*****************************************************************
* Neveprise Inc. Delphi FAQ					*
*****************************************************************
* Section: DirectX		Topic:   Enum video modes 	*
* Created: July 27th, 1999	Revised: July 27th, 1999 	*
* Updates: www.neveprise.de	Info:	 support@neveprise.de	*
*****************************************************************

Q: How can I enumerate all available video modes? How to declare the callback?

A: Finding an enumeration function in DirectX is not hard, but the problem
	is how to declare the required callback function and what the
	lpContext param can be used for. What we do is to write one single
	function that retrieves all needed information as TStrings. This
	function contains the call to EnumDisplayModes() and in the var
	part our callback.
	The advantage of using TStrings as result is, that we have readable
	(for the user) and internal DirectX values in one object without
	declaring complex custom types. Perhaps you know that a string
	in TStrings can have an additional pointer to TObject (using
	AddObject() etc.) we can combine both information.


//a "pseudo-record" as TObject, it contains information that is needed
//later when we want to set a mode

TDisplayMode_SD = class (TObject)
   Width:         cardinal;
   Height:        cardinal;
   BitDepth:      cardinal;
end;

//the function to call from your app, Modes will contain a list with all
//modes, Driver can be nil (default device, *not* recommended) or a valid
//GUID. How to get it, please look up "enumerating display/ graphic modes"
//in this FAQ.

function EnumDisplayModes_SD(Driver: PGUID; var Modes: TStringList): boolean;
var DD:     IDirectDraw;  //temporary DirectDraw object, needed to query DD2
    DD2:    IDirectDraw2; //temporary DirectDraw2 object
     //callback function that fills the list
     function Enum_CallBack(const Desc: TDDSurfaceDesc; Context: Pointer):
              HResult; stdcall;
     var DisMod: TDisplayMode_SD; //"record" holding the data
     begin
        DisMod:=TDisplayMode_SD.Create;
        with DisMod do begin
             Width:=    Desc.dwWidth; //fill with values
             Height:=   Desc.dwHeight;
             BitDepth:= Desc.ddpfPixelFormat.dwRGBBitCount;
             // ..and assign to stringlist as TObject
             TStringList(Context).AddObject(IntToStr(Width)+' x '+
                         IntToStr(Height)+' Pixels x '+
                         IntToStr(BitDepth)+' bit color', DisMod);
        end;
        Result:=DDEnumRet_OK; //continue enumeration
     end;
begin
Result:=false;
DXStat:='Create DirectDraw'; //create temp. DDraw1
if DXCHeck(DirectDrawCreate(nil,DD,nil))=false then Exit;
DXStat:='Query DirectDraw2'; //create temp. DDraw2 by Querying
if DXCheck(DD.QueryInterface(IID_IDirectDraw2, DD2))=false then Exit;
DXStat:='EnumDisplayModes'; //start enumeration
if DXCheck(DD2.EnumDisplayModes(0, nil, Modes,
   @Enum_CallBack))=false then Exit;
ReleaseCOM(DD2);
ReleaseCOM(DD);
Result:=true;
end;

//now you have TStrings, use it this way:

//this fills a combobox (cbVideoModes) with all device modes

slModes:=TStringList.Create;
if EnumDisplayModes_SD(slModes)=true then cbVideoModes.Items:=slModes;

//if an item is selected, we can retrieve the modes this way to pass'em
//to DirectDrawCreate etc.

var ModeDD: TDisplayMode_SD;
TObject(ModeDD):=slModes.Objects[cbVideoModes.ItemIndex];



	Blazko