Normas de Codificação QGIS

Estas normas devem ser seguidas por todos os programadores de QGIS



Class in QGIS begin with Qgs and are formed using camel case.


  • QgsPoint

  • QgsMapCanvas

  • QgsRasterLayer


Class member names begin with a lower case m and are formed using mixed case.

  • mMapCanvas

  • mCurrentExtent

All class members should be private. Public class members are STRONGLY discouraged. Protected members should be avoided when the member may need to be accessed from Python subclasses, since protected members cannot be used from the Python bindings.

Mutable static class member names should begin with a lower case s, but constant static class member names should be all caps:

  • sRefCounter


Accessor Functions

Class member values should be obtained through accesssor functions. The function should be named without a get prefix. Accessor functions for the two private members above would be:

  • mapCanvas()

  • currentExtent()

Ensure that accessors are correctly marked with const. Where appropriate, this may require that cached value type member variables are marked with mutable.


Os nomes das funções começam com uma letra minúscula e são formados usando um misto de letras minúsculas e maiúsculas. O nome da função deve transmitir algo sobre o propósito da função.

  • updateMapExtent()

  • setUserOptions()

Para a consistência entre o QGIS API e o Qt API existente, as abreviaturas devem ser evitadas. Por exemplos: `` setDestinationSize`` em vez de `` setDestSize``, `` setMaximumValue`` em vez de `` setMaxVal``.

Acronyms should also be camel cased for consistency. E.g. setXml instead of setXML.

Argumentos da função

Function arguments should use descriptive names. Do not use single letter arguments (e.g. setColor( const QColor& color ) instead of setColor( const QColor& c )).

Pay careful attention to when arguments should be passed by reference. Unless argument objects are small and trivially copied (such as QPoint objects), they should be passed by const reference. For consistency with the Qt API, even implicitly shared objects are passed by const reference (e.g. setTitle( const QString& title ) instead of setTitle( QString title ).

Function Return Values

Return small and trivially copied objects as values. Larger objects should be returned by const reference. The one exception to this is implicitly shared objects, which are always returned by value. Return QObject or subclassed objects as pointers.

  • int maximumValue() const

  • const LayerSet& layers() const

  • QString title() const (QString is implicitly shared)

  • QList< QgsMapLayer* > layers() const (QList is implicitly shared)

  • QgsVectorLayer *layer() const; (QgsVectorLayer inherits QObject)

  • QgsAbstractGeometry *geometry() const; (QgsAbstractGeometry is abstract and will probably need to be casted)

API Documentation

It is required to write API documentation for every class, method, enum and other code that is available in the public API.

QGIS uses Doxygen for documentation. Write descriptive and meaningful comments that give a reader information about what to expect, what happens in edge cases and give hints about other interfaces he could be looking for, best practices and code samples.


Method descriptions should be written in a descriptive form, using the 3rd person. Methods require a \since tag that defines when they have been introduced. You should add additional \since tags for important changes that were introduced later on.

 * Cleans the laundry by using water and fast rotation.
 * It will use the provided \a detergent during the washing programme.
 * \returns True if everything was successful. If false is returned, use
 * \link error() \endlink to get more information.
 * \note Make sure to manually call dry() after this method.
 * \since QGIS 3.0
 * \see dry()

Members Variables

Member variables should normally be in the private section and made available via getters and setters. One exception to this is for data containers like for error reporting. In such cases do not prefix the member with an m.

 * \ingroup core
 * Represents points on the way along the journey to a destination.
 * \since QGIS 2.20
class QgsWaypoint
   * Holds information about results of an operation on a QgsWaypoint.
   * \since QGIS 3.0
  struct OperationResult
    QgsWaypoint::ResultCode resultCode; //!< Indicates if the operation completed successfully.
    QString message; //!< A human readable localized error message. Only set if the resultCode is not QgsWaypoint::Success.
    QVariant result; //!< The result of the operation. The content depends on the method that returned it. \since QGIS 3.2

Qt Designer

Classes geradas

QGIS classes that are generated from Qt Designer (ui) files should have a Base suffix. This identifies the class as a generated base class.


