fix: improve InteractiveViewer programmatic transformations

[ndonkoHenri]

Fix #4642
Fix #5728

Example

import flet as ft


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

    async def handle_zoom_in(e: ft.Event[ft.Button]):
        await i.zoom(1.2)

    async def handle_zoom_out(e: ft.Event[ft.Button]):
        await i.zoom(0.8)

    async def handle_pan(e: ft.Event[ft.Button]):
        await i.pan(dx=50, dy=50)

    async def handle_reset(e: ft.Event[ft.Button]):
        await i.reset()

    async def handle_reset_slow(e: ft.Event[ft.Button]):
        await i.reset(animation_duration=ft.Duration(seconds=2))

    async def handle_save_state(e: ft.Event[ft.Button]):
        await i.save_state()

    async def handle_restore_state(e: ft.Event[ft.Button]):
        await i.restore_state()

    page.add(
        i := ft.InteractiveViewer(
            min_scale=0.1,
            max_scale=5,
            boundary_margin=ft.Margin.all(20),
            content=ft.Image(src="https://picsum.photos/500/500"),
        ),
        ft.Row(
            wrap=True,
            controls=[
                ft.Button("Zoom In", on_click=handle_zoom_in),
                ft.Button("Zoom Out", on_click=handle_zoom_out),
                ft.Button("Pan", on_click=handle_pan),
                ft.Button("Save State", on_click=handle_save_state),
                ft.Button("Restore State", on_click=handle_restore_state),
                ft.Button("Reset (instant)", on_click=handle_reset),
                ft.Button("Reset (slow)", on_click=handle_reset_slow),
            ],
        ),
    )


ft.run(main)

Summary by Sourcery

Enable robust programmatic zooming, panning, resetting, and state management on InteractiveViewer while enforcing boundary and scale constraints and enrich the Python API with more descriptive properties and examples.

Bug Fixes:

• Fix programmatic zoom, pan, and reset actions to correctly respect min/max scales and boundary margins

Enhancements:

• Add matrix-based scaling and translation logic to enforce viewport boundaries in Dart code
• Improve Python InteractiveViewer API documentation with detailed descriptions for properties like constrained, boundary_margin, clip_behavior, and scale_factor
• Include a new example demonstrating programmatic transformations in InteractiveViewer

Documentation:

• Augment interactive_viewer documentation with a programmatic transformations example
• Update enum and class docstrings for clarity in the Python SDK

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[Copilot]

Pull Request Overview

This PR enhances documentation across several Flet controls, particularly focusing on the InteractiveViewer control. The changes include improved docstrings with more detailed explanations, formatting improvements, and a new example demonstrating programmatic transformations.

• Enhanced documentation for InteractiveViewer properties with expanded explanations and usage notes
• Added documentation for enum values in ImageRepeat and improved formatting in VisualDensity and other types
• Created a new example showcasing programmatic transformations in InteractiveViewer
• Implemented boundary-aware transformation logic in the Dart implementation

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
sdk/python/packages/flet/src/flet/controls/types.py	Updated docstrings for UrlTarget, ClipBehavior, ImageRepeat, and VisualDensity enums with improved formatting and descriptions
sdk/python/packages/flet/src/flet/controls/core/interactive_viewer.py	Enhanced documentation for InteractiveViewer properties with detailed explanations, changed default value of boundary_margin to use factory function
sdk/python/packages/flet/docs/controls/interactiveviewer.md	Added new section for programmatic transformations example
sdk/python/examples/controls/interactive_viewer/transformations.py	New example file demonstrating zoom, pan, reset, and state save/restore operations
packages/flet/lib/src/controls/interactive_viewer.dart	Implemented boundary-aware transformation logic with helper methods for scaling and panning operations

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