diff --git a/package-lock.json b/package-lock.json
index c95ce99..74b78dd 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "graphfx",
-  "version": "0.0.1",
+  "version": "0.0.8",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -2405,6 +2405,535 @@
       "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
       "dev": true
     },
+    "fsevents": {
+      "version": "1.2.7",
+      "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-1.2.7.tgz",
+      "integrity": "sha512-Pxm6sI2MeBD7RdD12RYsqaP0nMiwx8eZBXCa6z2L+mRHm2DYrOYwihmhjpkdjUHwQhslWQjRpEgNq4XvBmaAuw==",
+      "dev": true,
+      "optional": true,
+      "requires": {
+        "nan": "2.13.2",
+        "node-pre-gyp": "0.10.3"
+      },
+      "dependencies": {
+        "abbrev": {
+          "version": "1.1.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "ansi-regex": {
+          "version": "2.1.1",
+          "bundled": true,
+          "dev": true
+        },
+        "aproba": {
+          "version": "1.2.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "are-we-there-yet": {
+          "version": "1.1.5",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "delegates": "1.0.0",
+            "readable-stream": "2.3.6"
+          }
+        },
+        "balanced-match": {
+          "version": "1.0.0",
+          "bundled": true,
+          "dev": true
+        },
+        "brace-expansion": {
+          "version": "1.1.11",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "balanced-match": "1.0.0",
+            "concat-map": "0.0.1"
+          }
+        },
+        "chownr": {
+          "version": "1.1.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "code-point-at": {
+          "version": "1.1.0",
+          "bundled": true,
+          "dev": true
+        },
+        "concat-map": {
+          "version": "0.0.1",
+          "bundled": true,
+          "dev": true
+        },
+        "console-control-strings": {
+          "version": "1.1.0",
+          "bundled": true,
+          "dev": true
+        },
+        "core-util-is": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "debug": {
+          "version": "2.6.9",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "ms": "2.0.0"
+          }
+        },
+        "deep-extend": {
+          "version": "0.6.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "delegates": {
+          "version": "1.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "detect-libc": {
+          "version": "1.0.3",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "fs-minipass": {
+          "version": "1.2.5",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "minipass": "2.3.5"
+          }
+        },
+        "fs.realpath": {
+          "version": "1.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "gauge": {
+          "version": "2.7.4",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "aproba": "1.2.0",
+            "console-control-strings": "1.1.0",
+            "has-unicode": "2.0.1",
+            "object-assign": "4.1.1",
+            "signal-exit": "3.0.2",
+            "string-width": "1.0.2",
+            "strip-ansi": "3.0.1",
+            "wide-align": "1.1.3"
+          }
+        },
+        "glob": {
+          "version": "7.1.3",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "fs.realpath": "1.0.0",
+            "inflight": "1.0.6",
+            "inherits": "2.0.3",
+            "minimatch": "3.0.4",
+            "once": "1.4.0",
+            "path-is-absolute": "1.0.1"
+          }
+        },
+        "has-unicode": {
+          "version": "2.0.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "iconv-lite": {
+          "version": "0.4.24",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "safer-buffer": "2.1.2"
+          }
+        },
+        "ignore-walk": {
+          "version": "3.0.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "minimatch": "3.0.4"
+          }
+        },
+        "inflight": {
+          "version": "1.0.6",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "once": "1.4.0",
+            "wrappy": "1.0.2"
+          }
+        },
+        "inherits": {
+          "version": "2.0.3",
+          "bundled": true,
+          "dev": true
+        },
+        "ini": {
+          "version": "1.3.5",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "is-fullwidth-code-point": {
+          "version": "1.0.0",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "number-is-nan": "1.0.1"
+          }
+        },
+        "isarray": {
+          "version": "1.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "minimatch": {
+          "version": "3.0.4",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "brace-expansion": "1.1.11"
+          }
+        },
+        "minimist": {
+          "version": "0.0.8",
+          "bundled": true,
+          "dev": true
+        },
+        "minipass": {
+          "version": "2.3.5",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "safe-buffer": "5.1.2",
+            "yallist": "3.0.3"
+          }
+        },
+        "minizlib": {
+          "version": "1.2.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "minipass": "2.3.5"
+          }
+        },
+        "mkdirp": {
+          "version": "0.5.1",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "minimist": "0.0.8"
+          }
+        },
+        "ms": {
+          "version": "2.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "needle": {
+          "version": "2.2.4",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "debug": "2.6.9",
+            "iconv-lite": "0.4.24",
+            "sax": "1.2.4"
+          }
+        },
+        "node-pre-gyp": {
+          "version": "0.10.3",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "detect-libc": "1.0.3",
+            "mkdirp": "0.5.1",
+            "needle": "2.2.4",
+            "nopt": "4.0.1",
+            "npm-packlist": "1.2.0",
+            "npmlog": "4.1.2",
+            "rc": "1.2.8",
+            "rimraf": "2.6.3",
+            "semver": "5.6.0",
+            "tar": "4.4.8"
+          }
+        },
+        "nopt": {
