### General Algorithm Description Example

Source: https://docs.qgis.org/3.44/en/docs/documentation_guidelines/writing.html

Start algorithm descriptions with general expressions rather than specific actions. This example describes a point layer input generating a polygon layer output.

```rst
Takes a point layer and generates a polygon layer containing the...

```

--------------------------------

### Install QGIS Server Package

Source: https://docs.qgis.org/3.44/en/docs/training_manual/qgis_server/install.html

Installs the QGIS Server package. Use the second command to also install server plugins.

```bash
apt install qgis-server --no-install-recommends --no-install-suggests
```

```bash
# if you want to install server plugins, also:
apt install python3-qgis
```

--------------------------------

### Install QtCreator on Debian

Source: https://docs.qgis.org/3.44/en/docs/developers_guide/qtcreator.html

Use this command to install QtCreator and its documentation on Debian-based systems.

```bash
sudo apt install qtcreator qtcreator-doc

```

--------------------------------

### QgsTask Execution Output Example

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/tasks.html

Illustrates the typical output logs generated during the execution of QgsTask instances, showing task start, completion, and final results.

```text
 1RandomIntegerSumTask(0): Started task "waste cpu subtask shortest"
 2RandomIntegerSumTask(0): Started task "waste cpu short"
 3RandomIntegerSumTask(0): Started task "waste cpu mini"
 4RandomIntegerSumTask(0): Started task "waste cpu subtask long"
 5RandomIntegerSumTask(3): Task "waste cpu subtask shortest" completed
 6RandomTotal: 25452 (with 100 iterations)
 7RandomIntegerSumTask(3): Task "waste cpu mini" completed
 8RandomTotal: 23810 (with 100 iterations)
 9RandomIntegerSumTask(3): Task "waste cpu subtask long" completed
10RandomTotal: 26308 (with 100 iterations)
11RandomIntegerSumTask(0): Started task "waste cpu long"
12RandomIntegerSumTask(3): Task "waste cpu long" completed
13RandomTotal: 22534 (with 100 iterations)
```

--------------------------------

### Install NGINX

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Installs the NGINX web server, an alternative to Apache for serving QGIS Server.

```bash
apt install nginx

```

--------------------------------

### Install pyogctest

Source: https://docs.qgis.org/3.44/en/docs/developers_guide/ogcconformancetesting.html

Install pyogctest in a virtual environment. Ensure you activate the environment before installation.

```bash
virtualenv venv
source venv/bin/activate
pip install pyogctest
```

--------------------------------

### Install Apache Service on Windows

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Run the apache-install.bat script as administrator to install the Apache OSGeo4W Web Server service.

```bash
> apache-install.bat
Installing the 'Apache OSGeo4W Web Server' service
The 'Apache OSGeo4W Web Server' service is successfully installed.
Testing httpd.conf....
Errors reported here must be corrected before the service can be started.
...
```

--------------------------------

### Test QGIS Server Installation

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Run this command to verify if QGIS Server is installed correctly. A successful output indicates the server is functioning.

```bash
/usr/lib/cgi-bin/qgis_mapserv.fcgi

```

--------------------------------

### Install spawn-fcgi Package

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Command to install the spawn-fcgi package, recommended for production use due to better performance.

```bash
apt install spawn-fcgi
```

--------------------------------

### Enable, Start, and Check Xvfb Service Status

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Enables the Xvfb service to start on boot, starts it immediately, and checks its current status using systemd.

```bash
systemctl enable --now xvfb.service
systemctl status xvfb.service

```

--------------------------------

### Install fcgiwrap Package

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Command to install the fcgiwrap package. Easier to set up than spawn-fcgi but slower due to process creation per request.

```bash
apt install fcgiwrap
```

--------------------------------

### Install Qt Tools for Translation

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/plugins/plugins.html

Install the necessary Qt development tools for managing translation files on Debian-based systems.

```bash
sudo apt install qttools5-dev-tools

```

--------------------------------

### Enable and Start QGIS Server systemd Service

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Commands to enable the QGIS Server systemd service to start on boot and start it immediately.

```bash
systemctl enable --now qgis-server
```

