Since it is a root privilege application as Martin pointed out,
I tried putting the usual

[Settings]
gtk-primary-button-warps-slider = false

in /etc/gtk-3.0/settings.ini

It didn't work !

I tried putting it in /root/.config/gtk-3.0/settings.ini

It didn't work !

So it seems that tablet mode has been hard coded into rpmdrake.
Definitely needs to be fixed.

Playing with this on Mageia 8 (I shall try 7), I cannot pin down your complaint (even if Martin was able to comprehend it). It seems that if you reduce the window width enough, you do indeed get a self-hiding L-R scroll bar in the lower RH panel; but it does not hide anything that cannot be scrolled into view. But I seem to recall that this scrolling did not work well in the past. M7 to try.

Re "The last line of the description section of rpmdrake always must be clickable in order to open a sub-menu", I do not see it. "clickable last line"? "to open a sub-menu"? Do you mean the lower expandable sections 'Details', 'Files' etc?

Are you able to attach a screenshot which illustrates the point you are making?
TIA

Re /etc/gtk-3.0/settings.ini, this M8 system including most things does not have it. Again to check on M7.

CC: (none) => lewyssmith

Created attachment 12282 [details]
screen without mouse over last line

Created attachment 12283 [details]
screen with mouse over last line

@Lewis
The usual workaround to suppress the disappearing horizontal scroll bar has no effect.
Note also the vertical scroll bar is always displayed.
Thus the behavior of scroll bars must be hard coded into rpmdrake :(

Thanks, now I understand the problem. I couldn't figure it out before because
I learned of the problem a long time ago and developed the habit of using
the workaround of always starting with the last section and then expanding the
sections above it. It became a habit to the point I do it without thinking
about why I was doing it.

Other then expanding the last section first, I'm not aware of any other
workarounds.

CC: (none) => davidwhodgins

It is not hard coded in rpmdrake, it is the GTK default setting. You can override it by creating a /root/.config/gtk-3.0/settings.ini file containing

  [Settings]
  gtk-overlay-scrolling = false

The gtk-primary-button-warps-slider setting mentioned earlier controls how the window scrolls when you click on the scroll bar - set to true to enable proportional scrolling, set to false to enable one-page-at-a-time scrolling.

CC: (none) => mageia

@ André: thanks for the screenshots, which certainly showed where the issue occurs. It is puzzling that when the mouse is outside the pane, the horizontal scroll bar remains while the vertical one disappears.
My tests showed them showing or not together; I shall attach screenshots showing this.

Running on a fully furnished Mageia 7 system under Mate;
 $ sudo ls -l /root/.config/gtk-3.0/settings.ini
ls: cannot access '/root/.config/gtk-3.0/settings.ini': No such file or directory
 $ sudo ls -l /etc/gtk-3.0/settings.ini
ls: cannot access '/etc/gtk-3.0/settings.ini': No such file or directory
In both cases, the path up to the final '/' exists; just not 'settings.ini'.
Is there a moral here?

After a lot of playing around, one can certainly confirm the problem thus:
When the rpmdrake window is sufficiently narrow to warrant a horizontal scroll bar in the lower RH pane, which may be shown only when the mouse pointer is over that pane, this scroll-bar hides the last information heading to expand, "New dependencies" [uncertain translation]; so it can never be clicked to expand it.

(In reply to Dave Hodgins from comment #6)
> Other then expanding the last section first, I'm not aware of any other
> workarounds.
This does not work if the horizontal scroll bar shows, because it always hides that last section/line.

Obvious solution: Expand the entire window sideways to obviate the need for the horizontal scroll bar! My tests needed the window to be quite squashed to make it appear.

Try removing (or copy to a backup) the gtk-3.0/settings.ini files. If my bloated system does not have them, do they really matter?

Idea for rpmdrake: simply add a blank line or 2 below the last subheading line, so it does not sit right at at the bottom of the pane. Easy-peasy?
------------------------------------------------------------------
Scrolling behaviour of this bottom RH pane is weird. Often it does not scroll down - the vertical scroll bar is already near/at the bottom with only the top part of the information visible. The solution to this is click it to close it, then click again - when all the info becomes visible by scrolling.

Created attachment 12284 [details]
The bottom RH panel with no mouse over & no scroll bars

As attachment heading.

Created attachment 12285 [details]
Bottom RH panel with mouse over showing Horizonatl scroll bar hiding the last line

As attachment heading.

Yeah, I can reproduce the OP behaviour with a "tiny" rpmdrake window.

Let me explain: I have a 1920x1080 resolution monitor.
Even if rpmdrake opens with default settings, I can't reproduce the behaviour because the window is sufficiently large/wide to not have an horizontal bar...

But, I reduce the window in wide direction to make it appear...
So, the workaround is to expand your window. But on low-level resolution this can be problematic.

So, reporter, with which screen resolution do you get such behaviour?

Severity: normal => minor
CC: (none) => ouaurelien

Just confirmed the bug on Mageia 8, so changing its provenance accordingly.
My screen resolution is 1366x768, and you really have to squeeze the window to get the horizontal scroll bar. And when you do, there is not enough room to display the package list - especially its name/short description.

I think we can pass this to the tools maintainers

Version: 7 => Cauldron
CC: lewyssmith => (none)
Assignee: bugsquad => mageiatools
Whiteboard: (none) => MGA7TOO MGA8TOO

@Aurélien
My screen isn't especially wide.
If I display rpmdrake full screen and reduce the left panel (so I don't see everything in that panel), the horizontal scroll bar USUALLY disappears.
But with the default (partial screen), it is always there, even if I configure gtk3 to NOT use the overlay scroll bars.
(It seems that all other applications follow my gtk3 settings.)

Note that the overlay bar will display if there are any lines the lower right panel longer than the width of the panel.  But the long lines always wrap, so everything is visible.
EXCEPT the last line in that panel, with mouse over.
Whatever the gtk3 settings.

Since it affects Cauldron as well, it might be a good idea to correct this before release.
As noted in comment 8, adding a blank line at the end of the display will solve the problem.
Since it will then be the second-to-last line that needs to be clicked on.

I just discovered that the setting

gtk-overlay-scrolling

is only recognized by gtk-3.0 starting with version 3.24.9

We only have version 3.24.8 in mga7
Which explains why suppressing disappearing scroll bars didn't work.

So gtk+3.0 needs to be updated to at least the next version.
I filed bug 28357

Rpmdrake will still need to be modified (by adding a blank line)
since even if one wants disappearing scroll bars, we need to be able to click on the last line.

A further observation :
If the description of the particular package is short, or there are no long lines in the description (both often the case),
or if the user has a newer wide monitor, there might be no problem clicking on the last non-blank line.

But there are many packages with many description lines and/or long lines in the description.
And many users without the newer wider monitors.

I changed the description to better reflect the problem and indicate the solution.

Summary: rpmdrake should ALWAYS display a horizontal scroll bar, to avoid hiding the clickable last line. => rpmdrake should ALWAYS display a blank line at the bottom of the lower right panel, so the last non-blank line is always clickable.