+          "version": "4.0.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "abbrev": "1.1.1",
+            "osenv": "0.1.5"
+          }
+        },
+        "npm-bundled": {
+          "version": "1.0.5",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "npm-packlist": {
+          "version": "1.2.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "ignore-walk": "3.0.1",
+            "npm-bundled": "1.0.5"
+          }
+        },
+        "npmlog": {
+          "version": "4.1.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "are-we-there-yet": "1.1.5",
+            "console-control-strings": "1.1.0",
+            "gauge": "2.7.4",
+            "set-blocking": "2.0.0"
+          }
+        },
+        "number-is-nan": {
+          "version": "1.0.1",
+          "bundled": true,
+          "dev": true
+        },
+        "object-assign": {
+          "version": "4.1.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "once": {
+          "version": "1.4.0",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "wrappy": "1.0.2"
+          }
+        },
+        "os-homedir": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "os-tmpdir": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "osenv": {
+          "version": "0.1.5",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "os-homedir": "1.0.2",
+            "os-tmpdir": "1.0.2"
+          }
+        },
+        "path-is-absolute": {
+          "version": "1.0.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "process-nextick-args": {
+          "version": "2.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "rc": {
+          "version": "1.2.8",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "deep-extend": "0.6.0",
+            "ini": "1.3.5",
+            "minimist": "1.2.0",
+            "strip-json-comments": "2.0.1"
+          },
+          "dependencies": {
+            "minimist": {
+              "version": "1.2.0",
+              "bundled": true,
+              "dev": true,
+              "optional": true
+            }
+          }
+        },
+        "readable-stream": {
+          "version": "2.3.6",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "core-util-is": "1.0.2",
+            "inherits": "2.0.3",
+            "isarray": "1.0.0",
+            "process-nextick-args": "2.0.0",
+            "safe-buffer": "5.1.2",
+            "string_decoder": "1.1.1",
+            "util-deprecate": "1.0.2"
+          }
+        },
+        "rimraf": {
+          "version": "2.6.3",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "glob": "7.1.3"
+          }
+        },
+        "safe-buffer": {
+          "version": "5.1.2",
+          "bundled": true,
+          "dev": true
+        },
+        "safer-buffer": {
+          "version": "2.1.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "sax": {
+          "version": "1.2.4",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "semver": {
+          "version": "5.6.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "set-blocking": {
+          "version": "2.0.0",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "signal-exit": {
+          "version": "3.0.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "string-width": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "code-point-at": "1.1.0",
+            "is-fullwidth-code-point": "1.0.0",
+            "strip-ansi": "3.0.1"
+          }
+        },
+        "string_decoder": {
+          "version": "1.1.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "safe-buffer": "5.1.2"
+          }
+        },
+        "strip-ansi": {
+          "version": "3.0.1",
+          "bundled": true,
+          "dev": true,
+          "requires": {
+            "ansi-regex": "2.1.1"
+          }
+        },
+        "strip-json-comments": {
+          "version": "2.0.1",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "tar": {
+          "version": "4.4.8",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "chownr": "1.1.1",
+            "fs-minipass": "1.2.5",
+            "minipass": "2.3.5",
+            "minizlib": "1.2.1",
+            "mkdirp": "0.5.1",
+            "safe-buffer": "5.1.2",
+            "yallist": "3.0.3"
+          }
+        },
+        "util-deprecate": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true,
+          "optional": true
+        },
+        "wide-align": {
+          "version": "1.1.3",
+          "bundled": true,
+          "dev": true,
+          "optional": true,
+          "requires": {
+            "string-width": "1.0.2"
+          }
+        },
+        "wrappy": {
+          "version": "1.0.2",
+          "bundled": true,
+          "dev": true
+        },
+        "yallist": {
+          "version": "3.0.3",
+          "bundled": true,
+          "dev": true
+        }
+      }
+    },
     "function-bind": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.1.tgz",
@@ -3821,6 +4350,13 @@
       "integrity": "sha1-VgiurfwAvmwpAd9fmGF4jeDVl8g=",
       "dev": true
     },
+    "nan": {
+      "version": "2.13.2",
+      "resolved": "https://registry.npmjs.org/nan/-/nan-2.13.2.tgz",
+      "integrity": "sha512-TghvYc72wlMGMVMluVo9WRJc0mB8KxxF/gZ4YYFy7V2ZQX9l7rgbPg7vjS9mt6U5HXODVFVI2bOduCzwOMv/lw==",
+      "dev": true,
+      "optional": true
+    },
     "nanomatch": {
       "version": "1.2.13",
       "resolved": "https://registry.npmjs.org/nanomatch/-/nanomatch-1.2.13.tgz",
@@ -4676,6 +5212,7 @@
         "capture-exit": "1.2.0",
         "exec-sh": "0.2.2",
         "fb-watchman": "2.0.0",
+        "fsevents": "1.2.7",
         "micromatch": "3.1.10",
         "minimist": "1.2.0",
         "walker": "1.0.7",
diff --git a/package.json b/package.json
index d48be09..0ea1424 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "graphfx",
-  "version": "0.0.6",
+  "version": "0.0.9",
   "description": "Graph image processing pipeline",
   "main": "src/index.js",
   "scripts": {
diff --git a/src/graph.js b/src/graph.js
index 6dae141..01dde98 100644
--- a/src/graph.js
+++ b/src/graph.js
@@ -1,10 +1,14 @@
 import * as nodes from './nodes';
+import {MultiSubject} from './helpers/listener';
 