--------------------------------

### QGIS Development Server Output Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/development_server.html

This is an example of the log output you might see when the QGIS Development Server is running and handling requests.

```log
QGIS Development Server listening on http://localhost:8000
CTRL+C to exit
127.0.0.1 [lun gen 20 15:16:41 2020] 5140 103ms "GET /wfs3/?MAP=/tests/testdata/qgis_server/test_project.qgs HTTP/1.1" 200
127.0.0.1 [lun gen 20 15:16:41 2020] 3298 2ms "GET /wfs3/static/jsonFormatter.min.js HTTP/1.1" 200
127.0.0.1 [lun gen 20 15:16:41 2020] 1678 3ms "GET /wfs3/static/jsonFormatter.min.css HTTP/1.1" 200
127.0.0.1 [lun gen 20 15:16:41 2020] 1310 5ms "GET /wfs3/static/style.css HTTP/1.1" 200
127.0.0.1 [lun gen 20 15:16:43 2020] 4285 13ms "GET /wfs3/collections?MAP=/tests/testdata/qgis_server/test_project.qgs HTTP/1.1" 200

```

--------------------------------

### GetCapabilities Request URL Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/basics.html

Example of a URL to execute a GetCapabilities request. The REQUEST parameter specifies the request name.

```url
http://localhost/qgisserver?
REQUEST=GetCapabilities
&...

```

--------------------------------

### Install Xvfb Package

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Installs the X Virtual Frame Buffer package using apt. This is required for running QGIS Server in a headless environment.

```bash
apt install xvfb

```

--------------------------------

### Set Default Project and Serve

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Configure the QGIS_PROJECT_FILE environment variable to specify a default project and then start QGIS Server using spawn-fcgi.

```bash
export QGIS_PROJECT_FILE=/home/qgis/projects/world.qgs
spawn-fcgi -f /usr/lib/bin/cgi-bin/qgis_mapserv.fcgi \
           -s /var/run/qgisserver.socket \
           -U www-data -G www-data -n

```

--------------------------------

### DescribeLayer Request Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wms.html

Example URL for a DescribeLayer request to get information about layers in QGIS Server.

```http
http://localhost/qgisserver?
SERVICE=WMS
&REQUEST=DescribeLayer
&SLD_VERSION=1.1.0
&LAYERS=mylayer1

```

--------------------------------

### Setting Up Task Dependencies

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/tasks.html

This example demonstrates how to set up dependencies between tasks. Tasks can be configured to run after other tasks, before their parent task, or with no specific order. Use addSubTask() to define these relationships.

```python
longtask = RandomIntegerSumTask('waste cpu long', 20)
shorttask = RandomIntegerSumTask('waste cpu short', 10)
minitask = RandomIntegerSumTask('waste cpu mini', 5)
shortsubtask = RandomIntegerSumTask('waste cpu subtask short', 5)
longsubtask = RandomIntegerSumTask('waste cpu subtask long', 10)
shortestsubtask = RandomIntegerSumTask('waste cpu subtask shortest', 4)

# Add a subtask (shortsubtask) to shorttask that must run after
# minitask and longtask has finished
shorttask.addSubTask(shortsubtask, [minitask, longtask])
# Add a subtask (longsubtask) to longtask that must be run
# before the parent task
longtask.addSubTask(longsubtask, [], QgsTask.ParentDependsOnSubTask)
# Add a subtask (shortestsubtask) to longtask
longtask.addSubTask(shortestsubtask)

QgsApplication.taskManager().addTask(longtask)
```

--------------------------------

### Install HelloWorld Plugin Manually

Source: https://docs.qgis.org/3.44/en/docs/server_manual/plugins.html

Steps to manually install the HelloWorld plugin for QGIS Server testing. This involves creating a directory, downloading the plugin ZIP, and unzipping it.

```bash
mkdir -p /var/www/qgis-server/plugins
cd /var/www/qgis-server/plugins
wget https://github.com/elpaso/qgis-helloserver/archive/master.zip
unzip master.zip
mv qgis-helloserver-master HelloServer
```

