In Windows 8 and WinJS 1.0 it was exceedingly difficult (though not impossible) to create a custom layout object for the WinJS ListView control. As such it was one area of WinJS that I never investigated!

What made it difficult was that the ListView worked entirely on absolute CSS positioning, which meant that the location of every item had to be individually calculated within the layout object’s code. This also caused various performance issues as well.

For WinJS 2.0 on Windows 8.1, the WinJS team rewrote the layout engine of the ListView to leverage relative positioning such that it could let the app host’s layout engine do most of the work. This both improved performance and made it orders of magnitude more easy to write a custom layout. In fact, the simplest layout object hardly needs to do anything at all, because the default behavior (via flexbox with block elements) produces a simple vertical layout just like you get when throwing a bunch of div’s into an HTML page.

From there you can start to build out other behaviors you want:

  • Non-vertical layouts
  • Virtualization support
  • Keyboard support
  • Drag and drop general visual indicators
  • Drag and drop reordering and positional indicators
  • Animations

To explore all the details, I have 17 pages in Appendix B, “WinJS Extras” in my free ebook’s second edition (preview), which includes a minimal vertical layout, a minimal horizontal layout, two dimensional layouts, and non-linear layouts. For the latter I borrowed some code from Mike Mastrangelo of the WinJS team that was used in a short demo at //build 2013. The appendix also includes a short video demonstration of this.

B-3 (circle layout)


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