Rivendellaudio/CODINGSTYLE

This is the CODINGSTYLE file for the Rivendell package.

OVERVIEW:
This file, CODINGSTYLE, describes the coding style guidelines for writing
new code, how to submit patches to be incorporated into the official
Rivendell Git repository, and other code related information. General info
on the Rivendell project can be found at the http://www.rivendellaudio.org/
web page and also in the 'README' and 'INSTALL' files.  

The code style used for Rivendell is a somewhat idiosyncratic mixture of
the style generally used for Qt C++ programs combined with the classic UNIX
C style. Some of the specifics include:


LINE LENGTH:
Should not be longer than 78 characters unless doing so would severely
compromise the readability of the code. Where it is necessary to break a
line, it should be done at a point that preserves maximum clarity and ease
of reading.

Good:
  *report+=QString(" ")+
    logLine(i)->startTime(RDLogLine::Logged).toString("hh:mm:ss")+
    QString::asprintf(" - cart %06d [",logLine(i)->cartNumber())+
    q->value(1).toString()+"] "+QObject::tr("is not playable")+"\n";

Bad:
  *report+=QString(" ")+logLine(i)->startTime(RDLogLine::Logged).toString("hh:mm:ss")+QString::asprintf(" - cart %06d [",logLine(i)->cartNumber())+q->value(1).toString()+"] "+QObject::tr("is not playable")+"\n";


INDENTATION:
Should be two spaces per level. This helps to keep the line length down.

Good:
  if(to_line<0) {
    to_line=size();
    for(int i=from_line;i<size();i++) {
      if(logLine(i)->timeType()==RDLogLine::Hard) {
	to_line=i;
	i=size();
	if(sched_time!=NULL) {
	  *sched_time=logLine(i)->startTime(RDLogLine::Logged);
	}
      }
    }
  }

Bad:
  if(to_line<0) {
          to_line=size();
	  for(int i=from_line;i<size();i++) {
                  if(logLine(i)->timeType()==RDLogLine::Hard) {
	                  to_line=i;
	                  i=size();
	                  if(sched_time!=NULL) {
	                          *sched_time=logLine(i)->startTime(RDLogLine::Logged);
	                  }
                   }
           }
  }


CURLY BRACES:
Conditional statements (such as 'if' and 'for') should *always* use curly
braces, even where the affected block is but one line long. The opening
brace should be on the same line as the conditional and the closing one on
a line by itself. This style greatly facilitates debugging, allowing a
single line to be provisionally commented out or additional lines to be
provisionally added without making the enclosing conditional syntactically
invalid.

Good:
  if(i==12) {
    printf("i is equal to twelve!\n");
  }

Bad:
  if(i==12)
    printf("i is equal to twelve!\n");


PADDING WHITESPACE:
Wherever possible, there should be no whitespace between constants/variables
and operators. This helps to keep the line length down.

Good:
  for(int i=from_line;i<size();i++) {
    if(logLine(i)->timeType()==RDLogLine::Hard) {
      to_line=i;
    }
  }

Bad:
  for(int i = from_line; i < size(); i++) {
    if(logLine(i)->timeType() == RDLogLine::Hard) {
      to_line = i;
    }
  }


CLASS NAMES:
Should have the initial letter of each word capitalized, e.g. 'ThisIsMyClass'.
If the class is part of the librd convenience library (in 'lib/'), the name
should be prefaced with the uppercase letters 'RD', e.g. 'RDThisIsMyClass'.


METHOD NAMES:
Public method names as well as signal and slot method names should follow
the general style used by Qt. A special convention for Rivendell is to
reserve names beginning with an uppercase letter for private methods only.

