Capítulo 7. GUI System


7.1. GUI desktop environment
7.2. GUI communication protocol
7.3. GUI infrastructure
7.4. GUI applications
7.5. Fonts
7.5.1. Fontes (tipos de letra) básicas
7.5.2. Font rastarization
7.6. Sandbox
7.7. Remote desktop
7.8. X server connection
7.8.1. X server local connection
7.8.2. X server remote connection
7.8.3. X server chroot connection
7.9. Área de transferência (Clipboard)

There are several choices for the full featured GUI desktop environment on the Debian system.

[Dica] Dica

Dependency packages selected by a task metapackage may be out of sync with the latest package transition state under the Debian unstable/testing environment. For task-gnome-desktop, you may need to adjust package selections as follows:

  • Start aptitude(8) as sudo aptitude -u.

  • Move cursor to "Tasks" and press "Enter".

  • Move cursor to "End-user" press "Enter".

  • Move cursor to "GNOME" press "Enter".

  • Move cursor to task-gnome-desktop and press "Enter".

  • Move cursor to "Depends" and press "m" (manually selected).

  • Move cursor to "Recommends" and press "m" (manually selected).

  • Move cursor to "task-gnome-desktop and press "-". (drop)

  • Adjust selected packages while dropping problematic ones causing package conflicts.

  • Press "g" to start install.

This chapter will focus mostly on the default desktop environment of Debian: task-gnome-desktop offering GNOME on wayland.

GUI communication protocol used on the GNOME desktop can be:

Please check site for how Wayland architecture is different from X Window architecture.

From user's perspective, differences can be colloquially summarized as:

  • Wayland is a same-host GUI communication protocol: new, simpler, faster, no setuid root binary

  • X Window is a network-capable GUI communication protocol: traditional, complex, slower, setuid root binary

For applications using Wayland protocol, the access to their display contents from a remote host is supported by the VNC or RDP. See Secção 7.7, “Remote desktop”

Modern X servers have the MIT Shared Memory Extension and communicate with their local X clients using the local shared memory. This bypasses the network transparent Xlib interprocess communication channel and gains performance. This situation was the background of creating Wayland as a local-only GUI communication protocol.

Using the xeyes program started from the GNOME terminal, you can check GUI communication protocol used by each GUI application.

 $ xeyes
  • If the mouse cursor is on an application such as "GNOME terminal" which uses Wayland display server protocol, eyes don't move with the mouse cursor.

  • If the mouse cursor is on an application such as "xterm" which uses X Window System core protocol, eyes move with the mouse cursor exposing not-so-isolated nature of X Window architecture.

As of April 2021, many popular GUI applications such as GNOME and LibreOffice (LO) applications have been migrated to the Wayland display server protocol. I see xterm, gitk, chromium, firefox, gimp, dia, and KDE applications still use X Window System core protocol.

[Nota] Nota

For both the xwayland on Wayland or the native X Window System, the old X server configuration file "/etc/X11/xorg.conf" shouldn't exist on the system. The graphics and input devices are now configured by the kernel with DRM, KMS, and udev. The native X server has been rewritten to use them. See "modedb default video mode support" in the Linux kernel documentation.

Here are notable GUI infrastructure packages for the GNOME on Wayland environment.

Here, "[auto]" means that these packages are automatically installed when task-gnome-desktop is installed.

[Dica] Dica

gnome-tweaks is the indispensable configuration utility. For example:

  • You can force "Over-Amplification" of sound volume from "General".

  • You can force "Caps" to become "Esc" from "Keyboard & Mouse" -> "Keyboard" -> "Additional Layout Option".

Many useful GUI applications are available on Debian now. Installing software packages such as scribus (KDE) on GNOME desktop environment are quite acceptable since corresponding functionality is not available under GNOME desktop environment. But installing too many packages with duplicated functionalities may clutter your system.

Here is a list of GUI applications which caught my eyes.

