xP: deal with macOS/Blink for good

xP/public/xP.js

@@ -132,13 +132,9 @@ class RelayRpc extends EventTarget {
 function utf8Encode(s) { return new TextEncoder().encode(s) }
 function utf8Decode(s) { return new TextDecoder().decode(s) }
 
-// On macOS, the Alt/Option key transforms characters, which basically breaks
-// all event.altKey shortcuts, so require combining them with Control as well
-// on that system.
 function hasShortcutModifiers(event) {
-	// This method of detection only works with Blink browsers, as of writing.
-	return event.altKey && !event.metaKey &&
-		(navigator.userAgentData?.platform === 'macOS') === event.ctrlKey
+	return (event.altKey || event.escapePrefix) &&
+		!event.metaKey && !event.ctrlKey
 }
 
 const audioContext = new AudioContext()
@@ -826,7 +822,22 @@ document.addEventListener('visibilitychange', event => {
 	}
 })
 
+// On macOS, the Alt/Option key transforms characters, which basically breaks
+// all event.altKey shortcuts, so implement Escape prefixing on that system.
+// This method of detection only works with Blink browsers, as of writing.
+let lastWasEscape = false
 document.addEventListener('keydown', event => {
+	event.escapePrefix = lastWasEscape
+	if (lastWasEscape) {
+		lastWasEscape = false
+	} else if (event.code == 'Escape' &&
+			navigator.userAgentData?.platform === 'macOS') {
+		event.preventDefault()
+		event.stopPropagation()
+		lastWasEscape = true
+		return
+	}
+
 	if (rpc.ws == undefined || !hasShortcutModifiers(event))
 		return
 
@@ -874,4 +885,4 @@ document.addEventListener('keydown', event => {
 	}
 
 	event.preventDefault()
-})
+}, true)