QmlWeb/Qml.js/Design Questions and Decisions

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< QmlWeb‎ | Qml.js
Revision as of 08:55, 4 March 2015 by Akreuzkamp (talk | contribs)

This page intends to collect questions about software architecute and software design, pros and cons as well as the decisions made on the topic.

Runtime Architecture

Getter/Setter Technique

Possibilities:

C++ style getters and setters
this.width(); and this.setWidth(width);
  • pro/con: C++ style
  • pro: fast in all browsers
Transparent getter/setter using Object.defineProperty
Object.defineProperty(this, "width", { get function(){}, set: function(){} });
  • pro: nice while debugging
  • con: worse performance in IE
  • con: horrible performance in Firefox
Transparent getter/setter using literal notation
  • pro: nice while debugging
  • con: worse performance in IE
  • con: you can't use object literals and inheritance at the same time in a standard compliant manner


Benchmark: http://jsperf.com/getter-setter/7

Decision: Use C++ style getters and setters

Storing properties

As we're using setters and getters in either way, we need to store the actual property value separated. There're multiple possibilities for that:

Private member using closures
Private member using like _width
Using property objects and direct object references
Using property indexes and a properties array
  • pro: If done right, it might provide weak references
Using a properties object and access it per name
  • con: Bad bad bad performance

Handling bindings

Let the bindings depend on each other and make them set the value on update
  • pro: Seems logically like the right thing. After all it's the bindings that define the dependencies
  • con: How to know when a property gets overwritten and thus the binding is invalidated?
Let the properties depend on each other and make them reevaluate the binding when needed