modified:   CMakeLists.txt
	modified:   cmake/OpenCVFindLibsGUI.cmake

When with_gtk is selected but GTK3 is not present the current logic
fails to check for GTK2. This edit corrects this.

When GTK3 is not found, HAVE_GTK was being set to TRUE. This edit
ensures that HAVE_GTK is only set if GTK3 or GTK2 (meeting minimum
version requirements) is present.
Selection logic for printing 'GTK: No' when the libraries are not found
has also been removed so the message is printed when GTK is not found or
selected in common with other libraries.

Changes committed:
	modified:   CMakeLists.txt
	modified:   cmake/OpenCVFindLibsGUI.cmake

The new logic will select GTK+3 by default if WITH_GTK is selected. If
the GTK+3 libraries are not found, then GTK+2 libraries will be selected
if found.
This can be overridden by using WITH_GTK_2_X to force selection of GTK+2
(if found).

specific code. As a result of this, HAVE_GTK3 no longer needs to be
exposed.

The use of HAVE_GTK, and HAVE_ GTK3 have been changed to mirror the
method used by HAVE_QT and HAVE_QT5.
 On branch gtk3
 Changes to be committed:
        modified:   CMakeLists.txt
        modified:   cmake/OpenCVFindLibsGUI.cmake
        modified:   cmake/templates/cvconfig.h.in
        modified:   modules/highgui/src/window.cpp
        modified:   modules/highgui/src/window_gtk.cpp

	modified:   CMakeLists.txt
	modified:   cmake/OpenCVFindLibsGUI.cmake

When with_gtk is selected but GTK3 is not present the current logic
fails to check for GTK2. This edit corrects this.

When GTK3 is not found, HAVE_GTK was being set to TRUE. This edit
ensures that HAVE_GTK is only set if GTK3 or GTK2 (meeting minimum
version requirements) is present.
Selection logic for printing 'GTK: No' when the libraries are not found
has also been removed so the message is printed when GTK is not found or
selected in common with other libraries.

Changes committed:
	modified:   CMakeLists.txt
	modified:   cmake/OpenCVFindLibsGUI.cmake

The new logic will select GTK+3 by default if WITH_GTK is selected. If
the GTK+3 libraries are not found, then GTK+2 libraries will be selected
if found.
This can be overridden by using WITH_GTK_2_X to force selection of GTK+2
(if found).

specific code. As a result of this, HAVE_GTK3 no longer needs to be
exposed.

The use of HAVE_GTK, and HAVE_ GTK3 have been changed to mirror the
method used by HAVE_QT and HAVE_QT5.
 On branch gtk3
 Changes to be committed:
        modified:   CMakeLists.txt
        modified:   cmake/OpenCVFindLibsGUI.cmake
        modified:   cmake/templates/cvconfig.h.in
        modified:   modules/highgui/src/window.cpp
        modified:   modules/highgui/src/window_gtk.cpp

Update to cmake files for to include minimum versions, and tidy up gtk operation.

Files updated:
CMakeLists.txt:
  WITH_GTK now uses Gtk3 by default. If not found then Gtk2 is used.
  WITH_GTK_2_X forces Gtk2.x use

cmake/OpenCVFindLibsGUI.cmake
  Updated selection logic to implement methodology described above.
  Implemented warning if Gtk3 not found (and not overridden)
  Implemented error if Gtk does not meet minimum required version

cmake/OpenCVMinDepVersions.cmake
  Added minimum Gtk version of 2.18.0

The OpenGL library is not supported on Gtk3 which uses the cairo
library for rendering. Cairo, in turn uses hardware acceleration when
supported by the underlying system. Some improvement to performance
may be gained by useing the cairo-gl and cairo-glx libraries included
on modern Gtk3 systems.

See the cairo documentation for further information. The following
link may also be of interest.

http://lists.cairographics.org/archives/cairo/2012-October/023609.html

A new option WITH_GTK3 has been added to the cmake configure system to enable compilation under Gtk version 3.The flag HAVE_GTK3 is also introduced to select the new Gtk3 code in the source files. (Gtk2 is disbled when Gtk3 is selected).

window_gtk.cpp has been modified to remove obsolete (and deleted from libgtk 3) and introduce new Gtk3 code in its place when compiled for Gtk3.

To compile for Gtk2, disable WITH_GTK3 in cmake. To build for Gtk3 both WITH_GTK and WITH_GTK3 must be selected.

* There's no OPENCV_BINARY_DIR variable;
* No need to append CMakeFiles/CMakeTmp, as CMake does it for you;
* Output variables are unused;
* Wrong usage of CMAKE_FLAGS;
* Small quoting and style issues.

Now the HAVE_* macros are set using cvconfig.h. Previously most
of them already were there, but were always undefined. One,
HAVE_COCOA, I had to add.

This also makes the CMake code more consistent; now, WITH_* variables
are always checked in cmake/*, while HAVE_* variables are checked in
modules/highgui/CMakeLists.txt.

I don't know why it didn't work for the original author, but it definitely
works now.

Also, removing explicit include path configuration,
since QT_USE_FILE takes care of that.

Issue #2868