modified scroll so it won't work on mouse selection.

Instead, it specifically only works on 'up', 'down', 'left' and 'right'
keyboard presses (alongside any typing edits).
Also, changed the cursor position used for the calculation so that
shift+arrow selection is visible.

typewriter-scrolling.js

@@ -4,7 +4,7 @@ CodeMirror.commands.scrollSelectionToCenter = function (cm) {
     if (cm.getOption("disableInput")) {
         return CodeMirror.Pass;
     }
-    var cursor = cm.getCursor('anchor');
+    var cursor = cm.getCursor('head');
     var charCoords = cm.charCoords(cursor, "local");
     var top = charCoords.top;
     var halfLineHeight = (charCoords.bottom - top) / 2;
@@ -18,12 +18,14 @@ CodeMirror.defineOption("typewriterScrolling", false, function (cm, val, old) {
         linesEl.style.paddingTop = null;
         cm.off("changes", onChanges);
         cm.off("cursorActivity", onCursorActivity);
+        cm.off("keyHandled", onKeyHandled);
         cm.off("refresh", onRefresh);
     }
     if (val) {
         onRefresh(cm);
         cm.on("changes", onChanges);
         cm.on("cursorActivity", onCursorActivity);
+        cm.on("keyHandled", onKeyHandled);
         cm.on("refresh", onRefresh);
     }
 });
@@ -47,7 +49,6 @@ function onCursorActivity(cm) {
     else {
         linesEl.classList.remove("selecting")
     }
-    cm.execCommand("scrollSelectionToCenter");
 }
 function onRefresh(cm) {
     const halfWindowHeight = cm.getWrapperElement().offsetHeight / 2;
@@ -56,4 +57,10 @@ function onRefresh(cm) {
     if (cm.getSelection().length === 0) {
         cm.execCommand("scrollSelectionToCenter");
     }
+}
+function onKeyHandled(cm, name, event) {
+    console.log(name);
+    if (name === "Up" || name === "Down" || name === "Left" || name === "Right") {
+        cm.execCommand("scrollSelectionToCenter");
+    }
 }