fix: settings are read from db multiple times a second

[lklimek]

Problem statement

Settings are read from DB a few times with every repaint of UI.

Solution

This pull request introduces a caching mechanism for application settings to improve performance and ensure atomic updates. The key changes include adding a settings cache to AppContext, implementing methods to manage the cache, and updating database interaction logic to integrate with the cache. Additionally, direct database calls in the UI layer have been replaced with AppContext methods to ensure proper cache handling.

Caching Mechanism Enhancements:

• Added a settings cache to AppContext: Introduced a RwLock-protected cached_settings field to store settings and allow concurrent reads while ensuring exclusive writes during updates (src/context.rs, [1] [2].
• Implemented cache invalidation logic: Added the invalidate_settings_cache method to clear the cache and return a guard to prevent race conditions during database updates (src/context.rs, src/context.rsR485-R551).
• Integrated caching in settings retrieval: Updated get_settings to first check the cache before querying the database, and to update the cache after a database read (src/context.rs, src/context.rsR485-R551).

Database Interaction Updates:

• Encouraged use of AppContext methods: Added documentation to database methods (e.g., update_main_password, update_dash_core_execution_settings) to discourage direct calls and ensure proper caching behavior (src/database/settings.rs, [1] [2] [3] [4] [5].

UI Layer Improvements:

• Replaced direct database calls with AppContext methods: Updated UI components to use AppContext methods for settings updates and retrieval, ensuring cache consistency:
  • add_connection_indicator now uses get_settings instead of directly querying the database (src/ui/components/top_panel.rs, src/ui/components/top_panel.rsL162-R165).
  • update_dash_core_execution_settings calls in NetworkChooserScreen now use AppContext (src/ui/network_chooser_screen.rs, src/ui/network_chooser_screen.rsL123).
  • Password updates in AddNewWalletScreen and ImportWalletScreen now use AppContext (src/ui/wallets/add_new_wallet_screen.rs, [1]; src/ui/wallets/import_wallet_screen.rs, [2].

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[Copilot]

Pull Request Overview

This PR introduces a caching mechanism for application settings to address performance issues where settings were being read from the database multiple times per second during UI repaints.

• Adds a RwLock-protected settings cache to AppContext to reduce database reads
• Implements cache invalidation with atomic updates using guard patterns
• Replaces direct database calls in UI components with AppContext methods

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/context.rs	Adds settings cache infrastructure with invalidation methods and cached retrieval
src/database/settings.rs	Adds documentation discouraging direct database method usage
src/ui/components/top_panel.rs	Updates to use cached settings via AppContext instead of direct DB calls
src/ui/network_chooser_screen.rs	Removes direct database access, uses AppContext method
src/ui/wallets/add_new_wallet_screen.rs	Removes direct database access for password updates
src/ui/wallets/import_wallet_screen.rs	Removes direct database access for password updates
src/backend_task/system_task/mod.rs	Adds cache invalidation for theme preference updates

[pauldelucia]

One comment. But it fixes the issue and code looks good otherwise.