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Synergy Developer and Porting Guide
===================================
This document is under development.
Code Organization
-----------------
The synergy source code organization is:
. -- root makefiles, some standard documentation
cmd -- program source code
launcher -- synergy launcher for Windows
synergyc -- synergy client
synergys -- synergy server
config -- stuff for autoconf/automake
dist -- files for creating distributions
nullsoft -- files for creating Nullsoft NSIS installer (Windows)
rpm -- files for creating RPMs
doc -- placeholder for documentation
examples -- example files
lib -- library source code
arch -- platform dependent utility library
base -- simple utilities
client -- synergy client library
common -- commonly needed header files
io -- I/O
mt -- multithreading
net -- networking
platform -- platform dependent display/window/event stuff
server -- synergy server library
synergy -- synergy shared client/server code library
Note how the utility code required by the programs is placed into
separate library directories. This makes the makefiles a little
more awkward but makes for a cleaner organization. The top level
directory has only the standard documentation files and the files
necessary to configure and build the rest of the project.
Coding Style Guide
------------------
Synergy uses many coding conventions. Contributed code should
following these guidelines.
- Symbol Naming
Names always begin with a letter (never an underscore). The first
letter of interior names are always capitalized. Acronyms should
be all uppercase. For example: myTextAsASCII.
Names come it two flavors: leading capital and leading lowercase.
The former have the first character capitalized and the latter
don't. In the following table, leading capital names are indicated
by `Name' and leading lowercase names by `name'.
The naming convention for various things are:
* Exceptions -- X + Name XMyException
* Interfaces -- I + Name IMyInterface
* Template Classes -- T + Name TMyTemplate<>
* Other Classes -- C + Name CMyClass
* Enumerations -- E + Name EMyEnumeration
* Constants -- k + Name kMyConstant
* Data Members -- m_ + name m_myDataMember
* Methods -- name myMethod
* Functions -- name myFunction
* Variables -- name myVariable
Exceptions are types that get thrown and are generally derived
(possibly indirectly) from XBase. Interfaces are derived (possibly
indirectly) from IInterface and have only pure virtual functions.
Other classes are classes that aren't exceptions or interfaces.
Constants include global constants and enumerants.
Method names should usually have the form `verbObject'. For example:
* isGameOn()
* getBeer()
* pressPowerButton()
* setChannel()
In general, use `get' and `set' to read and write state but use `is'
to read boolean state. Note that classes that contain only `is',
`get', and `set' are probably plain old data; you might want to
consider using public data members only or, better, refactor your
design to have classes that actually do something more than just
hold data.
- File Naming
Each class should have one source and one header file. If the
class is named `CMyClass' then the source file should be named
`CMyClass.cpp' and the header file `CMyClass.h'.
Headers files not containing a class should have some meaningful
name with a leading capital (e.g. `Version.h').
Source files without a header file have a leading lowercase name.
Only files containing the entry point for an application should
lack a header file.
- Dependencies
* No circular library dependencies
Library dependencies form an acyclic graph. Conceptually
libraries can be arranged in layers where each library only
references libraries in layers below it, not in the same layer
or layers above it. The makefiles build the lowest layer
libraries first and work upwards.
* Avoid circular uses-a relationships
When possible, design classes with one-way uses-a relationships
and avoid cycles. This makes it easier to understand the code.
However, sometimes it's not always practical so it is permitted.
* Included files in headers
Headers should #include only the necessary headers. In
particular, if a class is referenced in a header file only as a
pointer or a reference then use `class COtherClass;' instead of
`#include "COtherClass.h".'
* #include syntax
Non-synergy header files must be included using angle brackets
while synergy header files must be included using double quotes.
#include "CSynergyHeader.h"
#include <systemheader.h>
The file name in a #include must not be a relative path unless
it's a system header file and it's customary to use a relative
path, e.g. `#include <sys/types.h>'. Use compiler options to
add necessary directories to the include search path.
* Included file ordering
Files should be included in the following order:
* Header for source file
The first include for CMyClass.cpp must be CMyClass.h.
* Other headers in directory, sorted alphabetically
* Headers for each library, sorted alphabetically per library
Include headers from the library closest in the dependency graph
first, then the next farthest, etc. Sort alphabetically within
each library.
