random code to allow you to type using binary search

testing/binary-keyboard.js

@@ -0,0 +1,50 @@
+/*
+Binary search keyboard for typing with
+the touchscreen
+*/
+
+function showChars(x,chars) {
+  var lines = Math.round(Math.sqrt(chars.length)*2);
+  g.setFontAlign(0,0);
+  var sy = Math.round(200/lines);
+  var sx = sy;
+  g.setFont("Vector", sy-2);
+  var y = (240 - lines*sy);
+  var last = 0;
+  for (var i=0;i<lines;i++) {
+    var n = Math.round(chars.length*(i+1)/lines);
+    var xo = x + (120 - sx*(n-last-1))/2;
+    for (var j=last;j<n;j++)
+      g.drawString(chars[j], xo + (j-last)*sx, y + sy*i)
+    last = n;
+  }
+}
+
+function show(chars,callback) {
+  g.clear();
+  if (chars.length==1) {
+    callback(chars);
+    return;
+  }
+  var m = chars.length/2;
+  charl=chars.slice(0,m);
+  charr=chars.slice(m);
+  showChars(0,charl);
+  showChars(120,charr);
+  setWatch(() => {
+    clearWatch();
+    show(charl,callback);
+  }, BTN4);
+  setWatch(() => {
+    clearWatch();
+    show(charr,callback);
+  }, BTN5);
+}
+
+function getCharacter() {
+  return new Promise(resolve => {
+    show("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789",resolve);
+  });
+}
+
+getCharacter().then(print)