  • QgsPluginManagerBase

  • QgsUserOptionsBase


Todos os diálogos devem implementar dicas de ajuda para todos os ícones das barras de ferramentas e outros componentes relevantes. As dicas de ajuda são um grande auxílio para utilizadores novos ou experientes conhecerem as funcionalidades.

Certifique que a ordem das abas para os widgets é atualizada toda vez que a composição de uma janela mudar.

Ficheiros C++


a implementação de C++ e os cabeçalhos dos ficheiros devem ter uma extensão .cpp e .h, respetivamente. O nome do arquivo deve ser todo em minúsculas e, no caso das classes, corresponder ao nome da classe.

Example: Class QgsFeatureAttribute source files are qgsfeatureattribute.cpp and qgsfeatureattribute.h


In case it is not clear from the statement above, for a filename to match a class name it implicitly means that each class should be declared and implemented in its own file. This makes it much easier for newcomers to identify where the code is relating to specific class.

Cabeçalho padrão e licença

Cada arquivo de código fonte deve conter um cabeçalho de acordo com o seguinte exemplo:

  qgsfield.cpp - Describes a field in a layer or table
  Date : 01-Jan-2004
  Copyright: (C) 2004 by Gary E.Sherman
  Email: sherman at
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.


Há um template para o Qt Creator no git. Para use-lo, copie-no do arquivo doc/qt_creator_license_template para uma pasta local, ajuste o endereço de e-mail e - caso necessário - o nome e configure o QtCreator para usá-lo: menuselection:Tools –> Options –> C++ –> File Naming.

Nome das variáveis

Os nomes de variáveis locais começam com uma letra minúscula e são formados usando um misto de letras minúsculas e maiúsculas. Não usar prefixos como my ou the.


  • mapCanvas

  • mapCanvas

Enumerated Types

Enumerated types should be named in CamelCase with a leading capital e.g.:

enum UnitType

Do not use generic type names that will conflict with other types. e.g. use UnkownUnit rather than Unknown

Constantes Globais & Macros

Constantes globais e macros devem ser escritas em caixa alta e linha (_) por exemplo.:

const long GEOCRS_ID = 3344;


Comments to class methods should use a third person indicative style instead of the imperative style:

 * Creates a new QgsFeatureFilterModel, optionally specifying a \a parent.
explicit QgsFeatureFilterModel( QObject *parent = nullptr );
~QgsFeatureFilterModel() override;

Sinais e Slots da Qt

All signal/slot connects should be made using the «new style» connects available in Qt5. Futher information on this requirement is available in QEP #77.

Avoid use of Qt auto connect slots (i.e. those named void on_mSpinBox_valueChanged). Auto connect slots are fragile and prone to breakage without warning if dialogs are refactored.


Qualquer editor de texto/ambiente de desenvolvimento (IDE) pode ser usado para editar códigos do QGIS, contanto que os seguintes requisitos sejam atendidos.


Set your editor to emulate tabs with spaces. Tab spacing should be set to 2 spaces.


In vim this is done with set expandtab ts=2


Source code should be indented to improve readability. There is a scripts/ that looks up the changed files and reindents them using astyle. This should be run before committing. You can also use scripts/ to indent individual files.

As newer versions of astyle indent differently than the version used to do a complete reindentation of the source, the script uses an old astyle version, that we include in our repository (enable WITH_ASTYLE in cmake to include it in the build).


Braces should start on the line following the expression:

if( foo == 1 )
  // do stuff
  // do something else

Compatibilidade da Interface de Programação da Aplicação

There is API documentation for C++.

We try to keep the API stable and backwards compatible. Cleanups to the API should be done in a manner similar to the Qt sourcecode e.g.

class Foo
     * This method will be deprecated, you are encouraged to use
     * doSomethingBetter() rather.
     * \deprecated use doSomethingBetter()
    Q_DECL_DEPRECATED bool doSomething();

     * Does something a better way.
     * \note added in 1.1
    bool doSomethingBetter();

     * This signal will be deprecated, you are encouraged to
     * connect to somethingHappenedBetter() rather.
     * \deprecated use somethingHappenedBetter()
#ifndef Q_MOC_RUN
    bool somethingHappened();

     * Something happened
     * \note added in 1.1
    bool somethingHappenedBetter();

SIP Bindings

Some of the SIP files are automatically generated using a dedicated script.

