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PIXELFORMATDESCRIPTOR

The PIXELFORMATDESCRIPTOR structure describes the pixel format of a drawing surface.

typedef struct tagPIXELFORMATDESCRIPTOR { // pfd   
  WORD  nSize; 
  WORD  nVersion; 
  DWORD dwFlags; 
  BYTE  iPixelType; 
  BYTE  cColorBits; 
  BYTE  cRedBits; 
  BYTE  cRedShift; 
  BYTE  cGreenBits; 
  BYTE  cGreenShift; 
  BYTE  cBlueBits; 
  BYTE  cBlueShift; 
  BYTE  cAlphaBits; 
  BYTE  cAlphaShift; 
  BYTE  cAccumBits; 
  BYTE  cAccumRedBits; 
  BYTE  cAccumGreenBits; 
  BYTE  cAccumBlueBits; 
  BYTE  cAccumAlphaBits; 
  BYTE  cDepthBits; 
  BYTE  cStencilBits; 
  BYTE  cAuxBuffers; 
  BYTE  iLayerType; 
  BYTE  bReserved; 
  DWORD dwLayerMask; 
  DWORD dwVisibleMask; 
  DWORD dwDamageMask; 
} PIXELFORMATDESCRIPTOR; 

Members

nSize
Specifies the size of this data structure. This value should be set to sizeof(PIXELFORMATDESCRIPTOR).
nVersion
Specifies the version of this data structure. This value should be set to 1.
dwFlags
A set of bit flags that specify properties of the pixel buffer. The properties are generally not mutually exclusive; you can set any combination of bit flags, with the exceptions noted. The following bit flag constants are defined.
Value Meaning
PFD_DRAW_TO_WINDOW The buffer can draw to a window or device surface.
PFD_DRAW_TO_BITMAP The buffer can draw to a memory bitmap.
PFD_SUPPORT_GDI The buffer supports GDI drawing. This flag and PFD_DOUBLEBUFFER are mutually exclusive in the current generic implementation.
PFD_SUPPORT_OPENGL The buffer supports OpenGL drawing.
PFD_GENERIC_ACCELERATED The pixel format is supported by a device driver that accelerates the generic implementation. If this flag is clear and the PFD_GENERIC_FORMAT flag is set, the pixel format is supported by the generic implementation only.
PFD_GENERIC_FORMAT The pixel format is supported by the GDI software implementation, which is also known as the generic implementation. If this bit is clear, the pixel format is supported by a device driver or hardware.
PFD_NEED_PALETTE The buffer uses RGBA pixels on a palette-managed device. A logical palette is required to achieve the best results for this pixel type. Colors in the palette should be specified according to the values of the cRedBits, cRedShift, cGreenBits, cGreenShift, cBluebits, and cBlueShift members. The palette should be created and realized in the device context before calling wglMakeCurrent.
PFD_NEED_SYSTEM_PALETTE Defined in the pixel format descriptors of hardware that supports one hardware palette in 256-color mode only. For such systems to use hardware acceleration, the hardware palette must be in a fixed order (for example, 3-3-2) when in RGBA mode or must match the logical palette when in color-index mode.

When this flag is set, you must call SetSystemPaletteUse in your program to force a one-to-one mapping of the logical palette and the system palette. If your OpenGL hardware supports multiple hardware palettes and the device driver can allocate spare hardware palettes for OpenGL, this flag is typically clear.

This flag is not set in the generic pixel formats.

PFD_DOUBLEBUFFER The buffer is double-buffered. This flag and PFD_SUPPORT_GDI are mutually exclusive in the current generic implementation.
PFD_STEREO The buffer is stereoscopic. This flag is not supported in the current generic implementation.
PFD_SWAP_LAYER_BUFFERS Indicates whether a device can swap individual layer planes with pixel formats that include double-buffered overlay or underlay planes. Otherwise all layer planes are swapped together as a group. When this flag is set, wglSwapLayerBuffers is supported.

You can specify the following bit flags when calling ChoosePixelFormat.

