ChoosePixelFormat

The ChoosePixelFormat function attempts to match an appropriate pixel format supported by a device context to a given pixel format specification.

int ChoosePixelFormat(
  HDC  hdc,  // device context to search for a best pixel format 
             // match
  CONST PIXELFORMATDESCRIPTOR *  ppfd 
             // pixel format for which a best match is sought
);

Parameters

hdc
Specifies the device context that the function examines to determine the best match for the pixel format descriptor pointed to by ppfd.
ppfd
Pointer to a PIXELFORMATDESCRIPTOR structure that specifies the requested pixel format. In this context, the members of the PIXELFORMATDESCRIPTOR structure that ppfd points to are used as follows:
nSize
Specifies the size of the PIXELFORMATDESCRIPTOR data structure. Set this member to sizeof(PIXELFORMATDESCRIPTOR).
nVersion
Specifies the version number of the PIXELFORMATDESCRIPTOR data structure. Set this member to 1.
dwFlags
A set of bit flags that specify properties of the pixel buffer. You can combine the following bit flag constants by using bitwise-OR.

If any of the following flags are set, the ChoosePixelFormat function attempts to match pixel formats that also have that flag or flags set. Otherwise, ChoosePixelFormat ignores that flag in the pixel formats:

PFD_DRAW_TO_WINDOW
PFD_DRAW_TO_BITMAP
PFD_SUPPORT_GDI
PFD_SUPPORT_OPENGL

If any of the following flags are set, ChoosePixelFormat attempts to match pixel formats that also have that flag or flags set. Otherwise, it attempts to match pixel formats without that flag set:

PFD_DOUBLEBUFFER
PFD_STEREO

If the following flag is set, the function ignores the PFD_DOUBLEBUFFER flag in the pixel formats:

PFD_DOUBLEBUFFER_DONTCARE

If the following flag is set, the function ignores the PFD_STEREO flag in the pixel formats:

PFD_STEREO_DONTCARE

iPixelType
Specifies the type of pixel format for the function to consider:

PFD_TYPE_RGBA
PFD_TYPE_COLORINDEX

cColorBits
Zero or greater.
cRedBits
Not used.
cRedShift
Not used.
cGreenBits
Not used.
cGreenShift
Not used.
cBlueBits
Not used.
cBlueShift
Not used.
cAlphaBits
Zero or greater.
cAlphaShift
Not used.
cAccumBits
Zero or greater.
cAccumRedBits
Not used.
cAccumGreenBits
Not used.
cAccumBlueBits
Not used.
cAccumAlphaBits
Not used.
cDepthBits
Zero or greater.
cStencilBits
Zero or greater.
cAuxBuffers
Zero or greater.
iLayerType
Specifies one of the following layer type values:

PFD_MAIN_PLANE
PFD_OVERLAY_PLANE
PFD_UNDERLAY_PLANE

bReserved
Not used.
dwLayerMask
Not used.
dwVisibleMask
Not used.
dwDamageMask
Not used.

Return Values

If the function succeeds, the return value is a pixel format index (one-based) that is the closest match to the given pixel format descriptor.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

You must ensure that the pixel format matched by the ChoosePixelFormat function satisfies your requirements. For example, if you request a pixel format with a 24-bit RGB color buffer but the device context offers only 8-bit RGB color buffers, the function returns a pixel format with an 8-bit RGB color buffer.

The following code sample shows how to use ChoosePixelFormat to match a specified pixel format:

PIXELFORMATDESCRIPTOR pfd = { 
    sizeof(PIXELFORMATDESCRIPTOR),  //  size of this pfd 
    1,                     // version number 
    PFD_DRAW_TO_WINDOW |   // support window 
    PFD_SUPPORT_OPENGL |   // support OpenGL 
    PFD_DOUBLEBUFFER,      // double buffered 
    PFD_TYPE_RGBA,         // RGBA type 
    24,                    // 24-bit color depth 
    0, 0, 0, 0, 0, 0,      // color bits ignored 
    0,                     // no alpha buffer 
    0,                     // shift bit ignored 
    0,                     // no accumulation buffer 
    0, 0, 0, 0,            // accum bits ignored 
    32,                    // 32-bit z-buffer     
    0,                     // no stencil buffer 
    0,                     // no auxiliary buffer 
    PFD_MAIN_PLANE,        // main layer 
    0,                     // reserved 
    0, 0, 0                // layer masks ignored 
    }; 
    HDC  hdc;
    int  iPixelFormat; 
 
iPixelFormat = ChoosePixelFormat(hdc, &pfd);

QuickInfo

  Windows NT: Use version 3.5 and later.
  Windows: Use Windows 95 and later.
  Windows CE: Unsupported.
  Header: Declared in wingdi.h.
  Import Library: Link with gdi32.lib.

See Also

OpenGL on Windows NT and Windows 95 Overview, Win32 Functions, DescribePixelFormat, GetPixelFormat, SetPixelFormat