Re: Slow image display over network

[joakim@verona.se]

Lars Magne Ingebrigtsen <larsi@gnus.org> writes:

> Daniel Pittman <daniel@rimspace.net> writes:
>
>> Aw, heck.  I saved you the time: PNG loading does create the X image and
>> pixmap during the load process, confirming my guesswork.  I didn't check the
>> other image loaders, but they would sensibly behave the same way, showing the
>> same result.
>
> Right.  Image load pushes the image over X, even though we're not
> actually going to display it?
>
> That means that the way Gnus displays images is as pessimal as
> possible.  When reading a HTML message with images, Gnus calls
> (image-size (create-image ...)) to find out the size, and then if it's
> too big, it rescales the image down.  And this means that the huge image
> has to be transferred first over the slow X connection, and then
> rescaled, and then probably transferred again?
>
> Is this really necessary?  :-)  Why can't image transfer to the X server
> wait until the `put-image' call?

If you look at the imagemagick loader, there is an attempt there at
image "pinging", figuring out stuff about images withouth actualy
loading them. The pinging there is done to avoid loading an entire image
stack when you only want one image index in the stack. Maybe this ping
code could be generalized and exposed to lisp. I've noticed the need
myself several times.

(I hope that was relevant to your question)

-- 
Joakim Verona