--------------------------------

### DescribeFeatureType WFS Request Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wfs.html

Example URL for a DescribeFeatureType request to get schema information for a specific layer. Ensure the MAP parameter points to a valid QGIS project file.

```http
http://localhost/qgisserver?
SERVICE=WFS
&VERSION=1.1.0
&REQUEST=DescribeFeatureType
&TYPENAME=countries

```

--------------------------------

### Filter Airports by Name Pattern

Source: https://docs.qgis.org/3.44/en/docs/user_manual/print_layout/layout_items/layout_tables.html

Example of filtering features using a LIKE operator to exclude names starting with 'AN'.

```sql
NAME NOT LIKE 'AN%'
```

--------------------------------

### Load Data Files on Startup

Source: https://docs.qgis.org/3.44/en/docs/user_manual/introduction/qgis_configuration.html

Starts QGIS with specified vector and raster files loaded. Ensure you are in the correct directory or provide the full path to the files.

```bash
qgis ./raster/landcover.img ./gml/lakes.gml
```

--------------------------------

### Get Start Point of Geometry

Source: https://docs.qgis.org/3.44/en/docs/user_manual/expressions/functions_list.html

Returns the first node of a geometry. Useful for identifying the origin of a linestring or other linear geometries.

```sql
geom_to_wkt(start_point(geom_from_wkt('LINESTRING(4 0, 4 2, 0 2)')))
```

--------------------------------

### Get First Vertex of Polygon Boundary

Source: https://docs.qgis.org/3.44/en/docs/training_manual/spatial_databases/geometry.html

Extract the starting point (vertex) of the linestring that forms the boundary of a polygon geometry from 'myPolygonTable'.

```sql
select st_startpoint(myGeometry)
from (
    select st_boundary(geom) as myGeometry
    from myPolygonTable) as foo;
```

--------------------------------

### Get Nth Element of Array

Source: https://docs.qgis.org/3.44/en/docs/user_manual/expressions/functions_list.html

Retrieves an element from an array by its position (index). Supports positive indices from the start and negative indices from the end.

```qgis_expression
array_get(array('a','b','c'),1)
```

```qgis_expression
array_get(array('a','b','c'),-1)
```

--------------------------------

### Start QGIS with a Specific Project

Source: https://docs.qgis.org/3.44/en/docs/user_manual/introduction/qgis_configuration.html

Use the `--project` option to open QGIS with a predefined project file. All layers within the specified project will be loaded.

```bash
qgis --project /path/to/your/project.qgz
```

--------------------------------

### Lesson Introduction Markup

Source: https://docs.qgis.org/3.44/en/docs/training_manual/appendix/contribute.html

Begin a lesson by writing the markup phrase 'Lesson', followed by the lesson name, and then a line of equal signs for the title underline. A short description and introduction follow.

```rst
**The goal for this lesson:**


```

--------------------------------

### Get QGIS Prefix Path

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/intro.html

This code snippet demonstrates how to retrieve the QGIS installation prefix path. This is useful for configuring standalone scripts.

```python
QgsApplication.prefixPath()
```

--------------------------------

### Example metadata.txt for a QGIS Plugin

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/plugins/plugins.html

A comprehensive example of a metadata.txt file, including mandatory and optional fields like name, version, author, description, and advanced options such as plugin dependencies and experimental flags.

```ini
; the next section is mandatory

[general]
name=HelloWorld
email=me@example.com
author=Just Me
qgisMinimumVersion=3.0
description=This is an example plugin for greeting the world.
    Multiline is allowed:
    lines starting with spaces belong to the same
    field, in this case to the "description" field.
    HTML formatting is not allowed.
about=This paragraph can contain a detailed description
    of the plugin. Multiline is allowed, HTML is not.
version=version 1.2
tracker=http://bugs.itopen.it
repository=http://www.itopen.it/repo
; end of mandatory metadata

; start of optional metadata
category=Raster
changelog=The changelog lists the plugin versions
    and their changes as in the example below:
    1.0 - First stable release
    0.9 - All features implemented
    0.8 - First testing release

; Tags are in comma separated value format, spaces are allowed within the
; tag name.
; Tags should be in English language. Please also check for existing tags and
; synonyms before creating a new one.
tags=wkt,raster,hello world

; these metadata can be empty, they will eventually become mandatory.
homepage=https://www.itopen.it
icon=icon.png

; experimental flag (applies to the single version)
experimental=True

; deprecated flag (applies to the whole plugin and not only to the uploaded version)
deprecated=False

; if empty, it will be automatically set to major version + .99
qgisMaximumVersion=3.99

; Since QGIS 3.8, a comma separated list of plugins to be installed
; (or upgraded) can be specified.
; The example below will try to install (or upgrade) "MyOtherPlugin" version 1.12
; and any version of "YetAnotherPlugin".
; Both "MyOtherPlugin" and "YetAnotherPlugin" names come from their own metadata's
; name field
plugin_dependencies=MyOtherPlugin==1.12,YetAnotherPlugin