Header pre-processing

All the information to properly build the SIP file must be found in the C++ header file. Some macros are available for such definition:

  • Use #ifdef SIP_RUN to generate code only in SIP files or #ifndef SIP_RUN for C++ code only. #else statements are handled in both cases.

  • Use SIP_SKIP to discard a line

  • The following annotations are handled:

    • SIP_FACTORY: /Factory/

    • SIP_OUT: /Out/

    • SIP_INOUT: /In,Out/

    • SIP_TRANSFER: /Transfer/

    • SIP_PYNAME(name): /PyName=name/

    • SIP_KEEPREFERENCE: /KeepReference/

    • SIP_TRANSFERTHIS: /TransferThis/

    • SIP_TRANSFERBACK: /TransferBack/

  • private sections are not displayed, except if you use a #ifdef SIP_RUN statement in this block.

  • SIP_PYDEFAULTVALUE(value) can be used to define an alternative default value of the python method. If the default value contains a comma ,, the value should be surrounded by single quotes '

  • SIP_PYTYPE(type) can be used to define an alternative type for an argument of the python method. If the type contains a comma ,, the type should be surrounded by single quotes '

A demo file can be found in tests/scripts/sipifyheader.h.

Generating the SIP file

The SIP file can be generated using a dedicated script. For instance:

scripts/ src/core/qgsvectorlayer.h > python/core/qgsvectorlayer.sip

As soon as a SIP file is added to one of the source file (python/core/core.sip, python/gui/gui.sip or python/analysis/analysis.sip), it will be considered as generated automatically. A test on Travis will ensure that this file is up to date with its corresponding header.

Older files for which the automatic creation is not enabled yet are listed in python/auto_sip.blacklist.

Improving sipify script

If some improvements are required for sipify script, please add the missing bits to the demo file tests/scripts/sipifyheader.h and create the expected header tests/scripts/ This will also be automatically tested on Travis as a unit test of the script itself.

Coding Style

Here are described some programming hints and tips that will hopefully reduce errors, development time and maintenance.

Where-ever Possible Generalize Code

If you are cut-n-pasting code, or otherwise writing the same thing more than once, consider consolidating the code into a single function.

Isto irá:

  • permitir que as alterações sejam feitas num só local em vez de em vários lugares

  • help prevent code bloat

  • make it more difficult for multiple copies to evolve differences over time, thus making it harder to understand and maintain for others

Prefer Having Constants First in Predicates

Prefer to put constants first in predicates.

0 == value em vez de value == 0

This will help prevent programmers from accidentally using = when they meant to use ==, which can introduce very subtle logic bugs. The compiler will generate an error if you accidentally use = instead of == for comparisons since constants inherently cannot be assigned values.

Whitespace Can Be Your Friend

Adicionar espaços entre operadores, declarações e funções torna mais fácil para os humanos analisar o código.

O que é mais fácil de ler, isto:

if (!a&&b)

ou isto:

if ( ! a && b )


scripts/ will take care of this.

Colocar os comandos em linhas separadas

When reading code it’s easy to miss commands, if they are not at the beginning of the line. When quickly reading through code, it’s common to skip lines if they don’t look like what you are looking for in the first few characters. It’s also common to expect a command after a conditional like if.


if (foo) bar();

baz(); bar();

It’s very easy to miss part of what the flow of control. Instead use

if (foo)


Indent access modifiers

Access modifiers structure a class into sections of public API, protected API and private API. Access modifiers themselves group the code into this structure. Indent the access modifier and declarations.

class QgsStructure
     * Constructor
     explicit QgsStructure();

Book recommendations

You should also really read this article from Qt Quarterly on designing Qt style (APIs)

Créditos de contribuições

Os contribuidores de novas funções são encorajados a informar as pessoas sobre sua contribuição: