Fixes #4057 - MASSIVE! Fully implements ColorScheme->Scheme + VisualRole + Colors.->SchemeManager.

[tig]

HUGE PR

This PR introduces a significant refactoring of Terminal.Gui's Configuration Management system, addressing issue #4057 and a bunch of other related issues. The changes include:

• *Significant refactor and upgrade of ConfigurationManager
  • Simplifies and cleans up naming (e.g. SerializableConfigruationProperty -> ConfigProperty).
  • Uses [ModuleInitalizer] to ensure that CM caches the original values of all [ConfigProperty]s and provides APIs for resetting those values back (ConfigurationManager.ResetToHardCodedValues).
  • Removes all lame/complex code that tried to tie CM to Application.Init. Instead CM is simply process-wide.
  • Makes CM OFF BY DEFAULT. Apps must call ConfigurationManager.Enable to enable it.
• Renames ColorScheme to Scheme. Enables SchemeManager.GetCurrentSchemes() as the API that replaces the old ColorSchemes static class.
• Introduces VisualRole to replace string-based ColorSchemes[???] identifiers.
• Changes View.Scheme API signficantly
  • View.ColorScheme -> View.Scheme
  • NEW: View.HasScheme to indicate whether a Scheme was explicitly set or not.
  • NEW: Get/SetScheme (used by Scheme get/set). Enable...
  • NEW: GettingScheme/OnGettingScheme cancellable event
  • NEW: SettingScheme/OnSettingScheme cancellable event
  • GONE: Scheme is no longer virtual (the above addressses).
• HighlightStyle.Hover is DISABLED in this PR. to be fixed in HighlightStyle.Hover etc... needs a different implementation  #3753.

Much of the vast churn in this PR was done to finally address a slew of non-deterministic unit test problems having to do with static state. There are still some non-CM related issues buried in there, but I've killed most of them here. Note: Any unit test that uses Configuration.Enable MUST NOT be in Parallelizable. However, if you don't call Enable or use Application it's highly likely Parallelizable will work.

IMPORTANT: If you rely on View.Scheme being null ... STOP. Instead use HasScheme.

Fixes

• Fixes Rename ColorScheme to Scheme and Migrate Colors to ConfigurationManager.Themes #4057
• Fixes Make Theme Manager a better Singleton for Better Testability #4059
• Fixes ConfigurationManager - DeepMemberwiseClone does not do what it says #4072
• Fixes ConfigurationManager - It's stupid that it tries to be scoped by Application.Init #4073
• Fixes Add events for GetNormalColor etc.... #4016
• Fixes Rename TextStyle Style #4084
• Fixes ConfigurationManager: Applied and Updated events are clumsy #2871
• Fixes ConfigurationManager - It's a bug for any SomeProperty = DefaultSomeProperty if SomeProperty isn't nullable #4021
• Fixes Add View.GetSizeRequiredForSubViews() #4089

Proposed Changes/Todos

• Rename ColorScheme to Scheme
• Introduce VisualRole enum
• Refactor/Fix ConfigManager to be more robust and thread safe.
• Refactor CM to make accessing Schemes work better.
• Replace View.GetXXXColor () with View.GetAttributeForRole ()
• Add dozens of new unit tests, fix a bunch of old unit tests that were non-deterministic.
• Ensure new Scheme and Attribute related APIs in View are fully baked and thought through.
• Make CM.Enable more rational - Have it take ConfigLocation
• Fix bad implementation of View.Enable in View.Drawing, built-in Views and Scenarios.
• Update Text Styles scenario to show more
• Identify and fix why sometimes Style is misapplied/artifacts
• On Load() "Schemes": [] doesn't accept partial dict. Just overwrites dest.
• Make sure above addresses ConfigurationManager - It's a bug for any SomeProperty = DefaultSomeProperty if SomeProperty isn't nullable #4021
• Figure out how to reduce the in-memory size of the config (currently ~126kb!)

