Hi All I'll try keep this brief, but wanted to get feedback and opinions on a number of issues which I have run into. I'll be touching on
o Issues with getting a TileList to redraw/refresh the tiles o Selection issues and differences between selections made by a user, or programmatically. o Binding and redraw issues. o Pose questions about approaches for best performance (also related to binding) o Show you an interesting problem I am hoping to re-implement after the binding feedback where I want my TileList to do some complex resizing of the tiles. I am working on an app that besides being under NDA, its too big to show any working parts that demonstrate some of these performance and drawing issues, but over time I have started to be bothered by some things that make me feel like I'm doing something fundamentally wrong in some cases. So here is a little app that although a bit contrived does manage to touch on some of the issues I want to shed some light on. http://labs.lhsw.com/~cgalpin/flex/Problem/bin/Problem.html Right click to see the source. Its a simple little app [1] that loads some xml data, creates a Product object [2] that gets put into a Arraycollection which is used as a dataProvider for a few views. It has a thumbnail and detail view which shows the products in a TileList and shows a "detailed view" on the current selection. You can switch to a grid view to see the products in a very basic grid, and the selections are maintained across views. In both views you can change the name and price of the selected products and also delete/undelete the selected products. The TileList has a slider and checkbox that are mostly unimplemented right now (see below for what they are for). There is a little status panel near the bottom that shows selection states to help you keep track of some of that stuff. I set this up to be able to show some issues I have run into, and get feedback on work arounds or t see what I am doing right/wrong in certain situations. The general idea is I want to be able to modify the data properties (including adding and removing products) and have the views redraw/update appropriately. Here are some of the issues this app shows - let me know your thoughts. 1. Tiles not redrawing properly. Select all tiles and click delete, then undo delete. You'll see the thumbnail labels dont draw until you scroll or resize. Even in my brain dead little thumbnail implementation this is an issue. My real app thumbnails are far more complex. 2. Odd issues related to selections. In general what I have implemented works, however there are some subtle issues related to programmatically setting the selectedIndex and/or selectedIndices that you will see if you look at the status output. First you'll see the selectedIndex changes when setting selectedIndices (just switch views to see). Even if you set the selectedIndex, the selectedIndex will be -1 but when set to the other list, it gets changed to 0. But also after programmatically setting the selectedIndices you cannot uses the shift key to extend selections. you have to start with a user driven single select to reset state and then can use shift. you can use ctrl though. odd stuff. I think there are some bugs here. Do you have better ideas on how to maintain the selections without bugs? 3. Binding issues. We have seen performance problems with out app once there are thousands of thumbnails and I want to resolve them. Currently it's using XML objects in an XLListCollection and we get a lot of "free" binding with that which is nice, but I think the binding to xml objects is a big part (we see lots of events firing off causing lots of extra work when we don't expect it) as well as the wieght of the thumbnail object. So, in this demo I use pure objects and show 2 ways of trying to maintain state. The binding works as expected - see setting the price for example, but I fear this could be a performance issue for us. If you update 5 properties as part of an operation, you only want one event thrown to have objects redraw, not 5 of them. Also you'll see I had to pass the price to the ProductImage::getOverlayPrice method in order to get it to fire. In the real world you end up having to pass all properties in that are depended on, and every change causes that method to be called which can get expensive when really it only needed to be called once. Ideally I'd like to be able to update Product object and when done, throw an event that signals the redraw - see next. The name is not bindable, so after changing it, I have tried a variety of ways to refresh the TileList and the details view, but they never refresh. The grid refreshes on invalidateList(), but it contains no custom renderers right now and I fear that will change once I do. but if I can just force a redraw/refresh when something changes, this may be a better approach. Besides getting the non-binding approach to work, what's going to give me the best performance? Can i use binding but limit the amount of work done for the actual event on change, and only aply the changes in updateDisplayList()? I'd like to pick a strategy to take when beefing up my thumbnail implementation. Remember there could be thousands of products and I could apply a half dozen property changes to all of them in one operation (think apply a discount or something) and want that to be reflected in all views efficiently 4. Last but not least, my real app has a pretty cool way of showing the thumbnails. Instead of the slider driving the width of the tile, it actually drives the width of the image on the tile. So instead of being a fixed 60x60 as they are now, when you slide the slider the image width changes, forcing the tile to redraw accordingly. The most significant effect is that since we maintain the aspect ration on the image, the height increases as well. Then, the checkbox can be selected, and instead of the thumbnail images all being the same size, they are drawn to their relative size. So the largest width and height are computed and then the number pixles per inch are determined and they are all drawn scaled to that. This lets you see the relative size differences. It realy looks cool. I have this working in my existing app by extending TileList but I think my meddling may be influencing/exhasperating some of the redrawing problems I occasionally get (like #1 above for example). Once I get some feedback on the approach to take for handling binding I want to implement that in this demo and get feedback. if you have any thoughts before then, please let me know. I just don't want that to cloud the issues the simple cases already exposes. Hopefully someone will just show me I'm doing something stupid for all of the above! Thanks for reading this far and have a good weekend, charles [1] Please ignor stuff like the creationPolicy="all" on the ViewStack - just wanted to put something quick and dirty to get my point across. No effort has been made to show best practices for the most part, and I'm open to any feedback - just don't let it distract you from the issues I am after. [2] One of my goals is too see how hard it will be to convert out app from using XML as the underlying objects in an XMLListCollection to using pure objects - to resolve memory leaks and improve performance.
