`TypeError: invalid type` in `setfunc` of `make_callback_returnable` on Python 3.13

[Rjvs]

Describe the bug

I'm hitting this in toga-cocoa’s TogaTable when using rubicon-objc 0.5.3 with Python 3.13 on macOS 26.3.1 (a). It looks like the setfunc installed by make_callback_returnable in ctypes_patch.py raises TypeError: invalid type at line 286:

ctypes.memmove(ptr, ctypes.addressof(value), actual_size)

The exceptions are “ignored” (non-crashing) but indicate struct parameters aren’t being marshalled correctly into the callback.

How to reproduce the bug

It looks like any @objc_method that takes a struct parameter triggers this.

Minimum example code

from rubicon.objc import NSPoint, objc_method, objc_property
from rubicon.objc.runtime import load_library, objc_id

NSTableView = ObjCClass("NSTableView")

class MyTableView(NSTableView):
    @objc_method
    def canDragRowsWithIndexes_atPoint_(
        self,
        rowIndexes,
        mouseDownPoint: NSPoint,
    ) -> bool:
        return False

Screenshots

No response

Environment details

• macOS 26.3.1 (a) (25D771280a), Apple Silicon
• Python 3.13 (Briefcase-packaged)
• Briefcase 0.4.1
• toga-cocoa 0.5.3
• rubicon-objc 0.5.3

Logs

2026-04-21 11:26:28.956 Connie[93191:127588242] TypeError: invalid type
2026-04-21 11:26:28.959 Connie[93191:127588242] Exception ignored on calling ctypes callback function <function make_callback_returnable.<locals>.setfunc at 0x10b5fd9e0>:
2026-04-21 11:26:28.959 Connie[93191:127588242] Traceback (most recent call last):
2026-04-21 11:26:28.959 Connie[93191:127588242]   File "{redacted}/connie/build/connie/macos/app/Connie.app/Contents/Resources/app_packages/rubicon/objc/ctypes_patch.py", line 286, in setfunc
2026-04-21 11:26:28.959 Connie[93191:127588242]     ctypes.memmove(ptr, ctypes.addressof(value), actual_size)

Additional context

Would this fix?

@SETFUNC
def setfunc(ptr, value, size):
    actual_size = ctypes.sizeof(ctype)
    if size != 0 and size != actual_size:
        raise ValueError(
            f"setfunc for ctype {ctype}: Requested size {size} "
            f"does not match actual size {actual_size}"
        )

    # value is already the expected type or another ctypes instance
    if isinstance(value, ctypes.Structure):
        ctypes.memmove(ptr, ctypes.addressof(value), actual_size)
        return

    # value is a tuple/list of field values (e.g. NSPoint as (x, y))
    if isinstance(value, (tuple, list)):
        value = ctype(*value)
        ctypes.memmove(ptr, ctypes.addressof(value), actual_size)
        return

    # value is raw bytes
    if isinstance(value, (bytes, bytearray)):
        value = ctype.from_buffer_copy(value)
        ctypes.memmove(ptr, ctypes.addressof(value), actual_size)
        return

    # last resort — single-value construction
    value = ctype(value)
    ctypes.memmove(ptr, ctypes.addressof(value), actual_size)

[freakboy3742]

We're going to need more details here, because your minimal reproduction example doesn't run as provided. At the very least, it needs an import of ObjCClass, and a call to appkit = load_library("AppKit"); but even with those changes, running that code doesn't raise any visible error.

You've also written "macOS 25" multiple times - based on your later reference to "Sequoia", I presume you actually mean "macOS 15"? Can you provide the exact version number?

The most confusing part is that the code you've provided as a reproduction case is almost literally present in Toga's own source code; and I don't see any exceptions of any kind when I run one of Toga's Table examples.

Can you provide any more details on what you're doing to generate this error?

[Rjvs]

Sorry for the confusion; I'm using latest Toga with latest Briefcase on MacOS 26.3.1 (a) and seeing the exception as documented above spamming me as I'm debugging other issues. I reported it here because it seems like a rubicon issue and it seemed wrong to provide Toga as the repro but on reflection that might have been more helpful. I don't think I'm doing anything odd, my TogaTable is just;

        self.table = toga.Table(
            headings=["Name", "Image", "Status", "ID", "Kind"],
            accessors=["name", "image", "status", "cid", "kind"],
            data=app.container_source,
            style=Pack(flex=1),
        )

[freakboy3742]

I've tried running on Tahoe 26.4.1 on an M1 Mac (running through Parallels), with Rubicon 0.5.3, and beeware/toga@90a34bb6 - and I don't see any problem running the Toga examples/table or examples/table_source, with either Python 3.14.4 or 3.13.13.

If Toga is needed to reproduce the problem, that's fine; but we need a complete and unambiguous reproduction case before we're able to diagnose anything. The constructor you've provided for an instance of Table looks fine in itself; but there's any number of potential issues in your container_source that might cause unusual interactions. We also need to know how you're triggering the exception - is it on startup? When you click on a row? When you drag a row? Does it matter where you start the drag?