Accidental zoom causes tiles to fail to download when original zoom is resumed

[GoogleCodeExporter]

What steps will reproduce the problem?
 1. Interrupt downloading of tiles at a given zoom level X by either of: a) accidental use of scroll wheel on a mouse, or b) clicking the zoom bar, moving the thumb, or hitting the up/dn arrows on the keyboard
 2. Return to the original zoom level X by clicking the zoom bar (or dragging the thumb)
 3. 'Interrupted' tiles will not download except by: a) enabling 'Force download' and nudging the mouse, or b) panning such that all 'stuck' or 'interrupted' tiles are well off screen, download others, and then pan back to the 'stuck' tiles.

What is the expected output? What do you see instead?
Expected that the tiles would resume downloading at whatever zoom level is 
chosen (or resumed). Instead, tiles at the original zoom level become 'stuck' 
and do not download except by the methods outlined above in 3a or 3b.

What version of the product are you using? On what operating system?
0.7.7.1, Windows 7 Ultimate 64-bit. This may be helpful or not, to know that I 
am using a dual-screen extended monitor setup with resolution at 2280px wide x 
1920px high.

Please provide any additional information below.
Example for clarity, in case the report is a bit vague. Set the zoom level to 
2, for instance, and download some tiles, for instance from Virtual Earth 
Terrain. Before the entirety of the screen finishes, use the mouse wheel or 
other methods per above, to change the zoom level up or down. Quickly return to 
the original zoom using the zoom bar before the tiles associated with the 
'accidental' zoom finish downloading. The tiles that were interrupted at zoom=2 
(the originals) appear stuck for far longer than one would expect if the tiles 
at the 'accidental' zoom level all finished being downloaded out of the queue. 
I let this sit for > 2 mins and they stayed stuck. My network download tests at 
33 Mbit/sec. A zoom=2 screen takes ~25 sec to fill my monitors.

Original issue reported on code.google.com by ler...@gmail.com on 24 Apr 2012 at 4:48

[GoogleCodeExporter]

In your high resolution setup a lot of things will go wrong! every time you 
change zooms I bet you are sending more than 50 tiles to the download queue.
I will recommend you to download all the tiles in advanced for the area(s) you 
need. 

Nothing should really be 'Interrupted' at least not from our end, it could be 
that server receive unusually high request and just drops some of them. Our 
download Queue is a "Last In First Out" and during normal operation that is 
just what you need. 

There are many things that affect the speedy display of the tiles in 
GMapCatcher, Yes one of them been the tiles download speed. You network 
download tests can be very high but your tiles download speed is definitively 
not that fast, the map tile servers do not respond that fast to our requests, 
and sending more than 4 treads at a time will just get your IP banned for 24 
hours.

Original comment by heldersepu on 24 Apr 2012 at 1:14

• Changed state: WontFix

[GoogleCodeExporter]

@heldersepu, thanks for your consideration of this.

Original comment by ler...@gmail.com on 24 Apr 2012 at 3:59