Tabela 7.3. List of notable GUI applications

pacote popcon tamanho do pacote tipo descrição
evolution V:29, I:219 475 GNOME Gestor de Informações Pessoais (groupware e email)
thunderbird V:57, I:134 168690 GTK Email client (Mozilla Thunderbird)
kontact V:1, I:14 2152 KDE Gestor de Informações Pessoais (groupware e email)
libreoffice-writer V:167, I:423 39325 LO processador de texto
abiword V:1, I:11 5133 GNOME processador de texto
calligrawords V:0, I:7 5717 KDE processador de texto
scribus V:1, I:22 30370 KDE desktop publishing editor to edit PDF files
glabels V:0, I:4 1326 GNOME editor de etiquetas
libreoffice-calc V:166, I:418 32969 LO folha de cálculo
gnumeric V:5, I:20 9933 GNOME folha de cálculo
calligrasheets V:0, I:5 10890 KDE folha de cálculo
libreoffice-impress V:149, I:415 9930 LO apresentação
calligrastage V:0, I:5 5102 KDE apresentação
libreoffice-base V:116, I:289 7465 LO gestão de base de dados
kexi V:0, I:2 7576 KDE gestão de base de dados
libreoffice-draw V:150, I:416 14596 LO editor de gráficos vectoriais (desenho)
inkscape V:42, I:188 84892 GNOME editor de gráficos vectoriais (desenho)
karbon V:0, I:6 3473 KDE editor de gráficos vectoriais (desenho)
dia V:4, I:30 3727 GTK editor de fluxogramas e diagramas
gimp V:58, I:315 19706 GTK editor de gráficos bitmap (pintura)
shotwell V:16, I:217 6451 GTK organizador de fotos digitais
digikam V:2, I:12 2646 KDE organizador de fotos digitais
darktable V:6, I:17 22902 GTK lighttable and darkroom for photographers
planner V:0, I:4 1146 GNOME gestão de projectos
calligraplan V:0, I:2 18517 KDE gestão de projectos
gnucash V:3, I:11 32304 GNOME contas pessoais
homebank V:0, I:2 1114 GTK contas pessoais
lilypond V:0, I:8 7337 - music typesetter
kmymoney V:0, I:2 12036 KDE contas pessoais
librecad V:3, I:18 7893 Qt-app computer-aided design (CAD) system (2D)
freecad I:19 53 Qt-app computer-aided design (CAD) system (3D)
kicad V:2, I:15 98707 GTK electronic schematic and PCB design software
xsane V:14, I:165 2346 GTK frontend para digitalizador (scanner)
libreoffice-math V:144, I:419 1963 LO editor de fórmulas/equações matemáticas
calibre V:8, I:35 55048 KDE conversor de e-books e gestor de biblioteca
fbreader V:1, I:14 3074 GTK leitor de e-book
evince V:105, I:313 956 GNOME visualizador de documentos (pdf)
okular V:43, I:115 14646 KDE visualizador de documentos (pdf)
x11-apps V:27, I:454 2437 pure X-app xeyes(1), etc.
x11-utils V:171, I:581 712 pure X-app xev(1), xwininfo(1)etc.

Many useful scalable fonts are available for users on Debian. User's concern is how to avoid redundancy and how to configure parts of installed fonts to be disabled. Otherwise, useless font choices may clutter your GUI application menus.

Debian system uses FreeType 2.0 library to rasterise many scalable font formats for screen and print:

The following table is compiled in the hope to help users to chose appropriate scalable fonts with clear understanding of the metric compatibility and the glyph coverage. Most fonts cover all Latin fonts, Greek, and Cyril character glyphs. The final choice of activated fonts can also be affected by your aesthetics. These fonts can be used for the screen display or for the paper printing.