Good:
class RDLogPlay
{
 Q_OBJECT
 public:
  RDLogPlay(int id,RDEventPlayer *player,QObject *parent=0);
  QString serviceName() const;
  void setServiceName(const QString &svcname);

 private slots:
  void transTimerData();
  void graceTimerData();

 signals:
  void renamed();
  void reloaded();
  void transportChanged();

 private:
  bool StartEvent(int line,RDLogLine::TransType trans_type,int trans_length,
		  RDLogLine::StartSource src,int mport=-1,int duck_length=0);
  bool StartAudioEvent(int line);
};

Bad:
class RDLogPlay
{
 Q_OBJECT
 public:
  RDLogPlay(int id,RDEventPlayer *player,QObject *parent=0);
  QString servicename() const;
  void set_service_name(const QString &svcname);

 private slots:
  void TransTimerData();
  void grace_timer_data();

 signals:
  void RENAMED();
  void Reloaded();
  void transport_changed();

 private:
  bool startEvent(int line,RDLogLine::TransType trans_type,int trans_length,
		  RDLogLine::StartSource src,int mport=-1,int duck_length=0);
  bool startAudioEvent(int line);
};


VARIABLE NAMES:
*All* variables should be lowercase only, with uppercase being reserved for
class and method names. Words should be separated by underscores.

Good:
  int log_position_number=1;

Bad:
  int logPositionNumnber=1;

Class variables should be prefaced with a short base name that is common to
all, followed by an underscore. For example, the class 'MyClass' might use
'myclass_', as in 'myclass_foo1', 'myclass_foo2', etc. Local variables
(including function parameter names) should be kept short, preferably a
single word.


NULL POINTERS
Null pointers should always be represented by using the 'NULL' keyword,
rather than 0.

Good:
  int *foo=NULL;
  if(foo==NULL) {
    printf("The foo variable is null!\n");
  }

Bad:
  int *foo=0;
  if(foo==0) {
    printf("The foo variable is null!\n");
  }


SQL STATEMENTS:
When embedding SQL statements in code, the following guidelines should be
followed:

1) All identifier fields should be enclosed in backticks (ASCII 0x2C)
characters (NOT to be confused with apostrophes, see below).

Good:
  sql="select `FIELD1`,`FIELD2` from `MY_TABLE` where `ID`=2";

Bad:
Good:
  sql="select FIELD1,FIELD2 from MY_TABLE where ID=2";


2) All string literals should be delimited with the apostrophe character,
*not* quotes. The previous use of quotes is a MySQL-ism that is now strongly
discouraged.

Good:
  sql="select `FIELD1` from `MY_TABLE` where `FIELD2`='foobar'";

Bad:
  sql="select `FIELD1` from `MY_TABLE` where `FIELD2`="foobar";
 

3) All identifiers are uppercase-only, while SQL operators
   should be all lowercase. This helps improve readability.

Good:
  sql="select `FIELD1`,`FIELD2` from `MY_TABLE` where `ID`=2";

Bad:
  sql="SELECT `FIELD1`,`FIELD2` FROM `MY_TABLE` WHERE `ID`=2";


4) Long or complex SQL statements should be broken into multiple lines in
   a manner to enhance the readability of both C++ and SQL. For 'select'
   queries that return more than two fields per row, each field should be
   commented with its ordinal number to assist in determining the
   appropriate value to give to 'RDSqlQuery::value()' for referencing
   the fields.

Good:
  sql=QString("select ")+
    "`CART`.`TITLE`,"+         // 00
    "`CART`.`ARTIST`,"+        // 01
    "`CART`.`PUBLISHER`,"+     // 02
    "`CART`.`COMPOSER`,"+      // 03
    "`CART`.`USAGE_CODE`,"+    // 04
    "`CUTS`.`ISRC`,"+          // 05
    "`CART`.`ALBUM`,"+         // 06
    "`CART`.`LABEL`,"+         // 07
    "`CUTS`.`ISCI`,"+          // 08
    "`CART`.`CONDUCTOR`,"+     // 09
    "`CART`.`USER_DEFINED`,"+  // 10
    "`CART`.`SONG_ID`,"+       // 11
    "`CUTS`.`DESCRIPTION`,"+   // 12
    "`CUTS`.`OUTCUE` "+        // 13
    "from `CART` left join `CUTS` "+
    "on `CART`.`NUMBER`=`CUTS`.`CART_NUMBER` where "+
    "`CUTS`.`CUT_NAME`='"+RDEscapeString(button->cutName())+"'";

