Ubuntu 24.04 gtk4 tweaks

Ubuntu 24.04.2 LTS (noble) uses GNOME 46 and GNOME 4 apps run on top of the gtk4 toolkit.

GNOME supports different types of devices and screen resolutions. In this scenario the target system is a PC with a single GNOME Workspace on a 100dpi screen. The screen provides enough horizontal space to work with a single taskbar which includes the active window list.

The old system setup used the GNOME Flashback desktop environment on GNOME 3, which provides a similar look & feel to the preceeding GNOME 2 version. GNOME Flashback consists of the Metacity Window Manager and the GNOME Panel taskbar.

GNOME Panel left	GNOME Panel right

Metacity is still available for Ubuntu 24.04, but Metacity is a gtk3 X11 window manager and will not support Wayland, so this is a dead-end in the long term. To support modern apps and features the setup was changed to use a gtk4 environment with a similar user experience to GNOME Flashback.

Switch from GNOME Flashback to GNOME 4 Classic

Different Ubuntu Desktop Environments can be selected from the login menu after a logout from the current session.

The best choice on Ubuntu 24.04 is GNOME Classic on Xorg. Even if Wayland is supposed to replace X11 in Linux, the GNOME Classic on Wayland session has still too many issues.

• GNOME Panel has been replaced with GNOME Shell in GNOME 4, which only works with the Mutter window manager

• Mutter is not compatible with old GNOME Panel addons, but it is highly configurable via GNOME Extensions. The extensions are installed and managed via the Extension Manager.

  $ sudo apt install gnome-shell-extensions
  $ sudo apt install gnome-shell-extension-manager
  

The best solution for a single taskbar on a GNOME 4 desktop are the extensions:

• Dash-to-Panel
• ArcMenu

  -> Menu->Menu Layout: Traditional Gnome Menu
  -> Menu->Tweaks->Category Activation: Mouse Hover
  -> General->Position: Left
  

• the menu entries can be managed via the Alacarte menu editor.

  $ sudo apt install alacarte
  

• for CPU temperatures Freon replaces the old sensor-applet for the GNOME Panel.

  $ sudo apt install lm-sensors
  

• to display the current weather next to the clock Weather O'Clock replaces the old GNOME Panel gweather applet.

  $ sudo apt install gnome-weather
  

GNOME Dash-to-Panel+ArcMenu left	GNOME Dash-to-Panel+ArcMenu right

Allow window positioning for gtk4 startup applications

The gtk4 runtime does not support to set the window position anymore.

• gtk4 is modelled on Wayland, which (unlike X11) does not expose toplevel positions to clients.
• there is no longer a way to do this in gtk4, all window management is done through the window manager. the window manager positions top level windows by its own strategy (to avoid some security risks).
• the gtk_window_move() API from gtk3 does not work under Wayland, and it has been removed in gtk4.
  • gtk_window_move
  • Adapt to GdkWindow API changes
  • Adapt to GtkWindow API changes
• this type of operation is only possible through manipulation via the GNOME Shell.
• the geometry option like --geometry=100x50+10+10 of older X11 applications will ignore the X/Y-position.

The Windows Calls extension provides access to the Windows.Move API of the GNOME Shell, and can be called via D-Bus messages.

$ gdbus call --session --dest org.gnome.Shell --object-path /org/gnome/Shell/Extensions/Windows --method org.gnome.Shell.Extensions.Windows.List | python3 -c 'import sys; a=eval(sys.stdin.read()); print (a[0])' | jq '.[] | select(.wm_class_instance=="ghostty")'
  {
    "in_current_workspace": true,
    "wm_class": "com.mitchellh.ghostty",
    "wm_class_instance": "ghostty",
    "title": "~",
    "pid": 3873,
    "id": 3149279314,
    "frame_type": 0,
    "window_type": 0,
    "focus": false
  }
$ gdbus call --session --dest org.gnome.Shell --object-path /org/gnome/Shell/Extensions/Windows --method org.gnome.Shell.Extensions.Windows.Move 3149279314 10 10

It is very useful to have an option to set the position of startup windows. Here is a simple start_win_at shell script, that takes the window position, the application name and parameters as argument, and can be called from the autostart folder.

$ start_win_at 10 10 ghostty --window-width=100 --window-height=50 --theme="Adwaita Dark"

The script works for any application opening a single window and has to

1. wait for the Window Calls extension to be available on startup,
2. start the application,
3. find the window id as soon as the window is displayed, and
4. move the window to the requested position.

Note: There are extensions like Another Window Session Manager that can restore the window size and position from the last session, but this is not the same like a clean startup configuration.

