Class CBitmapContext

class CBitmapContext : public CGraphicsContext;

Description

An abstract, device-independent, interface to bitmapped graphics contexts.

This holds the setting used to draw to a CBitmapDevice.

The default settings of a CBitmapContext object immediately after construction are:

drawing mode is EDrawModePen (pen and brush colours used as they are)

no clipping rectangle

pen settings are: black, solid, single pixel width

brush style is null

no text font selected

The classes CFbsBitGc and CWindowGc are derived from this class.

Derivation

• CBase - Base class for all classes to be instantiated on the heap

• CGraphicsContext - Abstract base class for all graphics contexts

• CBitmapContext - An abstract, device-independent, interface to bitmapped graphics contexts

Members

Defined in CBitmapContext:
AlphaBlendBitmaps(), AlphaBlendBitmaps(), BitBlt(), BitBlt(), BitBltMasked(), Clear(), Clear(), CopyRect(), Reserved_CBitmapContext_1(), Reserved_CBitmapContext_2(), Reserved_CBitmapContext_3(), Reserved_CGraphicsContext_2(), SetFaded(), SetFadingParameters()

Inherited from CBase:
Delete(), Extension_(), operator new()

Inherited from CGraphicsContext:
CancelClippingRect(), CancelClippingRegion(), Device(), DiscardBrushPattern(), DiscardFont(), DrawArc(), DrawBitmap(), DrawBitmapMasked(), DrawEllipse(), DrawLine(), DrawLineBy(), DrawLineTo(), DrawPie(), DrawPolyLine(), DrawPolygon(), DrawRect(), DrawRoundRect(), DrawText(), DrawTextExtended(), DrawTextVertical(), EAlternate, EAnd, ECenter, EDashedPen, EDiamondCrossHatchBrush, EDotDashPen, EDotDotDashPen, EDottedPen, EDrawModeAND, EDrawModeANDNOT, EDrawModeNOTAND, EDrawModeNOTANDNOT, EDrawModeNOTOR, EDrawModeNOTORNOT, EDrawModeNOTPEN, EDrawModeNOTSCREEN, EDrawModeNOTXOR, EDrawModeOR, EDrawModeORNOT, EDrawModePEN, EDrawModeWriteAlpha, EDrawModeXOR, EForwardDiagonalHatchBrush, EHorizontalHatchBrush, EInvertPen, EInvertScreen, ELeft, ELogicalOp, ENullBrush, ENullPen, EOr, EPatternedBrush, EPenmode, ERearwardDiagonalHatchBrush, ERight, ESolidBrush, ESolidPen, ESquareCrossHatchBrush, EVerticalHatchBrush, EWinding, EWriteAlpha, EXor, GetUnderlineMetrics(), JustificationInPixels(), MapColors(), MoveBy(), MoveTo(), Plot(), Reserved(), Reset(), SetBrushColor(), SetBrushOrigin(), SetBrushStyle(), SetCharJustification(), SetClippingRect(), SetClippingRegion(), SetDrawMode(), SetOrigin(), SetPenColor(), SetPenSize(), SetPenStyle(), SetStrikethroughStyle(), SetUnderlineStyle(), SetWordJustification(), TBrushStyle, TDrawMode, TDrawModeComponents, TDrawTextExtendedParam, TDrawTextParam, TFillRule, TPenStyle, TTextAlign, UseBrushPattern(), UseFont()

virtual void Clear()=0;

Description

Clears the whole bitmap.

The cleared area is filled with the current brush colour.

This pure virtual function is implemented in derived classes.

virtual void Clear(const TRect &aRect)=0;

Description

Clears a rectangular area of a bitmap.

The cleared area is filled with the current brush colour.

This pure virtual function is implemented in derived classes.

Parameters

const TRect &aRect The rectangle to clear.

virtual void CopyRect(const TPoint &aOffset, const TRect &aRect)=0;

Description

Copies a rectangle.

This pure virtual function is implemented in derived classes.

Parameters

const TPoint &aOffset The offset from the top left corner of the rectangle to be copied to the top left corner of the copy. const TRect &aRect The rectangular area to be copied.

virtual void BitBlt(const TPoint &aPoint, const CFbsBitmap *aBitmap)=0;

Description

Performs a bitmap block transfer.

This pure virtual function is implemented in derived classes.

Parameters

const TPoint &aPoint The destination for the top left corner of the transferred bitmap. It is relative to the top left corner of the destination bitmap, which may be the screen. const CFbsBitmap *aBitmap A memory-resident bitmap.

virtual void BitBlt(const TPoint &aPoint, const CFbsBitmap *aBitmap, const TRect &aRect)=0;

Description

Performs a bitmap block transfer of a rectangular piece of a bitmap.

If the specified rectangle is larger than the bitmap then the bitmap is padded with white.

This pure virtual function is implemented in derived classes.