```

--------------------------------

### Task Execution Log Output

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/tasks.html

Example log output showing the sequence of events during task execution, including task start, progress, and completion messages.

```log
1RandomIntegerSumTask(0): Started task "waste cpu subtask short"
2RandomTaskFromFunction(0): Started task Waste cpu 1
3RandomTaskFromFunction(0): Started task Waste cpu 2
4RandomTaskFromFunction(0): Task Waste cpu 2 completed
5RandomTotal: 23263 ( with 100 iterations)
6RandomTaskFromFunction(0): Task Waste cpu 1 completed
7RandomTotal: 25044 ( with 100 iterations)
```

--------------------------------

### Test QGIS Server Binary with Query String

Source: https://docs.qgis.org/3.44/en/docs/server_manual/config.html

This example demonstrates how to test the QGIS server binary from the command line using the QUERY_STRING variable, useful for simulating requests like GetCapabilities.

```bash
PGSERVICEFILE=/etc/pg_service.conf \
QUERY_STRING="MAP=/home/projects/world.qgs&SERVICE=WMS&REQUEST=GetCapabilities" \
/usr/lib/cgi-bin/qgis_mapserv.fcgi
```

--------------------------------

### Plugin Zip Structure Example

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/plugins/releasing.html

Illustrates the expected directory and file layout for a QGIS plugin's zip archive to ensure proper validation and installation.

```plaintext
plugin.zip
  pluginfolder/
  |-- i18n
  |   |-- translation_file_de.ts
  |-- img
  |   |-- icon.png
  |   |-- iconsource.svg
  |-- __init__.py
  |-- LICENSE
  |-- Makefile
  |-- metadata.txt
  |-- more_code.py
  |-- main_code.py
  |-- README
  |-- ui_Qt_user_interface_file.ui


```

--------------------------------

### Get Vector Layer Renderer

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/vector.html

Retrieve the renderer object associated with a vector layer to inspect or modify its symbology. This is the starting point for controlling how features are drawn.

```python
renderer = layer.renderer()
```

--------------------------------

### Example of running QGIS Server container

Source: https://docs.qgis.org/3.44/en/docs/server_manual/containerized_deployment.html

Output showing a QGIS Server container running, including its ID, image, command, status, and port mappings.

```text
CONTAINER ID   IMAGE         COMMAND                  CREATED         STATUS         PORTS                    NAMES
4de8192da76e   qgis-server   "/tini -- /home/qgis…"   3 seconds ago   Up 2 seconds   0.0.0.0:5555->5555/tcp   qgis-server

```

--------------------------------

### Get Y Coordinate of Specific Vertex in Geometry

Source: https://docs.qgis.org/3.44/en/docs/user_manual/expressions/functions_list.html

Retrieves the y coordinate of a specific vertex within a geometry. Vertex indices start at 0, and negative indices count from the end.

```sql
y_at( geom_from_wkt( 'POINT(4 5)' ), 0 )
```

--------------------------------

### Run QGIS from Build Directory

Source: https://docs.qgis.org/3.44/en/docs/developers_guide/qtcreator.html

Navigate to the build directory and execute the QGIS binary to run the compiled application.

```bash
cd $HOME/dev/cpp/QGIS/build-master-qtcreator
./output/bin/qgis

