Re: Patch to make progressive loading optional

Jon Colverson wrote:
> 
> Hello. I've attached a patch to gqview (1.5.4) that adds an option to
> enable or disable progressive loading. I wanted this because I don't
> like the visual results during decoding of progressive JPEGs and it
> seems that non-progressive decoding is faster (I haven't made any
> measurements to back that up).

Progressive is a bit slower because it updates the screen after each chunk of
data is decoded, the screen updates can make decoding very slow for progressive
jpegs and pngs.

> The patch adds a gboolean parameter to image_loader_start() to specify
> whether the image should be loaded progressively or not. If not, it just
> uses gdk_pixbuf_new_from_file() to load the image, and then signals that
> it completed if there was no error. This obviously makes the interface
> unresponsive during loading.

An option like this I would consider, but the unresponsive-while-loading side
effect is what I would like to avoid.

> Non-progressive loading is only used for loading the current image (not
> for preloading, or thumbnails etc.) If the user selects an image that is
> already partly pre-loaded, the pre-loading is cancelled and the image is
> reloaded non-progressively.
> 
> The diff is a bit hard to read for the part in image_read_ahead_check(),
> but it looks more complicated than it is.
> 
> Are you interested in including this patch in GQview? If so, I'll write
> the documentation for it.

Please try the attached patch (to a clean GQview 1.5.4). Would something like
this be sufficient, or is it still too slow?

The patch forces delay_flip for all images, the delay_flip ability was
introduced as a full screen option in 1.5.2 - this simply enables it everywhere.


Greetings,
John

-- 
John Ellis <[email protected]>

http://gqview.sourceforge.net <GQview> | http://gqapplets.sourceforge.net
http://gqmpeg.sourceforge.net <GQmpeg> |                  <panel applets>

Index: image.c
===================================================================
RCS file: /devel/cvs/gqview/src/image.c,v
retrieving revision 1.109
diff -u -r1.109 image.c
--- image.c	18 Nov 2004 00:18:23 -0000	1.109
+++ image.c	23 Dec 2004 05:56:20 -0000
@@ -3111,6 +3111,8 @@
 
 void image_set_delay_flip(ImageWindow *imd, gint delay)
 {
+	delay = TRUE;
+
 	if (!imd ||
 	    imd->delay_flip == delay) return;
 
@@ -3233,7 +3235,7 @@
 	imd->auto_refresh_id = -1;
 	imd->auto_refresh_interval = -1;
 
-	imd->delay_flip = FALSE;
+	imd->delay_flip = TRUE;
 
 	imd->func_update = NULL;
 	imd->func_complete = NULL;