Re: Zoom prblems in print preview

[Jean Bréfort <jean brefort normalesup org>]

Le vendredi 07 octobre 2005 à 07:30 +0200, Jean Bréfort a écrit :
> Le jeudi 06 octobre 2005 à 17:48 -0400, Jody Goldberg a écrit :
> > On Thu, Oct 06, 2005 at 03:05:18PM -0600, Andreas J. Guelzow wrote:
> > > > xev to see what events ctrl-+ and ctrl-- are sending.
> > >
> > > You only mention that it happens with + and -. Do you have the same
> > > effect with ctrl-+ and ctrl--?
> >
> > The code would be the same.  I'm seeing some asymetry on zooming in
> > an out with CVS head.  Out then In does not restore the same zoom.
> > It looks like the display resolution may impact things.
>
> It is not a keyboard problem. If I click on the zoom in and zoom out
> buttons, I get the same effect, it always zoom in, although not with the
> same speed, zoom in is more efficient ;).
> This occurs only on my amd64, not on my x86 laptop.
> I should be able to find some time to fix that during next week.

In the end, I found very easily what's wrong:
Index: libgnomeprintui/gnome-print-job-preview.c
===================================================================
RCS
file: /cvs/gnome/libgnomeprintui/libgnomeprintui/gnome-print-job-preview.c,v
retrieving revision 1.91
diff -u -5 -r1.91 gnome-print-job-preview.c
--- libgnomeprintui/gnome-print-job-preview.c   22 Sep 2005 14:49:30
-0000      1.91
+++ libgnomeprintui/gnome-print-job-preview.c   7 Oct 2005 08:03:52
-0000
@@ -887,11 +887,11 @@
                gdouble zoomx = width  / ((jp->paw + PAGE_PAD * 2) *
jp->nx + PAGE_PAD * 2);
                gdouble zoomy = height / ((jp->pah + PAGE_PAD * 2) *
jp->ny + PAGE_PAD * 2.);

                zoom = MIN (zoomx, zoomy);
        } else
-               zoom = jp->zoom_factor * factor * (xdpi + ydpi) / (72. *
2.);
+               zoom = jp->zoom_factor * factor;
        jp->zoom_factor = CLAMP (zoom, GPMP_ZOOM_MIN, GPMP_ZOOM_MAX);
        gnome_canvas_set_pixels_per_unit (jp->canvas, jp->zoom_factor);

        g_object_set (G_OBJECT (jp->zoom.z1), "sensitive", (!
CLOSE_ENOUGH (jp->zoom_factor, 1.0)), NULL);
        g_object_set (G_OBJECT (jp->zoom.zi), "sensitive", (!
CLOSE_ENOUGH (jp->zoom_factor, GPMP_ZOOM_MAX)), NULL);

if xdpi + ydpi is not 144., the zoom factor is multiplied each time by a
constant. If this constant is larger than sqrt(2), <control>-- will zoom
in instead of zooming out. Things work quite well when I remove this
factor. Also this explains the asymetry.

Cheers,
Jean