```

--------------------------------

### Prevent Plugins from Loading at Startup

Source: https://docs.qgis.org/3.44/en/docs/user_manual/introduction/qgis_configuration.html

Use `--noplugins` to avoid loading all installed plugins when QGIS starts. Plugins can still be accessed and managed via the Plugins Manager.

```bash
qgis --noplugins
```

--------------------------------

### Get Measure Coordinate at Vertex

Source: https://docs.qgis.org/3.44/en/docs/user_manual/expressions/functions_list.html

Retrieves the m coordinate of a specific vertex in a geometry. Indices start at 0, and negative values count from the end. Returns NULL if the geometry has no m value.

```sql
m_at(geom_from_wkt('LineStringZM(0 0 0 0, 10 10 0 5, 10 10 0 0)'), 1)
```

--------------------------------

### Load a QGIS Project

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/loadproject.html

Instantiate QgsProject and load a project file. Ensure necessary imports if not in the QGIS console.

```python
from qgis.core import QgsProject
# Get the project instance
project = QgsProject.instance()
# Print the current project file name (might be empty in case no projects have been loaded)
# print(project.fileName())

# Load another project
project.read('testdata/01_project.qgs')
print(project.fileName())
```

--------------------------------

### Enable Apache Modules and Site

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Enables the `fcgid` and `rewrite` Apache modules and activates the QGIS Server virtual host configuration.

```bash
a2enmod fcgid
a2enmod rewrite
a2ensite qgis.demo

```

--------------------------------

### Execute SQL Query with REGEXP - DB Manager

Source: https://docs.qgis.org/3.44/en/docs/user_manual/plugins/core_plugins/plugins_db_manager.html

Use the REGEXP function in SQL queries within the DB Manager for pattern matching. This example filters features where the 'name' field starts with 'A'.

```sql
SELECT * FROM places WHERE name REGEXP '^A';
```

--------------------------------

### Get Z Coordinate of Specific Vertex in Geometry

Source: https://docs.qgis.org/3.44/en/docs/user_manual/expressions/functions_list.html

Retrieves the z coordinate of a specific vertex within a geometry. Returns NULL if the geometry has no z value. Vertex indices start at 0, and negative indices count from the end.

```sql
z_at(geom_from_wkt('LineStringZ(0 0 0, 10 10 5, 10 10 0)'), 1)
```

--------------------------------

### QGIS Development Server Help Output

Source: https://docs.qgis.org/3.44/en/docs/server_manual/development_server.html

Invoking the server with the -h flag displays available command-line options for configuration.

```bash
Usage: qgis_mapserver [options] [address:port]
QGIS Development Server

Options:
-h, --help        Displays this help.
-v, --version     Displays version information.
-l <logLevel>     Sets log level (default: 0)
                    0: INFO
                    1: WARNING
                    2: CRITICAL
-p <projectPath>  Path to a QGIS project file (*.qgs or *.qgz),
                    if specified it will override the query string MAP argument
                    and the QGIS_PROJECT_FILE environment variable

Arguments:
addressAndPort    Listen to address and port (default: "localhost:8000")
                    address and port can also be specified with the environment
                    variables QGIS_SERVER_ADDRESS and QGIS_SERVER_PORT


```

--------------------------------

### Configure RPATH and Installation Properties

Source: https://docs.qgis.org/3.44/en/docs/developers_guide/unittesting.html

Sets target properties for the executable, including RPATH settings for build and installation, and defines installation destinations.

```cmake
SET_TARGET_PROPERTIES(qgis_${testname}
PROPERTIES
# skip the full RPATH for the build tree
SKIP_BUILD_RPATHTRUE
# when building, use the install RPATH already
# (so it doesn't need to relink when installing)
BUILD_WITH_INSTALL_RPATH TRUE
# the RPATH to be used when installing
INSTALL_RPATH ${QGIS_LIB_DIR}
# add the automatically determined parts of the RPATH
# which point to directories outside the build tree to the install RPATH
INSTALL_RPATH_USE_LINK_PATH true)
```

