CWindowGc Class Reference

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

This method is supported from version 8.1

See also: CFbsBitGc::AlphaBlendBitmaps()

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

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

This method is supported from version 8.1

See also: CFbsBitGc::AlphaBlendBitmaps()

Performs a bitmap block transfer.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

See also: CBitmapContext::BitBlt()

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

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Note: if the rectangle aSource is larger than the bitmap then the bitmap will be padded with white.

See also: CBitmapContext::BitBlt()

Performs a bitmap block transfer on a bitmap to which the window server already has a handle.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

This function should be used in preference to the CFbsBitmap overload if the bitmap is to be used more than once, as it is a lot quicker.

See also: CBitmapContext::BitBlt()

Performs a bitmap block transfer of a rectangular piece of a bitmap to which the window server already has a handle.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

This function should be used in preference to the CFbsBitmap overload if the bitmap is to be used more than once, as it is a lot quicker.

Note: if the rectangle aSource is larger than the bitmap then the bitmap will be padded with white.

See also: CBitmapContext::BitBlt()

Performs a masked bitmap block transfer of a memory resident source bitmap.

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

A black and white (binary) mask bitmap is used. 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.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

See also: CBitmapContext::BitBltMasked()

Performs a masked bitmap block transfer of a window server bitmap.

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

A black and white (binary) mask bitmap is used. 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.

This function should be used in preference to the CFbsBitmap overload if the bitmap is to be used more than once, as it is a lot quicker.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

See also: CBitmapContext::BitBltMasked()

Cancels the clipping rectangle.

See also: SetClippingRect()

Cancels the current clipping region.

Clears the whole window.

The cleared area is filled with the current brush colour.

See also: CBitmapContext::Clear()

Clears a rectangular area of a window.

The cleared area is filled with the current brush colour.

See also: CBitmapContext::Clear()

Completes construction.

Copies a rectangle from any part of the screen into the window that the gc is active on.

The copy part of the operation applies to the whole rectangle, irrespective of whether or not it within the window, however the "paste" is clipped to the drawing area.

The rectangle is specified in window coordinates (if the top-left of the rectangle is (0,0) then the area of the screen it specifies has its top-left at the top left corner of the window, if it is (-10,-10) then it starts 10 pixels above and to the left of the window).

Note: shadows in the source rectangle will be copied. None of the area drawn to will gain shadowing (even if the window is already in shadow).

This version of this function is only really suitable for testing.

See also: CBitmapContext::CopyRect()

Frees the graphics context to be used with another window.

This method should be called when the application has completed drawing to the window.

Returns a pointer to the device, more specifically a CWsScreenDevice, for the screen that the WindowGc was last activated on. If the WindowGc has not been activated at all, it then returns the device that was passed to its constructor.

The user should be careful when calling this function since it can return the screen device of any screen in the system. Hence, the return value of this function will be useful only if the user is aware of how the WindowGc was used before this function is called.

Discards a non-built-in brush pattern.

This frees up the memory used for the bitmap, if it is not being shared by another process.

If no brush pattern has been set when this function is called, it has no effect.

See also: CGraphicsContext::DiscardBrushPattern()

Discards a font.

This frees up the memory used (if the font is not being shared with some other process).

Note that if no font is in use when this function is called, then there is no effect.

See also: CGraphicsContext::DiscardFont()

Draws an arc (a portion of an ellipse).

The point aStart is used to define one end of a line from the geometric centre of the ellipse. The point of intersection between this line and the ellipse defines the start point of the arc. The point aEnd is used to define one end of a second line from the geometric centre of the ellipse. The point of intersection between this line and the ellipse defines the end point of the arc. The pixels at both the start point and the end point are drawn.

The arc itself is the segment of the ellipse in an anti-clockwise direction from the start point to the end point.

Notes

A rectangle is used in the construction of the ellipse of which the arc is a segment. This rectangle is passed as an argument of type TRect.

A wide line arc is drawn with the pixels distributed either side of a true ellipse, in such a way that the outer edge of the line would touch the edge of the construction rectangle. In other words, the ellipse used to construct it is slightly smaller than that for a single pixel line size.

If aStart or aEnd are the ellipse centre then the line that defines the start/end of the arc defaults to one extending vertically above the centre point.

If aStart and aEnd are the same point, or points on the same line through the ellipse centre then a complete unfilled ellipse is drawn.

Line drawing is subject to pen colour, width and style and draw mode

See also: CGraphicsContext::DrawArc()

Draws a bitmap at a specified point.

The function does a compress/stretch based on its internally stored size in twips. Note that if the twips value of the bitmap is not set then nothing is drawn (this is the default situation).

