https://bugs.documentfoundation.org/show_bug.cgi?id=173060
Bug ID: 173060
Summary: Writer: auto-scroll timer during drag-selection never
runs with gtk3/kf6 VCL plugins (works with gen)
Product: LibreOffice
Version: 25.8.5.2 release
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Writer
Assignee: [email protected]
Reporter: [email protected]
When extending a selection by dragging with the left mouse button held down and
moving the pointer to the bottom edge of the window, the view should keep
scrolling on its own so the selection can continue past the visible page. With
the gtk3 and kf6 VCL plugins this self-running scroll never starts at all.
Holding the mouse perfectly still stops the scrolling completely, and every
further selected line requires another small pointer movement. The user
experience is severe stuttering, but the underlying behaviour is that nothing
drives the scroll except the user's own hand.
With SAL_USE_VCLPLUGIN=gen the timer-driven auto-scroll does work. There is a
narrow band near the bottom scrollbar and window frame where the pointer can be
held completely still and the view keeps advancing on its own at a steady rate,
roughly two lines per step. The band is hard to hit in practice, but it exists
and it is reproducible. No such position exists anywhere in or around the
window with gtk3 or kf6.
Steps to reproduce:
1. Open a Writer document of about 30 pages of plain text.
2. Click at the start of the text and hold the left mouse button down.
3. Drag the pointer to the bottom edge of the window and hold it perfectly
still.
4. Observe whether the view keeps scrolling with no further pointer motion.
Actual results:
gtk3 and kf6: scrolling stops the instant the pointer stops moving. Every
further selected line needs a new pointer movement.
gen: scrolling continues on its own while the pointer is held still over the
narrow band described above.
Expected results:
While the button is held and the pointer is at or beyond the bottom edge,
auto-scroll should run on a timer independently of further pointer motion, as
it does with the gen plugin.
Additional information, each item verified by testing rather than assumed:
- Smooth scroll (Tools, Options, Writer, View) on and off: no difference.
- Skia: no difference. Note that on Linux Skia only links against the gen
plugin, so it can only be tested there. Presence of libvulkan in the process
map was used to confirm Skia was genuinely active in that run.
- Display path: reproduced natively on Wayland (gtk3) and through XWayland (kf6
and gen).
- Document size: reproduced with a 276 KB flat ODF file of 1100 paragraphs.
- User profile: reproduced with a fresh throwaway profile, so no carried-over
setting is involved.
Because the difference lies between LibreOffice's own VCL plugins, and because
gtk3 shows the same failure while having nothing to do with KDE, this does not
look like a compositor or desktop-environment issue. Several user reports
elsewhere attribute this behaviour to Plasma 6; that attribution does not match
this measurement.
Limitations of this report, stated plainly: all observations come from one
machine and one user, judged by eye rather than instrumented. No other desktop
environment and no older LibreOffice version were tested on this hardware, so
this report does not establish whether the behaviour is a regression.
System:
LibreOffice 25.8.5.2 580(Build:2)
TUXEDO OS (Ubuntu 24.04 noble base), kernel 6.17.0-124040-tuxedo
KDE Plasma 6.6.5, KWin 6.6.5, Wayland session
Qt 6.10.2, GTK 3.24.41
GPU: AMD Radeon 880M/890M (Strix)
Display scaling: 1.4 internal panel, 1.1 on two external 1440p screens
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