This function reads the mode that has been selected from OS2.INI, and determines which modes from the asr array are valid. It then matches the user-selected mode to the modes available in the asr array. The asr array is used by QueryAndSelectNativeMode, as well as by OS2_PM_DRV_QUERYSCREENRESOLUTIONS(), which is the driver entry point used by static mode set. (See Multiple Resolution Support for more details.) The asr is an array of structures of type:

typedef struct _SCREENRESOLUTION {
   ULONG width;
   ULONG height;
   ULONG colors;
   ULONG planes;
   ULONG floptions;
} SCREENRESOLUTION;

QueryAndSelectNativeMode() initially determines the memory size of the S3 adapter. Having done this, it then calls SetObtainableModes(), which reads the SVGADATA.PMI file for the S3 adapter. Then, it sets the DSP_RESOLUTION_OBTAINABLE (bit 6) of floptions for each resolution in the SCREENRESOLUTION table that is also found in the .PMI file. Next, QueryAndSelectNativeModes() calls Get_User_Mode, which reads OS2.INI and looks for a user-selected resolution. If it is unable to find one, QueryAndSelectNativeModes() searches the asr array for a mode marked as the default. In the case of the S3 driver, the video mode is 640 x 480 x 8 bits-per-pel.

At this point, the S3 driver calls the base video handler to set the mode and then calls KlugeReset(), which sets up the drawing engine and clears the display. (The mode is set again in FillPdb.) Next, QueryAndSelectNativeMode() searches the aResTable for a mode that matches the resolution and color depth requested by the user, and the amount of memory available on the card. When it finds a match, it sets the global variable HWResolution, and then calls CacheManager(), which then sets up pointers to hardware and cache maps. (Further information on CacheManager and the hardware and cache maps can be found in Cache Management.)