Tabela 7.4. List of notable TrueType and OpenType fonts

pacote popcon tamanho sans serif mono note on font
fonts-cantarell V:37, I:273 836 59 - - Cantarell (GNOME 3, display)
fonts-noto I:133 35 61 63 40 Noto fonts (Google, multi-lingual with CJK)
fonts-dejavu I:462 39 58 68 40 DejaVu (GNOME 2, MCM:Verdana, extended Bitstream Vera)
fonts-liberation2 V:48, I:333 4261 56 60 40 Liberation fonts for LibreOffice (Red Hat, MCMATC)
fonts-croscore V:10, I:47 5278 56 60 40 Chrome OS: Arimo, Tinos and Cousine (Google, MCMATC)
fonts-crosextra-carlito I:276 2732 57 - - Chrome OS: Carlito (Google, MCM:Calibri )
fonts-crosextra-caladea I:275 258 - 55 - Chrome OS: Caladea (Google, MCM:Cambria ) (Latin only )
fonts-freefont-ttf V:55, I:257 6656 57 59 40 GNU FreeFont (extended URW Nimbus)
fonts-quicksand I:358 392 56 - - Debian task-desktop, Quicksand (display, Latin only)
fonts-hack V:9, I:89 2508 - - 40 P A typeface designed for source code Hack (Facebook)
fonts-sil-gentiumplus I:39 5756 - 54 - Gentium SIL
fonts-sil-charis V:2, I:12 8900 - 59 - Charis SIL
fonts-urw-base35 V:46, I:94 11095 56 60 40 URW Nimbus (Sans, Roman No. 9 L, Mono L, MCAHTC)
fonts-ubuntu V:1, I:5 4103 58 - 33 P Ubuntu fonts (display)
fonts-terminus V:0, I:1 450 - - 33 Cool retro terminal fonts
ttf-mscorefonts-installer V:1, I:61 92 56? 60 40 Downloader of Microsoft non-free fonts (see below)


  • "MCM" stands for "metric compatible with fonts provided by Microsoft"

  • "MCMATC" stands for "metric compatible with fonts provided by Microsoft: Arial, Times New Roman, Courier New"

  • "MCAHTC" stands for "metric compatible with fonts provided by Adobe: Helvetica, Times, Courier"

  • Numbers in font type columns stands for the rough relative "M" width for the same point size font.

  • "P" in mono font type columns stands for its usability for programming having clearly distinguishable "0"/"O" and "1"/"I"/"l".

  • The ttf-mscorefonts-installer package downloads Microsoft's "Core fonts for the Web" and installs Arial, Times New Roman, Courier New, Verdana, ... . These installed font data are non-free data.

Many free Latin fonts have their lineage traced to URW Nimbus family or Bitstream Vera.

[Dica] Dica

If your locale needs fonts not covered well by the above fonts, please use aptitude to check under task packages listed under "Tasks" -> "Localization". The font packages listed as "Depends:" or "Recommends:" in the localization task packages are the primary candidates.

Many mostly GUI applications on Linux are available in binary formats from non-Debian sources.

[Atenção] Atenção

Binaries from these sites may include proprietary non-free software packages.

There is some raison d'être for these binary format distributions for Free Software aficionados using Debian since these can accommodate clean set of libraries used for each application by the respective upstream developer independent of the ones provided by Debian.

The inherent risk of running external binaries can be reduced by using the sandbox environment which leverages modern Linux security features (see Secção 4.7.4, “Linux security features”.

  • For binaries from AppImage and some upstream sites, run them in firejail with manual configuration.

  • For binaries from FLATHUB, run them in Flatpak . (No manual configuration required.)

  • For binaries from snapcraft, run them in Snap . (No manual configuration required. Compatible with daemon programs.)

The xdg-desktop-portal package provides a standardized API to common desktop features. See xdg-desktop-portal (flatpak) and xdg-desktop-portal (snap)

This sandbox environment technology is very much like apps on smart phone OS where apps are executed under controlled resource accesses.

Some large GUI applications such as web browsers on Debian also use sandbox environment technology internally to make them more secure.

There are several ways to connect from an application on a remote host to the X server including xwayland on the local host.

Access to the local X server by the local applications which use X core protocol can be locally connected through a local UNIX domain socket. This can be authorized by the authority file holding access cookie. The authority file location is identified by the "$XAUTHORITY" environment variable and X display is identified by the "$DISPLAY" environment variable. Since these are normally set automatically, no special action is needed, e.g. "gitk" as the following.

username $ gitk
[Nota] Nota

For xwayland, XAUTHORITY holds value like "/run/user/1000/.mutter-Xwaylandauth.YVSU30".

For clipping text to clipboard, see Secção 1.4.4, “Mouse operations”.

For clipping graphics to clipboard, see Secção 11.6, “Ferramentas de dados gráficos”.

Some CLI commands can manipulate character clipboard (PRIMARY and CLIPBOARD), too.