Abstract Ctypes Interface

This project provides an abstract base class AbstractDialogWindow for creating Windows dialogs using ctypes and user32.dll calls directly.

Usage

To create a window, inherit from AbstractDialogWindow and implement the required abstract methods.

Class Name

You must define a _class_name for your window class. This string is used to register the window class with the OS.

class MyDialog(AbstractDialogWindow):
    _class_name = 'MyUniqueDialogClass'

Window Procedure (wnd_proc)

You must implement the wnd_proc method to handle window messages. It is crucial to handle WM_DESTROY to properly close the application loop.

Additionally, you should handle WM_CREATE to initialize the window geometry and create controls.

    def wnd_proc(self, hwnd, msg, wparam, lparam):
        if msg == win32con.WM_CREATE:
            self.invalidate_geometry()
            self.create_controls()
            return 0

        elif msg == win32con.WM_DESTROY:
            self.destroy()
            PostQuitMessage(0)
            return 0
        
        # ... handle other messages ...

        return DefWindowProc(hwnd, msg, wparam, lparam)

Geometry and Sizing (invalidate_geometry)

The invalidate_geometry method is used to adjust the window size and position to ensure the client area matches the desired dimensions, accounting for window borders and decorations.

The Client Rectangle refers to the actual usable surface area inside the window borders and title bar. This is the canvas where your application draws its UI and places controls.

There is a 18x39 pixel offset between GetWindowRect and GetClientRect. This is due to a ~8px border shadowing around the window itself, and GetWindowRect will include this as part of the window.

If you create a window that is 400x160, the GetClientRect would be 382x121. So if you want to create a window that is 400x160 (client area), you'll have to set the width and the height in CreateWindow or CreateWindowEx to 418x199.

Calculations:

client_width = 400
client_height = 160

# Centering on monitor
(monitor_width - (client_width + 18)) // 2
(monitor_height - (client_height + 39)) // 2

# Window dimensions
client_width + 18, client_height + 39

The extra ~31px spacing from the top of the window is due to the size of the title bar. There isn't any shadowing around the top edge of the window itself.

     ┌───────────────────────────────────────┐
     │               Title Bar               │ ← ~31 pixels tall
     ├───────────────────────────────────────┤   (GetWindowRect)
     │                                       │
     │                                       │
     │           Client  Rectangle           │
     │            (GetClientRect)            │
     │                                       │
~8px │                                       │ ~8px
   ← │                                       │ →
     └───────────────────────────────────────┘ 
    ↓ ~8px       border shadowing        ~8px ↓
                 (GetWindowRect)