Mobile support

It would be great if the tool supports mobile touch, so it can be used on devices such as tablets with a pencil.

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Progress:

• Responsive UI (#787)
• touch support (#788)
• make the touch areas for the resize handles larger (they shouldn’t appear visually larger though) (#790)
• two-finger pan/zoom (#788)
• fix press&hold on canvas triggering selection (maybe it’s not fixed? hard to tell) → fix by disabling user-select everywhere (#790)
• edit text (#790)
• delete objects (toolbar button?) (#788)
• finalize line creation (#788)
  • fix how existing finalize action deletes last line (#790)
• refactor menu/edit toggles to be actions (#793)
• make 🍔/🎨 buttons radios or otherwise show that they’re selected (#793)
• “reset zoom” button/indicator ⏩ #965
• undo/redo buttons (#793)
• desktop pinch-zoom (Safari GestureEvents, Chrome/FF simulated ctrl+wheel)
• apple-touch-icon for adding to home screen ⏩ #820
• test pointercancel ⏩ #966
• test two-finger gestures programmatically ⏩ #966
• abort tap selection if a second pointerdown (i.e. for pan/zoom) occurs before the first pointer moves too far ⏩ #966
• desktop pinch-zoom centered around cursor ⏩ #940
• fix scrollbar offsets to account for toolbar (or resize canvas) ⏩ #934
• re-add lock button somewhere ⏩ #819

Optional:

• multiple selection ⏩ #966
• two-finger gestures while creating a line ⏩ #966
• support releasing one finger from a two-finger gesture to switch back to select/edit mode (the reverse currently works) ⏩ #966

[vjeux]

I think that there are a few things here:

• Make sure we react to touch events
• Update the layout on mobile so that 3/4 of the view are not just the left page
• Optimize touch interactions. We can double finger drag to resize an element. Figure out how selection and pan interact…
• Add visible buttons for copy paste, undo…

We don’t need to do everything at once, every small improvement would be welcome

[hmaurer]

Basic support might be as simple as switching from mouse events to pointer events (onMouseDown -> onPointerDown, etc).