[Development] Enabling of QtDBus in Qt 5.4 and 5.5

[Morten Johan Sørvig]

> On 11 Dec 2014, at 02:42, Thiago Macieira <thiago.macieira at intel.com> wrote:
> 
> Dear all
> 
> My well-intentioned changes to unbreak the building of the OS X builds for 
> 5.4.0 have apparently had unexpected consequences. After reviewing the 
> situation, I've created https://codereview.qt-project.org/101843 to fix the 
> issues (note: updates for Windows pending). Once that one is in 5.4 and merged 
> to 5.5, I'll submit another fix for 5.5 changing the configure behaviour.
> 
> configure option:		Qt 5.4.0		Qt 5.4.1		Qt 5.5†
> none				configure1	runtime		configure2
> -dbus				runtime		runtime		configure2
> -dbus-linked			linked		linked		linked
> --dbus=runtime		runtime		runtime		runtime
> -no-dbus			disabled		disabled		disabled
> 
> Explanation:
> * runtime: dynamically open libdbus-1 at runtime
> * linked: link to libdbus-1
> * configure1: check at configure time if libdbus-1 is present in the system 
>   and then enable "runtime" mode
> * configure2: check at configure time if libdbus-1 is present in the system;
>   if it is, enable "linked" mode, otherwise "runtime"
> 
> In other words: starting with Qt 5.4.1, QtDBus will be enabled FOR ALL BUILDS. 
> The library is safe enough in dynamic mode that it will simply say that it 
> could not connect to the bus or peer, so it should not be a problem to have it 
> present.
> 
> †: unless we get the rewrite to drop libdbus-1 requirements in time for 5.5, 
> but I think it's unlikely. Maybe Qt 5.6.

I’m wondering, do we want to keep the “none” behavior to “runtime” for OS X?

libdbus-1 (and pkg-config) may be installed for two reasons:
1) As a dependency for Qt.
2) As a dependency for something else (some other homebrew package, or an unrelated dev project).

I think 2) is more common, and that a default Qt build should use stock OS X only.

Morten