PencilKit Framework for PyObjC

Warnings

• breaking PyObjC frequently drops support for older Python versions. PyObjC 12.0 dropped support for Python 3.9, and PyObjC 11.0 dropped Python 3.8. Ensure your Python version is compatible with the PyObjC version you are installing.
  Fix: Upgrade your Python environment to Python 3.10 or later for PyObjC 12.x (including this package). Always check `requires_python` on PyPI or the PyObjC changelog for specific version requirements.
• breaking PyObjC 11.1 changed how initializer methods (`init` family) are modeled, now correctly reflecting that they 'steal' a reference to `self` and return a new one, as per clang's ARC documentation. This affects object lifecycle and reference counting.
  Fix: Review code that interacts with object initialization, especially custom subclasses or factory methods, to ensure correct reference handling. Explicit memory management is rarely needed in Python, but understanding the underlying Objective-C semantics is crucial for correct behavior.
• gotcha PyObjC is a macOS-specific library and will not install or run on other operating systems. The frameworks it wraps (like PencilKit) are Apple-proprietary.
  Fix: Only use `pyobjc-framework-pencilkit` in macOS environments. For cross-platform drawing or GUI development, consider alternative libraries.
• gotcha Unlike Objective-C, where sending a message to `nil` (equivalent to Python `None`) is a no-op, attempting to call a method on a Python `None` object (which PyObjC translates from `nil`) will raise an `AttributeError`.
  Fix: Always check for `None` before calling methods on PyObjC-wrapped objects that might originate from Objective-C `nil` values. E.g., `if my_obj is not None: my_obj.doSomething_()`.
• gotcha Key-Value Observing (KVO) is not supported for pure Python objects. If you need KVO compatibility for properties of Python objects, they must inherit from `NSObject`. For observable sequence or dictionary instance variables, use `NSMutableArray` or `NSMutableDictionary` instead of Python lists or dictionaries.
  Fix: Ensure custom classes requiring KVO inherit from `AppKit.NSObject` or `Foundation.NSObject`. Use `Foundation.NSMutableArray` and `Foundation.NSMutableDictionary` for collections that will be observed.

Install

• pip install pyobjc-framework-pencilkit Install latest version

Imports

• PKCanvasView

  from PencilKit import PKCanvasView

  PyObjC framework wrappers expose their classes directly under the framework's name, not the PyPI package name.
• PKToolPicker

  from PencilKit import PKToolPicker

  Classes are imported directly from the top-level framework module.

Quickstart

This quickstart demonstrates how to create a basic macOS application using PyObjC that displays a `PKCanvasView` and a `PKToolPicker` for drawing. It sets up a standard Cocoa application window and integrates PencilKit components, allowing for user interaction with an Apple Pencil or trackpad/mouse.

import AppKit
import Foundation
import PencilKit
from PyObjCTools import AppHelper

class PyPencilKitDelegate(AppKit.NSObject):
    def applicationDidFinishLaunching_(self, notification):
        # Create a window
        self.window = AppKit.NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(
            Foundation.NSRect((100, 100), (600, 400)),
            AppKit.NSWindowStyleMaskTitled | AppKit.NSWindowStyleMaskClosable | AppKit.NSWindowStyleMaskResizable,
            AppKit.NSBackingStoreBuffered,
            False
        )
        self.window.setTitle_("PyObjC PencilKit Demo")
        self.window.setDelegate_(self)

        # Create a PKCanvasView
        self.canvasView = PencilKit.PKCanvasView.alloc().initWithFrame_(self.window.contentView().bounds())
        self.canvasView.setAutoresizingMask_(AppKit.NSViewWidthSizable | AppKit.NSViewHeightSizable)
        self.canvasView.setDrawingPolicy_(PencilKit.PKCanvasViewDrawingPolicyAnyInput) # Allow finger drawing

        # Create and configure a PKToolPicker
        self.toolPicker = PencilKit.PKToolPicker.alloc().init()
        self.toolPicker.setVisible_forFirstResponder_(True, self.canvasView) # Make visible for the canvas
        self.toolPicker.addObserver_(self.canvasView) # Canvas observes tool changes

        self.window.contentView().addSubview_(self.canvasView)
        self.window.makeKeyAndOrderFront_(None)

        # Make canvas first responder to receive drawing input
        self.window.makeFirstResponder_(self.canvasView)

    def applicationShouldTerminateAfterLastWindowClosed_(self, sender):
        return True

if __name__ == "__main__":
    app = AppKit.NSApplication.sharedApplication()
    delegate = PyPencilKitDelegate.alloc().init()
    app.setDelegate_(delegate)
    AppHelper.runEventLoop()