mwp dependency obsolescence

[stronnag]

Introduction

Recently, a number of third party Gtk+-3 components that are significant mwp dependencies (libchamplain and its dependencies, libgdl) became obsolescent and are effectively unmaintained upstream. This is likely to be an ongoing problem.

libchamplain

libchamplain is responsible for drawing the map and the artefacts on the map (symbols, lines). Its dependencies

• clutter, which manages OpenGL objects) and
• cogl, low level OpenGL API

were declared obsolete some time ago (when GTK4 was announced) and are unmaintained.

Visible Effects

• Using the some versions of some Wayland display compositor, where a mission contains more than c. 40 waypoints, it may not be possible to 'pick' WP icons and tool tips may give invalid information. Messages of the form:

(org.stronnag.mwp:36371): Clutter-WARNING **: 11:41:27.914: The required ID of 62 does not refer to an existing actor; this usually implies that the pick() of an actor is not correctly implemented or that there is an error in the glReadPixels() implementation of the GL driver.

may be displayed on stderr.

The workaround is to use XWayland to run mwp, by setting GDK_BACKEND=x11 in $HOME/.config/mwp/cmdopts. However this is not a perfect mitigation.

With GDK_BACKEND=x11 set, in some cases 'picking' map symbols may not be possible. This is alleviated by moving the mouse off the map and back again. This was a result of mwp displaying modal dialogues over that map; mwp has addressed this as far as possible by making (all) dialogues non-modal, with an unavoidable increase in internal complexity.

Compositors

The following compositors are not affected

• wayfire
• labwc
• Probably all other wlroots based compositor

The following compositors are affected (i.e. buggy, broken)

• Mutter (GNOME Shell)

libgdl (Gnome Docking Library)

libgdl manages the dock on the right hand side. Its dependencies include Glib2. A recent update to Glib2 (to 2.74.0) breaks the way that libgdl sets object properties.

Visible Effects

• Messages on stderr such as:

(org.stronnag.mwp:35733): Gdl-CRITICAL **: 11:34:52.350: gdl_dock_item_grip_realize: assertion 'grip->priv->label != NULL' failed

and

(org.stronnag.mwp:35733): Gtk-CRITICAL **: 11:34:52.426: gtk_widget_get_preferred_width: assertion 'GTK_IS_WIDGET (widget)' failed

• It is no longer possible to drag 'dock items' to reposition in the dock.
• It is necessary to have dock items shown as 'names' rather than 'icons' (this is done automatically by mwp based on runtime GLib2 version).

Workaround

It may be possible to use a version of GLIb2 less than 2.74.0. For example with GLib2 2.72.3 installed in $HOME/.local/lib, launching mwp as:

LD_LIBRARY_PATH=$LIB_LIBRARY_PATH:$HOME/.local/lib mwp

may fix the issue. This may be automated with a script or alias if desired.

Migrating mwp to GTK4

The long term solution is to migrate mwp to GTK4 (and its dependencies):

• Is significant effort
• Not practical at the moment

The Gtk4 replacements for libchamplain and libgdl are not currently sufficiently functional to meet mwp's needs:

• libshumate (libchamplain replacement) is missing important functionality (like the capability to drag symbols)
• libpanel (`libgdl potential replacement) is so poorly documented as to make it unfit even for investigation.

GTK4 migration may happen at some stage ...

[stronnag]

Just to make things even harder, libchamplain 0.12.21 (patch version update only) now links against libsoup-3.0 (vice libsoup-2.4) for any prior version. Which means mwp has to migrate to libsoup-3.0 also (done in #130, un-amused).

[stronnag]

The Gtk4 migration has started, it may take some time ....

[stronnag]

5 weeks on, some progress:

• Pretty much all UI / dialogs migrated to Gtk4
• Maps and other geo-related artefacts (libshumate)
• Home made panel (with hide / show button, static only user defined widget configuration)
• Missions (from files) and FWA / Safehomes (file or MSP), (new) Mission Editor
• LTM, quite a bit of MSP
• BBL replay (and probably OTX as well)
• LOS / Terrain Analysis
• Static (KML) Overlays
• General Aviation (ADSB tracks)

To Do (as least)

• Read / write missions to / from the FC
• Geozones
• Preferences dialog
• Lots of little details
• Robotic voice announcements
• CRSF, S.Port, MPM / Flysky telemetry

Caveats

• Will require a modern OS (no more concessions to 4 year old stuff)
• Arch Linux, FreeBSD 14, Debian Testing, Alpine Edge, Fedora latest, Ubuntu 24.04 etc.

[stronnag]

To Do (as least)

• Read / write missions to / from the FC
• Geozones
• Preferences dialog
• Lots of little details
• Robotic voice announcements
• CRSF, S.Port, MPM / Flysky telemetry

[stronnag]

There is now a public mwp4 branch and RC1 build. Welcome to the future.

[stronnag]

mwp is a now gtk4 application.