Allow multiple Mappings windows

[Lorp]

Multiple Mappings windows will allow users to have a complete view of a variable font with more than 2 axes, with changes in all axes visualized. A button could potentially create all windows necessary for the axes in the font, so for a 20-axis font 10 Mappings windows would be created.

[davelab6]

https://developer.mozilla.org/en-US/docs/Web/API/VisualViewport could help make room by "zooming out"

[Lorp]

The main functionality, handling multiple View windows, is now implemented in a54ddec. New View windows are created with the same size as the last-created window and positioned at an offset of (20,20) from it. This has the disadvantage of obscuring previous View windows.

How about this logic for new View window layout?

• Size: take the dimensions of the last-created View window.
• Position: find space for the new View window in the document as close to the top as possible — if no rectangle large enough exists, then expand the canvas downwards to create space.

This way, we leave it to the user to decide whether very small View windows are ever created.

[Lorp]

Zooming the viewport, à la Prezi, is intriguing. However the reduction of size of UI elements (text labels, axis sliders, draggable mappings, window title bars, etc.) seems to be an overwhelming disadvantage in this situation.

[davelab6]

I'm not sure, I think its OK to make all the UI read-only once zoomed out a certain amount, the point is to see an overview, and interaction can require zooming in.

[Lorp]

I’m still thinking this will lead to interminable discussion over the ideal UI for various zooms, a kind of opsz axis for UI.

How about the following approach?

• A button opens a new window, "Mini views", by default containing small versions of enough 2D graphs to cover all axes (thus 16 Mini Views for a 31-axis font).
• Delete any Mini Views you don’t need.
• Add new Mini Views for custom 2-axis combos by clicking "Add Mini View" on a suitable large View.
• Click on a Mini View to open a large View, then edit mappings on those two axes.
• Reorder Mini Views by dragging.

This approach means just a single zoom scale for me to pick, along with its UI specifics. I suggest dropping all backgrounds, only showing the mappings. Maybe the Mini Views are so simple graphically that users can choose the zoom for them all with a slider, like setting the scale for image thumbnails in macOS Finder.

The only additional issue is preserving state so that you don’t need to set up Views and Mini Views each time you open a given font in Fencer. The solution to this is to key the window states to the filename or font name in LocalStorage.