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Note: this member function uses the bitmap's size in twips and does a stretch/compress blit using a linear DDA.

See also: CGraphicsContext::DrawBitmap()

Draws a bitmap in a rectangle.

The bitmap is compressed/stretched to fit the specified rectangle. Note that if the twips value of the bitmap is not set then nothing is drawn (this is the default situation).

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Notes: this member function uses the bitmap's size in pixels and does a stretch/compress blit using a linear DDA.

See also: CGraphicsContext::DrawBitmap()

Draws a specified rectangle from a bitmap into another rectangle.

The function compresses/stretches the specified rectangle from the bitmap to fit the destination rectangle. Note that if the twips value of the bitmap is not set then nothing is drawn (this is the default situation).

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Note: this member function uses rectangle sizes in pixels and does a stretch/compress blit using a linear DDA.

See also: CGraphicsContext::DrawBitmap()

Draws a specified rectangle from a bitmap and its mask into another rectangle.

The function compresses/stretches the specified rectangle from the bitmap to fit the destination rectangle. The mask bitmap can be used as either a positive or negative mask. Masked pixels are not mapped to the destination rectangle.

A black and white (binary) mask bitmap is used. 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.

If mask bitmap's display mode is EColor256, the function does AplhaBlending and ignores aInvertMask parameter.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Note: this member function uses rectangle sizes in pixels and does a stretch/compress blit using a linear DDA.

Draws a specified rectangle from a wserv bitmap and its mask into another rectangle.

The function compresses/stretches the specified rectangle from the bitmap to fit the destination rectangle. The mask bitmap can be used as either a positive or negative mask. Masked pixels are not mapped to the destination rectangle.

A black and white (binary) mask bitmap is used. 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.

If mask bitmap's display mode is EColor256, the function does AplhaBlending and ignores aInvertMask parameter.

Windows that store their redraw commands will only store drawing position and a handle to bitmaps that are drawn in it. The bitmap handle is just a pointer to the bitmap in the FBSERV heap. At some point later WSERV may need to draw that window again and it will just replay the stored commands including the draw bitmap. However, if the client has changed the content of the bitmap, WSERV will effectively draw a different bitmap when it replays the commands.

Note: this member function uses rectangle sizes in pixels and does a stretch/compress blit using a linear DDA.

Draws and fills an ellipse.

The ellipse is drawn inside the rectangle defined by the aRect argument. Any TRect that has odd pixel dimensions, has the bottom right corner trimmed to give even pixel dimensions before the ellipse is constructed.

The column and row of pixels containing the bottom right co-ordinate of the aRect argument are not part of the rectangle.

Note: a wide outline ellipse is drawn with the pixels distributed either side of a true ellipse, in such a way that the outer edge of the line touches the edge of the construction rectangle. In other words, the ellipse used to construct it is smaller than that for a single pixel line size.

See also: CGraphicsContext::DrawEllipse()

Draws a straight line between two points.

See also: CGraphicsContext::DrawLine()

Draws a straight line relative to the current internal drawing position, using a vector.

The start point of the line is the current internal drawing position. The vector aVector is added to the internal drawing position to give the end point of the line

See also: CGraphicsContext::DrawLineBy()

Draws a straight line from the current internal drawing position to a point.

See also: CGraphicsContext::DrawLineTo()

Draws and fills a pie-shaped slice of an ellipse.

Outlines are subject to the current pen colour, width, style and draw mode. Set the pen to ENullPen for no outline. The fill is subject to brush style (colour, hash or pattern), the origin and the current drawing mode. Set the brush to ENullBrush for no fill.

The point aStart is used to define one end of a line to the centre of the ellipse. The point of intersection between this line and the ellipse defines the start point of the arc bounding the pie slice. The point aEnd is used to define one end of a second line to the centre of the ellipse. The point of intersection between this line and the ellipse defines the end point of the arc bounding the pie slice. The pixels at the end point are not drawn.

The pie slice itself is the area bounded by: the arc of the ellipse in an anticlockwise direction from the start point to the end point; the straight line from the start point from the geometric centre of the ellipse; the straight line from the end point from the geometric centre of the ellipse.

The line drawn by the pen goes inside the rectangle given by the aRect argument.

Notes:

A rectangle is used in the construction of the pie slice. This rectangle is passed as an argument of type TRect. The curved edge of the pie slice is an arc of an ellipse constructed within the rectangle.

A wide line edged pie slice has the arc drawn with the pixels distributed either side of a true ellipse. This is done in such a way that the outer edge of the line would touch the edge of the construction rectangle. In other words, the ellipse used to construct it is slightly smaller than that for a single pixel line size.