To run an application when a GNOME session starts, a script like terminal1.desktop has to be placed in the .config/autostart folder of the home directory. The command itself must be avaible in the shell PATH (so the the scripts folder should be added to the PATH).

Note: It is also possible to manage startup-applications with the gnome-tweaks tool. But on GNOME 4 gnome-tweaks has some issues and sometimes overrides old autostart entries.

Workaround for broken gtk3 window resize

Old GNOME 3 gtk3 apps are still supported in the GNOME 4 environment. But in the Ubuntu 24.04 Xorg session the gtk3 windows are not resizable after startup. This is a known issue and can be resolved by the command:

$ pkill -HUP mutter-x11-fram

see: Mutter on X11 with Gnome 46, some windows no shadows, not resizable

The script fix_gtk3_win_resize waits for Mutter to be available before the SIGHUP is send. To run this script when a GNOME session starts, a autostart script like fix_gtk3_win_resize.desktop has to be placed in the .config/autostart folder of the home directory.

Fix appearance of gtk3 applications

GNOME 4 tries to provide the Look & Feel of gtk4 apps to old gtk3 apps and snap applications like Firefox & Thunderbird. One difference is that just the upper corners of the windows are rounded.

To add rounded corners to all windows the Rounded Window Corners Reborn extension can be installed (see: https://github.com/flexagoon/rounded-window-corners).

Improve font rendering in terminal emulator

GNOME Classic uses the DejaVu Sans Mono font as standard Monospace console font.

$ fc-match Monospace
  DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"

The font-size and antialiasing can be changed in the gnone-tweaks font dialog. For a 100dpi IPS LCD screen a 13pt font-size and grayscale antialiasing seems to be the best choice for the GNOME Adwaita Dark theme with light text on a dark background. The subpixel-antialiasing shows slight vertical color-shadows on some chars.

grayscale antialiasing	subpixel antialiasing	no antialiasing

Another aspect which affects readability is the vertical space between text lines. In gnome-terminal the 13pt Monospace font uses a default cell-size of 10x21 pixel for each character. In the gnome-terminal Preferences dialog it is only possible to increase the cell-spacing of a selected custom font.

Since the 13pt Monospace font uses a quite large vertical spacing, a reduction by 1 pixel is reasonable. This can be accomplished by a different terminal emulator with more configuration options like ghostty.

$ ghostty --theme="Adwaita Dark" --font-family="DejaVu Sans Mono" --font-size=13 --adjust-cell-height=0

DejaVu Sans Mono 13pt (10x20 cell)	DejaVu Sans Mono 12pt (10x19 cell)

Using a terminal emulator with its own font rendering has also the advantage, that the global system settings do not affect the console font and can keep using subpixel-antialiasing (which looks better for proportional fonts). ghostty uses grayscale-antialiasing as a default.

For comparision the JetBrains Mono font which is configured as the ghostty default font is also a good console font. For the 12pt font ghostty uses a cell-size of 10x22 with a quite large vertical spacing. But this can easily be configured to use a cell-size of 10x20.

$ ghostty --theme="Adwaita Dark" --adjust-cell-height=-2

JetBrains Mono 12pt (10x22 cell)	JetBrains Mono 12pt (10x20 cell)

Comparision with GNOME Flashback Ubuntu Mono fonts

The old GNOME Flashback session used the Ubuntu Mono console font. This font is still available on Ubuntu 24.04, but it looks slightly different.

Ubuntu 24.04 updated the Ubuntu font family to a slimmer version. The new terminal font has the same 'Ubuntu Mono' name as the old 2011 font from Ubuntu 22.04 (see: Ubuntu font & Ubuntu Sans Mono Font Family).

It is possible to switch back and forth between the current and the old console font from Ubuntu 22.04 (note that sometimes gnome-terminal shows just 'boxes' after the switch and a reboot is required). (see: How to Restore the Old Fonts in Ubuntu 24.04 LTS)

$ sudo apt install fonts-ubuntu-classic
$ sudo apt install fonts-ubuntu

The classic Ubuntu Mono font is smaller for the same font-size, and also uses a smaller cell-spacing. So terminal dimensions will differ when switching between the fonts. The classic Ubuntu Mono font looks good in 12pt and 13pt sizes, but looks blurry with 14pt.

$ ghostty --font-family="Ubuntu Mono" --theme="Adwaita Dark" --font-size=12 --font-variation=wght=400 --adjust-cell-height=0

size	classic Ubuntu Mono	24.04 Ubuntu Mono
12pt
13pt

The new 12pt Ubuntu Mono font matches the dimensions of the old 13pt classic Ubuntu Mono font when redered with a cell-size of 9x18. For some characters like the t in the screenshot the vertical lines of the new font appear too thin.