Navigation Panel rework

[bdlukaa]

The current implementation for Navigation Panel lacks so much funcionalities, flexibility and fidelity.

• Top navigation
  We currently only have left navigation. On top navigation, the default page transition should be horizontal instead of vertical
• Minimal display mode
  This would also require to do some changes to the Scaffold widget
• Automatic display mode
  The current implementation for automatic display mode can be broken easily and it's not flexible.
• Selected indicators
  We currently only have one selected indicator: sliding horizontally. We must add more
• Pane footer
  Currently only one tile can be added in the footer. In the official docs, there can be multiple tiles
• Back button
  This also would required some changes to the Scaffold widget, as well as removing Window's top bar and implement a custom one.

Learn more:

• Official documentation

[bdlukaa]

This rework will be done once windows gets stable. The window's top bar needs to be customized, and depending on third party projects, such as bitsdojo_window, is not a viable option, because fluent_ui is supopsed to run on other platforms too.

Learn more:

• Support for UWP: ☂ Add support for UWP flutter/flutter#14967

[bdlukaa]

Started working on this at https://github.com/bdlukaa/fluent_ui/tree/navigation

[bdlukaa]

So here's my progress on the navigation branch:

I made the whole navigation implementation again from scratch. I removed the Scaffold widget and implemented ScaffoldPage. Implemented NavigationView, that has:

• Open, Compact and Top Navigation. Minimal pane is still missing.
• App Top Bar, with back button and option to implement window close buttons
• Automatic Display Mode working

Here's what's missing:

• Implement Scrollbar on Open and Compact modes.
• Add the More pane button on the Top display mode.
• Open Minimal pane when the button is tapped.
• Change between Open and Compact mode when the button is tapped
• Selected indicators

[bdlukaa]

More progress on it:

• Implemented a scrollbar on open, compact and minimal display mode
• Open the minimal pane when the button is tapped
• Change between open and compact mode when the button is tapped

[bdlukaa]

More issues found:

• The scrollbar is throwing an error:

The following assertion was thrown during a scheduler callback:
The provided ScrollController is currently attached to more than one ScrollPosition.

The Scrollbar requires a single ScrollPosition in order to be painted.

When Scrollbar.isAlwaysShown is true, the associated Scrollable widgets must have unique ScrollControllers. The PrimaryScrollController is used by default for ScrollViews with an Axis.vertical ScrollDirection, unless the ScrollView has been provided its own ScrollController. More than one Scrollable may have tried to use the PrimaryScrollController of the current context.

When the exception was thrown, this was the stack
#0      RawScrollbarState._maybeTriggerScrollbar.<anonymous closure>.<anonymous closure>
package:flutter/…/widgets/scrollbar.dart:990
#1      RawScrollbarState._maybeTriggerScrollbar.<anonymous closure>
package:flutter/…/widgets/scrollbar.dart:1014

• If the navigation view does not have a top bar, the navigation selected indicator is rendered incorrectly