73969 - Should throttle interlaced GIF loading redraws

Status: VERIFIED FIXED

(Core :: Graphics: ImageLib, defect, P2)

Description

[Simon Fraser [no longer active]]

When loading interlaced GIFs, we do the funky draw-in-stripes thing. However, 
with imglih2, loading these types of images feels slower than it did before.

It seems that we're redrawing the image frame many times as the interlaced GIF is 
loading, which slows down the loading process. We should throttle these redraws, 
only redrawing the frame every 250ms or so.

Comment 1

[saari (gone)]

Yeah, we're not throttling the GIF decoder at all right now. We used to only
update every 10 scan lines I believe, and that appears to be about what IE does.
Right now we update for every scan line.

For interlaced GIFs in particular, we used to do this funky thing where we'd
replicate the scan line so you didn't see stripes, but rather a pixelization
that progressively sharpens, so maybe that is changing your perception too (in
addition to us doing too many updates).

Any image in particular that feels slow to you?

Comment 2

[Adam D. Moss]

Going off-topic a touch, but if the previous style of
progressive display of interlaced GIFs isn't coming
back any time soon then you need to be clearing the
image's mask to all-transparent before drawing, since
you're not truly validating the image's valid rect
(just sparse scanlines within it) and hence you're drawing
uncleared rubbish-memory in between the truly validated
scanlines (very evident on X11).

Comment 3

[Peter Trudelle]

->moz0.9.1

Comment 4

[saari (gone)]

Hyatt checked in the throttle code

Comment 5

[Terri Preston]

Hmm, coding issue, marking verified