Output(OS_ALTPOLYGON)

The OS_ALTPOLYGON style specifies that the Output function draws a polygon and fills it using the alternate-filling method. GDI calls Output with this style when an application calls functions, such as the Polygon function (GDI.36), and the current polygon-filling mode is ALTERNATE.

The graphics driver must support the OS_ALTPOLYGON style if the PC_ALTPOLYGON bit is set in the dpPolygonals member of the GDIINFO structure.

Parameters

lpDestDev

Points to a PDEVICE or PBITMAP structure specifying the destination device or bitmap.

wCount

Specifies the POINT structures in the array pointed to by the lpPoints parameter.

lpPoints

Points to an array of POINT structures containing wCount elements. Each point represents a vertex of the polygon.

lpPPen

Points to a PPEN structure that specifies the physical pen to draw the border of the polygon.

lpPBrush

Points to a PBRUSH structure that specifies the physical brush to fill the polygon.

lpDrawMode

Points to a DRAWMODE structure containing the drawing information to draw and fill the polygon.

lpClipRect

Points to a RECT structure containing coordinates for the clipping rectangle. If the lpClipRect parameter is NULL, the clipping rectangle is the entire display surface.

Return Value

The return value is 1 if the function is successful. Otherwise, it is zero if the function encounters an unrecoverable error. The return value is -1 if the function does not support the given style and wants GDI to simulate the output.

Comment

The Output function fills the interior of the polygon first, then draws the border.

To fill the polygon, Output calculates the polygon outline and fills it according to the alternate-filling method. Alternate filling typically fills every other closed area within a polygon. In general, a given area should be filled if a horizontal ray, starting in the area and continuing through the left edge of the polygon, crosses an odd number of polygon sides.

To draw the border, Output draws a line segment from the first point in the array to the second, from the second to the third, and so on. If the last line segment does not end at the first point, Output draws this line segment to ensure a closed figure.

Although the Output function can use device hardware to draw and fill polygons, the function either must provide the same capability when drawing to a main memory bitmap, or returns a value of -1 to direct GDI to simulate the output using polylines and scan lines.

See Also

Output(OS_WINDPOLYGON)