Add codemirror option to show trailing space (#7493)

* codemirror edit/trailingspace addon (default off)

* refactor as codemirror-trailingspace plugin

* copy cm-trailingspace styles from cm demo

plugins/tiddlywiki/codemirror-trailingspace/config-language.multids

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+title: $:/language/codemirror/
+
+showTrailingSpace/hint: Show trailing space
+showTrailingSpace/info: Trailing space on each line will be decorated as per theme CSS.

plugins/tiddlywiki/codemirror-trailingspace/config/showTrailingSpace.tid

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+title: $:/config/codemirror/showTrailingSpace
+type: bool
+text: true

plugins/tiddlywiki/codemirror-trailingspace/files/addon/edit/trailingspace.css

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+.cm-trailingspace {
+  background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAQAAAACCAYAAAB/qH1jAAAABmJLR0QA/wD/AP+gvaeTAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3RJTUUH3QUXCToH00Y1UgAAACFJREFUCNdjPMDBUc/AwNDAAAFMTAwMDA0OP34wQgX/AQBYgwYEx4f9lQAAAABJRU5ErkJggg==);
+  background-position: bottom left;
+  background-repeat: repeat-x;
+}

plugins/tiddlywiki/codemirror-trailingspace/files/addon/edit/trailingspace.js

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+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: https://codemirror.net/5/LICENSE
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    mod(require("../../lib/codemirror"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+  CodeMirror.defineOption("showTrailingSpace", false, function(cm, val, prev) {
+    if (prev == CodeMirror.Init) prev = false;
+    if (prev && !val)
+      cm.removeOverlay("trailingspace");
+    else if (!prev && val)
+      cm.addOverlay({
+        token: function(stream) {
+          for (var l = stream.string.length, i = l; i && /\s/.test(stream.string.charAt(i - 1)); --i) {}
+          if (i > stream.pos) { stream.pos = i; return null; }
+          stream.pos = l;
+          return "trailingspace";
+        },
+        name: "trailingspace"
+      });
+  });
+});

plugins/tiddlywiki/codemirror-trailingspace/files/tiddlywiki.files

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+{
+	"tiddlers": [
+		{
+			"file": "addon/edit/trailingspace.css",
+			"fields": {
+				"type": "text/css",
+				"title": "$:/plugins/tiddlywiki/codemirror/addon/edit/trailingspace.css",
+				"tags": "[[$:/tags/Stylesheet]]"
+			}
+		},{
+			"file": "addon/edit/trailingspace.js",
+			"fields": {
+				"type": "application/javascript",
+				"title": "$:/plugins/tiddlywiki/codemirror/addon/edit/trailingspace.js",
+				"module-type": "codemirror"
+			}
+		}
+	]
+}

plugins/tiddlywiki/codemirror-trailingspace/plugin.info

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+{
+	"title": "$:/plugins/tiddlywiki/codemirror-trailingspace",
+	"name": "CodeMirror Show Trailing Space",
+	"description": "Show trailing space in CodeMirror",
+	"parent-plugin": "$:/plugins/tiddlywiki/codemirror",
+	"list": "readme"
+}

plugins/tiddlywiki/codemirror-trailingspace/readme.tid

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+title: $:/plugins/tiddlywiki/codemirror-trailingspace/readme
+
+This plugin contains the [[trailingspace|https://codemirror.net/5/doc/manual.html#addon_trailingspace]]
+addon for CodeMirror, and provides a default style (red squiggles).
+
+First install the [[CodeMirror plugin|$:/plugins/tiddlywiki/codemirror]].
+

plugins/tiddlywiki/codemirror-trailingspace/settings/showTrailingSpace.tid

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+title: $:/core/ui/ControlPanel/Settings/codemirror/showTrailingSpace
+tags: $:/tags/ControlPanel/Settings/CodeMirror
+caption: {{$:/language/codemirror/showTrailingSpace/hint}}
+
+\define lingo-base() $:/language/codemirror/showTrailingSpace/
+<<lingo hint>>
+
+<$checkbox tiddler="$:/config/codemirror/showTrailingSpace" field="text" checked="true" unchecked="false" default="true">
+  <$link to="$:/config/codemirror/showTrailingSpace"><<lingo info>></$link>
+</$checkbox>
+