added CodeMirror ruler support

browser/components/CodeEditor.js

@@ -14,6 +14,7 @@ const { ipcRenderer } = require('electron')
 CodeMirror.modeURL = '../node_modules/codemirror/mode/%N/%N.js'
 
 const defaultEditorFontFamily = ['Monaco', 'Menlo', 'Ubuntu Mono', 'Consolas', 'source-code-pro', 'monospace']
+const buildCMRulers = rulers => rulers.map(ruler => ({ column: ruler }))
 
 function pass (name) {
   switch (name) {
@@ -91,9 +92,11 @@ export default class CodeEditor extends React.Component {
   }
 
   componentDidMount () {
+    const { rulers } = this.props
     this.value = this.props.value
 
     this.editor = CodeMirror(this.refs.root, {
+      rulers: buildCMRulers(rulers),
       value: this.props.value,
       lineNumbers: this.props.displayLineNumbers,
       lineWrapping: true,
@@ -198,6 +201,10 @@ export default class CodeEditor extends React.Component {
       needRefresh = true
     }
 
+    if (prevProps.rulers !== this.props.rulers) {
+      this.editor.setOption('rulers', buildCMRulers(this.props.rulers))
+    }
+
     if (prevProps.indentSize !== this.props.indentSize) {
       this.editor.setOption('indentUnit', this.props.indentSize)
       this.editor.setOption('tabSize', this.props.indentSize)
@@ -407,6 +414,7 @@ export default class CodeEditor extends React.Component {
 
 CodeEditor.propTypes = {
   value: PropTypes.string,
+  rulers: PropTypes.arrayOf(Number),
   mode: PropTypes.string,
   className: PropTypes.string,
   onBlur: PropTypes.func,

browser/components/MarkdownEditor.js

@@ -258,6 +258,7 @@ class MarkdownEditor extends React.Component {
           fontSize={editorFontSize}
           indentType={config.editor.indentType}
           indentSize={editorIndentSize}
+          rulers={config.editor.rulers}
           displayLineNumbers={config.editor.displayLineNumbers}
           scrollPastEnd={config.editor.scrollPastEnd}
           storageKey={storageKey}

browser/components/MarkdownSplitEditor.js

@@ -110,6 +110,7 @@ class MarkdownSplitEditor extends React.Component {
           displayLineNumbers={config.editor.displayLineNumbers}
           indentType={config.editor.indentType}
           indentSize={editorIndentSize}
+          rulers={config.editor.rulers}
           scrollPastEnd={config.editor.scrollPastEnd}
           fetchUrlTitle={config.editor.fetchUrlTitle}
           storageKey={storageKey}

lib/main.html

@@ -89,6 +89,7 @@
   <script src="../node_modules/codemirror/addon/search/matchesonscrollbar.js"></script>
   <script src="../node_modules/codemirror/addon/search/jump-to-line.js"></script>
   <script src="../node_modules/codemirror/addon/dialog/dialog.js"></script>
+  <script src="../node_modules/codemirror/addon/display/rulers.js"></script>
 
   <script src="../node_modules/raphael/raphael.min.js"></script>
   <script src="../node_modules/flowchart.js/release/flowchart.min.js"></script>