doc: Add guiconfig documentation

Add documentation for the new GUI configuration interface in the
Application Development guide.

Also update all the images, touch up the language a bit, and tweak some
minor stuff:

 - Say *.conf instead of .conf to make it clearer that .conf isn't the
   literal name

 - Add a missing -D<board> argument when running cmake

 - Use figure:: instead of image::. Comes out left-aligned and with
   space between the images, which looks nicer.

 - Explain what '- -' and '-*-' means in the terminal menuconfig.

tkinter isn't included by default in many Python installations, despite
being part of the Python standard library, so also add the required
packages to the Development Environment Setup section of the manual. Add
a note to the Application Development section as well, to help
debugging.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

doc/application/index.rst

@@ -1146,7 +1146,7 @@ inter-dependencies between options, see the :ref:`configuration_options`.
 .. note::
 
     Dependencies between options can also be viewed in the interactive
-    configuration interface, which is explained in the
+    configuration interface, which is described in the
     :ref:`override_kernel_conf` section. It will have the most up-to-date
     dependencies, and also shows which dependencies are currently unsatisfied.
 
@@ -1214,23 +1214,25 @@ The example below shows a comment line and an override setting
 Overriding the Default Configuration
 ------------------------------------
 
-An interactive configuration interface is available for making temporary
-changes to the configuration. This can be handy during development.
+Making temporary changes to the configuration can be handy during development.
+There are two interactive configuration interfaces available for changing the
+configuration: ``menuconfig``, which runs in the terminal, and ``guiconfig``, a
+graphical configuration interface.
 
 .. note::
 
    The configuration can also be changed by editing :file:`zephyr/.config` in
-   the application build directory by hand. Using the configuration interface
-   is safer, as it correctly handles dependencies between configurations
-   symbols.
+   the application build directory by hand. Using one of the configuration
+   interfaces is usually safer, as they correctly handle dependencies between
+   configuration symbols.
 
-To make a setting permanent, you should set it in a :file:`.conf` file, as
+To make a setting permanent, you should set it in a :file:`*.conf` file, as
 described above in :ref:`application_set_conf`.
 
-The steps below will run the interactive configuration interface:
+Follow these steps to run the configuration interfaces.
 
 #. Create a build directory :file:`<home>/app/build` inside your application
-   directory and generate build files inside it with CMake, as follows:
+   directory and generate build files inside it with CMake:
 
    .. code-block:: bash
 
@@ -1240,63 +1242,102 @@ The steps below will run the interactive configuration interface:
       cd %userprofile%\app
 
       mkdir build && cd build
-      cmake -GNinja ..
+      cmake -GNinja -D<board> ..
 
-#. Run the following command from the build directory (:file:`<home>/app/build`)
-   to start the configuration interface:
+#. Use this command to run the terminal-based ``menuconfig`` interface:
 
    .. code-block:: bash
 
        ninja menuconfig
 
-   The configuration interface is shown below:
+   Use this command to run the graphical ``guiconfig`` interface:
 
-   .. image:: figures/app_kernel_conf_1.png
-        :align: center
-        :alt: Main Configuration Menu
+   .. code-block:: bash
+
+       ninja guiconfig
+
+   .. note::
+
+       If you get an import error for ``tkinter`` when trying to run
+       ``guiconfig``, you are missing required packages. See
+       :ref:`installation_linux`. The package is usually called something like
+       ``python3-tk``/``python3-tkinter``.
+
+       ``tkinter`` is not included by default in many Python installations,
+       despite being part of the standard library.
 
