(Better late than never, i guess...) Your code was *almost* right. The problem is that the sizes of the widgets are not known until they are "realized" (made "real" by having their actual X windows created). You hardly ever need to create Adjustments, but can simply use the ones that get created automatically. 
$ diff -u monk.pl.orig monk.pl
--- monk.pl.orig        2008-01-27 12:04:05.921317488 -0500
+++ monk.pl     2008-01-27 12:03:44.446582144 -0500
@@ -44,15 +44,18 @@
                     $y > $portrait[1] ? $portrait[1] : $y + 2);
     }
 
-    # all these values are the same as default, except the first. the
+se
-    # values are just for testing. the eventual plan is to adjust the
+m
-    # so the viewport is centered, but even with static values it
-    # doesn't work.
-    my $ha = Gtk2::Adjustment->new(50, 0, 1, 0.1, 0.9, 1);
-    my $va = Gtk2::Adjustment->new(50, 0, 1, 0.1, 0.9, 1);
-
-    $sw->set_hadjustment($ha);
-    $sw->set_vadjustment($va);
+    #
+    # After the widgets are create and know their size, scroll to the
+    # middle of the image.  Notice the halfway point is actually
+    # (upper-pagesize)/2, not upper/2 --- otherwise you'll attempt to
+    # scroll out of bounds.
+    # 
+    $sw->signal_connect_after (realize => sub {
+        my $va = $_[0]->get_vadjustment;
+       $va->set_value (($va->upper - $va->page_size) / 2);
+        my $ha = $_[0]->get_hadjustment;
+       $ha->set_value (($ha->upper - $ha->page_size) / 2);
+    });
 
     $mw->set_title("$file ${x}x${y}");
     $mw->show_all();

[download]

In reply to Re: setting scrollbar position of a Gtk2 ScrolledWindow by Anonymous Monk
in thread setting scrollbar position of a Gtk2 ScrolledWindow by revdiablo

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