> > [...] but also try to remember those awful, counterintuitive
> > Mosaic mouseclick scrolls.
Hey, don't say that. I think it's nice that xterm still uses
the athena scrollbar, in contrast to other terminal emulators.
(But then I'm also a vim user and I favor RPN calculators.)
[snip]
> but the application must "install" accelerators, e.g.
> XtInstallAccelerators(), to link a possible source hierarchy
> of the event with the destination widget that should handle
> them. I don't think the Athena Paned widget does this
> automatically, but could be wrong.
>
> Anyway, it seems some code changes may be required after all
> and I don't have a solution or further time to work on it but
> I thought this might be of use to anyone who has.
Some time ago Joerg also asked whether it was possible to do
"intelligent scrolling" in xditview like in gv (i.e., scrolling
by columns from top left to bottom right and then jumping to
the next page). I haven't had much time to look into this,
but I think that implementing intelligent scrolling will
only be possible with some nontrivial changes to the xditview
source, for the very simple reason that xditview is currently
not aware of the scrolling at all -- scrolling is completely
handled by the widget code, without any feedback from xditview.
Nevertheless, with a few limitations, simple scrolling via
the keyboard within a page can be made to work. As Ralph
has already noted, the primary difficulty lies in the fact
that the scroll commands must be given to the scrollbars,
whereas we would like to be able to keep the pointer in the
actual display area. The athena widget set does provide a
generalized mechanism called "accelerators" for this (e.g.,
to invoke menu items from the keyboard). Accelerators act
in most aspects like normal event translations, but there
are a few caveats involved:
1. The accelerators must be explicitly "installed", and
they are valid only for the particular *instance* of the
widget. In our case that means that if the scrollbar
gets destroyed and then recreated, the accelerators are
lost. Therefore I suggest that we keep the scrollbars
always visible. (Otherwise you would probably need to
keep track of resizes, guessing when scrollbars get
created and then again installing the accelerators.
Remember that the viewport widget currently controls
all of this autonomously.)
2. Events (key or button) do not get passed upward in the
hierarchy by a widget if that widget has any translations
for that type of event (key or button). That means
you may not have any key translations for the "clip",
"viewport", or "label" widgets[*], neither in your
.Xdefaults / app-defaults / X resource data base,
nor in the builtin fallback resources. That means we
have to replace the builtin app-defaults and get rid
of or replace those translations in .Xdefaults and
/etc/X11/app-defaults/GXditview. [*]My idea here is to
install the accelerators on the "paned" widget, so that
keyboard scrolling works even with the pointer in the
"label" field at the bottom.
Another limitation to scrolling with the keyboard is that
without using the mouse the athena scrollbars can only be made
to scroll for a full length of the scrollbar. If you need
smaller steps, I guess the only way is by providing a dedicated
callback procedure that explicitly sets the position.
Within these limitations, making scrolling work from
the keyboard requires only small changes to the code.
I've attached a diff file for xditview.c (only one line to
be inserted) and a GXditview.ad file to replace the one in
groff/src/devices/xditview. (You may also need to get rid of
conflicting app-defaults elsewhere.) I've also chosen some
pretty pastel colors which are much easier on the eyes than
the default black & white setup.
