CMake question: ki18n_wrap_ui adds .h files as source files to a CMake target, what will happen?

[David Hurka]

Hi CMake fans: 

(Skip to the last paragraph for my question.)

KI18N provides the CMake macro “ki18n_wrap_ui()”, which is used like this:

> ki18n_wrap_ui( myApp_SRCS myApp_dialog.ui )

or like this (since KF 5.62):

> ki18n_wrap_ui( myApp myApp_dialog.ui )

In both cases it creates “ui_myApp_dialog.h” using `uic`, which contains a C++ 
class for this dialog. This header file is added to the list “myApp_SRCS” or 
to the target “myApp”.

Internally, it works roughly as follows:

1. Generate the ui_....h filename (in the build/ directory):

> get_filename_component(_basename ${_tmp_FILE} NAME_WE)
> set(_header ${CMAKE_CURRENT_BINARY_DIR}/ui_${_basename}.h)

2. Create this C++ .h file [...]

3. Add this filename as source file to the target / SRCS list:

> if(TARGET ${_sources})
>     target_sources(${_sources} PRIVATE ${_header})
> else()
>     list(APPEND ${_sources} ${_header})
> endif()

Now I wonder why this *header file* is added as a *source file* to the target. 
Other source files will include <ui_myApp_dialog.h>, so it should be enough 
when this header file is found somewhere in the include search paths.

Is this how source file lists of a CMake target work? .cpp source files are 
compiled to .o files, and .h source files are only used as #include search 
path?

Cheers, David