[gst-devel] location of include headers

[Thomas Vander Stichele]

Hello people,

I have looked at some other projects as to where they install their 
headers and come to the conclusion that we might think about changing 
ours.

The problem is fairly simple : some of our headers *need* to point to 
other headers in the same package using < > which sets the compiler off 
looking for headers in the standard locations and the user-supplied 
locations.  They *need* to do this because these headers get installed 
system-wide and could thus be used by external apps as well.

The way I see it is that, you should use "..." if the header is in the 
source tree only and not meant to be installed, and <...> if the header 
you're doing this in is meant to be installed, as well as the header 
you're pulling in.

Now, this causes problems.  Take the editor for example.  The 
editor.h file in gst/editor is the entry point.  It contains includes 
like this :

#include <gst/editor/gsteditorbin.h>

So that, when an external app wants to work with the installed gst-editor, 
this will correctly point to this other installed header.

Now, there's a problem with this, and that's why I suspect the other 
projects (gtk, eel, pango, freetype, ...) use another level in their 
include installation.

The problem is this : when you already have a previously installed set of 
header files, and you include them as <gst/editor/gsteditorbin.h>, the 
installed set will take preference to be included, since they are in the 
standard include prefix.

The other projects basically solve this by sticking in another level, so 
that the dir from which everything starts needs to be EXPLICITLY added to 
the compile lines.

So what does this mean for us ?

We could go two ways :

a) drop the gst/ prefix from all the #include lines and add 
-I/$(prefix)/include/gst to all the compile lines that need it

b) put all gst header files in something like
   $(prefix)/include/gstreamer and start the tree from there
   (so that editor.h would end up in 
  $(prefix)/include/gstreamer/gst/editor/editor.h)


I prefer b) since 1) we need to change less source code and 2) other 
projects do it similarly.

I'm sure all of you have at some point been stung by things failing to 
compile where the ultimate reason was that some old header stuff was 
floating around.  This should not be allowed to happen.

So, what do you think ? Agree ? Not ? If y'all agree I'll work on doing 
this quickly.  I'd prefer to get this done before 0.4.0.

Thanks,
Thomas

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