
   * value should be used.  Otherwise, it will fill in aResult with the
   * computed padding, in pixels, and return PR_TRUE.
   *
   * XXXldb This ought to be required to return true for non-containers
   * so that we don't let specified padding that has no effect change
   * the computed padding and potentially the size.
   */
  virtual PRBool GetWidgetPadding(nsIDeviceContext* aContext,
                                  nsIFrame* aFrame,
                                  PRUint8 aWidgetType,
                                  nsMargin* aResult) = 0;

  /**
   * This method can return PR_FALSE to indicate that no special
   * overflow area is required by the native widget. Otherwise it will
   * fill in aResult with the desired overflow area, in twips, relative
   * to the widget origin, and return PR_TRUE.
   */
  virtual PRBool GetWidgetOverflow(nsIDeviceContext* aContext,
                                   nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
                                   nsRect* aResult)
  { return PR_FALSE; }

  /**
   * Get the minimum border-box size of a widget, in *pixels* (in
   * |aResult|).  If |aIsOverridable| is set to true, this size is a
   * minimum size; if false, this size is the only valid size for the
   * widget.
   */
  NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                  nsIFrame* aFrame,
                                  PRUint8 aWidgetType,
                                  nsSize* aResult,
                                  PRBool* aIsOverridable)=0;

  NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                nsIAtom* aAttribute, PRBool* aShouldRepaint)=0;

  NS_IMETHOD ThemeChanged()=0;

  /**
   * Can the nsITheme implementation handle this widget?
   */
  virtual PRBool ThemeSupportsWidget(nsPresContext* aPresContext,
                                     nsIFrame* aFrame,
                                     PRUint8 aWidgetType)=0;

  virtual PRBool WidgetIsContainer(PRUint8 aWidgetType)=0;

  /**
   * Does the nsITheme implementation draw its own focus ring for this widget?
   */
  virtual PRBool ThemeDrawsFocusForWidget(nsPresContext* aPresContext,
                                          nsIFrame* aFrame,
                                          PRUint8 aWidgetType)=0;
  
  /**
    * Should we insert a dropmarker inside of combobox button?
   */
  virtual PRBool ThemeNeedsComboboxDropmarker()=0;
};

NS_DEFINE_STATIC_IID_ACCESSOR(nsITheme, NS_ITHEME_IID)

// Creator function
extern NS_METHOD NS_NewNativeTheme(nsISupports *aOuter, REFNSIID aIID, void **aResult);

#endif