QGIS Plugin Builder

Concepts

Plugin Builder provides you a working template from which you can create your own plugin.

The steps to using Plugin Builder are fairly simple:

  1. Open the Plugin Builder from within QGIS
  2. Fill out the required information
  3. Click OK
  4. Designate where to store your new plugin
  5. Compile your resource file
  6. Install the plugin
  7. Test it

Running Plugin Builder

When you run Plugin Builder you will see a dialog with text fields. Each text field contains a hint inside it in greyed out text that will disappear when you start typing text into it. There is also a tooltip containing help information that will appear when you hover over each text field:

_images/pluginbuilder.png

The descriptions give you a hint about what is required for each field. The following sections describe the required and optional parameters in greater detail.

Required Parameters

Class name

This is the name that will be used to create the Python class for your plugin. The name should be in CamelCase with no spaces. Plugin Builder will accept an all lower case class name but this should be avoided since it isn’t in line with Python coding style. Examples of valid class names are:

  • MyPlugin
  • PluginBuilder
  • ScriptRunner
Module name

This is the name that will be used to create the Python module ( file) for your plugin. The name should be in lowercase with words separated using underscores. Plugin Builder will accept any case module name but this should be avoided since it isn’t in line with Python coding style. Examples of valid module names are:

  • detect_features
  • detector
Plugin name

This is a title for your plugin and will be displayed in the QGIS plugin manager and the plugin installer. It will also be used as the menu name that appears in the QGIS Plugin menu. You can use the Class name, or make it more readable. Some examples:

  • My Plugin
  • Plugin Builder
  • ScriptRunner
Description
This is a one line description of the plugin’s function and is displayed in both the Plugin Manager and Plugin Installer. Keep it short yet descriptive so the purpose of the plugin can be easily determined.
Version number
This is the version number of your plugin. Plugin Builder suggests 0.1, but you can start with any number. The Plugin Installer uses the version number to identify which plugins you have installed are upgradeable so it is important to increment it as you release new versions.
Minimum QGIS version
This is the minimum version of QGIS required for your plugin to work. If your plugin uses features only present in a newer version, be sure to set this field accordingly to prevent problems for those running older versions. Version 2.0 of Plugin Builder defaults this field to 2.0.
Text for the menu item

This is the text that will appear in the menu. In the example below, the plugin name is Frog Pond and the text for the menu item is displayed to the right of it:

_images/plugin_menu.png

In general you shouldn’t use the same text for the plugin name and the menu item; if you do your menu will look like this:

_images/redundant_menu.png
Author/Company
Put your name or company name here—this information is used in writing the copyright statement in the source files of your plugin, as well as being displayed in the Plugin Installer and on the QGIS plugin repository.
Email address
Put an address where users of your plugin can contact you. This information is written to the copyright header of your source files and also displayed on the QGIS plugin repository listing for your plugin.
Menu

Choose an appropriate location for your plugin’s menu based on its main functionality. This will place your menu under one of the following main menus:

  • Plugins
  • Database
  • Raster
  • Vector
  • Web

If none of the specific categories apply (Database, Raster, Vector, Web), choose Plugins. Your choice is also written to the category field in metadata.txt.

Results

When you click OK, Plugin Builder creates your new plugin for you and displays the results:

_images/plugin_results.png

The results dialog tells you where your plugin was saved, the location of your QGIS plugin directory, and what to do next. This same information is contained in the README.html and README.txt files in your generated plugin directory.

Compiling the resource file

After you generate your plugin the resource file needs to be compiled before it is functional in QGIS.

The resource file contains definitions of media used in your plugin. Upon generation, this contains one entry for icon.png, the icon file for the plugin.

To compile the resource file into Python code, use the pyrcc4 utility that comes as part of your PyQt installation:

pyrcc4 -o resources.py resources.qrc

Once the resource file is compiled, the generated plugin can be loaded in QGIS.

Deploying

To deploy your new plugin during development, you have two choices:

  1. Copy the entire plugin directory to your QGIS plugins directory
  2. Use the QGIS_PLUGINPATH environment variable to point to the directory where your development plugin(s) are located

The Copy Method

To deploy in this fashion, simply copy your plugin directory to the location of your QGIS plugins. By platform, this location is:

  • Linux: .qgis2/python/plugins in your home directory, typically found at

    /home/gsherman/.qgis2/python/plugins

  • Mac OS X: .qgis2/python/plugins in your home directory, typically

    /Users/gsherman/.qgis2/python/plugins

  • Windows: %HOMEPATH%\.qgis2\python\plugins, by default,
    • C:\Users\gsherman\.qgis2\python\plugins on versions later than XP,
    • C:\Documents and Settings\gsherman\.qgis2\python\plugins on XP

Since each plugin must be contained in its own subdirectory in .qgis2/python/plugins, make sure you copy the directory, not the files in the directory.

If your operating system supports gmake (GNU make), you can use the deploy target of the Makefile in your plugin directory to deploy directly to .qgis2/python/plugins:

make deploy

The Environment Variable Method

Using the QGIS_PLUGINPATH environment variable you can tell QGIS to look in an additional location for plugins. This can be handy for development, allowing you to test your plugin without copying it to .qgis2/python/plugins.

