Consolidate Button configuration

[provencher]

Describe the problem

It is frustrating to configure buttons, as they have so many things to set in child game objects:

• Icon needs a new material instance, and to be set on the icon GO
• Text and text color need to be set on the TMP GO
• Event routing requires setting several scripts linked together
• Backplate and button dimensions are controlled on independent game objects

Beyond that, styling buttons is tedious and requires a lot of duplication.

Describe the solution you'd like

It would be great to have a scriptable object that controls:

• Color (font and icon)
• Scale / Dimensions
• Text anchors
• Image anchors

This scriptable object would be akin to a CSS class that determines the style of all buttons using it.

In the button component, there is a single script that lets you easily set the icon and text, without manually playing with the materials and TMP components.

Everything other than the top layer of the button should be hidden and auto generated.
This would massively simplify the scene structure at edit time, and make it easier for users to set up complex UIs.

[Troy-Ferrell]

Related #6410

[xwipeoutx]

I'd like to one more to this - the OnClick handler is a huge scroll down on the default button prefabs, and doesn't exactly jump out of the screen. This ought be pulled up and made more obvious, too.

Edit: Clearly wrote this comment before seeing #6410 . Good stuff :)

[IssueSyncBot]

We appreciate your feedback and thank you for reporting this issue.

Microsoft Mixed Reality Toolkit version 2 (MRTK2) is currently in limited support. This means that Microsoft is only fixing high priority security issues. Unfortunately, this issue does not meet the necessary priority and will be closed. If you strongly feel that this issue deserves more attention, please open a new issue and explain why it is important.

Microsoft recommends that all new HoloLens 2 Unity applications use MRTK3 instead of MRTK2.

Please note that MRTK3 was released in August 2023. It features an all-new architecture for developing rich mixed reality experiences and has a minimum requirement of Unity 2021.3 LTS. For more information about MRTK3, please visit https://www.mixedrealitytoolkit.org.

Thank you for your continued support of the Mixed Reality Toolkit!