Delphi enumerating devices using code _php Tutorial

Delphi Enumerating devices using code

Now Delphi (2010, XE) has its own related units (... sourcertlwin) for DirectX.
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Enumeration functions
function Directsoundenumerate (
Lpdsenumcallback:tdsenumcallback; callback function
Lpcontext:pointer//user pointer
): HRESULT; stdcall; Returns the error code, and returns S_OK if successful (0)

Directsoundenumerate the desired callback function for the prototype:
Tdsenumcallback = function (
Lpguid:pguid; GUID of Device
Lpcstrdescription:pchar; Device description
Lpcstrmodule:pchar; Module identification
Lpcontext:pointer//user pointers provided by directsoundenumerate
): BOOL; stdcall; Returns true to indicate that you want to continue the enumeration without returning false if you continue to search.

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This is the common code:
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Unit unit1;

Interface

Uses
Windows, messages, Sysutils, variants, classes, graphics, controls, forms,
dialogs, Stdctrls;

Type
Tform1 = Class (Tform)
Listbox1:tlistbox; Only a list box is placed on the form
Procedure Formcreate (Sender:tobject);
End

Var
Form1:tform1;

Implementation

{$r *.DFM}

Uses DirectSound; //!

function Enumcallback (lpguid:pguid; lpcstrdescription, Lpcstrmodule:pchar;
Lpcontext:pointer): BOOL; stdcall;
Begin
Form1.listbox1.items.add (lpcstrdescription);
Result: = true;
End

Procedure Tform1.formcreate (Sender:tobject);
Begin
Directsoundenumerate (Enumcallback, nil);
End

End.

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Using the form controls directly in the callback function is not good and is modified as follows:
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Uses DirectSound;

function Enumcallback (lpguid:pguid; lpcstrdescription, Lpcstrmodule:pchar;
Lpcontext:pointer): BOOL; stdcall;
Begin
Tstrings (Lpcontext). Add (Lpcstrdescription);
Result: = true;
End

Procedure Tform1.formcreate (Sender:tobject);
Begin
Directsoundenumerate (Enumcallback, Listbox1.items);
End

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For more information:
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Uses DirectSound;

function Enumcallback (lpguid:pguid; lpcstrdescription, Lpcstrmodule:pchar;
Lpcontext:pointer): BOOL; stdcall;
Begin
If Lpguid <> nil then tstrings (lpcontext). Add (Guidtostring (lpguid^));
Tstrings (Lpcontext). Add (Lpcstrdescription);
If Lpcstrmodule <> nil then tstrings (lpcontext). Add (Lpcstrmodule);
Tstrings (Lpcontext). Add (EMPTYSTR);
Result: = true;
End

Procedure Tform1.formcreate (Sender:tobject);
Begin
Directsoundenumerate (Enumcallback, Listbox1.items);
End

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