Franknoirot/live system theme (#358)

* Only show the Replay Onboarding button in file settings
Resolves #351. Eventually we will implement more sophisticated
logic for which settings should be shown where.

Signed-off-by: Frank Noirot <frank@kittycad.io>

* Remove unnecessary console.log

Signed-off-by: Frank Noirot <frank@kittycad.io>

* Respond to system theme changes in real-time
If the user has their "theme" setting to "system".
I tried to use the [XState invoked callback approach](https://xstate.js.org/docs/guides/communication.html#invoking-callbacks),
but I could not find any way to respond to the latest context/state values within the
media listener; I kept receiving stale state.

Signed-off-by: Frank Noirot <frank@kittycad.io>

---------

Signed-off-by: Frank Noirot <frank@kittycad.io>

src/components/GlobalStateProvider.tsx

@@ -15,7 +15,7 @@ import {
   settingsMachine,
 } from 'machines/settingsMachine'
 import { toast } from 'react-hot-toast'
-import { setThemeClass } from 'lib/theme'
+import { setThemeClass, Themes } from 'lib/theme'
 import {
   AnyStateMachine,
   ContextFrom,
@@ -87,10 +87,21 @@ export const GlobalStateProvider = ({
     commandBarMeta: settingsCommandBarMeta,
   })
 
-  useEffect(
-    () => setThemeClass(settingsState.context.theme),
-    [settingsState.context.theme]
-  )
+  // Listen for changes to the system theme and update the app theme accordingly
+  // This is only done if the theme setting is set to 'system'.
+  // It can't be done in XState (in an invoked callback, for example)
+  // because there doesn't seem to be a good way to listen to
+  // events outside of the machine that also depend on the machine's context
+  useEffect(() => {
+    const matcher = window.matchMedia('(prefers-color-scheme: dark)')
+    const listener = (e: MediaQueryListEvent) => {
+      if (settingsState.context.theme !== 'system') return
+      setThemeClass(e.matches ? Themes.Dark : Themes.Light)
+    }
+
+    matcher.addEventListener('change', listener)
+    return () => matcher.removeEventListener('change', listener)
+  }, [settingsState.context])
 
   // Auth machine setup
   const [authState, authSend] = useMachine(authMachine, {

src/lib/commands.ts

@@ -73,8 +73,6 @@ export function createMachineCommand<T extends AnyStateMachine>({
         arg.defaultValue as keyof typeof state.context
       ] as string | undefined
 
-      console.log(arg.name, { defaultValueFromContext })
-
       const options =
         arg.options instanceof Array
           ? arg.options.map((o) => ({

src/lib/theme.ts

@@ -4,17 +4,18 @@ export enum Themes {
   System = 'system',
 }
 
+// Get the theme from the system settings manually
 export function getSystemTheme(): Exclude<Themes, 'system'> {
-  return typeof window !== 'undefined' &&
-    'matchMedia' in window &&
-    window.matchMedia('(prefers-color-scheme: dark)').matches
+  return typeof window !== 'undefined' && 'matchMedia' in window
+    ? window.matchMedia('(prefers-color-scheme: dark)').matches
       ? Themes.Dark
       : Themes.Light
+    : Themes.Light
 }
 
+// Set the theme class on the body element
 export function setThemeClass(theme: Themes) {
-  const systemTheme = theme === Themes.System && getSystemTheme()
-  if (theme === Themes.Dark || systemTheme === Themes.Dark) {
+  if (theme === Themes.Dark) {
     document.body.classList.add('dark')
   } else {
     document.body.classList.remove('dark')

src/machines/settingsMachine.ts

@@ -1,7 +1,7 @@
 import { assign, createMachine } from 'xstate'
 import { BaseUnit, baseUnitsUnion } from '../useStore'
 import { CommandBarMeta } from '../lib/commands'
-import { Themes } from '../lib/theme'
+import { Themes, getSystemTheme, setThemeClass } from '../lib/theme'
 
 export const SETTINGS_PERSIST_KEY = 'SETTINGS_PERSIST_KEY'
 
@@ -79,6 +79,7 @@ export const settingsMachine = createMachine(
     initial: 'idle',
     states: {
       idle: {
+        entry: ['setThemeClass'],
         on: {
           'Set Theme': {
             actions: [
@@ -87,6 +88,7 @@ export const settingsMachine = createMachine(
               }),
               'persistSettings',
               'toastSuccess',
+              'setThemeClass',
             ],
             target: 'idle',
             internal: true,
@@ -188,6 +190,13 @@ export const settingsMachine = createMachine(
           console.error(e)
         }
       },
+      setThemeClass: (context, event) => {
+        const currentTheme =
+          event.type === 'Set Theme' ? event.data.theme : context.theme
+        setThemeClass(
+          currentTheme === Themes.System ? getSystemTheme() : currentTheme
+        )
+      },
     },
   }
 )

src/machines/settingsMachine.typegen.ts

@@ -21,6 +21,15 @@ export interface Typegen0 {
       | 'Set Theme'
       | 'Set Unit System'
       | 'Toggle Debug Panel'
+    setThemeClass:
+      | 'Set Base Unit'
+      | 'Set Default Directory'
+      | 'Set Default Project Name'
+      | 'Set Onboarding Status'
+      | 'Set Theme'
+      | 'Set Unit System'
+      | 'Toggle Debug Panel'
+      | 'xstate.init'
     toastSuccess:
       | 'Set Base Unit'
       | 'Set Default Directory'