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README for developers | |
===================== | |
The Frescobaldi LilyPond sheet music editor is written in Python and uses | |
Qt for its user interface, via the PyQt bindings (Python3 with Qt5 for the | |
current development from version 3 onwards, Python2/3 with Qt4 for the previous | |
stable release from version 2. Any future development will be done with | |
Python3 and Qt5.) | |
All code and application data is in the frescobaldi_app/ directory. The | |
frescobaldi script just imports frescobaldi_app.main. You can simply run | |
./frescobaldi from the command line after unpacking Frescobaldi. | |
You can also install the 'frescobaldi_app' package in the system- or user-wide | |
python directories and the frescobaldi script in your PATH. The distutils-based | |
installation procedure can do this. | |
'frescobaldi_app' is not a real package: on startup, the absolute | |
'frescobaldi_app' directory is added to sys.path and its own __path__ is cleared | |
so all modules and packages inside frescobaldi_app are available as toplevel | |
modules and packages. | |
Running Frescobaldi in an interactive shell | |
=========================================== | |
To test features or to experiment, you can run Frescobaldi in an interactive | |
Python shell. It is recommended to open a shell (e.g. by simply running python | |
without arguments, or by using Dreampie or IPython) and then enter: | |
from frescobaldi_app.debug import * | |
This ensures the application starts up and uses the correct SIP API (2) for | |
QString and QVariant. This will also install some handlers that print | |
debugging information on certain events. And it imports the most used modules. | |
Currently Python 3.2 and newer is supported. | |
How Frescobaldi is organized | |
============================ | |
There can be one or more mainwindow.MainWindow instances and one or more | |
document.Document instances (when the last Document is closed, another one is | |
always constructed). The app module keeps references to those and contains the | |
Signals emitted when something changes. | |
Many parts inside Frescobaldi need to store or cache additional information or | |
add features to Documents, MainWindows etc. Instead of clobbering those basic | |
classes with an ever-growing number of unrelated groups of methods, a different | |
approach is chosen: the plugin module. | |
This keeps all classes small and only have methods that directly apply to | |
themselves and not to other parts of Frescobaldi (separation of concerns). | |
So e.g. the resultfiles, highlighter or documentinfo modules contain classes | |
for objects that coexist with a Document, and providing their own relevant | |
methods, while keeping a weak reference to the Document. | |
Exchange of messages is done as much as possible using signals (PyQt4 signals | |
or from the signals module), or event filters, so adding new features changes as | |
less existing code as possible. | |
Some important modules: | |
main: Entry point | |
info: Information about the application, such as the version | |
toplevel: Adds the path of frescobaldi_app to sys.path, clears __path__ | |
so all modules inside frescobaldi_app can be imported as | |
toplevel modules and packages | |
app: Central hub with global signals, also keeping references to | |
mainwindow and document instances | |
mainwindow: MainWindow (QMainWindow) | |
document: Document (QTextDocument) | |
view: View (QPlainTextEdit) | |
menu: Here the menubar is constructed (by importing all the relevant | |
modules and adding the actions they define) | |
plugin: A simple way to extend objects without them knowing it | |
metainfo: Stores (optionally) meta information about the document, such | |
as last cursor position, whether to enable auto indent, etc | |
panel: The base class of all dock widgets | |
panelmanager: Add new dock widget tools here | |
symbols: Provides icons of LilyPond-generated SVG files that draw | |
themselves in the default text color. | |
Some completely generic modules (don't have anything to do with Frescobaldi or | |
LilyPond): | |
qpopplerview: PDF viewer widget using the popplerqt4 binding to Poppler-Qt4 | |
signals: An alternative to Qt signals that allows for connections to have | |
priorities, and objects don't have to be Qt objects | |
cachedproperty: Caches properties that can be asynchronously computed | |
slexer: A Stateful Lexer, used to build regular expression-based parsers | |
hyphenator: Hyphenate text using hyphenation dictionaries | |
node: A list-like type to build tree structures with | |
cursortools: Some useful functions manipulating QTextCursor instances | |
portmidi: Access the PortMidi library in different ways | |
midifile: Load and play MIDI files | |
Contributing, Coding Style | |
========================== | |
A clean pythonic coding style is preferred, with short methods and method names, | |
and small modules and classes that encapsulate functionality in a sensible way. | |
See also PEP8 (http://www.python.org/dev/peps/pep-0008/) | |
Indent: 4 spaces indent with no tabs | |
Case: ClassName, module_name, methodname() (or methodName() for classes that | |
inherit from Qt classes). Instance attributes that are not meant to be | |
used from outside an instance are prefixed with an underscore, e.g. | |
self._document. | |
There is a habit, inspired by Qt, to use setters and getters for such | |
attributes: obj.setDocument(document) and obj.document(). | |