Value Meaning
PFD_DEPTH_DONTCARE The requested pixel format can either have or not have a depth buffer. To select a pixel format without a depth buffer, you must specify this flag. The requested pixel format can be with or without a depth buffer. Otherwise, only pixel formats with a depth buffer are considered.
PFD_DOUBLEBUFFER
_DONTCARE
The requested pixel format can be either single- or double-buffered.
PFD_STEREO_DONTCARE The requested pixel format can be either monoscopic or stereoscopic.

With the glAddSwapHintRectWIN extension function, two new flags are included for the PIXELFORMATDESCRIPTOR pixel format structure.

Value Meaning
PFD_SWAP_COPY Specifies the content of the back buffer in the double-buffered main color plane following a buffer swap. Swapping the color buffers causes the content of the back buffer to be copied to the front buffer. The content of the back buffer is not affected by the swap. PFD_SWAP_COPY is a hint only and might not be provided by a driver.
PFD_SWAP_EXCHANGE Specifies the content of the back buffer in the double-buffered main color plane following a buffer swap. Swapping the color buffers causes the exchange of the back buffer's content with the front buffer's content. Following the swap, the back buffer's content contains the front buffer's content before the swap. PFD_SWAP_EXCHANGE is a hint only and might not be provided by a driver.

iPixelType
Specifies the type of pixel data. The following types are defined.
Value Meaning
PFD_TYPE_RGBA RGBA pixels. Each pixel has four components in this order: red, green, blue, and alpha.
PFD_TYPE_COLORINDEX Color-index pixels. Each pixel uses a color-index value.

cColorBits
Specifies the number of color bitplanes in each color buffer. For RGBA pixel types, it is the size of the color buffer, excluding the alpha bitplanes. For color-index pixels, it is the size of the color-index buffer.
cRedBits
Specifies the number of red bitplanes in each RGBA color buffer.
cRedShift
Specifies the shift count for red bitplanes in each RGBA color buffer.
cGreenBits
Specifies the number of green bitplanes in each RGBA color buffer.
cGreenShift
Specifies the shift count for green bitplanes in each RGBA color buffer.
cBlueBits
Specifies the number of blue bitplanes in each RGBA color buffer.
cBlueShift
Specifies the shift count for blue bitplanes in each RGBA color buffer.
cAlphaBits
Specifies the number of alpha bitplanes in each RGBA color buffer. Alpha bitplanes are not supported.
cAlphaShift
Specifies the shift count for alpha bitplanes in each RGBA color buffer. Alpha bitplanes are not supported.
cAccumBits
Specifies the total number of bitplanes in the accumulation buffer.
cAccumRedBits
Specifies the number of red bitplanes in the accumulation buffer.
cAccumGreenBits
Specifies the number of green bitplanes in the accumulation buffer.
cAccumBlueBits
Specifies the number of blue bitplanes in the accumulation buffer.
cAccumAlphaBits
Specifies the number of alpha bitplanes in the accumulation buffer.
cDepthBits
Specifies the depth of the depth (z-axis) buffer.
cStencilBits
Specifies the depth of the stencil buffer.
cAuxBuffers
Specifies the number of auxiliary buffers. Auxiliary buffers are not supported.
iLayerType
Ignored. Earlier implementations of OpenGL used this member, but it is no longer used.
bReserved
Specifies the number of overlay and underlay planes. Bits 0 through 3 specify up to 15 overlay planes and bits 4 through 7 specify up to 15 underlay planes.
dwLayerMask
Ignored. Earlier implementations of OpenGL used this member, but it is no longer used.
dwVisibleMask
Specifies the transparent color or index of an underlay plane. When the pixel type is RGBA, dwVisibleMask is a transparent RGB color value. When the pixel type is color index, it is a transparent index value.
dwDamageMask
Ignored. Earlier implementations of OpenGL used this member, but it is no longer used.

Remarks

Please notice carefully, as documented above, that certain pixel format properties are not supported in the current generic implementation. The generic implementation is the Microsoft GDI software implementation of OpenGL. Hardware manufacturers may enhance parts of OpenGL, and may support some pixel format properties not supported by the generic implementation.

See Also

OpenGL on Windows NT, Windows 2000, and Windows 95/98, Structures, ChoosePixelFormat, DescribePixelFormat, GetPixelFormat, SetPixelFormat


  

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