--------------------------------

### Download and Prepare Sample Project Data

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

These commands download and extract sample QGIS project data, including a world map and a spatialite database, which can be used for testing QGIS Server.

```bash
mkdir /home/qgis/projects/
cd /home/qgis/projects/
wget https://github.com/qgis/QGIS-Training-Data/archive/release_3.22.zip
unzip release_3.22.zip
mv QGIS-Training-Data-release_3.22/exercise_data/qgis-server-tutorial-data/world.qgs .
mv QGIS-Training-Data-release_3.22/exercise_data/qgis-server-tutorial-data/naturalearth.sqlite .

```

--------------------------------

### Pagination Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/ogcapif.html

Demonstrates how to paginate through a long list of features using `limit` and `offset` query parameters.

```APIDOC
## GET /collections/{collectionId}/items?limit=10&offset=10

### Description
Retrieves features with pagination applied.

### Endpoint
`/collections/{collectionId}/items.json?offset=10&limit=10`
```

--------------------------------

### PostgreSQL Service File Example

Source: https://docs.qgis.org/3.44/en/docs/user_manual/managing_data_source/opening_data.html

Define connection parameters using a service name in a `.pg_service.conf` file. This allows for reusable connection configurations.

```ini
[water_service]
host=192.168.0.45
port=5433
dbname=gisdb
user=paul
password=paulspass

[wastewater_service]
host=dbserver.com
dbname=water
user=waterpass


```

--------------------------------

### DescribeLayerResponse XML Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wms.html

Example XML response for a DescribeLayer request, showing layer descriptions.

```xml
<DescribeLayerResponse xmlns="http://www.opengis.net/sld" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ows="http://www.opengis.net/ows" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:se="http://www.opengis.net/se" xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.1.0/DescribeLayer.xsd">
    <Version>1.1.0</Version>
    <LayerDescription>
        <owsType>wfs</owsType>
        <se:OnlineResource xlink:href="http://localhost/qgisserver" xlink:type="simple"/>
        <TypeName>
            <se:FeatureTypeName>my_vector_layer</se:FeatureTypeName>
        </TypeName>
    </LayerDescription>
    <LayerDescription>
        <owsType>wcs</owsType>
        <se:OnlineResource xlink:href="http://localhost/qgisserver" xlink:type="simple"/>
        <TypeName>
            <se:FeatureTypeName>my_raster_layer</se:FeatureTypeName>
        </TypeName>
    </LayerDescription>
</DescribeLayerResponse>

```

--------------------------------

### WFS GetFeature response example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wfs.html

This is an example of a WFS FeatureCollection response, showing sorted features.

```xml
<wfs:FeatureCollection xmlns:wfs="http://www.opengis.net/wfs" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" xmlns:ows="http://www.opengis.net/ows" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:qgs="http://www.qgis.org/gml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wfs http://schemas.opengis.net/wfs/1.1.0/wfs.xsd http://www.qgis.org/gml http://192.168.1.15/qgisserver?SERVICE=WFS&VERSION=1.1.0&REQUEST=DescribeFeatureType&TYPENAME=places&OUTPUTFORMAT=text/xml; subtype%3Dgml/3.1.1">
    <gml:boundedBy>
        ...
    </gml:boundedBy>
    <gml:featureMember>
        <qgs:places gml:id="places.90">
            <qgs:name>Zagreb</qgs:name>
        </qgs:places>
    </gml:featureMember>
    <gml:featureMember>
        <qgs:places gml:id="places.113">
            <qgs:name>Yerevan</qgs:name>
        </qgs:places>
    </gml:featureMember>
    <gml:featureMember>
        <qgs:places gml:id="places.111">
            <qgs:name>Yaounde</qgs:name>
        </qgs:places>
    </gml:featureMember>
</wfs:FeatureCollection>