-#. Change configuration symbols to their desired values as follows:
+   The two interfaces are shown below:
+
+   .. figure:: figures/menuconfig.png
+        :alt: menuconfig interface
+
+   .. figure:: figures/guiconfig.png
+        :alt: guiconfig interface
+
+   ``guiconfig`` always shows the help text and other information related to
+   the currently selected item in the bottom window pane. In the terminal
+   interface, press :kbd:`?` to view the same information.
+
+   .. note::
 
-   * Use the arrow keys to navigate the menu.
+      If you prefer to work in the ``guiconfig`` interface, then it's a good
+      idea to check any changes to Kconfig files you make in *single-menu
+      mode*, which is toggled via a checkbox at the top. Unlike full-tree
+      mode, single-menu mode will distinguish between symbols defined with
+      ``config`` and symbols defined with ``menuconfig``, showing you what
+      things would look like in the ``menuconfig`` interface.
+
+#. Change configuration values in the ``menuconfig`` interface as follows:
+
+   * Navigate the menu with the arrow keys.
 
      .. note::
 
         Common `Vim <https://www.vim.org>`_ key bindings are supported as well.
 
-   * Press :kbd:`Enter` or :kbd:`Space` to enter submenus and choices, which
-     appear with ``--->`` next to them. Press :kbd:`ESC` returns to the parent
-     menu.
+   * Press :kbd:`Enter` to enter menus and choices, which appear with ``--->``
+     next to them. Press :kbd:`ESC` to return to the parent menu.
 
-   * Press :kbd:`Space` to toggle or configure a symbol value. Boolean
-     configuration symbols are shown with :guilabel:`[ ]` brackets, while
-     numeric and string-valued configuration symbols are shown with
-     :guilabel:`( )` brackets.
+   * Press :kbd:`Space` to change symbol values. Boolean configuration symbols
+     are shown with :guilabel:`[ ]` brackets, while numeric and string-valued
+     configuration symbols are shown with :guilabel:`( )` brackets. Symbol
+     values that can't be changed are indicated with :guilabel:`- -` and
+     :guilabel:`-*-`.
 
      .. note::
 
         You can also press :kbd:`Y` or :kbd:`N` to set a boolean configuration
-        symbol, to the corresponding value.
+        symbol to the corresponding value.
 
    * Press :kbd:`?` to display information about the currently selected symbol.
      Press :kbd:`ESC` or :kbd:`Q` to return from the information display to the
      menu.
 
-#. After configuring the kernel options for your application, press
-   :kbd:`Q` to bring up the save-and-quit dialog:
+   In the ``guiconfig`` interface, either click on the image next to the symbol
+   to change its value, or double-click on the row with the symbol.
+   Double-clicking only works for changing the value if the symbol has no
+   children. Double-clicking a symbol with children will show/hide its children
+   instead.
+
+   ``guiconfig`` also supports keyboard controls: :kbd:`Space` toggles values,
+   and :kbd:`Enter` opens/closes menus.
+
+#. Pressing :kbd:`Q` in the ``menuconfig`` interface will bring up the
+   save-and-quit dialog (if there are changes to save):
 
-   .. image:: figures/app_kernel_conf_2.png
-      :align: center
+   .. figure:: figures/menuconfig-quit.png
       :alt: Save and Quit Dialog
 
-#. Press :kbd:`Y` to save the kernel configuration options to the default
-   filename (:file:`zephyr/.config`).
+   Press :kbd:`Y` to save the kernel configuration options to the default
+   filename (:file:`zephyr/.config`). You will typically save to the default
+   filename unless you are experimenting with different configurations.
 
-   Typically, you will save to the default filename unless you are
-   experimenting with various configuration scenarios.
+   The ``guiconfig`` interface will also prompt for saving the configuration on
+   exit if it has been modified.
 
    .. note::
 
-      At present, the configuration file used during building is always
+      The configuration file used during the build is always
       :file:`zephyr/.config`. If you have another saved configuration that you
       want to build with, copy it to :file:`zephyr/.config`. Make sure to back
       up your original configuration file.
@@ -1305,26 +1346,42 @@ The steps below will run the interactive configuration interface:
       default on Linux and macOS. Use the ``-a`` flag to see them.
 
