Writing Guidelines¶

Writing Documentation
- Headlines
- Lists
- Inline Tags
- Label/reference
- Figures and Images
  - Pictures
  - Replacement
  - Figure
  - Tables
- Index
- Special Comments
- Code Snippets
- Footnotes
Managing Screenshots
- Add new Screenshots
- Translate Screenshots
Documenting Processing algorithms

In general, when creating reST documentation for the QGIS project, please follow the Python documentation style guidelines. For convenience, we provide a set of general rules we rely on for writing QGIS documentation below.

Writing Documentation ¶

Headlines ¶

To each webpage of the documentation corresponds a .rst file.

Sections used to structure the text are identified through their title which is underlined (and overlined for the first level). Same level titles must use same character for underline adornment. In QGIS Documentation, you should use following styles for chapter, section, subsection and minisec.

********
Chapter
********

Section
=======

Subsection
----------

Minisec
.......

Subminisec
^^^^^^^^^^

Lists ¶

Lists are useful for structuring the text. Here are some simple rules common to all lists:

Start all list items with a capital letter
Do not use punctuation after list items that only contain a single simple sentence
Use period ( . ) as punctuation for list items that consist of several sentences or a single compound sentence

Inline Tags ¶

You can use some tags inside the text to emphasize some items.

Menu GUI: to mark a complete sequence of menu selections, including selecting submenus and choosing a specific operation, or any subsequence of such a sequence.
```
:menuselection:`menu --> submenu`
```
Dialog and Tab title: Labels presented as part of an interactive user interface including window title, tab title, button and option labels.
```
:guilabel:`title`
```
Filename or directory
```
:file:`README.rst`
```
Icon with popup text belonging to Icon
```
|icon| :sup:`popup_text`
```
(see image below).
Keyboard shortcuts
```
:kbd:`Ctrl+B`
```
will show Ctrl+B

When describing keyboard shortcuts, the following conventions should be used:
- Letter keys are displayed using uppercase: S
- Special keys are displayed with an uppercase first letter: Esc
- Key combinations are displayed with a + sign between keys, without spaces: Shift+R
User text
```
``label``
```

Label/reference ¶

References are used to place anchors inside the text. It then helps you create and call hyperlinks between sections or page.

The example below creates the anchor of a section (e.g., Label/reference title)

.. _my_anchor:

Label/reference
---------------

To call the reference in the same page, use

see my_anchor_ for more information.

which will return:

see my_anchor for more information.

Notice how it will jump to the following line/thing following the ‘anchor’. Normally to declare this label you do not need to use apostrophes but you do need to use empty lines before and after the anchor.

Another way to jump to the same place from anywhere in the documentation is to use the :ref: role.

see :ref:`my_anchor` for more information.

which will display the caption instead (in this case the title of this section!):

see Label/reference for more information.

So reference 1 (my_anchor) and reference 2 (Label/reference). Because the reference often displays a full caption, there is not really the need to use the word section. Note that you can also use a custom caption to describe the reference

see :ref:`Label and reference <my_anchor>` for more information.

returning:

see Label and reference for more information.

Figures and Images ¶

Pictures ¶

To insert an image, use

.. image:: /static/common/logo.png
   :width: 10 em

which returns

Replacement ¶

You can put an image inside text or add an alias to use everywhere. To use an image inside a paragraph, first create an alias in the source/substitutions.txt file:

.. |nice_logo| image:: /static/common/logo.png
               :width: 2 em

and then call it in your paragraph:

My paragraph begins here with a nice logo |nice_logo|.

This is how the example will be displayed:

My paragraph begins here with a nice logo .

In order to render in GitHub a preview of the documentation that is the closest to html rendering, you will also need to add the image replacement call at the end of the file you changed. This can be done by copy-pasting it from the substitutions.txt or by executing the scripts/find_set_subst.py script.

Note

Currently, to ensure consistency and help in the use of QGIS icons a list of aliases is built and available in the Substitutions chapter.

