| #define SETCOLORTABLE 4 |
| short Control(lpDevice, SETCOLORTABLE, lpColorEntry, lpColor) | |||
| LPPDEVICE lpDevice; | |||
| LPWORD lpColorEntry; | |||
| LPLONG lpColor; |
The SETCOLORTABLE escape sets an RGB color-table entry. If the device
cannot supply the exact color, the function sets the entry to the closest possible
approximation of the color.
lpDevice
Points to a PDEVICE structure specifying the destination device.
lpColorEntry
Points to a COLORTABLE_STRUCT structure. The COLORTABLE_STRUCT structure has the following form:
typedef struct tagCOLORTABLE_STRUCT {
WORD Index;
LONG rgb;
lpColor
Points to a 32-bit variable that receives the RGB color value selected by the device driver to represent the requested color value.
The return value is positive if the escape is successful. Otherwise, it is negative.
A device's color table is a shared resource; changing the system display color for one window changes it for all the windows.
The SETCOLORTABLE escape has no effect on devices with fixed-color tables.
This escape is intended for use by both printer and display drivers. However, the EGA and VGA color drivers do not support it. It should not be used with palette-capable display devices.
It is used by applications that want to change the palette used by the display driver. However, since the driver's color-mapping algorithms will probably no longer work with a different palette, an extension has been added to this escape.
If the color index pointed to by the lpColorEntry parameter is 0xFFFFH, the driver is to leave all color-mapping functionality to the calling application. The application will necessarily know the proper color-mapping algorithm and take responsibility for passing the correctly mapped physical color to the driver (instead of the logical RGB color) in functions such as RealizeObject and ColorInfo.
For example, if the device supports 256 colors with palette indexes of 0 through 255, the application would determine which index contains the color that it wants to use in a certain brush. It would then pass this index in the low byte of the logical color passed to RealizeObject. The driver would then use this color exactly as passed instead of performing its usual color-mapping algorithm. If the application wants to reactivate the driver's color-mapping algorithm (that is, if it restores the original palette when switching from its window context), then the color index pointed to by lpColorEntry should be 0xFFFEH.