```

--------------------------------

### authorizedLayerAttributes Example

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/server.html

Example of implementing `authorizedLayerAttributes` to hide specific attributes, such as the 'role' attribute, from the user.

```APIDOC
## authorizedLayerAttributes

### Description
Used to limit the visibility of a specific subset of attributes. The `attributes` argument returns the current set of visible attributes.

### Method
`authorizedLayerAttributes(self, layer, attributes)`

### Parameters
* `layer` (`QgsMapLayer`): The layer for which to authorize attributes.
* `attributes` (`list`): A list of currently authorized attribute names.

### Returns
* `list`: A list of attribute names that should be visible.

### Example

```python
def authorizedLayerAttributes(self, layer, attributes):
    return [a for a in attributes if a != "role"]
```
```

--------------------------------

### Layer Type Parameters Example

Source: https://docs.qgis.org/3.44/en/docs/developers_guide/processingtesting.html

Demonstrates specifying vector or raster layers as parameters, including their type and relative path.

```yaml
params:
  PAR: 2
  STR: string
  LAYER:
    type: vector
    name: polys.gml
  OTHER: another param

```

--------------------------------

### Example Action URL Construction

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/vector_properties.html

This example demonstrates how to construct a URL for an action, incorporating map functions and URL encoding. It's useful for passing parameters to web tools or external applications.

```html
http://localhost:8000?/[% url_encode(map('file', 'index.php')) %]
```

--------------------------------

### layerFilterExpression Example

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/server.html

Example of implementing `layerFilterExpression` to restrict results to features where the 'role' attribute is 'user'.

```APIDOC
## layerFilterExpression

### Description
Used to add an Expression to limit the results. For example, to limit to features where the attribute `role` is equal to `user`.

### Method
`layerFilterExpression(self, layer)`

### Parameters
* `layer` (`QgsMapLayer`): The layer for which to apply the filter.

### Returns
* `string`: An expression string.

### Example

```python
def layerFilterExpression(self, layer):
    return "$role = 'user'"
```
```

--------------------------------

### Install Apache and mod_fcgid

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Installs the necessary Apache web server and the mod_fcgid module for FastCGI support.

```bash
apt install apache2 libapache2-mod-fcgid

```

--------------------------------

### QGIS Command Line Options Overview

Source: https://docs.qgis.org/3.44/en/docs/user_manual/introduction/qgis_configuration.html

This is a comprehensive list of QGIS command-line options. Each option controls a specific aspect of QGIS startup or behavior, such as displaying version information, creating snapshots, setting the interface language, or loading projects.

```bash
QGIS is a user friendly Open Source Geographic Information System.
Usage: /usr/bin/qgis.bin [OPTION] [FILE]
  OPTION:
        [-v, --version]     display version information and exit
        [-s, --snapshot filename]   emit snapshot of loaded datasets to given file
        [-w, --width width] width of snapshot to emit
        [-h, --height height]       height of snapshot to emit
        [-l, --lang language]       use language for interface text (changes existing override)
        [-p, --project projectfile] load the given QGIS project
        [-e, --extent xmin,ymin,xmax,ymax]  set initial map extent
        [-n, --nologo]      hide splash screen
        [-V, --noversioncheck]      don't check for new version of QGIS at startup
        [-P, --noplugins]   don't restore plugins on startup
        [-B, --skipbadlayers]     don't prompt for missing layers
        [-C, --nocustomization]     don't apply GUI customization
        [-z, --customizationfile path]      use the given ini file as GUI customization
        [-g, --globalsettingsfile path]     use the given ini file as Global Settings (defaults)
        [-a, --authdbdirectory path] use the given directory for authentication database
        [-f, --code path]   run the given python file on load
        [-F, --py-args arguments]   arguments for python. These arguments will be available for each python execution via 'sys.argv' including the file specified by '--code'. All arguments till '--' are passed to python and ignored by QGIS.
        [-d, --defaultui]   start by resetting user ui settings to default
        [--hide-browser]        hide the browser widget
        [--dxf-export filename.dxf]     emit dxf output of loaded datasets to given file
        [--dxf-extent xmin,ymin,xmax,ymax]      set extent to export to dxf
        [--dxf-symbology-mode none|symbollayer|feature] symbology mode for dxf output
        [--dxf-scale-denom scale]       scale for dxf output
        [--dxf-encoding encoding]       encoding to use for dxf output
        [--dxf-map-theme maptheme]      map theme to use for dxf output
        [--take-screenshots output_path]        take screen shots for the user documentation
        [--screenshots-categories categories]   specify the categories of screenshot to be used (see QgsAppScreenShots::Categories).
        [--profile name]        load a named profile from the user's profiles folder.
        [-S, --profiles-path path]  path to store user profile folders. Will create profiles inside a {path}\profiles folder
        [--version-migration]   force the settings migration from older version if found
        [--openclprogramfolder]         path to the folder containing the sources for OpenCL programs.
        [--help]                this text
        [--]            treat all following arguments as FILEs

  FILE:
    Files specified on the command line can include rasters,
    vectors, and QGIS project files (.qgs and .qgz):
     1. Rasters - supported formats include GeoTiff, DEM
        and others supported by GDAL
     2. Vectors - supported formats include ESRI Shapefiles
        and others supported by OGR and PostgreSQL layers using
        the PostGIS extension

