Fix mermaid display problem in the editing state. (#2334)

src/data/extra/web/js/graphpreviewer.js

@@ -188,7 +188,7 @@ class GraphPreviewer {
 
         if (p_svgNode.getAttribute('width').indexOf('%') != -1) {
             // Try maxWidth.
-            if (p_svgNode.style.maxWidth && p_svgNode.style.maxWidth.endsWith('px')) {
+            if (p_svgNode.style.maxWidth && p_svgNode.style.maxWidth.endsWith('px') && p_svgNode.style.maxWidth != "0px") {
                 p_svgNode.setAttribute('width', p_svgNode.style.maxWidth);
             } else {
                 // Set as window width.
@@ -220,10 +220,12 @@ class GraphPreviewer {
             return;
         }
 
-        if (p_svgNode.getAttribute('width').indexOf('%') == -1) {
+        let width = p_svgNode.getAttribute('width')
+        if (width && width.indexOf('%') == -1) {
             p_svgNode.width.baseVal.valueInSpecifiedUnits *= scaleFactor;
         }
-        if (p_svgNode.getAttribute('height').indexOf('%') == -1) {
+        let height = p_svgNode.getAttribute('height')
+        if (height && height.indexOf('%') == -1) {
             p_svgNode.height.baseVal.valueInSpecifiedUnits *= scaleFactor;
         }
     }

src/data/extra/web/js/svg-to-image.js

@@ -60,7 +60,7 @@ class SvgToImage {
         let url = domUrl.createObjectURL(blob);
         this.loadImage(url, p_opt, function(err, img) {
             domUrl.revokeObjectURL(url);
-            if (err) {
+            if (err || SvgToImage.checkCanvasToDataURL(img) === null) {
                 // try again for Safari 8.0, using simple encodeURIComponent
                 // this will fail with DOM content but at least it works with SVG.
                 let url2 = 'data:image/svg+xml,' + encodeURIComponent(p_svg.join(''));
@@ -74,4 +74,19 @@ class SvgToImage {
     static getUrl() {
         return window.URL || window.webkitURL || window.mozURL || window.msURL;
     }
+
+    static checkCanvasToDataURL(p_image) {
+        let canvas = document.createElement('canvas');
+        let ctx = canvas.getContext('2d');
+        canvas.height = p_image.height;
+        canvas.width = p_image.width;
+        ctx.drawImage(p_image, 0, 0);
+        let dataUrl = null;
+        try {
+            dataUrl = canvas.toDataURL();
+        } catch (err) {
+
+        }
+        return dataUrl
+    }
 }