package/opencv: add opengl support

In OpenCV, OpenGL is only used by highgui module.

OpenGL support is done using extensions from 3rd party framework: either
Qt5OpenGL with Qt5 (with GL support only, not GLES); or gtkglext (which
is not available in Buildroot) with gtk2

So, make OpenGL knob a sub-option of the Qt5 support option.

Note: we enclose both the GUI toolkit choice and the GL option in an
if-block, so that the GL option gets properly indented; having it
depend on WITH_QT5 is not enough, because it does not directly follow
it, so kconfig would not consider it for indenting.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
[yann.morin.1998@free.fr: tweak commit log about the if-block]
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/opencv/Config.in

@@ -52,9 +52,10 @@ config BR2_PACKAGE_OPENCV_LIB_HIGHGUI
 	  Include opencv_highgui (high-level gui and media i/o) module into the
 	  OpenCV build.
 
+if BR2_PACKAGE_OPENCV_LIB_HIGHGUI
+
 choice
 	prompt "gui toolkit"
-	depends on BR2_PACKAGE_OPENCV_LIB_HIGHGUI
 	help
 	  GUI toolkit to be used by the opencv_highgui module.
 
@@ -108,6 +109,25 @@ comment "qt5 support needs qt5"
 
 endchoice
 
+config BR2_PACKAGE_OPENCV_WITH_OPENGL
+	bool "opengl support"
+	# OpenGL support done using Qt5OpenGL, so depends on WITH_QT5
+	depends on BR2_PACKAGE_OPENCV_WITH_QT5
+	# OpenGL support requires Qt5OpenGL with GL support, not GLES
+	depends on BR2_PACKAGE_QT5_GL_AVAILABLE
+	depends on BR2_PACKAGE_HAS_LIBGL
+	select BR2_PACKAGE_QT5BASE_OPENGL
+	help
+	  Enable OpenGL for UI.
+
+comment "opengl support needs an OpenGL provider"
+	depends on BR2_PACKAGE_OPENCV_WITH_QT5
+	depends on !BR2_PACKAGE_QT5_GL_AVAILABLE || \
+		!BR2_PACKAGE_HAS_LIBGL
+
+endif # BR2_PACKAGE_OPENCV_LIB_HIGHGUI
+
+
 config BR2_PACKAGE_OPENCV_LIB_IMGCODECS
 	bool "imgcodecs"
 	select BR2_PACKAGE_OPENCV_LIB_IMGPROC

package/opencv/opencv.mk

@@ -264,6 +264,13 @@ else
 OPENCV_CONF_OPTS += -DWITH_JPEG=OFF
 endif
 
+ifeq ($(BR2_PACKAGE_OPENCV_WITH_OPENGL),y)
+OPENCV_CONF_OPTS += -DWITH_OPENGL=ON
+OPENCV_DEPENDENCIES += libgl
+else
+OPENCV_CONF_OPTS += -DWITH_OPENGL=OFF
+endif
+
 OPENCV_CONF_OPTS += -DWITH_OPENMP=$(if $(BR2_GCC_ENABLE_OPENMP),ON,OFF)
 
 ifeq ($(BR2_PACKAGE_OPENCV_WITH_PNG),y)