 
 export default class Graph {
 
     constructor() {
         this.nodes = [];
+        this.__nodesActive = 0;
+        this.__nodesActiveDebounce = null;
+        this.subject = new MultiSubject(['running', 'stopped']);
     }
 
     serialize() {
@@ -17,6 +21,19 @@ export default class Graph {
     static deserialize(nodes) {
         const graph = new Graph();
         graph.nodes = createNodes(nodes);
+        for (let {node} of graph.nodes) {
+          node.subject.on('running', (isRunning) => {
+            graph.__nodesActive += isRunning ? 1 : -1;
+            clearTimeout(graph.__nodesActiveDebounce);
+            graph.__nodesActiveDebounce = setTimeout(() => {
+              if (graph.__nodesActive > 0) {
+                graph.subject.next('running');
+              } else {
+                graph.subject.next('stopped');
+              }
+            }, 16);
+          });
+        }
         return graph;
     }
 
diff --git a/src/helpers/listener.js b/src/helpers/listener.js
new file mode 100644
index 0000000..1ed78af
--- /dev/null
+++ b/src/helpers/listener.js
@@ -0,0 +1,69 @@
+export class Subject {
+
+  constructor() {
+    this.__listeners = [];
+  }
+
+  next(val) {
+    for (let listener of this.__listeners) {
+      listener(val);
+    }
+  }
+
+  once() {
+    return new Promise((resolve) => {
+      const done = (val) => {
+        resolve(val);
+        this.off(done);
+      };
+      this.on(done);
+    })
+  }
+
+  on(fn) {
+    this.__listeners.push(fn);
+  }
+
+  off(fn) {
+    this.__listeners = this.__listeners.filter((listener) => listener !== fn);
+  }
+
+  destroy() {
+    this.__listeners = [];
+  }
+}
+
+
+
+export class MultiSubject {
+
+  constructor(types) {
+    this.__subjects = {};
+    for (let type of types) {
+      this.__subjects[type] = new Subject();
+    }
+  }
+
+  next(type, val) {
+    this.__subjects[type].next(val);
+  }
+
+  once(type) {
+    return this.__subjects[type].once();
+  }
+
+  on(type, fn) {
+    return this.__subjects[type].on(fn);
+  }
+
+  off(type, fn) {
+    this.__subjects[type].off(fn);
+  }
+
+  destroy() {
+    for (let type of Object.keys(this.__subjects)) {
+      this.__subjects[type].destroy();
+    }
+  }
+}
+
diff --git a/src/nodes/Canvas2d/Compose.js b/src/nodes/Canvas2d/Compose.js
index 28ac6ea..07ed447 100644
--- a/src/nodes/Canvas2d/Compose.js
+++ b/src/nodes/Canvas2d/Compose.js
@@ -130,6 +130,10 @@ export default class Compose extends Canvas2d {
         if (!width || !height) {
             return;
         }
+        if (!this.bg && !this.fg) {
+            return;
+        }
+
         canvas.width = width;
         canvas.height = height;
 
