[Development] New proposal for the tool naming

[Thiago Macieira]

Starting a new thread with some ideas based on the outcomes of the discussion. 
Many thanks to rittk, Simon, Lars and André who helped come up with this.

Note: this applies to the *tools* only. The library naming and installation 
paths for plugins and QML files has remained uncontested so far, so we appear 
to have a consensus.

The proposal:

1) we introduce a $libexecdir configuration option to qmake and QLibraryInfo. 
For backwards compatibility, this $libexecdir will receive the legacy names of 
QT_INSTALL_BINS and QLibraryInfo::BinariesPath. It will default to 
$prefix/libexec/qt5, which some distros will change to $prefix/lib/qt5/libexec.

This directory is *not* expected to be in $PATH on any system and therefore 
the documentation cannot assume it is.

In this directory, we'll install the tools not usually run by the user, tools 
that are often run by other tools. They will keep their current names. These 
tools are:
	qmake
	moc
	rcc
	uic
	qdbusxml2cpp
	qdbuscpp2xml
	lconvert
	lrelease
	lupdate
	qml*
	qhelpgenerator
	qhelpconverter
	qcollectiongenerator
	qdoc

2) the $bindir, defaulting to $prefix/bin, will now be found by qmake property 
QT_INSTALL_APPS and QLibraryInfo::ApplicationsPath. It contains end-user 
applications that retain backwards compatibility of purpose as well as output. 
Those applications are:
	qdbus
	qdbusviewer
	designer
	assistant
	linguist
	qglinfo
	pixeltool
	[creator]

I'm open to suggestions on whether some of the tools should be symlinked here 
(e.g., qmlscene5 -> $libexecdir/qmlscene).

3) In addition, we'll create a *new* tool also called qmake that will be 
installed to $bindir. This tool shall have the following behaviours:

 a) under most circumstances, it will simply find another qmake and pass 
through all arguments. That is:
	qmake -project
		basically will exec
	$someotherpath/qmake -project

 b) additionally, it accepts an extra argument (-select), which causes it to 
select a different Qt version. For example:
	qmake -qt=5 -project
	qmake -qt=4.8.4 CONFIG+=debug
	etc.
 As a shorthand, the option "-qtX" means "-qt=X".
 This argument will be stripped from the command-line before calling the real 
qmake.
 Without this option, it will fall back to a well-known environment variable 
(say, QT_SELECT=5). And if that is also missing, it selects some system-defined 
or user-defined default.

 c) it adds one extra option: -print-versions, which will list which Qt 
versions are known to this tool

 It is our intention that this new tool replace all pre-existing qmake found 
in $PATH. One tool to rule them all. Creator can query this tool to find all 
known Qt versions and populate its listing.

 In turn, the official Qt 5 documentation should always talk about qmake like 
so:
	qmake -qt5 "LIBS+=-L/usr/local/lib -lmysqlclient_r" mysql.pro

This allows the Troll qset function to be implemented like:
function qset() {
	local prefix=$(qmake -qt=$1 -query QT_INSTALL_PREFIX)
	if [ $? -gt 0 ]; then
		echo >&2 No such Qt version "$1"
	else
		export QT_SELECT=$1
		export QTDIR=$prefix
		local libdir=$(qmake -query QT_INSTALL_LIBS)
		export LD_LIBRARY_PATH=$libdir${LD_LIBRARY_PATH+:$LD_LIBRARY_PATH)
		export PKG_CONFIG_PATH=$libdir/pkgconfig:$PKG_CONFIG_PATH
		# optional:
		#PATH=$(qmake -query QT_INSTALL_BINS):$PATH
	fi
}
function qcd() { cd $QTDIR; }

Additionally, this tool may support options like -add-qt and -set-default-qt. 
I'm also open to adding an option -run-tool= (e.g., qmake -qt=5 -run-
tool=qmlplugindump) if that's of interest to people.

I haven't decided whether this tool should be a shell script, a perl script or 
another bootstrapped executable.

Please comment.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
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