Figure ¶

.. _figure_logo:

.. figure:: /static/common/logo.png
   :width: 20 em
   :align: center

   A caption: A logo I like

The result looks like this:

A caption: A logo I like¶

To avoid possible conflict with other references, always begin figure anchors with _figure_ and prefer using terms that can easily refer to the figure caption. While only the centered alignment is mandatory for the image, feel free to use any other options for figures (such as width, height, scale…) if needed.

The scripts will insert an automatically generated number before the caption of the figure in the generated PDF version of the documentation.

To use a caption (see My caption) just insert indented text after a blank line in the figure block.

Referencing to the figure can be done using the reference label like this

(see Figure_logo_).

It will show the anchor Figure_logo. You can use uppercase if you want. It can be used in the same .rst document but not in others. You can still use the :ref: role for reference from other files, but keep in mind that this returns the full caption of the image.

see :ref:`figure_logo`

returns:

see A caption: A logo I like

Tables ¶

To create a simple table

=======  =======  =======
x        y        z
=======  =======  =======
1        2        3
2        4
=======  =======  =======

Use a \ followed by an empty space to leave an empty space.

You can also use more complicated tables by drawing them using references and all

.. _my_drawn_table:

+---------------+--------------------+
| Windows       | macOS              |
+---------------+--------------------+
| |win|         | |osx|              |
+---------------+--------------------+
| and of course not to forget |nix|  |
+------------------------------------+

My drawn table, mind you this is unfortunately not regarded as a caption

You can reference to it like this my_drawn_table_.

The result:

Windows	macOS

and of course not to forget

My drawn table, mind you this is unfortunately not regarded as a caption

You can reference to it like this my_drawn_table.

Index ¶

An index is a handy way to help the reader easily find an information in a doc. QGIS documentation provides some essential indices. There are few rules to follow in order to keep a set of indices that are really useful (coherent, consistent and really connected to each other):

An index should be human readable, understandable and translatable; an index can be made from many words but you should avoid any unneeded _, -… characters to link them i.e., Loading layers instead of loading_layers or loadingLayers.
Always capitalize only the first letter of the index unless the word has a particular spelling, in which case keep using its spelling e.g., Loading layers, Atlas generation, WMS, pgsql2shp.
Keep an eye on the existing Index list in order to reuse the most convenient expression with the right spelling and avoid wrong duplicates.

Several index tags exist in RST. You can either use the inline :index: tag within the normal text.

QGIS allows to load several :index:`Vector formats` supported by GDAL/OGR ...

Or you can use the .. index:: block-level markup which links to the beginning of the next paragraph. Because of the rules mentioned above, it’s advised to use this latter tag as it’s easier to fulfill them.

.. index:: WMS, WFS, Loading layers

It’s also recommanded to use index parameters such as single, pair, see… in order to build a more structured and interconnected table of index. See Index generating for more information on index creation.

Special Comments ¶

Sometimes, you may want to emphasize some points of the description, either to warn, remind or give some hints to the user. In QGIS Documentation, we use reST special directives such as .. warning::, .. note:: and .. tip:: generating particular frames that highlight your comments. See Paragraph Level markup for more information. A clear and appropriate title is required for both warnings and tips.

.. tip:: **Always use a meaningful title for tips**

 Begin tips with a title that summarizes what it is about. This helps
 users to quickly overview the message you want to give them, and
 decide on its relevance.

Code Snippets ¶

You may also want to give examples and insert a code snippet. In this case, write the comment below a line with the :: directive inserted. However, for a better rendering, especially to apply color highlighting to code according to its language, use the code-block directive, e.g. .. code-block:: xml. More details at Showing code.

Note

While texts in note, tip and warning frames are translatable, be aware that code block frames do not allow translation. So avoid comments not related to code sample and keep this just as short as needed.

Footnotes ¶

Please note: Footnotes are not recognized by any translation software and it is also not converted to pdf format properly. So, if possible don’t use footnotes within any documentation.