Index: xditview.c
===================================================================
RCS file: /sources/groff/groff/src/devices/xditview/xditview.c,v
retrieving revision 1.1.1.1
diff -b -u -r1.1.1.1 xditview.c
--- xditview.c 1 Jun 2004 10:39:55 -0000 1.1.1.1
+++ xditview.c 25 May 2007 20:21:16 -0000
@@ -262,6 +262,7 @@
XtRealizeWidget (toplevel);
if (file_name)
SetPageNumber (page_number);
+ XtInstallAllAccelerators(paned,paned);
XtAppMainLoop(xtcontext);
return 0;
}
GXditview*shapeStyle: rectangle
GXditview.paned.allowResize: true
GXditview.paned.label.skipAdjust: true
GXditview.paned.viewport.skipAdjust: false
GXditview.paned.viewport.showGrip: false
GXditview.paned.viewport.allowVert: true
GXditview.paned.viewport.allowHoriz: true
GXditview.paned.viewport.forceBars: true
! viewport size = papersize * resol + scrollbarthickness + 1
! letter size paper
!GXditview.paned.viewport.width: 652
!GXditview.paned.viewport.height: 840
! a4 size paper
GXditview.paned.viewport.width: 635
GXditview.paned.viewport.height: 892
GXditview.paned.viewport.Scrollbar.thickness: 14
GXditview.paned.viewport.Scrollbar.background: Thistle
GXditview.paned.viewport.Scrollbar.foreground: Orchid
GXditview.paned.viewport.Scrollbar.thumb: None
GXditview.paned.viewport.dvi.background: LemonChiffon
GXditview.paned.viewport.background: Thistle
GXditview.paned.label.background: PeachPuff
GXditview.menu.background: Gold
GXditview.promptShell.promptDialog*background: Gold
GXditview.promptShell.promptDialog.accept.background: DarkOliveGreen1
GXditview.promptShell.promptDialog.cancel.background: RosyBrown1
GXditview.promptShell.promptDialog.value.background: Khaki
GXditview.paned.translations: #augment \
<Key>Next: NextPage()\n\
<Key>n: NextPage()\n\
<Key>space: NextPage()\n\
<Key>Return: NextPage()\n\
<Key>Prior: PreviousPage()\n\
<Key>p: PreviousPage()\n\
<Key>b: PreviousPage()\n\
<Key>BackSpace: PreviousPage()\n\
<Key>Delete: PreviousPage()\n\
<Key>g: SelectPage()\n\
<Key>o: OpenFile()\n\
<Key>r: Rerasterize()\n\
<Key>q: Quit()
GXditview.paned.viewport.clip.translations: #augment \
<Btn1Down>: XawPositionSimpleMenu(menu) MenuPopup(menu)
GXditview.paned.label.translations: #augment \
<Btn1Down>: XawPositionSimpleMenu(menu) MenuPopup(menu)
GXditview.paned.viewport.vertical.accelerators: #override \
<Key>k: StartScroll(Backward) NotifyScroll(FullLength) EndScroll()\n\
<Key>j: StartScroll(Forward) NotifyScroll(FullLength) EndScroll()\n\
<Key>Up: StartScroll(Backward) NotifyScroll(FullLength) EndScroll()\n\
<Key>Down: StartScroll(Forward) NotifyScroll(FullLength) EndScroll()
GXditview.paned.viewport.horizontal.accelerators: #override \
<Key>h: StartScroll(Backward) NotifyScroll(FullLength) EndScroll()\n\
<Key>l: StartScroll(Forward) NotifyScroll(FullLength) EndScroll()\n\
<Key>Left: StartScroll(Backward) NotifyScroll(FullLength) EndScroll()\n\
<Key>Right: StartScroll(Forward) NotifyScroll(FullLength) EndScroll()
GXditview.menu.nextPage.label: Next Page
GXditview.menu.previousPage.label: Previous Page
GXditview.menu.selectPage.label: Goto Page
GXditview.menu.print.label: Print
GXditview.menu.openFile.label: Open
GXditview.menu.quit.label: Quit
GXditview.promptShell.allowShellResize: true
GXditview.promptShell.promptDialog.value.translations: #override \
<Key>Return: Accept() \n\
<Key>Escape: Cancel()
GXditview.promptShell.promptDialog.accept.label: Accept
GXditview.promptShell.promptDialog.accept.translations: #override \
<BtnUp>: Accept() unset()
GXditview.promptShell.promptDialog.cancel.label: Cancel
GXditview.promptShell.promptDialog.cancel.translations: #override \
<BtnUp>: Cancel() unset()