Parameters

const TPoint &aPoint The destination for the top left corner of the transferred bitmap. It is relative to the top left corner of the destination bitmap, which may be the screen. const CFbsBitmap *aBitmap A memory-resident bitmap const TRect &aRect A rectangle defining the portion of the bitmap to transfer. Its coordinates are relative to the top left corner of the source bitmap.

virtual void BitBltMasked(const TPoint &aPoint, const CFbsBitmap *aBitmap, const TRect &aSourceRect, const CFbsBitmap *aMaskBitmap, TBool aInvertMask)=0;

Description

Performs a masked bitmap block transfer.

The mask bitmap can be used as either a positive or negative mask. Masked pixels are not mapped to the destination rectangle.

This function uses either a black and white (binary) mask bitmap, or if aMaskBitmap's display mode is EGray256, alpha blending is used. Use of any other mode may result in unpredictable results

With aInvertMask=EFalse, black pixels in the mask bitmap stop corresponding pixels in the source bitmap from being transferred to the destination rectangle. With aInvertMask=ETrue, white pixels in the mask bitmap stop corresponding pixels in the source bitmap from being transferred to the destination rectangle.

Note that if the mask bitmap is smaller than the source bitmap, then it is tiled across the bitmap. Note that the mask is applied before the piece of the bitmap is defined - the mask is tiled relative to the top left of the original source bitmap rather than the top left of the bitmap piece.

This pure virtual function is implemented in derived classes.

Parameters

const TPoint &aPoint The destination for the top left corner of the transferred bitmap. It is relative to the top left corner of the destination bitmap, which may be the screen. const CFbsBitmap *aBitmap A memory-resident source bitmap. const TRect &aSourceRect A rectangle defining the piece of the bitmap to be drawn, with co-ordinates relative to the top left corner of the bitmap. const CFbsBitmap *aMaskBitmap A mask bitmap TBool aInvertMask If EFalse, a source pixel that is masked by a black pixel is not transferred to the destination rectangle. If ETrue, then a source pixel that is masked by a white pixel is not transferred to the destination rectangle.

virtual void SetFaded(TBool aFaded)=0;

Description

Sets whether the graphics context is faded.

Parameters

TBool aFaded ETrue to fade the GC; EFalse to unfade it.

virtual void SetFadingParameters(TUint8 aBlackMap, TUint8 aWhiteMap)=0;

Description

Sets the fading parameters.

This function allows you to override the map used when drawing with a faded graphics context (GC). However if you draw to a faded window with a faded GC, then fading on the GC is ignored and the fading of the window is used.

Fading is used to change the colour of a window to make other windows stand out. Fading can either make a faded window closer to white or closer to black.

Fading re-maps colours in the faded GC to fall between the specified black and white map values. If aBlackMap=0 and aWhiteMap=255 then the colours are mapped unchanged. As the values converge the colours are mapped to a smaller range - so the differences between colours in the faded GC decrease. If the values are reversed then the colours are inverted (i.e. where the GC would be black, it is now white).

Parameters

TUint8 aBlackMap Black map fading parameter. Unfaded this is 0. TUint8 aWhiteMap White map fading parameter. Unfaded this is 255.

virtual TInt AlphaBlendBitmaps(const TPoint &aDestPt, const CFbsBitmap *aSrcBmp, const TRect &aSrcRect, const CFbsBitmap *aAlphaBmp, const TPoint &aAlphaPt)=0;

Description

Performs an alpha blending of the source data, aSrcBmp, with the CBitmapContext, using the data from aAlphaBmp as an alpha blending factor. The formula used is: (S * A + W * (255 - A)) / 255, where:

• S - a pixel from aSrcBmp;

• W - a pixel from the window;

• A - a pixel from aAlphaBmp; The contents of source and alpha bitmap are preserved. The calculated alpha blended pixels are written to the destination CBitmapContext.

Parameters

const TPoint &aDestPt const CFbsBitmap *aSrcBmp const TRect &aSrcRect const CFbsBitmap *aAlphaBmp const TPoint &aAlphaPt

Return value

TInt

virtual TInt AlphaBlendBitmaps(const TPoint &aDestPt, const CWsBitmap *aSrcBmp, const TRect &aSrcRect, const CWsBitmap *aAlphaBmp, const TPoint &aAlphaPt)=0;

Description

The method performs an alpha blending of the source data, aSrcBmp, with the CBitmapContext, using the data from aAlphaBmp as an alpha blending factor. For information on how this function works, see the other overload.

Parameters

const TPoint &aDestPt Position in the target the result should be drawn to. const CWsBitmap *aSrcBmp A pointer to the source bitmap. const TRect &aSrcRect The part of the source bitmap that should be used. const CWsBitmap *aAlphaBmp A pointer to the bitmap used as an alpha blending factor. const TPoint &aAlphaPt Position of the first pixel in the alpha bitmap that should be used as a source for the alpha blending. The size of the area is the same as the source bitmap area - aSrcRect parameter.

Return value

TInt

protected: virtual IMPORT_C void Reserved_CGraphicsContext_2();

Description

A reserved virtual function for future use.

protected: virtual IMPORT_C void Reserved_CBitmapContext_1();

Description

protected: virtual IMPORT_C void Reserved_CBitmapContext_2();

Description

protected: virtual IMPORT_C void Reserved_CBitmapContext_3();

Description