How to call DLL functions?
The script engine can import procedures and functions from external DLL files. Thus, you can extend your application by calling your own DLL functions.
How to import a DLL function in HEScript?¶
This is done thanks to the external keyword.
Syntax:
function functionName(arguments): resultType;
[callingConvention]; external "libName.dll" [name 'ExternalFunctionName'];
For example, the following declaration:
function MyFunction(arg: integer): integer; external 'CustomLib.dll';
imports a function called MyFunction from CustomLib.dll. The default calling convention, if not specified, is register.
HEScript allows you to declare a different calling convention (stdcall, register, pascal, cdecl, or safecall) and to use a different name for the DLL function, like the following declaration:
function MsgBox(hWnd: Pointer; lpText, lpCaption: String;
uType: Cardinal): Integer; stdcall; external "user32.dll" name 'MessageBoxW';
This imports the 'MessageBoxW' function from User32.dll (Windows API library), named 'MsgBox' to be used in the script, like:
procedure TestDLL;
var
S: String;
begin
S := InputBox("What do you want to show?", "Query", "");
MsgBox(0, S, "You entered:", MB_OK+MB_ICONINFORMATION);
end;
Warning
Pointer and out parameters are not handled by the script engine.
Other samples¶
The following Windows APIs can be imported into the HEScript engine with these declarations:
function GetDiskFreeSpace(root: AnsiString; var secPerCluster, bytesPerCluster, freeClusters, totalClusters: integer): boolean; stdcall; external "Kernel32.dll" name 'GetDiskFreeSpaceA';
function FindWindow(className, windowName: AnsiString): integer; stdcall; external "User32.dll" name 'FindWindowA';
function GetKeyState(virtKey: integer): smallint; stdcall; external "User32.dll";