Bad:
  sql="select `CART`.`TITLE`,`CART`.`ARTIST`,`CART`.`PUBLISHER`,`CART`.`COMPOSER`,`CART`.`USAGE_CODE`,`CUTS.ISRC`,`CART.ALBUM`,`CART.LABEL`,`CUTS`.`ISCI`,`CART`.`CONDUCTOR`,`CART`.`USER_DEFINED`,`CART`.`SONG_ID`,`CUTS`.`DESCRIPTION`,`CUTS.OUTCUE` from `CART` left join `CUTS` on `CART`.`NUMBER`=`CUTS`.`CART_NUMBER` where `CUTS`.`CUT_NAME`='"+RDEscapeString(button->cutName())+"'";


SCHEMA CHANGES:
Changes that alter the schema of the database must include:

  A) Incrementation of the 'RD_VERSION_DATABASE' value in 'lib/dbversion.h'.

  B) Code that implements the schema change, in the
     'utils/rddbmgr/updateschema.cpp' file.

  C) Code that implements an exact, perfect reversal of the schema change,
     in the 'utils/rddbmgr/revertschema.cpp' file.

  D) Updating of the schema map in the 'MainObject::InitializeSchemaMap()'
     method in the 'utils/rddbmgr/schemamap.cpp' file. (See the comment at
     the top of the method definition for details).

  E) Update the table documentation appropriately in 'docs/tables/'.

  F) [VERY IMPORTANT] - Document the changes to the schema in your
     'ChangeLog' entry, including the new value of 'RD_VERSION_DATABASE'.


FONT MANGEMENT:
All fonts used in Rivendell are managed by the RDFontEngine class, which
provides them on the basis of abstract "roles" so as to provide consistency
across the entire set of modules. See the file 'docs/apis/fonts.pdf' for
a detailed description of this sub-system, including screenshot examples.


WRITING TO THE SYSLOG:
Rivendell makes extensive use of the syslog(3) system found on all
POSIX-compliant systems. Sending messages to the syslog should almost
always be done by means of the following method in 'RDApplication':

  void RDApplication::syslog(int priority,const char *format,...)

The exception to the above is when the application context does not
include a global RDApplication object --e.g. in caed(8). For those
cases, the following static RDApplication method should be used:

  void RDApplication::syslog(RDConfig *c,int priority,const char *format,...)

For a discussion of the parameters of these methods, see the syslog(3) man
page. The 'priority' parameter should be one of the following values:

    LOG_ERR - Indicates that a fatal error has occurred; 'fatal' meaning
              that the program is unable to continue and will now exit.

LOG_WARNING - Indicates that a non-fatal error has occured; meaning
              that the program will continue to operate, but with
              possibly significant operational degradation. This would be
              appropriate for things like failure to connect to an
              external switcher or other device.

   LOG_INFO - Information useful for tracking operational state --e.g.
              a cart play-out has begun, a new Rivendell log has been
              loaded, etc.

  LOG_DEBUG - Information useful for tracking or verifying Rivendell
              software internal state. These messages will not normally
              be seen by users, but can be made visible to allow for
	      program debugging.  

NOTE: A 'facility' value should *not* be included in the 'priority'
argument. The appropriate 'facility' value, as determined by the
'SyslogFacility=' directive in rd.conf(5), will be added automatically.


DATE/TIME FORMATS:
The formats of date/time values presented in the Rivendell's GUI modules
are user-specifiable in RDAdmin->SystemSettings. Thus, when handling such,
the following facilities are available:

Value Inputs. The following classes are available:

RDDateTimeEdit - Subclass of QDateTimeEdit
    RDDateEdit - Subclass of QDateEdit
    RDTimeEdit - Subclass of QTimeEdit.

While the underlying Qt 'setDisplayFormat()' method remains available
in these subclasses, *it should never be used*, as the underlying display
formats are automatically derived and applied. In addition, these classes
have a number of additional methods for handling Rivendell-specific
situations (times to tenths-of-second precision, read-only states, etc).
See the specific headers in 'lib/' for details.

