A tile queue that can be aborted. #179
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This look great work Andreas! One quick question for me to understand: |
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Also browsers that do not support requestAnimationFrame benefit from this. Not all img.src are set at the same time, so when you change zoom levels quickly, the queue is cleared and we don't send out reqiests for all tiles. Regarding panning: mouse dragging gets more efficient with this change. On IPad, setting img.src freezes the browser, and now we don't do multiple set img.src operations at the same time. |
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Tested with a customer project using Chrome, FF and IE8: works like a charm |
This saves server requests, and because we use OpenLayers.Animation, setting img.src on a tile should not freeze iOS any more, so we can hopefully get rid of scheduleMoveGriddedTiles.
Saves 3 unnecessary instances creation and 6 parseFloat calls.
Since draw is the only tile operation that we defer, the tile queue can be an array of tiles and queue handling can be simplified. We now use the beforedraw event to defer drawing, and remove all occurrences of a tile from the tile queue when we draw it. Instead of layers that want to defer tile drawing having to override the tile's draw method, layers can now abort drawing by returning false from a beforedraw listener, and later call draw(true) to draw the tile directly, without clearing it first.
Only use it if no native requestAnimationFrame function is available. This should improve performance on mobile devices.
This results in a smaller queue that we don't have to unqueue from.
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Live examples updated. Try e.g. http://ahocevar.github.com/openlayers/tile-queue/examples/mobile.html |
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@elemoine's concerns about performance on iOS have been addressed, and browsers that support requestAnimationFrame can take full advantage of this new feature. Anybody willing to give a "go" on this? |
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@ahocevar I just tested the mobile.html example on the iPhone 4S. The experience is good, as good as with http://openlayers.org/dev/examples/mobile.html. I'll try with the iPad we have in the office tomorrow (if I manage to shut Angry Birds down :). Thanks for your effort on this, this a great patch. |
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Tested in Android 4.0.2 (default browser and Chrome Beta) |
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@ahocevar I'm planning to do that tonight. |
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Excellent patch @ahocevar. Please merge. |
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Thanks a lot @elemoine for taking the time to test, your feedback and the review! |
This saves us a significant amount of server requests when changing zoom levels often, and because we use OpenLayers.Animation, setting img.src on a tile should not freeze iOS any more during panning, so we can hopefully get rid of scheduleMoveGriddedTiles.
While at it, I also removed the spiralTileLoad function. Although definitely a masterpiece of coding art, I replaced it with the less elegant but more efficient approach of sorting tiles by distance from the viewport center.
There are no tests yet for the tile queue, and I haven't tested on a real IPad, so I don't know if it really improves performance as compared to scheduleMoveGriddedTiles.