This is for creating a footnote (showing as example 1)

blabla [1]_

Which will point to:

1

Updates of core plugins

Managing Screenshots ¶

Add new Screenshots ¶

Here are some hints to create new, nice looking screenshots. The images should be placed in a img/ folder, in the same folder as the referencing .rst file.

You can find some prepared QGIS-projects that are used to create screenshots in the ./qgis-projects folder of this repository. This makes it easier to reproduce screenshots for the next version of QGIS. These projects use the QGIS Sample Data (aka Alaska Dataset), which should be placed in the same folder as the QGIS-Documentation Repository.
Reduce the window to the minimal space needed to show the feature (taking the whole screen for a small modal window > overkill)
The less clutter, the better (no need to activate all the toolbars)
Don’t resize them in an image editor; the size will be set into the .rst files if necessary (downscaling the dimensions without properly upping the resolution > ugly)
Cut the background
Make the top corners transparent if the background is not white
Set print size resolution to 135 dpi (e.g. in Gimp set the print resolution Image ‣ Print size and save). This way, images will be at original size in html and at a good print resolution in the PDF. You can also use ImageMagick convert command to do a batch of images:
```
convert -units PixelsPerInch input.png -density 135 output.png
```
Save them in .png (no .jpeg artifacts)
The screenshot should show the content according to what is described in the text

Tip

If you are on Ubuntu, you can use the following command to remove the global menu function and create smaller application screens with menus:

sudo apt autoremove appmenu-gtk appmenu-gtk3 appmenu-qt

Translate Screenshots ¶

Here are some hints to create screenshots for your translated user guide. Translated images should be placed in a img/<your_language>/ folder, in the same folder as the referencing .rst file.

Use the QGIS projects included in QGIS-Documentation repository (in ./qgis_projects) These were used to produce the ‘original’ screenshots in the manual. The QGIS Sample Data (aka Alaska Dataset) should be placed in the same folder as the QGIS-Documentation Repository.
Same filename as the english ‘original’ screenshot
Reduce the window to the minimal space needed to show the feature (taking the whole screen for a small modal window > overkill)
The less clutter, the better (no need to activate all the toolbars)
Don’t resize them in an image editor; the size will be set into the .rst files if necessary (downscaling the dimensions without properly upping the resolution > ugly)
Cut the background
Save them in .png (no .jpeg artifacts)
The screenshot should show the content according to what is described in the text

Documenting Processing algorithms ¶

If you want to write documentation for Processing algorithms consider these guidelines:

Processing algorithm help files are part of QGIS User Guide, so use the same formatting as User Guide and other documentation.
Each algorithm documentation should be placed in the corresponding provider folder and group file, e.g. the algorithm Voronoi polygon belongs to the QGIS provider and to the group vectorgeometry. So the correct file to add the description is: source/docs/user_manual/processing_algs/qgis/vectorgeometry.rst.

Note

Before starting to write the guide, check if the algorithm is already described. In this case, you can enhance the existing description.
It is extremely important that each algorithm has an anchor that corresponds to the provider name + the unique name of the algorithm itself. This allows the Help button to open the Help page to the correct section. The anchor should be placed above the title, e.g. (see also the Label/reference section):
```
.. _qgisvoronoipolygons:

Voronoi polygons
----------------
```
To find out the algorithm name you can just hover the mouse on the algorithm in the Processing toolbox.
Avoid use “This algorithm does this and that…” as first sentence in algorithm description. Try to use more general expressions like:
```
Takes a point layer and generates a polygon layer containing the...
```
Avoid to describe what the algorithm does by replicating its name and please don’t replicate the name of the parameter in the description of the parameter itself. For example if the algorithm is Voronoi polygon consider to describe the Input layer like Layer to calculate the polygon from.
Indicate in the description whether the algorithm has a default shortcut in QGIS or supports in-place editing.
Add images! A picture is worth a thousand words! Use .png format and follow general guidelines for documentation (see the Figures and Images section for more info). Put the image file in the correct folder, i.e. the img folder next to the .rst file you are editing.
If necessary, add links to the “See also” section that provides additional information about the algorithm (e.g., publications or web-pages). Only add the “See also” section if there is really something to see. As a good practice, the “See also” section can be filled with links to similar algorithms.
Give clear explanation for algorithm parameters and outputs: take inspiration from existing algorithms.
Avoid to duplicate algorithm options detailed description. Add these information in the parameter description.
Avoid to add information about the vector geometry type in algorithm or parameter description without compelling reason as this information is already available in parameter description.

