Question

How do you determine the maximum number of display modes returnable by EnumDisplaySettings without incrementing the second parameter until the function fails.

Answer 1

According to MSDN’s Documentation on EnumDisplaySettings. It looks like your only option is to increment IModeNum

From Link:

Graphics mode indexes start at zero. To obtain information for all of a display device’s graphics modes, make a series of calls to EnumDisplaySettings, as follows: Set iModeNum to zero for the first call, and increment iModeNum by one for each subsequent call. Continue calling the function until the return value is zero.