 Finding a symbol in the menu tree and navigating to it can be tedious. To jump
-directly to a symbol, press the :kbd:`/` key. This brings up the following
-dialog, where you can search for symbols by name and jump to them:
+directly to a symbol, press the :kbd:`/` key (this also works in
+``guiconfig``). This brings up the following dialog, where you can search for
+symbols by name and jump to them. In ``guiconfig``, you can also change symbol
+values directly within the dialog.
 
-.. image:: figures/app_kernel_conf_3.png
-    :align: center
-    :alt: Menuconfig Search Dialog
+.. figure:: figures/menuconfig-jump-to.png
+    :alt: menuconfig jump-to dialog
+
+.. figure:: figures/guiconfig-jump-to.png
+    :alt: guiconfig jump-to dialog
 
 If you jump to a symbol that isn't currently visible (e.g., due to having
-unsatisfied dependencies) then *show-all mode* will be enabled. In show-all
-mode, all symbols are displayed, including currently invisible symbols. To
-disable show-all mode, press :kbd:`A`.
+unsatisfied dependencies), then *show-all mode* will be enabled. In show-all
+mode, all symbols are displayed, including currently invisible symbols. To turn
+off show-all mode, press :kbd:`A` in ``menuconfig`` or :kbd:`Ctrl-A` in
+``guiconfig``.
 
 .. note::
 
-    Show-all mode can't be disabled if there are no visible items in the menu.
+    Show-all mode can't be turned off if there are no visible items in the
+    current menu.
 
 To figure out why a symbol you jumped to isn't visible, inspect its
-dependencies by pressing :kbd:`?`. If you discover that the symbol depends on
-another symbol that isn't enabled, you can jump to that symbol, in turn, to see
-if it can be enabled.
+dependencies, either by pressing :kbd:`?` in ``menuconfig`` or in the
+information pane at the bottom in ``guiconfig``. If you discover that the
+symbol depends on another symbol that isn't enabled, you can jump to that
+symbol in turn to see if it can be enabled.
+
+.. note::
+
+   In ``menuconfig``, you can press :kbd:`Ctrl-F` to view the help of the
+   currently selected item in the jump-to dialog without leaving the dialog.
+
+For more information on ``menuconfig`` and ``guiconfig``, see the Python
+docstrings at the top of ``scripts/kconfig/menuconfig.py`` and
+``scripts/kconfig/guiconfig.py``.
 
 .. _application_dt:
 

doc/getting_started/installation_linux.rst

@@ -76,8 +76,8 @@ On Ubuntu:
 
    sudo apt-get install --no-install-recommends git cmake ninja-build gperf \
      ccache dfu-util device-tree-compiler wget \
-     python3-pip python3-setuptools python3-wheel xz-utils file make gcc \
-     gcc-multilib
+     python3-pip python3-setuptools python3-tk python3-wheel xz-utils file \
+     make gcc gcc-multilib
 
 On Fedora:
 
@@ -86,21 +86,21 @@ On Fedora:
 
    sudo dnf group install "Development Tools" "C Development Tools and Libraries"
    dnf install git cmake ninja-build gperf ccache dfu-util dtc wget \
-     python3-pip xz file glibc-devel.i686 libstdc++-devel.i686
+     python3-pip python3-tkinter xz file glibc-devel.i686 libstdc++-devel.i686
 
 On Clear Linux:
 
 .. code-block:: console
 
    sudo swupd bundle-add c-basic dev-utils dfu-util dtc \
-     os-core-dev python-basic python3-basic
+     os-core-dev python-basic python3-basic python3-tcl
 
 On Arch:
 
 .. code-block:: console
 
    sudo pacman -S git cmake ninja gperf ccache dfu-util dtc wget \
-       python-pip python-setuptools python-wheel xz file make
+       python-pip python-setuptools python-wheel tk xz file make
 
 .. important::
    Zephyr requires a recent version of CMake. Read through