SetPolyFillMode function (wingdi.h)

Article
02/22/2024

The SetPolyFillMode function sets the polygon fill mode for functions that fill polygons.

Syntax

int SetPolyFillMode(
  [in] HDC hdc,
  [in] int mode
);

Parameters

[in] hdc

A handle to the device context.

[in] mode

The new fill mode. This parameter can be one of the following values.

Value	Meaning
ALTERNATE	Selects alternate mode (fills the area between odd-numbered and even-numbered polygon sides on each scan line).
WINDING	Selects winding mode (fills any region with a nonzero winding value).

Return value

The return value specifies the previous filling mode. If an error occurs, the return value is zero.

Remarks

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 fill 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.

When the fill mode is WINDING, GDI fills any region that has a nonzero winding value. This value is defined as the number of times a pen used to draw the polygon would go around the region. The direction of each edge of the polygon is important.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wingdi.h (include Windows.h)
Library	Gdi32.lib
DLL	Gdi32.dll