Make coarse pointer check dynamic (#3572)

When a device has both a touch screen and a mouse, pointer: coarse
evaluates to false and then doesn't change even if the user begins to
use the touch screen.

In this PR pointer: coarse is replaced with any-pointer: coarse, which
checks if a touchscreen input is available. Event listeners for
touchstart and mousemove update isCoursePointer dynamically. So if the
user begins to move the mouse it changes to pointer: fine, if they then
touch the screen the pointer is returned to coarse.


https://github.com/tldraw/tldraw/assets/98838967/fb86bb44-ec11-4161-bb2f-0e8c3ee83eb6



### Change Type

<!-- ❗ Please select a 'Scope' label ❗️ -->

- [ ] `sdk` — Changes the tldraw SDK
- [x] `dotcom` — Changes the tldraw.com web app
- [ ] `docs` — Changes to the documentation, examples, or templates.
- [ ] `vs code` — Changes to the vscode plugin
- [ ] `internal` — Does not affect user-facing stuff

<!-- ❗ Please select a 'Type' label ❗️ -->

- [ ] `bugfix` — Bug fix
- [ ] `feature` — New feature
- [x] `improvement` — Improving existing features
- [ ] `chore` — Updating dependencies, other boring stuff
- [ ] `galaxy brain` — Architectural changes
- [ ] `tests` — Changes to any test code
- [ ] `tools` — Changes to infrastructure, CI, internal scripts,
debugging tools, etc.
- [ ] `dunno` — I don't know


### Test Plan

1. Load tldraw on a device with both coarse and fine pointer inputs
avaiable (e.g. an ipad with a keyboard and trackpad)
2. Switch between using the mouse and touch screen.
3. Handles on shapes should update dynamically. 

### Release Notes

- Add a brief release note for your PR here.

---------

Co-authored-by: Mime Čuvalo <mimecuvalo@gmail.com>
Co-authored-by: Steve Ruiz <steveruizok@gmail.com>

packages/editor/src/lib/hooks/useCoarsePointer.ts

@@ -4,27 +4,68 @@ import { useEditor } from './useEditor'
 /** @internal */
 export function useCoarsePointer() {
 	const editor = useEditor()
+
 	useEffect(() => {
+		// We'll track our own state for the pointer type
+		let isCoarse = editor.getInstanceState().isCoarsePointer
+
+		// 1.
+		// We'll use touch events / mouse events to detect coarse pointer.
+
+		// When the user touches the screen, we assume they have a coarse pointer
+		const handleTouchStart = () => {
+			if (isCoarse) return
+			isCoarse = true
+			editor.updateInstanceState({ isCoarsePointer: true })
+		}
+
+		// When the user moves the mouse, we assume they have a fine pointer
+		const handleMouseMove = () => {
+			if (!isCoarse) return
+			isCoarse = false
+			editor.updateInstanceState({ isCoarsePointer: false })
+		}
+
+		// Set up the listeners for touch and mouse events
+		window.addEventListener('touchstart', handleTouchStart)
+		window.addEventListener('mousemove', handleMouseMove)
+
+		// 2.
+		// We can also use the media query to detect / set the initial pointer type
+		// and update the state if the pointer type changes.
+
+		// We want the touch / mouse events to run even if the browser does not
+		// support matchMedia. We'll have to handle the media query changes
+		// conditionally in the code below.
+		const mql = window.matchMedia && window.matchMedia('(any-pointer: coarse)')
+
 		// This is a workaround for a Firefox bug where we don't correctly
 		// detect coarse VS fine pointer. For now, let's assume that you have a fine
 		// pointer if you're on Firefox on desktop.
-		if (
-			editor.environment.isFirefox &&
-			!editor.environment.isAndroid &&
-			!editor.environment.isIos
-		) {
-			editor.updateInstanceState({ isCoarsePointer: false })
-			return
+		const isForcedFinePointer =
+			editor.environment.isFirefox && !editor.environment.isAndroid && !editor.environment.isIos
+
+		const handleMediaQueryChange = () => {
+			const next = isForcedFinePointer ? false : mql.matches // get the value from the media query
+			if (isCoarse !== next) return // bail if the value hasn't changed
+			isCoarse = next // update the local value
+			editor.updateInstanceState({ isCoarsePointer: next }) // update the value in state
 		}
-		if (window.matchMedia) {
-			const mql = window.matchMedia('(pointer: coarse)')
-			const handler = () => {
-				editor.updateInstanceState({ isCoarsePointer: !!mql.matches })
-			}
-			handler()
+
+		if (mql) {
+			// set up the listener
+			mql.addEventListener('change', handleMediaQueryChange)
+
+			// and run the handler once to set the initial value
+			handleMediaQueryChange()
+		}
+
+		return () => {
+			window.removeEventListener('touchstart', handleTouchStart)
+			window.removeEventListener('mousemove', handleMouseMove)
+
 			if (mql) {
-				mql.addEventListener('change', handler)
-				return () => mql.removeEventListener('change', handler)
+				mql.removeEventListener('change', handleMediaQueryChange)
 			}
 		}
 	}, [editor])