[Cmake] cmSourceFilesCommand : SOURCE_FILES NAME file AS target

[Sebastien BARRE]

Hi

I'd like to enhance the SOURCE_FILES syntax from :
       SOURCE_FILES(NAME file1 file2 ...)
to :
       SOURCE_FILES(NAME file1 [AS target1] file2 [AS target2] ...)

Meaning : the source file file1 would be compiled to a target file named 
target1 (optionally).

Here is the reason. I'd like to achieve this :

IF (VTK_WRAP_TCL)
   SOURCE_FILES(RenderingTCL_SRCS
      vtkTkRenderWidget AS vtkTkRenderWidgetTcl
      vtkTkImageViewerWidget  AS vtkTkImageViewerWidgetTcl
      vtkTkImageWindowWidget AS vtkTkImageWindowWidgetTcl)
[...]
ENDIF (VTK_WRAP_TCL)

IF (VTK_WRAP_PYTHON)
   ADD_DEFINITIONS(-DVTK_PYTHON_BUILD)
   SOURCE_FILES(RenderingPython_SRCS
      vtkTkRenderWidget AS vtkTkRenderWidgetPython
      vtkTkImageViewerWidget  AS vtkTkImageViewerWidgetPython
      vtkTkImageWindowWidget AS vtkTkImageWindowWidgetPython)
ENDIF (VTK_WRAP_PYTHON)

In VTK, the vtkTkRenderWidget files are compiled two times : one to build a 
DLL for the Tcl interpreter, one other to build another DLL for the Tk 
widgets to be used within the Python Interpreter (with the define flag 
VTK_PYTHON_BUILD).

This was not a problem in the old tree, because the .obj files were 
separated on a *language* basis (i.e. all .obj belonging to the Tcl-build 
were in vtktcl/, and these belonging to the Python-build were in vtkpython/).

This is no more the case in the new tree : all .obj are in the same 
directory, on a component basis (Common, Rendering, etc.). This means that 
there is already a vtkTkRenderWidget.obj in the directory when the 
vtkTkRenderWidget file has to be compiled a second time (for Python) : clash !

I guess we could also use a copy command or another solution (any 
suggestion is welcome), but this enhancement to SOURCE_FILES adds a feature 
that might be useful in some other cases.

This change would require :
   - add a new private member to the cmSourceFile class :
       std::string m_TargetName;
   - add 2 new public members to the cmSourceFile class :
       std::string GetTargetName() const (returns target name if not empty, 
otherwise source name)
       void SetTargetName(const char *name) {m_TargetName = name;}
   - track every use of GetSourceName() in the CMake distrib and check if 
it has to be changed to GetTargetName()

What do you think folks ?