Dgb Log: Sep.5, 2008

I spend the whole day on revising a zooming in/out model. The current google map model is to use fixed size tiles but rendered at different levels. However, google map doesn't have the issue of Multiple Track Scrolling Synchronization (MTSS, oh yeah, i just coined a term) issues.

The new model design is to fully use the advantage of SVG:

• 1. Tiles will only be rendered at 1 zooming level. The scaling is done by scaling tiles rather than continuously fetching data from the server.
  


• 2. Buffer tiles are added automatically to the left and right of the track when scrolling and changing zooms.
  


• 3. Rounding errors. If the user drag on the zoomed in tracks, this could cause the tracks with high zooming with 0 pixel movement. This should be corrected, as the cumulative errors could be significant for alignment.
  


• 4. JumpTo: if adding 1 track buffer won't help, the entire track will fetch new data by jumpTo the desired locus directly. However, the ajax calls should be buffered and delayed, as the user may crazily click on 'jumpTo', could result in the effect that when the tiles data are retrieved, they have been removed from DOM already.
  

1,2,3 have been implemented so far.