Mac osx callback functions parameters: wrong values in 386 mode.
Using control callback function with a control (a button) apparently
results in wrong
parameter values when compiling to 386 (values are correct compiling
The attached case refers to a callback procedure myActionProc
(lControlRef: ControlRef; PartCode: ControlPartCode) applied to a push
- Compiling to ppc, everything is correct (in particular PartCode=
- Compiling to 386, the value of lControlRef is correct, but the
value of PartCode is wrong (a random value)
As I got the same results (first parameter, i.e. the ControlRef,
correct, others wrong) with callbacks with more parameters (as the ones
used with DataBrowser), it would seem related to different
architecture's parameter passing modes, but I couldn't get it out.
Thanks in advance for any suggestion.
(The following code is derived from the default FPC Carbon
Application 2.4.0 template).
err : OSStatus;
nibRef : IBNibRef;
window : WindowRef;
procedure myActionProc (lControlRef: ControlRef; PartCode:
// Create a Nib reference passing the name of the nib file
(without the .nib extension)
// CreateNibReference only searches into the application bundle.
err := CreateNibReference(CFSTR('main'), nibRef);
// Once the nib reference is created, set the menu bar.
"MainMenu" is the name of the menu bar
// object. This name is set in InterfaceBuilder when the nib is
err := SetMenuBarFromNib(nibRef, CFSTR('MenuBar'));
// Then create a window. "MainWindow" is the name of the window
object. This name is set in
// InterfaceBuilder when the nib is created.
err := CreateWindowFromNib(nibRef, CFSTR('MainWindow'), window);
SetRect(lRect, 10, 100, 110, 200);
theControlRef := NewControl(window, lRect, 'OK', true, 0, 0, 1,
// We don't need the nib reference anymore.
> Using control callback function with a control (a button) apparently
> results in wrong
> parameter values when compiling to 386 (values are correct compiling
> to ppc).
The default calling convention on non-i386 platforms is mostly the same as the C calling convention. On i386, it's different for Delphi compatibility. Add the "mwpascal;" modifier at the end of the function declaration to get the same calling convention behaviour as with MetroWerks Pascal (that's also the calling convention expected by the declarations in the macosall unit).
By adding an explicit typecast you make it impossible for the compiler to tell you that the routines are incompatible. Remove the ControlActionProcPtr typecast, and if you are using MacPas mode then also remove the "@". The compiler will then give an error if the callback's signature is wrong, and it will also print the signature of the expected type.