CALLDLL

[gaslouk]

Hi.

How can I use CALLDLL please?

What do I need to know about the DLL in order to use it properly?

Thanks.

[Walt Decker]

You first have to load the dll. If it is one of the WINAPI dlls it is probably loaded. The three WINAPI DLLs I know of that are automatically loaded are:

User32.DLL, Kernel32.dll and Gdi32.DLL Those three you can call by using:

CALLDLL #user32, "function name", param1, param2, param3
CALLDLL #kernel32, "function name", param1, param2, param3
CALLDLL #gdi32, "function name", param1, param2, param3

Second party dlls must be explicitly loaded with:

OPEN "DLL NAME" FOR DLL AS #SOMETAG

Then you use CALLDLL in the same form as for the WINAPI dlls using the appropriate functions and parameters.

You have to read the documentation for the dlls. This documentation will give the function names available, the parameter types required for each function, and the return value (if any).

[Rod]

It is a big subject, Pandora’s box kinda thing. Small steps start here.

alycesrestaurant.com/lbpe/ABCs%20of%20APIs%201.html#The%20ABCs%20of%20APIs%20Lesson%201

[Walt Decker]

Another resource can be found in the General Discussion thread topic "Things You Do Not Want to Know About the Win31 API".

Some commonly used WinAPI functions:

DLL: User32.dll
"SendMessageA", WinHndl AS ULONG, Msg AS ULONG, Param1 AS LONG, Param2 AS LONG, RetVal AS LONG
Msg is specific to the window/control
Param1 and Param2 are also specific to the window/control

"GetWindowTextLengthA", WinHndl AS ULONG, NumChars AS LONG
WinHndl is the handle of the form window or control
NumChars is the number of characters contained in the window name

"GetWindowTextA", WinHndl AS ULONG, WinTxt$ AS STRUCT, NumChars AS LONG, RetChars AS LONG
WinHndl is the handle of the form or control
WinTxt$ receives the text
NumChars is the number of characters to return in WinTxt$
RetChars is the number of characters returned or the lenght of the text if WinTxt$ is not large enough

"SetWindowTextA", WinHndl AS ULONG, WinTxt$ AS PTR, RetVal AS LONG
WinHndl is the handle of the form or control
WinTxt$ is the text to set
RetVal is a return value, non-zero on success

Gdi32.Dll:
"GetPixel", DevDc AS ULONG, Px AS LONG, Py AS LONG, Colour AS ULONG
DevDc is the device context
Px, Py are the coordinates of the point to query
Colour is the 32-bit color of the pixel

"MoveToEx", DevDc, Px AS LONG, Py AS LONG, 0 AS LONG, RetVal AS LONG
DevDc is the device context
Px, Py are the coordinates of the point
RetVal is the return value, non-zero on success

"LineTo", DevDc AS ULONG, Px AS LONG, Py AS LONG, RetVal AS LONG
Px, Py are the coordinates of the point
RetVal is the return value, non-zero on success

The 32-bit WinAPI is hugh and has grown with the advent of 64-bit architecture. I doubt if anyone really knows the WinAPI. That is why you have to read the documentation; however, functions in the WinAPI are not easy to find.

[gaslouk]

Thanks Team for the help.