If aStart or aEnd are the ellipse centre then the line that defines the start/end of the arc defaults to one extending vertically above the centre point.

If aStart and aEnd are the same point, or points on the same line through the ellipse centre then a complete filled ellipse is drawn. A line is also drawn from the edge to the ellipse centre.

See also: CGraphicsContext::DrawPie()

Draws a polyline using points in an array.

A polyline is a series of concatenated straight lines joining a set of points.

See also: CGraphicsContext::DrawPolyLine()

Draws a polyline using points in a list.

A polyline is a series of concatenated straight lines joining a set of points.

See also: CGraphicsContext::DrawPolyLine()

Draws and fills a polygon using points defined in an array.

The first TPoint in the array defines the start of the first side of the polygon. The second TPoint defines the second vertex (the end point of the first side and the start point of the second side) and so on. The final side of the polygon is drawn using the last TPoint from the array or list, and the line drawn to the start point of the first side.

Self-crossing polygons can be filled according to one of two rules, TFillRule::EAlternate (the default), or TFillRule::EWinding. To explain the difference between these rules, the concept of a winding number needs to be introduced. The area outside any of the loops of the polygon has a winding number of zero, and is never filled. An inside a loop which is bounded by an area with winding number 0 has a winding number of 1. If an area is within a loop that is bounded by an area with winding number 1, e.g. a loop within a loop, has a winding number of 2, and so on.

The filling of a polygon proceeds according to this algorithm:

If aFillRule is TFillRule::EAlternate (default) and it has an odd winding number, then fill the surrounding area.

If aFillRule is TFillRule::EWinding and it has a winding number greater than zero, then fill the surrounding area.

This function always causes a flush of the window server buffer.

See also: CGraphicsContext::DrawPolygon()

Draws and fills a polygon using points defined in a list.

The first TPoint in the list defines the start of the first side of the polygon. The second TPoint defines the second vertex (the end point of the first side and the start point of the second side) and so on. The final side of the polygon is drawn using the last TPoint from the array or list, and the line drawn to the start point of the first side.

Self-crossing polygons can be filled according to one of two rules, TFillRule::EAlternate (the default), or TFillRule::EWinding. To explain the difference between these rules, the concept of a winding number needs to be introduced. The area outside any of the loops of the polygon has a winding number of zero, and is never filled. An inside a loop which is bounded by an area with winding number 0 has a winding number of 1. If an area is within a loop that is bounded by an area with winding number 1, e.g. a loop within a loop, has a winding number of 2, and so on.

The filling of a polygon proceeds according to this algorithm:

If aFillRule is TFillRule::EAlternate (default) and it has an odd winding number, then fill the surrounding area.

If aFillRule is TFillRule::EWinding and it has a winding number greater than zero, then fill the surrounding area.

This function always causes a flush of the window server buffer.

See also: CGraphicsContext::DrawPolygon()

Draws and fills a rectangle.

The rectangle's border is drawn with the pen, and it is filled using the brush.

See also: CGraphicsContext::DrawRect()

Draws and fills a rectangle with rounded corners.

The rounded corners are each constructed as an arc of an ellipse. The dimensions of each corner (corner size and corner height) are given by aEllipse. See DrawArc() for a description of arc construction.

The line drawn by the pen (if any) goes inside the rectangle given by the TRect argument.

Notes:

Dotted and dashed pen styles cannot be used for the outline of a rounded rectangle.

If either corner size dimension is greater than half the corresponding rectangle length, the corner size dimension is reduced to half the rectangle size.

See also: CGraphicsContext::DrawRoundRect()

Draws horizontal text with no surrounding box.

The appearance of the text is subject to the drawing mode, the font, pen colour, word justification and character justification.

A panic occurs if this function is called when there is no font: see UseFont().

See also: CGraphicsContext::DrawText()

Draws horizontal text within a cleared box.

The appearance of the text is subject to the drawing mode, the font, pen colour, word justification and character justification. It is also subject to the background brush (set brush to ENullBrush for no effect on background).

A panic occurs if this function is called when there is no font: see UseFont().

Note: the text is clipped to the box. You must ensure that the specified string is not too large.

See also: CGraphicsContext::DrawText()

Draws vertical text in the specified direction.

A panic occurs if this function is called when there is no font: see UseFont().

Draws text vertically in the specified direction, within a box of the specified size.

A panic occurs if this function is called when there is no font: see UseFont().

Draws an abstract artwork. It does nothing if aDestRect values fall outside the window area.

Draws an abstract artwork. It does nothing if aDestRect values fall outside the window area.