feat: Search (Fixes #4)

[JuliusBairaktaris]

Description

This PR implements native-feeling text search functionality within the PDF viewer and resolves a long-standing deprecation warning regarding Toasts.

Changes

Search Feature

• Core Logic: Introduced a SearchController class in JavaScript that interfaces directly with the PDF.js text layer.
  • Utilizes a non-blocking indexing loop (via requestAnimationFrame) to ensure the UI remains responsive even during large document scans.
  • Performs case-insensitive substring matching against normalized text content.
• Native Integration: Added a search action to the top toolbar menu using a native SearchView, providing a familiar Android UX.
• Bridge Communication: Established a robust bi-directional bridge:
  • Java to JS: Uses evaluateJavascript to inject JSON command objects (find, findNext, closesearch) into a new onMessage handler.
  • JS to Java: Uses @JavascriptInterface callbacks to report search progress and match counts to the native UI.
• Visuals: Implemented Adobe-style highlight overlays (.search-highlight) that scale correctly with zoom.
• Navigation: Implemented "Next"/"Previous" navigation with circular (wrapping) logic, auto-scrolling to matches, and focus management.

UI Improvements

• Deprecation Fix: Replaced the deprecated Toast.setView() API with a custom, high-performance TextView overlay.
  • This eliminates the API warning and provides better control over z-index and visibility, resolving layout overlap issues.
• Assets: Added search icon vectors and necessary string translations.

Maintenance

• Cleaned up PdfViewer.java, removing legacy boilerplate and enforcing stricter type safety in bridge calls.

Fixes

• Resolves the Toast.setView() deprecation warning.
• Fixes occasional layout overlaps by properly managing the page number visibility and elevation.

Disclaimer: This PR was implemented with the assistance of Gemini 3 Pro.

[Copilot]

Pull request overview

This PR implements a comprehensive text search feature for the PDF viewer application and addresses a Toast deprecation warning by replacing the custom Toast view with a TextView overlay.

Key Changes:

• Added full-text search functionality with visual highlighting and navigation across PDF pages
• Replaced deprecated Toast.setView() with a custom TextView overlay for page number display
• Implemented bidirectional JavaScript-Android bridge communication for search operations

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 14 comments.

Show a summary per file

File	Description
viewer/main.css	Added CSS classes for search highlight containers and selected/unselected highlight styling
viewer/js/search_controller.js	New search controller implementing asynchronous text indexing, substring matching, and DOM-based highlight rendering
viewer/js/index.js	Integrated search controller with PDF.js rendering pipeline and added message handler for Android bridge communication
viewer/css/text_layer.css	Code formatting improvements (spacing, line breaks)
app/src/main/res/values/strings.xml	Added search-related string resources (action_search, search_hint, no_matches, match_status)
app/src/main/res/menu/pdf_viewer.xml	Added search action menu item with SearchView configuration
app/src/main/res/layout/pdfviewer.xml	Added page_number_view TextView to replace deprecated Toast implementation
app/src/main/res/drawable/ic_search_24dp.xml	New search icon vector drawable
app/src/main/java/app/grapheneos/pdfviewer/PdfViewer.java	Implemented search UI logic, replaced Toast with TextView, added JSON-based WebView bridge methods, and integrated search navigation with existing prev/next buttons

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