fix height of mermaid's diagrams

browser/components/MarkdownPreview.js

@@ -205,6 +205,7 @@ export default class MarkdownPreview extends React.Component {
     this.saveAsMdHandler = () => this.handleSaveAsMd()
     this.saveAsHtmlHandler = () => this.handleSaveAsHtml()
     this.printHandler = () => this.handlePrint()
+    this.resizeHandler = _.throttle(this.handleResize.bind(this), 100)
 
     this.linkClickHandler = this.handlelinkClick.bind(this)
     this.initMarkdown = this.initMarkdown.bind(this)
@@ -485,6 +486,10 @@ export default class MarkdownPreview extends React.Component {
       'scroll',
       this.scrollHandler
     )
+    this.refs.root.contentWindow.addEventListener(
+      'resize',
+      this.resizeHandler
+    )
     eventEmitter.on('export:save-text', this.saveAsTextHandler)
     eventEmitter.on('export:save-md', this.saveAsMdHandler)
     eventEmitter.on('export:save-html', this.saveAsHtmlHandler)
@@ -520,6 +525,10 @@ export default class MarkdownPreview extends React.Component {
       'scroll',
       this.scrollHandler
     )
+    this.refs.root.contentWindow.removeEventListener(
+      'resize',
+      this.resizeHandler
+    )
     eventEmitter.off('export:save-text', this.saveAsTextHandler)
     eventEmitter.off('export:save-md', this.saveAsMdHandler)
     eventEmitter.off('export:save-html', this.saveAsHtmlHandler)
@@ -797,6 +806,15 @@ export default class MarkdownPreview extends React.Component {
     )
   }
 
+  handleResize () {
+     _.forEach(
+      this.refs.root.contentWindow.document.querySelectorAll('svg[ratio]'),
+      el => {
+        el.setAttribute('height', el.clientWidth / el.getAttribute('ratio'))
+      }
+    )
+  }
+
   focus () {
     this.refs.root.focus()
   }