Add the default value of the parameter in italic, e.g.:

``Number of points`` [number]
  Number of points to create

  Default: *1*

Describe the type of input supported the parameters. There are several types available you can pick one from:

Parameter/Output type	Description	Visual indicator
Point vector layer	`vector: point`
Line vector layer	`vector: line`
Polygon vector layer	`vector: polygon`
Generic vector layer	`vector: any`
Vector field numeric	`tablefield: numeric`
Vector field string	`tablefield: string`
Vector field generic	`tablefield: any`
Raster layer	`raster`
Raster band	`raster band`
HTML file	`HTML`
Table layer	`table`
Expression	`expression`
Point geometry	`coordinates`
Extent	`extent`
CRS	`crs`
Enumeration	`enumeration`
List	`list`
Number	`number`
String	`string`
Boolean	`boolean`
Folder path	`folder`

The best option is studying an existing and well documented algorithm and copy all the useful layouts
If the algorithm does not provide any output just skip that section
When you are finished just follow the guidelines described in A Step By Step Contribution to commit your changes and make a Pull Request

Here is an example of an existing algorithm to help you with the layout and the description:

.. _qgiscountpointsinpolygon:

Count points in polygon
-----------------------
Takes a point and a polygon layer and counts the number of points from the
point layer in each of the polygons of the polygon layer.
A new polygon layer is generated, with the exact same content as the input polygon
layer, but containing an additional field with the points count corresponding to
each polygon.
.. figure:: img/count_points_polygon.png
  :align: center

  The labels in the polygons show the point count

An optional weight field can be used to assign weights to each point. Alternatively,
a unique class field can be specified. If both options are used, the weight field
will take precedence and the unique class field will be ignored.

``Default menu``: :menuselection:`Vector --> Analysis Tools`

Parameters
..........

  .. list-table::
   :header-rows: 1
   :widths: 20 20 20 40
   :stub-columns: 0

   *  - Label
      - Name
      - Type
      - Description
   *  - **Polygons**
      - ``POLYGONS``
      - [vector: polygon]
      - Polygon layer whose features are associated with the count of
        points they contain
   *  - **Points**
      - ``POINTS``
      - [vector: point]
      - Point layer with features to count
   *  - **Weight field**

        Optional
      - ``WEIGHT``
      - [tablefield: numeric]
      - A field from the point layer.
        The count generated will be the sum of the weight field of the
        points contained by the polygon.
   *  - **Class field**

        Optional
      - ``CLASSFIELD``
      - [tablefield: any]
      - Points are classified based on the selected attribute and if
        several points with the same attribute value are within the
        polygon, only one of them is counted.
        The final count of the points in a polygon is, therefore, the
        count of different classes that are found in it.
   *  - **Count field name**
      - ``FIELD``
      - [string]

        Default: 'NUMPOINTS'
      - The name of the field to store the count of points
   *  - **Count**
      - ``OUTPUT``
      - [vector: polygon]

        Default: [Create temporary layer]
      - Specification of the output layer type (temporary, file,
        GeoPackage or PostGIS table).
        Encoding can also be specified.


Outputs
.......

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 40
   :stub-columns: 0

   *  - Label
      - Name
      - Type
      - Description
   *  - **Count**
      - ``OUTPUT``
      - [vector: polygon]
      - Resulting layer with the attribute table containing the
        new column with the points count