* System headers
- C++
* C++ features
Synergy uses the following more recent C++ features:
* bool
* templates
* exceptions
* mutable
* new scoping rules
* the standard C++ library
Do not use the following C++ features:
* dynamic_cast
* run time type information
* namespaces and using (use std:: where necessary)
The new scoping rules say that the scope of a variable declared
in a for statement is limited to the for loop. For example:
for (int i = 0; i < 10; ++i) {
// i is in scope here
}
// i is not in scope here
for (int i = -10; i < 0; ++i) {
// an entirely new i is in scope here
}
// i is not in scope here
This is used routinely in synergy, but only in for loops. There
is a macro for `for' in lib/base/common.h when building under
Microsoft Visual C++ that works around the fact that that compiler
doesn't follow the new scoping rules. Use the macro if your
compiler uses the old scoping rules.
* Standard C++ library
The standard C++ library containers should always be used in favor
of custom containers wherever reasonable. std::string is used
throughout synergy but only as the CString typedef; always use
CString, never std::string except in the arch library. Synergy
avoids using auto_ptr due to some portability problems. Synergy
makes limited use of standard algorithms and streams but they can
be freely used in new code.
* Limited multiple inheritance
Classes should inherit implementation from at most one superclass.
Inheriting implementation from multiple classes can have unpleasant
consequences in C++ due to it's limited capabilities. Classes can
inherit from any number of interface classes. An interface class
provides only pure virtual methods. Synergy breaks this rule in
IInterface which implements the virtual destructor for convenience.
* No globals
Avoid global variables. All global variables must be static, making
it visible only with its source file. Most uses of global variables
are better served by static data members of a class. Global
constants are permitted in some circumstances.
Also avoid global functions. Use public static member functions in
a class instead.
These rules are violated by the main source file for each program
(except that the globals are still static). They could easily be
rewritten to put all the variables and functions into a class but
there's little to be gained by that.
* Private data only
If a class is plain-old-data (i.e. it has no methods) all of its
data members should be public. Otherwise all of its data members
should be private, not public or protected. This makes it much
easier to track the use of a member when reading code. Protected
data is not allowed because `protected' is a synonym for `public
to my subclasses' and public data is a Bad Thing. While it might
seem okay in this limited situation, the situation is not at all
limited since an arbitrary number of classes can be derived,
directly or indirectly, from the class and any of those classes
have full access to the protected data.
* Plain old data
A class that merely contains data and doesn't perform operations
on that data (other than reads and writes) is plain old data (POD).
POD should have only public data members and non-copy constructors.
It must not have any methods other than constructors, not even a
destructor or assignment operators, nor protected or private data.
Note that this definition of POD is not the definition used in the
C++ standard, which limits the contained data types to types that
have no constructors, destructors, or methods.
* Avoid using friend
Avoid declaring friend functions or classes. They're sometimes
necessary for operator overloading. If you find it necessary to
add friends to some class C, consider creating a utility class U.
A utility class is declared as the only friend of C and provides
only static methods. Each method forwards to a private method on
an object of C type (passed as a parameter to the U's method).
This makes maintenance easier since only U has friend access to C
and finding any call to U is trivial (they're prefixed by U::).
* Don't test for NULL when using `delete' or `delete[]'
It's unnecessary since delete does it anyway.
- Makefiles
Automake's makefiles (named Makefile.am) have a few requirements:
* Define the following macros at the top of the file:
NULL =
DEPTH = <relative-path-to-top-level>
VDEPTH = ./$(VPATH)/$(DEPTH)
<relative-path-to-top-level> is `..', `../..', `../../..', etc,
whichever references the top directory of the synergy tree. For
example, for a subdirectory of the top level use `..', for a
subdirectory of a subdirectory of the top level use `../..'.
* Lists should have one item per line and end in $(NULL). For
example:
EXTRA_DIST = \
kiwi.txt \
mango.cpp \
papaya.h \
$(NULL)
Indentation must use tabs in a makefile. Line continuations
(backslashes) should be aligned using tabs.
* Lists of files should be sorted alphabetically. Lists of
subdirectories must be in the desired build order.
