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GetNextResolution (csCode = 17)

The required GetNextResolution routine reports all display resolutions that the driver supports.

--> csPreviousDisplayModeID

ID of the previous display mode

<-- csDisplayModeID

ID of the display mode following csPreviousDisplayModeID.

<-- csHorizontalPixels

Number of pixels in a horizontal line

<-- csVerticalLines

Number of lines in a screen

<-- csRefreshRate

Vertical refresh rate of the screen

<-- csMaxDepthMode

Max relative bit depth for this DisplayModeID

GetNextResolution passes a csPreviousDisplayModeID value and returns the next supported display mode. The csDisplayModeID field is updated and the csHorizontalPixels, csVerticalLines, and csRefreshRate fields are set. The csMaxDepthMode field is also set with the highest supported video bit depth. This uses the same convention as in the past; kDepthMode1 is the first relative bit depth supported, not necessarily 1 bit per pixel. For futher information about depth modes, see the next section.

Observe these cautions:

• The DisplayModeID values used do not need to be the same as the ones Apple uses. However, the DisplayModeID value 0 and all values with the high bit set (0x80000000 through 0xFFFFFFFF) are reserved by Apple.
• To get the first resolution supported by a display, the caller will pass a value of kDisplayModeIDFindFirstResolution in the csPreviousDisplayModeID field of the VDResolutionInfoRec structure.
• To get the second resolution, the caller will pass the csDisplayModeID value of the first resolution in the structure's csPreviousDisplayModeID field.
• When a call has the last supported resolution in the csPreviousDisplayModeID field, the driver should return a value of kDisplayModeIDNoMoreResolutions in the csDisplayModeID field. No error should be returned.
• If an invalid value is passed in the csPreviousDisplayModeID field, the driver should return a paramErr value without modifying the structure.
• If the csPreviousDisplayModeID field is kDisplayModeIDCurrent, the driver should return information about the current displayModeID.

The constants just described are defined in the file Video.h and are listed in Data Structures.