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#ifndef nsIBlender_h___
#define nsIBlender_h___

#include "nscore.h"
#include "nsISupports.h"
#include "nsIRenderingContext.h"

// IID for the nsIBlender interface
#define NS_IBLENDER_IID    \
{ 0xbdb4b5b0, 0xf0db, 0x11d1, \
{ 0xa8, 0x2a, 0x00, 0x40, 0x95, 0x9a, 0x28, 0xc9 } }

//----------------------------------------------------------------------

// Blender interface
class nsIBlender : public nsISupports
{
public:
  NS_DEFINE_STATIC_IID_ACCESSOR(NS_IBLENDER_IID)

  /**
   * Initialize the Blender
   * @update dc 11/4/98
   * @param  aContext is where the blender can get info about the device its blending on
   * @result The result of the initialization, NS_OK if no errors
   */
  NS_IMETHOD Init(nsIDeviceContext *aContext) = 0;

  /**
   * NOTE: if we can make this static, that would be great. I don't think we can.
   * Blend source and destination nsDrawingSurfaces. Both drawing surfaces
   * will have bitmaps associated with them.
   * @param aSX x offset into source drawing surface of blend area
   * @param aSY y offset into source drawing surface of blend area
   * @param aWidth width of blend area
   * @param aHeight width of blend area
   * @param aSrc  source for the blending
   * @param aDest destination for blending
   * @param aDX x offset into destination drawing surface of blend area
   * @param aDY y offset into destination drawing surface of blend area
   * @param aSrcOpacity 0.0f -> 1.0f opacity value of source area. 1.0f indicates
   *        complete opacity.
   * @param aSecondSrc an optional second source drawing surface which is used in
   *        conjunction with the background color parameters to determine
   *        which pixels to blend
   * @param aSrcBackColor color of pixels in aSrc that should be
   *        considered "background" color
   * @param aSecondSrcBackColor color of pixels in aSrc that should be
   *        considered "background" color
   */
  NS_IMETHOD Blend(PRInt32 aSX, PRInt32 aSY, PRInt32 aWidth, PRInt32 aHeight,nsDrawingSurface aSrc,
                   nsDrawingSurface aDest, PRInt32 aDX, PRInt32 aDY, float aSrcOpacity,
                   nsDrawingSurface aSecondSrc = nsnull, nscolor aSrcBackColor = NS_RGB(0, 0, 0),
                   nscolor aSecondSrcBackColor = NS_RGB(0, 0, 0)) = 0;

  NS_IMETHOD Blend(PRInt32 aSX, PRInt32 aSY, PRInt32 aWidth, PRInt32 aHeight, nsIRenderingContext *aSrc,
                   nsIRenderingContext *aDest, PRInt32 aDX, PRInt32 aDY, float aSrcOpacity,
                   nsIRenderingContext *aSecondSrc = nsnull, nscolor aSrcBackColor = NS_RGB(0, 0, 0),
                   nscolor aSecondSrcBackColor = NS_RGB(0, 0, 0)) = 0;

  /**
   GetAlphas computes an array of alpha values for a rectangle of pixels, using
   the drawn-onto-black and the drawn-onto-white images. The pixels are
   returned in a new'ed array of aRect.width*aRect.height elements, in row-major
   order. This array must be freed by the caller.
  */
  NS_IMETHOD GetAlphas(const nsRect& aRect, nsDrawingSurface aBlack,
                       nsDrawingSurface aWhite, PRUint8** aAlphas) = 0;
};

#endif
