Generator Overview

The following diagram summarizes Shiboken’s role in the Qt for Python project.

_images/qtforpython-underthehood.png

An XML typesystem file is used to specify the types to be exposed to Python and to apply modifications to properly represent and manipulate the types in the Python World. For example, you can remove and add methods to certain types, and also modify the arguments of each method. These actions are inevitable to properly handle the data structures or types.

The final outcome of this process is a set of wrappers written in CPython, which can be used as a module in your Python code.

In a few words, the Generator is a utility that parses a collection of header and typesystem files, generating other files (code, documentation, etc.) as result.

Creating new bindings

_images/bindinggen-development.png

Creating new bindings

Each module of the generator system has an specific role.

  1. Provide enough data about the classes and functions.

  2. Generate valid code, with modifications from typesystems and injected codes.

  3. Modify the API to expose the objects in a way that fits you target language best.

  4. Insert customizations where handwritten code is needed.

_images/shibokenqtarch.png

Runtime architecture

The newly created binding will run on top of Shiboken which takes care of interfacing Python and the underlying C++ library.

Handwritten inputs

Creating new bindings involves creating several pieces of “code”: the header, the typesystem and, in most cases, the injected code.

header

A header with #include directives listing all the headers of the desired classes. This header is not referenced by the generated code. Alternatively, it is possible to pass a list of the headers of the desired classes directly on the command line. In this case, the command line option --use-global-header should be passed as well to prevent the headers from being suppressed in the generated code.

typesystem

XML files that provides the developer with a tool to customize the way that the generators will see the classes and functions. For example, functions can be renamed, have its signature changed and many other actions.

inject code

allows the developer to insert handwritten code where the generated code is not suitable or needs some customization.

Command line options

Usage

shiboken [options] header-file(s) typesystem-file

Options

--disable-verbose-error-messages

Disable verbose error messages. Turn the CPython code hard to debug but saves a few kilobytes in the generated binding.

--enable-parent-ctor-heuristic

This flag enable an useful heuristic which can save a lot of work related to object ownership when writing the typesystem. For more info, check Parentship heuristics.

--enable-pyside-extensions

Enable pyside extensions like support for signal/slots. Use this if you are creating a binding based on PySide.

--enable-return-value-heuristic

Enable heuristics to detect parent relationship on return values. For more info, check Return value heuristics.

--avoid-protected-hack

Avoid the use of the ‘#define protected public’ hack.

--use-isnull-as-nb_nonzero

If a class have an isNull() const method, it will be used to compute the value of boolean casts

--api-version=<version>

Specify the supported api version used to generate the bindings.

--documentation-only

Do not generate any code, just the documentation.

--drop-type-entries="<TypeEntry0>[;TypeEntry1;...]"

Semicolon separated list of type system entries (classes, namespaces, global functions and enums) to be dropped from generation. Values are fully qualified Python type names (‘Module.Class’), but the module can be omitted (‘Class’).

--use-global-header

Use the global headers passed on the command line in generated code.

--generation-set

Generator set to be used (e.g. qtdoc).

--skip-deprecated

Skip deprecated functions.

--diff

Print a diff of wrapper files.

--dryrun

Dry run, do not generate wrapper files.

--project-file=<file>

Text file containing a description of the binding project. Replaces and overrides command line arguments.

--clang-option=<option>

Option to be passed to clang

--clang-options=<option1>[,<option2>,...]>

Options to be passed to clang. When ‘-‘ is passed as the first option in the list, none of the options built into shiboken will be added, allowing for a complete replacement.

-I<path>, --include-paths=<path>[:<path>:...]

Include paths used by the C++ parser.

… _system-include-paths:

-isystem<path>, --system-include-paths=<path>[:<path>:...]

System include paths used by the C++ parser

-F<path>, --framework-include-paths=<path>[:<path>:...]

Framework include paths used by the C++ parser

--language-level=, -std=<level>

C++ Language level (c++11..c++17, default=c++14)

-T<path>, --typesystem-paths=<path>[:<path>:...]

Paths used when searching for type system files.

--output-directory=[dir]

The directory where the generated files will be written.

--license-file=[license-file]

File used for copyright headers of generated files.

--no-suppress-warnings

Show all warnings.

--silent

Avoid printing any message.

--debug-level=[sparse|medium|full]

Set the debug level.

--help

Display this help and exit.

--version

Output version information and exit.

QtDocGenerator Options

--doc-parser=<parser>

The documentation parser used to interpret the documentation input files (qdoc|doxygen).

--documentation-code-snippets-dir=<dir>

Directory used to search code snippets used by the documentation.

--documentation-data-dir=<dir>

Directory with XML files generated by documentation tool.

--documentation-extra-sections-dir=<dir>

Directory used to search for extra documentation sections.

--library-source-dir=<dir>

Directory where library source code is located.

--additional-documentation=<file>

List of additional XML files to be converted to .rst files (for example, tutorials).

Binding Project File

Instead of directing the Generator behavior via command line, the binding developer can write a text project file describing the same information, and avoid the hassle of a long stream of command line arguments.

The project file structure

Here follows a comprehensive example of a generator project file.

[generator-project]
generator-set = path/to/generator/CHOICE_GENERATOR
header-file = DIR/global.h" />
typesystem-file = DIR/typesystem_for_your_binding.xml
output-directory location="OUTPUTDIR" />
include-path = path/to/library/being/wrapped/headers/1
include-path = path/to/library/being/wrapped/headers/2
typesystem-path = path/to/directory/containing/type/system/files/1
typesystem-path = path/to/directory/containing/type/system/files/2
enable-parent-ctor-heuristic

Project file tags

The generator project file tags are in direct relation to the command line arguments. All of the current command line options provided by Shiboken were already seen on the The project file structure, for new command line options provided by additional generator modules (e.g.: qtdoc, Shiboken) could also be used in the generator project file following simple conversion rules.

For tags without options, just write as an empty tag without any attributes. Example:

--BOOLEAN-ARGUMENT

becomes

BOOLEAN-ARGUMENT

and

--VALUE-ARGUMENT=VALUE

becomes

VALUE-ARGUMENT = VALUE