int SetPolyFillMode(hDC,nPolyFillMode)
This function sets the polygon-filling mode for the GDI functions that use the polygon algorithm to compute interior points.
| Parameter | Type/Description |
| hDC | HDC Identifies the device context. | ||
| nPolyFillMode | int Specifies the new filling mode. The nPolyFillMode parameter may be either of the following values: | ||
| Value | Meaning | ||
| ALTERNATE | Selects alternate mode. | ||
| WINDING | Selects winding number mode. | ||
The return value specifies the previous filling mode. It is zero if there is an error.
In general, the modes differ only in cases where a complex, overlapping polygon must be filled (for example, a five-sided polygon that forms a five-pointed star with a pentagon in the center). In such cases, ALTERNATE mode fills every other enclosed region within the polygon (that is, the points of the star), but WINDING mode fills all regions (that is, the points and the pentagon).
When the filling mode is ALTERNATE, GDI fills the area between odd-numbered and even-numbered polygon sides on each scan line. That is, GDI fills the area between the first and second side, between the third and fourth side, and so on.
To fill all regions, WINDING mode causes GDI to compute and draw a border that encloses the polygon but does not overlap. For example, in WINDING mode, the five-sided polygon that forms the star is drawn as a ten-sided polygon with no overlapping sides; the resulting star is filled.