```

--------------------------------

### GetStyles Request Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wms.html

Example URL for a GetStyles request to retrieve layer styles from QGIS Server.

```http
http://localhost/qgisserver?
SERVICE=WMS
&REQUEST=GetStyles
&LAYERS=mylayer1,mylayer2

```

--------------------------------

### Enable and Start QGIS Server Service

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Enables and starts multiple QGIS Server service instances using systemd. This command iterates through four instances.

```bash
for i in 1 2 3 4; do systemctl enable --now qgis-server@$i.service; done

```

--------------------------------

### WMS GetFeatureInfo URL Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wms.html

An example URL demonstrating the structure of a GetFeatureInfo request with various parameters.

```http
http://localhost/qgisserver?
SERVICE=WMS
&VERSION=1.3.0
&REQUEST=GetMap
&MAP=/home/qgis/projects/world.qgs
&LAYERS=mylayer1,mylayer2,mylayer3
&CRS=EPSG:4326
&WIDTH=400
&HEIGHT=400
&INFO_FORMAT=text/xml
&TRANSPARENT=TRUE
&QUERY_LAYERS=mylayer1
&FEATURE_COUNT=3
&I=250
&J=250

```

--------------------------------

### DescribeFeatureType Response Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wfs.html

An example XML response from a DescribeFeatureType request, detailing the schema of the 'countries' layer.

```xml
<schema xmlns:ogc="http://www.opengis.net/ogc" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:qgs="http://www.qgis.org/gml" xmlns:gml="http://www.opengis.net/gml" targetNamespace="http://www.qgis.org/gml" version="1.0" elementFormDefault="qualified">
  <import schemaLocation="http://schemas.opengis.net/gml/3.1.1/base/gml.xsd" namespace="http://www.opengis.net/gml"/>
  <element type="qgs:countriesType" substitutionGroup="gml:_Feature" name="countries"/>
  <complexType name="countriesType">
    <complexContent>
      <extension base="gml:AbstractFeatureType">
        <sequence>
          <element minOccurs="0" type="gml:MultiPolygonPropertyType" maxOccurs="1" name="geometry"/>
          <element type="long" name="id"/>
          <element nillable="true" type="string" name="name"/>
        </sequence>
      </extension>
    </complexContent>
  </complexType>
</schema>

```

--------------------------------

### Test HelloWorld Plugin

Source: https://docs.qgis.org/3.44/en/docs/server_manual/plugins.html

Use this command to test the HelloWorld plugin on the QGIS Server. It sends a SERVICE=HELLO request and expects 'HelloServer!' as a response.

```bash
wget -q -O - "http://localhost/cgi-bin/qgis_mapserv.fcgi?SERVICE=HELLO"
 HelloServer!

```

--------------------------------

### WMTS GetCapabilities Request Example

Source: https://docs.qgis.org/3.44/en/docs/server_manual/services/wmts.html

Example URL for requesting WMTS capabilities. Requires specifying the service, request type, and the QGIS project file.

```http
http://localhost/?
```

```http
SERVICE=WMTS
&REQUEST=GetCapabilities
&MAP=/home/qgis/projects/world.qgs

```