Now:

Start: Color size: 4 b
Start: Attribute size: 48 b
Start: Base Scheme size: 2870 b
Start: PropertyInfo size: 48 b
Start: ThemeScope (0) size: 56 b
Start: ThemeScope (1) size: 3020 b
Start: HardCoded Schemes (5) size: 2870 b
Start: Themes dictionary (1) size: 22 Kb
Enabled: Themes dictionary (1) size: 22 Kb
After Load: Themes dictionary (8) size: 47 Kb
Total Settings Size: 52 Kb

• Fix dynamic theme re-loading in UI Catalog
• Revamp config.md Deep Dive
• Add a Schemes Scenario that shows all views and lets you play with applying different schemes
• Refactor GetViewsUnderMouse to GetViewsUnderLocation etc... to work better
• Enable the other new VisualRole (Active, HotActive, Highlight)
• Ensure all API docs are up-to-date
• Revamp drawing.md Deep Dive
• Re-do Hover with Highlight
• Fix spurious unit test failures seen in CI/CD

For Future PRs

• Revamp built-in Scheme's (e.g. what *is* Toplevel anyway?). #4086
• HighlightStyle.Hover etc... needs a different implementation  #3753
• Add INotifyPropertyChanged support to ConfigProperty
• Validate AOT stuff still works (I may defer this).

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

[Copilot]

Pull Request Overview

This PR refactors Terminal.Gui’s configuration and color management by renaming and restructuring APIs to improve clarity, thread-safety, and test reliability. Key changes include the renaming of ColorScheme to Scheme (with corresponding API changes), the introduction of the VisualRole enum, and various adjustments to unit tests and configuration to support the new design.

Reviewed Changes

Copilot reviewed 333 out of 333 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Examples/UICatalog/Scenarios/CollectionNavigatorTester.cs	Replaced ColorScheme usage with SchemeName.
Examples/UICatalog/Scenarios/Clipping.cs	Updated color API from ColorScheme to SchemeName.
Examples/UICatalog/Scenarios/CharacterMap/CharacterMap.cs	Converted ColorScheme assignments and left commented legacy code.
Examples/UICatalog/Scenarios/Buttons.cs	Updated scheme selection via SchemeName and iteration over schemes.
Examples/UICatalog/Scenarios/Arrangement.cs	Replaced direct ColorScheme access with GetAttributeForRole and SetScheme.
Examples/UICatalog/Scenarios/AllViewsTester.cs	Renamed settings pane to propertiesEditor and revised scheme handling.
Examples/UICatalog/Scenarios/Adornments.cs	Adjusted scheme updates using SetScheme.
Examples/UICatalog/Resources/config.json	Removed ColorSchemes block in favor of Schemes.
Examples/SelfContained/Program.cs, ReactiveExample/Program.cs, etc.	Added ConfigurationManager.Enable call.
Examples/CommunityToolkitExample/*	Updated color-related API usages to work with new Scheme naming.

Comments suppressed due to low confidence (1)

Examples/CommunityToolkitExample/LoginViewModel.cs:107

• Ensure that the renaming from 'ValidationColorScheme' to 'ValidationScheme' is applied consistently throughout the codebase and documentation.

    -                ValidationColorScheme = Colors.ColorSchemes ["Error"];

[BDisp]

Good work. I like it very much. The only repair I would like to express is when I press the keyboard keys down and up, on radio button or checked opened menus I can't see an indicator on what is currently selected. I know we can select by hot key, but that's the only thing I don't like in the v2 menus navigation.
Pressing F9 to open the menu, then press Cursor.Right and then press Esc will exit the UICatalog instead only closing the menu.

[tig]

Good work. I like it very much. The only repair I would like to express is when I press the keyboard keys down and up, on radio button or checked opened menus I can't see an indicator on what is currently selected. I know we can select by hot key, but that's the only thing I don't like in the v2 menus navigation.

Pressing F9 to open the menu, then press Cursor.Right and then press Esc will exit the UICatalog instead only closing the menu.

Thanks.

I'll be fixing those menu issues in #4013.

I couldn't address the selection thing without fixing Schemes first.

[tig]

[tig]

This is fun. Based on all this, I've been able to significantly improve how transparent shadows are drawn. Previously the shadow was a lame "highlight" of the Normal attribute of the underlying view. And the logic for what the underlying view as lame.

Now, each cell of the shadow actually is a smarter highlight of the underlying cell.