What is the windows API to change Screen refresh rate?

Question

Can some one specify the windows API, one need to use in order to be able to change programmatically the screen refresh rate?

Answer 1

I found this via a google search. Hope it helps some.

http://www.codeproject.com/KB/winsdk/changerefresh.aspx

http://msdn.microsoft.com/en-us/library/ms533260(VS.85).aspx

Answer 2

you can use ChangeDisplaySettings as described before. But you should use EnumDisplaySettings to get a list of valid combinations of (color dept, width, height, mode and frequency).

Sample code (in Delphi but translation should be trivial)

Get valid display modes

i := 0;
while EnumDisplaySettings(nil, i, dm) do begin
  Memo1.Lines.Add(Format('Color Depth: %d', [dm.dmBitsPerPel]));
  Memo1.Lines.Add(Format('Resolution: %d, %d', [dm.dmPelsWidth, dm.dmPelsHeight]));
  Memo1.Lines.Add(Format('Display mode: %d', [dm.dmDisplayFlags]));
  Memo1.Lines.Add(Format('Frequency: %d', [dm.dmDisplayFrequency]));
  Inc(i);
end;

Set display mode

// In this case i is an index in the list of valid display modes.
if EnumDisplaySettings(nil, i, dm) then begin
  // Sanity check!
  if ChangeDisplaySettings(dm, CDS_TEST) = 0) then
    ChangeDisplaySettings(dm, 0);  // Use CDS_UPDATEREGISTRY if this is the new default mode.
end;

It is very important to chose a valid combination!