feat: expose events (on_double_tap, on_pan_start) in WindowDragArea

[ndonkoHenri]

Resolves #5018

Test Code

import flet as ft


def main(page: ft.Page):
    page.vertical_alignment = ft.MainAxisAlignment.CENTER
    page.horizontal_alignment = ft.CrossAxisAlignment.CENTER
    page.spacing = 20

    page.add(
        ft.WindowDragArea(
            content=ft.Container(
                content=ft.Text("maximizable=True"),
                alignment=ft.alignment.center,
                bgcolor=ft.Colors.RED,
                width=300,
                height=200,
            ),
            maximizable=True,
            on_double_tap=lambda e: print("W1 on_double_tap"),
            on_pan_start=lambda e: print("W1 on_pan_start"),
        ),
        ft.WindowDragArea(
            content=ft.Container(
                content=ft.Text("maximizable=False"),
                alignment=ft.alignment.center,
                bgcolor=ft.Colors.BLUE,
                width=300,
                height=200,
            ),
            maximizable=False,
            on_pan_start=lambda e: print("W2 on_pan_start"),
        ),
    )


ft.app(target=main)

Summary by Sourcery

The pull request introduces new events (on_double_tap, on_pan_start) to the WindowDragArea control, allowing developers to handle double taps and pan start gestures within the drag area. It also modifies the control to inherit from GestureDetector instead of ConstrainedControl.

New Features:

• Expose on_double_tap event to handle double taps within the drag area.
• Expose on_pan_start event to handle pan start gestures within the drag area.
• Make the window maximizable on double tap if maximizable is set to True.
• Call start_dragging on the window to initiate window dragging on pan start.