CLIM-1233: Map Legend, opened by default

[renoirb]

Description

Opens the map legend by default when the map container has sufficient width to accommodate it.

Changes:

• Legend now opens automatically on page load when map container width ≥ 430px (the legend's max width)
• Uses map container's actual width rather than window width for better accuracy in comparison view
• No resize handling per requirements - state set only on initial mount

Implementation:

• Added useEffect in MapLegend component to check map container width on mount
• References existing MapLegendOpenControl.maxLegendWidth constant (430px)
• Uses Leaflet's map.getContainer().getBoundingClientRect() for precise measurement

Rationale

Why 430px instead of 768px:
The original requirement specified 768px screen width, but using the legend's actual max width (430px) is more semantically correct and provides better behavior:

• Checks if there's actual space for the legend itself
• Self-documenting code that references the legend's own width constant
• Automatically adjusts if MAX_LEGEND_WIDTH changes in future

Why map container width instead of window width:

• More accurate in comparison view where two maps sit side-by-side
• Each map's legend state becomes independent
• Uses Leaflet API properly via map.getContainer()

Testing

Manual testing needed:

• Regular map view: legend opens when container ≥ 430px
• Regular map view: legend closed when container < 430px
• Comparison map view: each legend opens/closes independently based on its map's width
• Behavior at exactly 430px boundary
• No resize handling - legend state persists after window resize

Related ticket

• CLIM-1233

Related PRs

• CLIM-1235: Map Legend hidden by Location Modal #644

Screenshots

• 2025-12-11

[renoirb]

Screenshots 2025-12-11

Opens automatically based on available space, even when resized.

We might want to bring a little bit down the spacing between the opened legend box and the search bar