diff --git a/src/nodes/Node.js b/src/nodes/Node.js
index 32e7760..4781fd5 100644
--- a/src/nodes/Node.js
+++ b/src/nodes/Node.js
@@ -1,5 +1,6 @@
 import {Inputs, Outputs} from './io';
 import uuidv4 from 'uuid/v4';
+import {MultiSubject} from '../helpers/listener';
 
 export default class Node {
 
@@ -12,13 +13,18 @@ export default class Node {
         this.__in.update = (name) => this.__update([name]);
         this.__scheduledUpdate = false;
         this.__currentUpdate = Promise.resolve();
+        this.__running = false;
         this._stopped = false;
+        this.subject = new MultiSubject(['running']);
     }
 
     __update(changes) {
         if (!this.__scheduledUpdate && !this._stopped) {
             this.__scheduledUpdate = true;
             this.__currentUpdate = this.__currentUpdate
+                .then(() => {
+                    this._running = true;
+                })
                 .then(async () => {
                     const startTag =`graphfx-update-start:${this.uid}`;
                     const endTag = `graphfx-update-end:${this.uid}`
@@ -27,6 +33,13 @@ export default class Node {
                     await this._update();
                     performance.mark(endTag)
                     performance.measure(`GraphFX<${this.name}>`, startTag, endTag)
+                })
+                .then(() => {
+                    this._running = false;
+                })
+                .catch((err) => {
+                    this._running = false;
+                    throw err;
                 });
         }
     }
@@ -35,6 +48,17 @@ export default class Node {
         throw new Error('_update method not implemented');
     }
 
+    get _running() {
+        return this.__running;
+    }
+
+    set _running(val) {
+        if (this.__running !== val) {
+            this.__running = val;
+            this.subject.next('running', this.__running);
+        }
+    }
+
     /**
      * Input getters
      */
diff --git a/src/nodes/WebGL/Channels.js b/src/nodes/WebGL/Channels.js
index a63a42d..ff23a32 100644
--- a/src/nodes/WebGL/Channels.js
+++ b/src/nodes/WebGL/Channels.js
@@ -4,7 +4,7 @@ import WebGL from './WebGl';
 export default class Channels extends WebGL {
 
     constructor() {
-        super('Greyscale by channel', {
+        super('Channels', {
             red: {
                 type: 'Number',
                 default: 1,
diff --git a/src/nodes/WebGL/WebGl.js b/src/nodes/WebGL/WebGl.js
index aa983fd..8821a10 100644
--- a/src/nodes/WebGL/WebGl.js
+++ b/src/nodes/WebGL/WebGl.js
@@ -153,17 +153,8 @@ export default class WebGL extends Node {
     _passes() {
         return [
             (gl, program, image) => {
-                console.log('pass1')
                 this._setParams(gl, program);
             },
-            (gl, program, image) => {
-                console.log('pass2')
-                this._setParams(gl, program);
-            },
-            (gl, program, image) => {
-                console.log('pass3')
-                this._setParams(gl, program);
-            }
         ]
     }
 
@@ -186,7 +177,9 @@ export default class WebGL extends Node {
     async _update() {
 
         const image = this.in.image.value;
-        if (!image) return;
+        if (!image) {
+            return;
+        }
         if (image.acquire) {
             image.acquire();
         }