Thursday, July 16, 2009

Autosizing of Grids, Canvasses and StackPanels

Deb: Moving from a relatively static environment, like Photoshop, to a dynamic environment like Silverlight/Blend, requires learning about autosizing and how visuals will behave when the browser is resized. One of the most challenging things for me to learn was the differences in behaviors between grids, canvasses and stackpanels.

I started with grids, the workhorse of the layout panels, and I got comfortable with setting the height and width to 'auto', and the alignment to stretch, and setting the margins to achieve the effect I was looking for. I learned how to set column and row sizes, locking certain ones and leaving others to size dynamically as the space changed.

I moved on to canvasses, learning how to place objects on the panel in a different way, but the autosizing aspect of the layout panel worked the same as the grid. I figured I had this dynamic sizing thing figured out. Then I got cocky and started sticking stackpanels into my grids, and suddenly things weren't working the way I expected. This video explains why:

video

I am not a developer, but I do have a strong intuitive understanding of hierarchies and trees. I had developed a mental model that said that if I picked 'auto' and 'stretch', my object would size to match the parent it was embedded in. Working with stackpanels forced me to reevaluate my mental model, to acknowledge that sometimes the sizing was driven by the children embedded in the object, and margins - as seen in the video - seem to be able to refer to both (in the example, the top and left margins are relative to the parent canvas but the right and bottom margins are relative to the 'children' buttons).

This is where trial and error has led me. If there is an explanation for these behaviors, a simplifying principle that can be applied in all cases, I would love to learn it -- I really like to understand why things are the way they are. Post a comment and let me know what you think!

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