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[stellation-res] #34471 Comment HoverText: Input Requested 
I've been looking further into #34471, and would like some input before
proceeding further.

BACKGROUND

* The Revision Selection dialog (Stellation CM plugin) uses hovertext to
show comments for branches and revisions. I plan to use similar dialogs
(and hovertext) for merge source selection and elsewhere as appropriate.
* The hovertext support was originally built under Linux Motif, and worked fine. 
It also worked under Windows (some months back).
* On GTK2, Hovertext (on a TreeViewer, at least) causes the GUI to become largely unresponsive. (It's possible to restore normal operation by resizing the dialog window, which clears the HoverText). As best I recall, Hovertext was always flaky under GTK, but until fairly recently other problems with the Eclipse GTK support kept me from 
using GTK.  (Bear in mind that Hovertext using GTK works in many other places
(e.g. Java Editor) without causing any problems.  A mystery).
* I am using GTK 2.0.2-4. The Eclipse R2.1 Pan document states that 2.0.6 is required. 
  (The current stable version is 2.2.1).
* I've spent a fair bit of time observing instrumented versions of the relevant classes 
(AbstractInformationControlManager, AbstractHoverInformationControlManager,
DefaultInformationControl, various mouse trackers, etc.). It's pretty clear that the problem is in GTK or the SWT wrapping thereof. (Briefly, once the hovertext/information control widget becomes visible, mouse events are no longer received by the underlying Tree widget, even in regions of the Tree widget which are _not_ covered by the higher-Z-order information control widget). The problem seems to be occuring in the mouse tracking mechanism. 

OPTIONS

There are at least 4 options now.

1. Upgrade to GTK 2.0.6 (or 2.2.1) and see if the bug is resolved.
This is the most appealing option ("let's just hope it goes away..."), but
may be difficult to do with my current distro (RedHat 7.3), at least without
some help from Mark or another Linux guru, since upgrading GTK will require
changing many other parts of my system; when I looked into it a few weeks
ago, the interdependencies seemed pretty tangled.

2. Report the bug to the Eclipse GTK folks and request a resolution.  I will
do this shortly in any case. However, (1) there is a similar bug,
unresolved, opened 2002-11-01 (#25632) and (2) there is a full-bore crunch
on currently to finalize the R2.1 release.  Realistically, I don't expect
this bug to be resolved soon.

3. Change the Revision Selection dialog to use a separate label field for
displaying the comment text for the current tree item.  I can easily make
this field update dynamically (without clicking) as the cursor pauses over a
given tree node.  The comment field would be placed above or below the Tree
widget, creating a certain cognitive disconnect between the comment and the
corresponding item.   In addition, the hovertext dynamically resizes per the
length and linecount of the comment; this is not available with a separate
label field (unless the dialog itself is resized dynamically, which is not
an appealing solution).
4. Implement (3) for GTK systems only, and keep using the current hovertext mechanism 
for Windows, Motif, and other platforms that support it.

My inclination is to try (1) (unless it's likely to trash my system), and if
that doesn't work, do  (2) and (3) simultaneously.  I'd rather not do (4)
unless it appears that GTK mouse tracker support can't or won't be fixed.

Comments ?

Jim
--
Jim Wright, IBM T.J. Watson Research Center
*** The Stellation project: Advanced SCM for Collaboration
*** http://www.eclipse.org/stellation
*** Work Email: jwright@xxxxxxxxxxxxxx ------- Personal Email: jim.wright@xxxxxxx

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