Using gettext in compiled Qt ui files with PySide

This recipe is based on the PyQt recipe found here. This is just the PySide port of it.

In some cases you might find yourself in the situation of wanting to use gettext in a PySide project in which you have .ui files generated using QtDesigner.

For those kind of situations is a good idea to extend the PySide compiler.

The following example shows how to do so in a distutils command.

class CompileUI(Command):
    """Build PyQt (.ui) files and resources."""

    description = "build PySide Qt GUIs (.ui)."

    user_options = [
        ('input-dir=', 'i', 'Input directory path where to search \'.ui\' files.'),
        ('output-dir=', 'o', 'Output directory path for the generated UI files.'),
        ('indent=', 'I', 'set indent width to N spaces, tab if N is 0 (default: 4)'),
        ('i18n-module', 'm', 'specify from which module the \'_()\' function '
                            'should be imported. Ex: mymodule.i18n'),
        ('ui-execute', 'x', 'generate extra code to test and display the class'),
        ('from-imports', 'F', 'generate imports relative to \'.\'')
    ]
    boolean_options = ['from-imports', 'ui-execute']

    def initialize_options(self):
        self.input_dir = None
        self.output_dir = None
        self.indent = 4
        self.i18n_module = None
        self.ui_execute = False
        self.from_imports = False

    def finalize_options(self):
        if self.input_dir is None:
            raise DistutilsOptionError("You need to specify the input "
                                      "directory from where to search for the "
                                      "'.ui' files")
        if self.output_dir is None:
            raise DistutilsOptionError("You need to specify the output "
                                      "directory for the generated files")
        if self.i18n_module is None:
            raise DistutilsOptionError("You need to specify from which module "
                                      "the '_()' function should be imported "
                                      "from. Example: mymodule.i18n")

    def run(self):
        for filename in os.listdir(self.input_dir):
            fpath = os.path.join(self.input_dir, filename)
            if not os.path.isfile(fpath):
                continue
            elif not filename.endswith('.ui'):
                continue
            self.compile_ui(fpath)


    def compile_ui(self, ui_file, py_file=None):
        """Compile the .ui files to python modules."""
        self._wrapuic(i18n_module=self.i18n_module)
        if py_file is None:
            py_file = os.path.join(
                self.output_dir,
                os.path.basename(ui_file).replace('.ui', '_ui.py')
            )

        fi = open(ui_file, 'r')
        fo = open(py_file, 'wt')
        try:
            from pysideuic import compileUi
            compileUi(fi, fo, execute=self.ui_execute, indent=self.indent,
                      from_imports=self.from_imports)
            log.info("Compiled %s into %s", ui_file, py_file)
        except ImportError:
            log.warn("You need to have pyside-tools installed in order to "
                    "compile .ui files.")
        except Exception, err:
            log.warn("Failed to generate %r from %r: %s", py_file, ui_file, err)
            if not os.path.exists(py_file) or not not file(py_file).read():
                raise SystemExit(1)
            return
        finally:
            fi.close()
            fo.close()

    _wrappeduic = False
    @classmethod
    def _wrapuic(cls, i18n_module=None):
        """Wrap uic to use gettext's _() in place of tr()"""
        if cls._wrappeduic:
            return

        try:
            from pysideuic.Compiler import compiler, qtproxies, indenter

            class _UICompiler(compiler.UICompiler):
                """Specialised compiler for qt .ui files."""
                def createToplevelWidget(self, classname, widgetname):
                    o = indenter.getIndenter()
                    o.level = 0
                    o.write('from %s import _' % i18n_module)
                    return super(_UICompiler, self).createToplevelWidget(
                        classname, widgetname
                    )
            compiler.UICompiler = _UICompiler

            class _i18n_string(qtproxies.i18n_string):
                """Provide a translated text."""
                def __str__(self):
                    return "_('%s')" % self.string.encode('string-escape')

            qtproxies.i18n_string = _i18n_string

            cls._wrappeduic = True
        except ImportError:
            log.warn("You need to have pyside-tools installed in order to "
                    "compile .ui files.")

And there you have it!