*****************************************************************
* Neveprise Inc. Delphi FAQ					*
*****************************************************************
* Section: Desktop		Topic:   Set screen resolution	*
* Created: July 27th, 1999	Revised: July 27th, 1999 	*
* Updates: www.neveprise.de	Info:	 support@neveprise.de	*
*****************************************************************

Q: How can I set another screen resolution?

A: A bit complicated, but we can use the WinAPI function Change-
	DisplaySettings():

interface

  TStructH_ScreenMode = record //let us declare a custom structure...
     ResolutionX:     integer; //"0" causes no change!
     ResolutionY:     integer;
     ColorDepth:      (Color16, Color256, HiColor, TrueColor, NoChange);
     SwitchMode:      (srTest, srDynamic, srAsDefault, srRestore);
     Rate:            integer;
  end;


implementation

function SetScreenResH(var Mode: TStructH_ScreenMode): integer;
var DisSet: TDevMode; //device mode
    cResult: variant; //result from ChangeDisplaySettings()
begin
Result:=-1;
DisSet.dmSize:=SizeOf(DisSet); //init structure
DisSet.dmDisplayFlags:=0; //no special flags
with DisSet do begin
     dmPelsWidth:=Mode.ResolutionX; //set width
     dmPelsHeight:=Mode.ResolutionY; //set height
     dmDisplayFrequency:=Mode.Rate; //set frequency
     //now the colour depth in bits per pixel	
     if Mode.ColorDepth=Color16 then dmBitsPerPel:=4;
     if Mode.ColorDepth=Color256 then dmBitsPerPel:=8;
     if Mode.ColorDepth=HiColor then dmBitsPerPel:=16;
     if Mode.ColorDepth=HiColor then dmBitsPerPel:=32;
     if Mode.ResolutionX<>0 then //0 means to set only other values, e.g. colours
	DisSet.dmFields:=dm_PelsWidth+dm_PelsHeight+dm_DisplayFlags; //set valid fields
     if Mode.ColorDepth<>NoChange then //colour should not be set...
	DisSet.dmFields:=dmFields+dm_BitsPerPel;
     if Mode.Rate<>0 then //0 means not to set refresh rate (recommended!!!)
	DisSet.dmFields:=DisSet.dmFields+dm_DisplayFrequency;
end;
case Mode.SwitchMode of //now check what we want to do
     //only for this session, shall be used	
     srDynamic:   cResult:=ChangeDisplaySettings(DisSet,0);
     //shall be used everytime (e.g. when rebooting still these settings)
     srAsDefault: cResult:=ChangeDisplaySettings(DisSet,cds_UpDateRegistry);
     //nothing shall be done, we just want to test if it is possible to set these modes
     srTest:      cResult:=ChangeDisplaySettings(DisSet,cds_Test);
     //reset to defaults (will not work if srAsDefault!)
     srRestore:   begin
                      with DisSet do begin //make invalid params
                           dmFields:=dm_PelsWidth+dm_PelsHeight+dm_DisplayFlags+dm_BitsPerPel;
                           dmPelsWidth:=0;
                           dmPelsHeight:=0;
                           dmBitsPerPel:=0;
                           cResult:=ChangeDisplaySettings(DisSet,cds_UpDateRegistry);
                      end;
                  end;
end;
case cResult of
     Disp_Change_Successful: Result:=0; //all okay, mode was set / can be set
     Disp_Change_Restart: Result:=1; //would work, but only if reboot is performed
     Disp_Change_BadFlags: Result:=3; //we used wrong parameters, e.g. 311 as width
     Disp_Change_Failed: Result:=3; //some error occured
     Disp_Change_BadMode: Result:=3; //could have worked, but it is very unstable
     Disp_Change_NotUpDated: Result:=2; //could not store as default, but worked for now
end;
end;





	Blazko