[Feat] OverviewMapWidget - Minimap for spatial navigation

[aivis-sjlee]

Target Use Case

Large-scale image viewers, GIS applications, and any visualization where users need spatial context while zoomed in. Common use cases include:

• Medical imaging (pathology slides, radiology)
• Satellite/aerial imagery analysis
• Large CAD drawings or floor plans
• Any map-based application requiring quick navigation overview

Users often lose spatial awareness when zoomed into a specific area. An overview map provides a thumbnail of the entire view with a highlighted box showing the current viewport position, allowing quick navigation by clicking on the minimap.

Proposal

import {Deck} from '@deck.gl/core';
import {OverviewMapWidget} from '@deck.gl/widgets';

const deck = new Deck({
  widgets: [
    new OverviewMapWidget({
      placement: 'bottom-right',
      maxSize: 200,
      collapsed: false,
      transitionDuration: 200,
      // Optional: provide custom thumbnail instead of auto-capture
      thumbnailUrl: 'https://example.com/overview.png',
      sourceWidth: 4096,
      sourceHeight: 4096
    })
  ]
});

Features:
Auto-captures current deck canvas as thumbnail (or accepts custom URL)
Shows viewport box indicating current view position
Click-to-navigate: click anywhere on minimap to pan the main view
Collapsible: toggle between expanded and minimized state
Supports both OrthographicView and MapView (WebMercator)
Follows deck.gl widget theming system