- Source Formatting
Every project has its own formatting style and no style satisfies
everyone. New code should be consistent with existing code:
* All files should include the copyright and license notice
* Use tabs to indent
* Tabs are 4 columns
* Lines should not extend past the 80th column
* Open braces ({) go on same line as introducing statement
`for (i = 0; i < 10; ++i) {' not
for (i = 0; i < 10; ++i)
{
* Close braces line up with introducing statement
* Open brace for function is on a line by itself in first column
* Close brace for function lines up with open brace
* Always use braces on: if, else, for, while, do, switch
* `else {' goes on its own line
* Always explicitly test pointers against NULL
e.g. `if (ptr == NULL)' not `if (ptr)'
* Always explicitly test integral values against 0
e.g. `if (i == 0)' not `if (i)'
* Put spaces around binary operators and after statements
e.g. `if (a == b) {' not `if(a==b){'
* C'tor initializers are one per line, indented one tab stop
* Other indentation should follow existing practice
* Use Qt style comments for extraction by doxygen (i.e. //! and /*!)
* Mark incomplete or buggy code with `FIXME'
- Other
* calls to LOG() should always be all on one line (even past column 80)
Class Relationships
-------------------
The doxygen documentation can help in understanding the relationships
between objects. Use `make doxygen' in the top level directory to
create the doxygen documentation into doc/doxygen/html. You must have
doxygen installed, of course.
FIXME -- high level overview of class relationships
Portability
-----------
Synergy is mostly platform independent code but necessarily has
platform dependent parts. The mundane platform dependent parts
come from the usual suspects: networking, multithreading, file
system, high resolution clocks, system logging, etc. Porting
these parts is relatively straightforward.
Synergy also has more esoteric platform dependent code. The
functions for low-level event interception and insertion,
warping the cursor position, character to keyboard event
translation, clipboard manipulation, and screen saver control
are often obscure and poorly documented. Unfortunately, these
are exactly the functions synergy requires to do its magic.
Porting synergy to a new platform requires the following steps:
- Setting up the build
- Adjusting lib/common/common.h
- Implementing lib/arch
- Implementing lib/platform
- Tweaks
Setting up the build:
The first phase is simply to create the files necessary to build the
other files. On Unix, synergy uses autoconf/automake which produces
a `configure' script that generates makefiles. On Windows, synergy
uses Visual C++ workspace and project files. If you're porting to
another Unix variant, you may need to adjust `configure.in',
`acinclude.m4', and Unix flavor dependent code in lib/arch.
Adjusting lib/common/common.h:
The lib/common/common.h header file is included directly or indirectly
by every other file. It prepares some platform dependent macros for
integer sizes and defines a macro for conveniently testing which
platform we're building on. That macro is named *_LIKE (e.g. UNIX_LIKE)
and has the value `1'. Exactly one *_LIKE macro must be defined by
common.h.
Implementing lib/arch:
Much platform dependent code lives in lib/arch. There are several
interface classes there and they must all be implemented for each
platform. See the interface header files for more information.
Platforms requiring special functions should create a class named
CArchMiscXXX where XXX is the platform name. The class should have
only static methods. Clients can include the appropriate header
file and make calls directly, surrounded by a suitable #ifdef/#endif.
Implementing lib/platform:
Most of the remaining platform dependent code lives in lib/platform.
The code there implements platform dependent window, clipboard, keyboard
and screen saver handling. If a platform is named XXX then the following
classes should be derived and implemented:
* CXXXClipboard : IClipboard
Provides clipboard operations. Typically, this class will
have helper classes for converting between various clipboard
data formats.
* CXXXEventQueueBuffer : IEventQueueBuffer
Provides operations for waiting for, posting and retrieving events.
Also provides operations for creating and deleting timers.
* CXXXKeyState : CKeyState
Provides operations for synthesizing key events and for mapping a
key ID to a sequence of events to generate that key.
* CXXXScreen : IScreen, IPrimaryScreen, ISecondaryScreen, IPlatformScreen
Provides screen operations.
* CXXXScreenSaver : IScreenSaver
Provides screen saver operations.
Tweaks:
Finally, each platform typically requires various adjustments here
and there. In particular, synergyc.cpp and synergys.cpp usually
require platform dependent code for the main entry point, parsing
arguments, and reporting errors. Also, some platforms may benefit
from a graphical user interface front end. These are generally
not portable and synergy doesn't provide any infrastructure for
the code common to any platform, though it may do so someday.
There is, however, an implementation of a GUI front end for Windows
that serves as an example.