To use this method, set the QGIS_PLUGINPATH environment variable to point to your development directory before starting QGIS. When QGIS starts up, all the directories in QGIS_PLUGINPATH will be searched and those containing valid plugins will be added to the Plugin Manager.

Testing

With your new plugin deployed, start up QGIS, open the Plugin Manager, and enable it. Then click on the tool or the menu item for the plugin to run it. If all is well, you should see something similar to this:

_images/plugin_test.png

If the plugin throws an error make sure you have compiled the resource file before deploying and testing.

Once the generated plugin is working it’s your turn to customize the user interface and add the needed code to make it do something useful.

Using the Makefile

The make file can be used to compile and deploy your plugin, assuming you are using an operating environment that supports GNU make. It also provides a number of other actions to aid in plugin development.

The following targets are supported

clean:Delete the compiled UI and resource files
compile:Compile the resource and UI files. This is the default target.
dclean:Same as derase but also removes any .svn entries
deploy:Deploy the plugin
derase:Remove the deployed plugin
doc:Build the documentation using Sphinx
package:Package the plugin using git archive
transclean:Delete all .qm (translation) files
transcompile:Compile translation files into .qm format
transup:Update the .ts (translation) files
upload:Upload the plugin to the QGIS repository
zip:Deploy the plugin and create a zip file suitable for uploading to the QGIS repository
test:Run unit tests and produce a coverage report.
pep8:Run python PEP8 check and produce a report.
pylint:Run python pylint check and produce a report listing any violations.

Using pb_tool

pb_tool is a Python command line tool for compiling and deploying QGIS plugins on Linux, Mac OS X, and Windows.

Features

pb_tool provides commands to aid in developing, testing, and deploying a QGIS Python Plugin:

  • Compile resource and UI files
  • Deploy to your plugins directory for testing in QGIS
  • Create a zip file for upload to a repository
  • Clean both compiled and deployed files
  • Build and clean documentation
  • Build translation files
  • Works on Windows, OS X, and Linux

Installation

You can install the tool using pip:

pip install pb_tool

To upgrade to the latest version, use:

pip install –upgrade pb_tool

You can also install using easy_install:

easy_install pb_tool

Usage

pb_tool requires a configuration file in order to do anything. Plugin Builder creates a working configuration file for you. By default, pb_tool assumes a file name of pb_tool.cfg, although you can specify a different one using the --config options in most commands.

To display the available commands, just enter pb_tool on the command line:

$ pb_tool
Usage: pb_tool [OPTIONS] COMMAND [ARGS]...

  Simple Python tool to compile and deploy a QGIS plugin. For help on a
  command use --help after the command: pb_tool deploy --help.

  pb_tool requires a configuration file (default: pb_tool.cfg) that declares
  the files and resources used in your plugin. Plugin Builder 2.6.0 creates
  a config file when you generate a new plugin template.

  See http://g-sherman.github.io/plugin_build_tool for for an example config
  file. You can also use the create command to generate a best-guess config
  file for an existing project, then tweak as needed.

Options:
  --help  Show this message and exit.

Commands:
  clean       Remove compiled resource and ui files
  clean_docs  Remove the built HTML help files from the...
  compile     Compile the resource and ui files
  create      Create a config file based on source files in...
  dclean      Remove the deployed plugin from the...
  deploy      Deploy the plugin to QGIS plugin directory...
  doc         Build HTML version of the help files using...
  list        List the contents of the configuration file
  translate   Build translations using lrelease.
  validate    Check the pb_tool.cfg file for mandatory...
  version     Return the version of pb_tool and exit
  zip         Package the plugin into a zip file suitable...

For more information on using pb_tool, see: http://g-sherman.github.io/plugin_build_tool

For help on getting started using pb_tool with Plugin Builder, see: http://spatialgalaxy.com/2014/10/09/qgis-plugin-development-with-pb-tool

Documenting your Plugin

Plugin Builder creates a Sphinx project for you in the help subdirectory of your plugin. To build the documentation you will need to install Sphinx using pip or easy_install. Once installed, you can build the documentation using make doc or change to the help subdirectory and use make html (this works on any platform).

Sphinx supports building other formats, including latex, text, qthelp, and epub.

Of course you need to actually write something to document your plugin by editing help/source/index.rst.

Once your documentation is complete you can distribute it with your plugin, as well as publishing it on a website. You can also add a Help button to the button box group on the dialog and connect it to a method to show your help file in the user’s default web browser. See the code in pluginbuilder.py for an example.

For an example of writing your documentation using Sphinx, you can view the source of this document.

The Repository

When your plugin is ready to be shared with the QGIS community, upload it to the QGIS plugin repository at http://plugins.qgis.org/plugins. Make sure to package it properly in zip format and test the zip before adding it to the repository.

When you add it to the repository, your plugin will show up in the Plugin Installer in QGIS, making it available for download and install by the community.