Improved tab support in dingus

 - changed tab size to 4
 - support for typing tab key + block indent/unindent.

dingus/dingus.css

@@ -14,4 +14,4 @@ p#text-controls { height: 1em; margin-top: 1em; }
 a#permalink { margin-left: 1em; }
 span.timing { font-weight: bold; }
 .selected { background-color: #eeeeee; }
-textarea#text { width: 100%; overflow: scroll; resize: vertical; height: 400px; font-family: monospace; white-space: pre; word-wrap: normal; background-color: white; color: black; }
+textarea#text { width: 100%; overflow: scroll; resize: vertical; height: 400px; font-family: monospace; white-space: pre; word-wrap: normal; background-color: white; color: black; tab-size: 4; }

dingus/dingus.js

@@ -149,3 +149,114 @@ $(document).ready(function() {
         $("iframe").on("load", onIframeLoad);
     }
 });
+
+// From: https://stackoverflow.com/a/45396754/77002
+$(function() { 
+	var enabled = true;
+	$("textarea").keydown(function(e) {
+
+		// Escape key toggles tab on/off
+		if (e.keyCode==27)
+		{
+			enabled = !enabled;
+			return false;
+		}
+
+		// Enter Key?
+		if (e.keyCode === 13 && enabled)
+		{
+			// selection?
+			if (this.selectionStart == this.selectionEnd)
+			{
+				// find start of the current line
+				var sel = this.selectionStart;
+				var text = $(this).val();
+				while (sel > 0 && text[sel-1] != '\n')
+				sel--;
+
+				var lineStart = sel;
+				while (text[sel] == ' ' || text[sel]=='\t')
+				sel++;
+
+				if (sel > lineStart)
+				{
+					// Insert carriage return and indented text
+					document.execCommand('insertText', false, "\n" + text.substr(lineStart, sel-lineStart));
+
+					// Scroll caret visible
+					this.blur();
+					this.focus();
+					return false;
+				}
+			}
+		}
+
+		// Tab key?
+		if(e.keyCode === 9 && enabled) 
+		{
+			// selection?
+			if (this.selectionStart == this.selectionEnd)
+			{
+				// These single character operations are undoable
+				if (!e.shiftKey)
+				{
+					document.execCommand('insertText', false, "\t");
+				}
+				else
+				{
+					var text = this.value;
+					if (this.selectionStart > 0 && text[this.selectionStart-1]=='\t')
+					{
+						document.execCommand('delete');
+					}
+				}
+			}
+			else
+			{
+				// Block indent/unindent trashes undo stack.
+				// Select whole lines
+				var selStart = this.selectionStart;
+				var selEnd = this.selectionEnd;
+				var text = $(this).val();
+				while (selStart > 0 && text[selStart-1] != '\n')
+					selStart--;
+				while (selEnd > 0 && text[selEnd-1]!='\n' && selEnd < text.length)
+					selEnd++;
+
+				// Get selected text
+				var lines = text.substr(selStart, selEnd - selStart).split('\n');
+
+				// Insert tabs
+				for (var i=0; i<lines.length; i++)
+				{
+					// Don't indent last line if cursor at start of line
+					if (i==lines.length-1 && lines[i].length==0)
+						continue;
+
+					// Tab or Shift+Tab?
+					if (e.shiftKey)
+					{
+						if (lines[i].startsWith('\t'))
+							lines[i] = lines[i].substr(1);
+						else if (lines[i].startsWith("    "))
+							lines[i] = lines[i].substr(4);
+					}
+					else
+						lines[i] = "\t" + lines[i];
+				}
+				lines = lines.join('\n');
+
+				// Update the text area
+				this.value = text.substr(0, selStart) + lines + text.substr(selEnd);
+				this.selectionStart = selStart;
+				this.selectionEnd = selStart + lines.length; 
+			}
+
+            parseAndRender();
+			return false;
+		}
+
+		enabled = true;
+		return true;
+	});
+});