QtSASS: Compile SCSS files to Qt stylesheets

Copyright © 2015 Yann Lanthony

Copyright © 2017–2018 Spyder Project Contributors

Overview

SASS brings countless amazing features to CSS. Besides being used in web development, CSS is also the way to stylize Qt-based desktop applications. However, Qt's CSS has a few variations that prevent the direct use of SASS compiler.

The purpose of this tool is to fill the gap between SASS and Qt-CSS by handling those variations.

Qt's CSS specificities

The goal of QtSASS is to be able to generate a Qt-CSS stylesheet based on a 100% valid SASS file. This is how it deals with Qt's specifics and how you should modify your CSS stylesheet to use QtSASS.

"!" in selectors

Qt allows to define the style of a widget according to its states, like this:

QLineEdit:enabled {
...
}

However, a "not" state is problematic because it introduces an exclamation mark in the selector's name, which is not valid SASS/CSS:

QLineEdit:!editable {
...
}

QtSASS allows "!" in selectors' names; the SASS file is preprocessed and any occurence of :! is replaced by :_qnot_ (for "Qt not"). However, using this feature prevents from having a 100% valid SASS file, so this support of ! might change in the future. This can be replaced by the direct use of the _qnot_ keyword in your SASS file:

QLineEdit:_qnot_editable { /* will generate QLineEdit:!editable { */
...
}

qlineargradient

The qlineargradient function also has a non-valid CSS syntax.

qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1, stop: 0.1 blue, stop: 0.8 green)

To support qlineargradient QtSASS provides a preprocessor and a SASS implementation of the qlineargradient function. The above QSS syntax will be replaced with the following:

qlineargradient(0, 0, 0, 1, (0.1 blue, 0.8 green))

You may also use this syntax directly in your QtSASS.

qlineargradient(0, 0, 0, 1, (0.1 blue, 0.8 green))
# the stops parameter is a list, so you can also use variables:
$stops = 0.1 blue, 0.8 green
qlineargradient(0, 0, 0, 0, $stops)

qrgba

Qt's rgba:

rgba(255, 128, 128, 50%)

is replaced by CSS rgba:

rgba(255, 128, 128, 0.5)

Executable usage

To compile your SASS stylesheet to a Qt compliant CSS file:

# If -o is omitted, output will be printed to console
qtsass style.scss -o style.css

To use the watch mode and get your stylesheet auto recompiled on each file save:

# If -o is omitted, output will be print to console
qtsass style.scss -o style.css -w

To compile a directory containing SASS stylesheets to Qt compliant CSS files:

qtsass ./static/scss -o ./static/css

You can also use watch mode to watch the entire directory for changes.

qtsass ./static/scss -o ./static/css -w

Set the Environment Variable QTSASS_DEBUG to 1 or pass the --debug flag to enable logging.

qtsass ./static/scss -o ./static/css --debug

API methods

compile(string, **kwargs)

Conform and Compile QtSASS source code to CSS.

This function conforms QtSASS to valid SCSS before passing it to sass.compile. Any keyword arguments you provide will be combined with qtsass's default keyword arguments and passed to sass.compile.

Examples:

>>> import qtsass
>>> qtsass.compile("QWidget {background: rgb(0, 0, 0);}")
QWidget {background:black;}

Arguments:

• string: QtSASS source code to conform and compile.
• kwargs: Keyword arguments to pass to sass.compile

Returns:

• Qt compliant CSS string

compile_filename(input_file, dest_file, **kwargs):

Compile and save QtSASS file as Qt compliant CSS.

Examples:

>>> import qtsass
>>> qtsass.compile_filename('dummy.scss', 'dummy.css')

Arguments:

• input_file: Path to QtSass file.
• dest_file: Path to destination Qt compliant CSS file.
• kwargs: Keyword arguments to pass to sass.compile

compile_filename(input_file, output_file, **kwargs):

Compile and save QtSASS file as Qt compliant CSS.

Examples:

>>> import qtsass
>>> qtsass.compile_filename('dummy.scss', 'dummy.css')

Arguments:

• input_file: Path to QtSass file.
• output_file: Path to write Qt compliant CSS.
• kwargs: Keyword arguments to pass to sass.compile

compile_dirname(input_dir, output_dir, **kwargs):

Compiles QtSASS files in a directory including subdirectories.

>>> import qtsass
>>> qtsass.compile_dirname("./scss", "./css")

Arguments:

• input_dir: Path to directory containing QtSass files.
• output_dir: Directory to write compiled Qt compliant CSS files to.
• kwargs: Keyword arguments to pass to sass.compile

enable_logging(level=None, handler=None):

Enable logging for qtsass.

Sets the qtsass logger's level to: 1. the provided logging level 2. logging.DEBUG if the QTSASS_DEBUG envvar is a True value 3. logging.WARNING

>>> import logging
>>> import qtsass
>>> handler = logging.StreamHandler()
>>> formatter = logging.Formatter('%(level)-8s: %(name)s> %(message)s')
>>> handler.setFormatter(formatter)
>>> qtsass.enable_logging(level=logging.DEBUG, handler=handler)

Arguments:

• level: Optional logging level
• handler: Optional handler to add

watch(source, destination, compiler=None, Watcher=None):

Watches a source file or directory, compiling QtSass files when modified.

The compiler function defaults to compile_filename when source is a file and compile_dirname when source is a directory.

Arguments:

• source: Path to source QtSass file or directory.
• destination: Path to output css file or directory.
• compiler: Compile function (optional)
• Watcher: Defaults to qtsass.watchers.Watcher (optional)

Returns:

• qtsass.watchers.Watcher instance

Contributing

Everyone is welcome to contribute!

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