Names for actions (e.g. file_open) and QSettings keys should always be | |
lowercase and use underscores where needed. | |
Write code so that adding or extending functionality later only adds lines, not | |
changes or removes existing lines. | |
Module imports: one per line. First the Python standard library imports, then | |
PyQt4, then the generic Frescobaldi imports and then imports from the current | |
package. The different groups separated by a blank line: | |
import os # stdlib imports | |
import sys | |
from PyQt4.QtCore import ... # PyQt4 imports | |
import app # generic Frescobaldi imports | |
import icons | |
from . import widget # imports from current package | |
Avoid platform specific code, but when it is really needed, you can test | |
for Windows: | |
if sys.platform.startswith('win'): | |
... | |
or: | |
if os.name == "nt": | |
... | |
Testing for Mac OS X can be done using: | |
if sys.platform.startswith('darwin'): | |
... | |
Adding Functionality | |
==================== | |
Separate out core functionality from its GUI. Put core functionality in a basic | |
module. For the GUI preferably make a new package/__init__.py, importing that | |
e.g. from menu.py while constructing the GUI. An example is the documentwatcher | |
base module, it automatically watches open documents on disk, simply by | |
listening to signals sent from app. It sends a documentChanged() signal when | |
something happens, nothing else. The externalchanges package that gets imported | |
from mainwindow.py, starts up the documentwatcher if the user has it enabled. | |
So the documentwatcher watcher is a module just capable of performing a task, | |
without needing to have logic for accessing the preferences, constructing a | |
particular GUI, etc. It could, like app and many other modules, be used almost | |
unchanged in any other application. | |
New features that add menu actions can be imported in menu.py, while building | |
the menu. Features that should run in a global background thread can have their | |
toplevel file (<feature>/__init__.py) imported from main.py or mainwindow.py, | |
loading as few as possible on first import. | |
Preparing patches or Pull Requests | |
================================== | |
When preparing a patch or pull request, please add new functionality first. | |
Old functionality that is superseded by the newer functions can be removed later | |
when the new functionality has been tested thoroughly. Change existing files | |
as less as possible. Preferably add new files and packages. | |
User Interface strings that are meant to be translated should be wrapped in | |
_("Message Text") constructs. See also README-translations for vital information | |
about how to use the translation mechanism and how to use variables inside | |
messages. | |
Objects that are longer-lived should be able to retranslate their GUIs. This can | |
be done by adding a method named translateUI(self), in which you set the texts | |
to the user interface objects, and calling app.translateUI() at the end of the | |
constructor. Frescobaldi will call your translateUI() method once and also take | |
care of calling it again when the user changes the UI language in the | |
preferences. You can also do this directly by connecting the method that sets | |
the texts to the app.languageChanged signal. | |
Guidelines for writing GUI texts | |
================================ | |
* Write short, directly and non-technical | |
* For help pages: each paragraph is one translatable string | |
* Avoid HTML in texts (but <code>\include</code> is OK) | |
* In help pages you can construct HTML using some helper functions | |
* Avoid hard line breaks (<br>) in any texts: use short paragraphs instead | |
* Use named format fields: not "page {0} of {1}" but "page {num} of {total}" | |
* Don't change existing strings just for cosmetics, it breaks translations | |
Testing and developing under Windows | |
==================================== | |
Linux is the recommended developing platform, but it might be necessary to test | |
specific functionality or behaviour under Windows. It can be difficult to get | |
all the dependencies right, especially the right combination of poppler, pyqt4 | |
and sip. | |
There is an easy way to get setup under Windows and be able to do quite a lot | |
of testing and development, you don't even need to install Python at all. | |
1. install a recent version of Frescobaldi into C:/Program Files/Frescobaldi, | |
using the Frescobaldi.Setup.exe installer | |
2. install Git Bash for Windows from http://msysgit.github.com/ | |
3. open up the Git Bash command prompt (now you're in a powerful UNIX shell!) | |
4. make a directory to do Frescobaldi development in: | |
mkdir dev | |
cd dev | |
5. download the frescobaldi source code from GitHub: | |
git clone https://github.com/wbsoft/frescobaldi.git | |
6. go to the frescobaldi directory and copy all the files from the installed | |
version, except for the frescobaldi_app directory: | |
cd frescobaldi | |
cp /c/Program\ Files/Frescobaldi/*.pyd . | |
cp /c/Program\ Files/Frescobaldi/frescobaldi.exe . | |
cp /c/Program\ Files/Frescobaldi/*.dll . | |
cp /c/Program\ Files/Frescobaldi/library.zip . | |
cp -r /c/Program\ Files/Frescobaldi/iconengines . | |
cp -r /c/Program\ Files/Frescobaldi/imageformats . | |
7. Now you can modify files in frescobaldi_app and run and test Frescobaldi: | |
./frescobaldi.exe | |
8. Make commits of your changes and either push them to a fork of yours of | |
frescobaldi on GitHub or send them via e-mail. | |