Animatr – GUI & Structure: Nesting Polymer Elements

The first step of rebuilding animatr was to remove all code and totally rebuild the GUI using a single custom element: <animatr-gui> using polymer. The GUI itself has three nested custom elements:

<animatr-titlebar> - Containins the windows’ title, close button, …
<animatr-toolbars> – Wrapper for the toolbars
<animatr-panels> – A wrapper to create a GUI using pannels that can be dragged.

The HTML code of the root element looks like this:

<head>
  <link href="packages/animatr_gui/elements/animatr-ui.html" rel="import" />
</head>
<body>
  <animatr-ui></animatr-ui>
</body>

The corresponding element HTML code is:

<polymer-element name="animatr-ui">
  <meta charset="utf-8"/>
  <link rel="import" href="animatr-titlebar.html">
  <link rel="import" href="animatr-toolbars.html">
  <link rel="import" href="animatr-panels.html">
  <link rel="import" href="animatr-panel-....html">
  <template>
      <animatr-titlebar id="animatr-titlebar"></animatr-titlebar>
      <animatr-toolbars id="animatr-toolbars"></animatr-toolbars>
      <animatr-panels id="animatr-panels"></animatr-panels>
  </template>
  <script type="application/dart" src="animatr-ui.dart"></script>
</polymer-element>
 

The Dart code for the custom element is:


import 'package:polymer/polymer.dart';

import 'dart:html';

import 'package:animatr_gui/elements/animatr-titlebar.dart';
import 'package:animatr_gui/elements/animatr-toolbars.dart';
import 'package:animatr_gui/elements/animatr-panels.dart';

import 'animatr-panel-....dart';

@CustomTag('animatr-ui')
class AnimatrUiElement extends PolymerElement {
  bool get applyAuthorStyles =&gt; true;

  ...PanelElement panel_...;

  AnimatrUiElement.created() : super.created() {
    panel_... = document.createElement('animatr-panel-...');
  }

  AnimatrTitlebarElement titlebar;

  AnimatrToolbarsElement toolbars;

  AnimatrPanelsElement panels;

  @observable Project currentProject;

  @override
  void enteredView() {
    super.enteredView();

    titlebar = $['animatr-titlebar'];
    toolbars = $['animatr-toolbars'];
    panels = $['animatr-panels'];

    titlebar.ui = this;
    panels.ui = this;

    panels.addPanel(panel_..., 'north/east/south/west/center');
   }
}

Nesting elements was complicated first. Assuming you have your project’s root file (mine is called animatr.html), you could import all elements in this file, at a central place. But this had some strange behaviour to me:
The outer elements get created first and thus, before all nested elements. Thus I wasn’t able to correctly query for the nested elements. Because the custom element wasn’t registered Google Dart had some type errors.

The solution was to import other elements within the custom element itself, right before the <template> tag.

I had another problem using special characters. It turned out that the charset settings (e.g. by using <meta charset=”utf-8″/>) is not propagated to custom elements. Thus make sure to include a <meta>-tag in your custom elements if you want to use custom elements.

Animatr – A first introduction

In this post I want to briefly introduce you to my most recent project called “animatr”. Animatr is a tool to create canvas animations. I will focus on advertisements but in theory you can create all types of animations and sizes. Even playing a video within the animation is possible.

The first version was developed about a year ago and was based on fabric.js But very soon I felt the framework limited me to their features. So I quickly decided to rewrite it as a web app on my own. Due to some specific webkit/chrome features I decided to finally rewrite the project using Google’s Dart and to make an app out of it using node-webkit.

The latest and third version is based on Google Dart, Node-Webkit and Polymer. While polymer is the replacement for web-ui.

I will write follow up blogs about concepts and code I use while developing animatr and give you examples. So far I can tell that detailed examples are rare. That’s why I felt to blog about it myself.

My blog

I have been thinking for years now if I should start blogging or not. Finally I decided to do so :)

I will be blogging about all web topics I will deal with. Nevertheless I want to focus on Dart + Polymer I have been working on recently.