Display process bar and zoomed old tiles instead of black blocks

[GoogleCodeExporter]

I think that when loading the pdf tiles, instead of showing tiles by tiles, 
there should be a "loading icon" (when you open a file), and the complete page 
should be shown when the page is completily loaded, instead of showing black 
blocks.. Also, when you adjust the zoom level, while the rerendering progress 
is loading, I think the old tiles (with the old zoom level) should be shown 
zoomed until the complete rerendering process is done.. This, instead of 
showing black blocks..

I have analized most of the pdf readers and this is what they do.. I think it 
looks better..

Original issue reported on code.google.com by jtc...@gmail.com on 19 Feb 2012 at 5:59

[GoogleCodeExporter]

It may look better, but I think it's less practical for paging.  If the new 
page is shown by tiles, you can start reading the next page sooner.

With zoom, yes, that would be nicer.

Original comment by arpruss on 20 Apr 2012 at 2:37