Value Outputs. The following methods are available for easily rendering
properly formatted date/time strings in GUI module contexts:

RDCoreApplication::timeString(const QTime &time,
                              const QString &padding="") const;
RDCoreApplication::tenthsTimeString(const QTime &time,
                                    const QString &padding="") const;
RDCoreApplication::shortDateString(const QDate &date) const;
RDCoreApplication::longDateString(const Date &date) const;

The methods above that involve time all include support for optionally 
specifying times with tenth-second precision. At present, the only place in 
Rivendell where this facility is used is when specifying the 'Start Time' and
'Grace Time' parameters in Rivendell logs. All other contexts should present
times to single-second precision.

These methods can be easily accessed in GUI module contexts via the global
'rda' pointer, as illustrated in the following code snippet:

*** snip snip ***
#include <rdapplication.h>
[..]
QDate my_date(2021,8,13);  // 13 August 2021
QString my_string=rda->shortDateString(my_date);
*** snip snip ***

N.B. - These date/time formats are for use when interacting with users in
a GUI context. They should *not* be used in other contexts, including
(but not necessarily limited to):
  1) SQL Statements. Standard SQL date-time formats apply, and should
     be hard-coded appropriately.
  2) Command-line Utilities. In the interest of providing stable interfaces
     for scripting purposes, date/time values in Rivendell command-line
     tools generally use ISO8601-compliant formats. Where this varies
     (due to application requirements), it should be documented in the
     appropriate manpage.
  3) Standardized APIs. Data interfaces for external systems (JSON, XML,
     etc) should continue to use the formats appropriate for those
     contexts.
  4) Syslog Messages. Any date/time references sent to syslog(3) should
     use ISO8601-compliant formats.


CONTRIBUTING CHANGES:
The primary code repository for Rivendell resides at GitHub, and can be
found at:

      https://github.com/ElvishArtisan/rivendell

Changes should be submitted in the form of a pull request [PR] against
the default branch ('v4' as of this writing). Information about drafting and
submitting PRs can be found at:

    https://help.github.com/en/articles/about-pull-requests


PULL REQUEST CHECKLIST:
Before submitting a pull request, the following guidelines should be
completed:

1) The code should compile without errors or warnings [the '-Werrors' switch
   for gcc(1) is your friend here!].

2) Add an entry to the 'ChangeLog' file at the base of the Rivendell source
   code tree, describing your changes. The format of the ChangeLog file has
   the most recent changes at the bottom of the file. Entries start with a
   date stamp and have a format like:

    YYYY-MM-DD NAME <EMAIL>
    * Description of change

For example:
    2007-02-23 John Coder <coder@example.com>
	* Modified the code in 'lib/rdimport_audio.cpp' to use the
	'RDCart::setMetadata()' and 'RDCut::setMetadata()' methods.

3) If your changes add, remove or change the behavior of one or more
   configuration entries in rd.conf(5), update the default configuration
   file ('conf/rd.conf-sample') accordingly. Similiarly, for PyPAD scripts,
   be sure to update the corresponding '<plugin-name>-exemplar' files.

4) If your changes alter any user-visible aspect (UI or behavior), update
   the user documentation appropriately. The documentation is written
   in DocBook 5 markup, and can be found at the following locations in
   the source tree:

   Operations Guide - 'docs/opsguide/'

   Manual pages - 'docs/manpages/'

   Internal and public APIs - 'docs/apis/'.

5) If you wish your work to be mentioned in the 'Credits' list displayed in
   rdadmin(1), add or modify the appropriate entry in the 'AUTHORS' file.
   Entries should be sorted by surname, then christian name of the author.


DEBUGGING/OPTIMIZATION AIDS:
The following classes exist for aiding the debugging and optimization
process:

   RDTimeArray. Record a series of code points with microsecond precision
   and then render the results to a QString. See 'lib/rdtimearray.h'.


QUESTIONS:
Questions about coding style, or indeed any aspect of Rivendell development,
are welcomed on the Rivendell-prog mailing list. Subscription information
and list archives are available at:

    http://caspian.paravelsystems.com/mailman/listinfo/rivendell-prog