From 9fa9b00fda6580fce709c4d29257c8dd51017ef5 Mon Sep 17 00:00:00 2001
From: wimrijnders <wrijnders@gmail.com>
Date: Fri, 29 Sep 2017 18:18:29 +0200
Subject: [PATCH] Network: Prevent image loading for hidden cluster nodes
 (#3492)

Fixes #3483.

If `shape: 'image'` is defined as option, this was used for initializing hidden cluster nodes during layout initialization.
However, because no image is being passed, this led to an exception.

This fix prevens shape `image` from being used for hidden cluster nodes. In addition, some extra fields for these nodes are
now overridden for some performance improvament.
---
 lib/network/modules/LayoutEngine.js           | 25 ++++++++++++++++---
 .../modules/components/shared/Label.js        |  2 +-
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/lib/network/modules/LayoutEngine.js b/lib/network/modules/LayoutEngine.js
index 7dc04b7e..ccee1a43 100644
--- a/lib/network/modules/LayoutEngine.js
+++ b/lib/network/modules/LayoutEngine.js
@@ -561,13 +561,32 @@ class LayoutEngine {
       if (positionDefined < 0.5 * indices.length) {
         let MAX_LEVELS = 10;
         let level = 0;
-        let clusterThreshold = 150;
-        // Performance enhancement, during clustering edges need only be simple straight lines.
+        let clusterThreshold = 150;  // TODO add this to options
+
+        //
+        // Define the options for the hidden cluster nodes
         // These options don't propagate outside the clustering phase.
+        //
+        // Some options are explicitly disabled, because they may be set in group or default node options.
+        // The clusters are never displayed, so most explicit settings here serve as performance optimizations.
+        //
+        // The explicit setting of 'shape' is to avoid `shape: 'image'`; images are not passed to the hidden
+        // cluster nodes, leading to an exception on creation.
+        //
+        // All settings here are performance related, except when noted otherwise.
+        //
         let clusterOptions = {
+          clusterNodeProperties:{
+            shape: 'ellipse',       // Bugfix: avoid type 'image', no images supplied
+            label: '',              // avoid label handling
+            group: '',              // avoid group handling
+            font: {multi: false},   // avoid font propagation
+          },
           clusterEdgeProperties:{
+            label: '',              // avoid label handling
+            font: {multi: false},   // avoid font propagation
             smooth: {
-              enabled: false
+              enabled: false        // avoid drawing penalty for complex edges
             }
           }
         };
diff --git a/lib/network/modules/components/shared/Label.js b/lib/network/modules/components/shared/Label.js
index 7a98af32..ab17918a 100644
--- a/lib/network/modules/components/shared/Label.js
+++ b/lib/network/modules/components/shared/Label.js
@@ -64,7 +64,7 @@ class Label {
 
     this.initFontOptions(options.font);
 
-    if (options.label !== undefined) {
+    if (options.label !== undefined && options.label !== null && options.label !== '') {
       this.labelDirty = true;
     }