Mega Code Archive
Callback a class
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This article demonstrates how to use an instance of a class as a callback.
If you wanted a windows callback to call an instance of a class, simply replace TMyClass with your classname, and TMyClass.MyCallBack with your method name.
type
TCallbackThunk = packed record
POPEDX: Byte;
MOVEAX: Byte;
SelfPtr: Pointer;
PUSHEAX: Byte;
PUSHEDX: Byte;
JMP: Byte;
JmpOffset: Integer;
end;
var
Callback: TCallbackThunk;
begin
inherited Create;
Callback.POPEDX := $5A;
Callback.MOVEAX := $B8;
Callback.SelfPtr := Self;
Callback.PUSHEAX := $50;
Callback.PUSHEDX := $52;
Callback.JMP := $E9;
Callback.JmpOffset := Integer(@TMyClass.MyCallBack) - Integer(@Callback.JMP) - 5;
//Call the WINAPI here, passing @CallBack at the callback proc, for example
EnumSystemLocales(TFNLocaleEnumProc(@Callback), LCID_SUPPORTED);
end;
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