package/opencv4: drop optional dependency on libgtk2

As we're about to remove libgtk2, we need to drop libgtk2 support
from opencv4. gtk3 support remains in place.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Woodrow Douglass <wdouglass@carnegierobotics.com>
[Arnout: add legacy handling]
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>

Config.in.legacy

@@ -146,6 +146,13 @@ endif
 
 comment "Legacy options removed in 2025.11"
 
+config BR2_PACKAGE_OPENCV4_WITH_GTK
+	bool "opencv4 gtk support has been removed"
+	select BR2_LEGACY
+	help
+	  Due to the removal of libgtk2, the gtk support of opencv4
+	  has been removed. gtk3 support is still available.
+
 config BR2_PACKAGE_OPENCV3_WITH_GTK
 	bool "opencv3 gtk support has been removed"
 	select BR2_LEGACY

package/opencv4/Config.in

@@ -81,15 +81,6 @@ choice
 config BR2_PACKAGE_OPENCV4_GUI_NONE
 	bool "none"
 
-config BR2_PACKAGE_OPENCV4_WITH_GTK
-	bool "gtk2"
-	depends on BR2_PACKAGE_LIBGTK2
-
-comment "gtk2 support needs libgtk2"
-	depends on BR2_USE_MMU # libgtk2 -> glib2
-	depends on BR2_TOOLCHAIN_HAS_SYNC_4
-	depends on !BR2_PACKAGE_LIBGTK2
-
 config BR2_PACKAGE_OPENCV4_WITH_GTK3
 	bool "gtk3"
 	depends on BR2_PACKAGE_LIBGTK3

package/opencv4/opencv4.mk

@@ -211,6 +211,7 @@ OPENCV4_CONF_OPTS += \
 	-DWITH_GDAL=OFF \
 	-DWITH_GPHOTO2=OFF \
 	-DWITH_GSTREAMER_0_10=OFF \
+	-DWITH_GTK_2_X=OFF \
 	-DWITH_LAPACK=OFF \
 	-DWITH_MATLAB=OFF \
 	-DWITH_OPENCL=OFF \
@@ -316,18 +317,11 @@ else
 OPENCV4_CONF_OPTS += -DWITH_GSTREAMER=OFF
 endif
 
-ifeq ($(BR2_PACKAGE_OPENCV4_WITH_GTK)$(BR2_PACKAGE_OPENCV4_WITH_GTK3),)
-OPENCV4_CONF_OPTS += -DWITH_GTK=OFF -DWITH_GTK_2_X=OFF
-endif
-
-ifeq ($(BR2_PACKAGE_OPENCV4_WITH_GTK),y)
-OPENCV4_CONF_OPTS += -DWITH_GTK=ON -DWITH_GTK_2_X=ON
-OPENCV4_DEPENDENCIES += libgtk2
-endif
-
 ifeq ($(BR2_PACKAGE_OPENCV4_WITH_GTK3),y)
-OPENCV4_CONF_OPTS += -DWITH_GTK=ON -DWITH_GTK_2_X=OFF
+OPENCV4_CONF_OPTS += -DWITH_GTK=ON
 OPENCV4_DEPENDENCIES += libgtk3
+else
+OPENCV4_CONF_OPTS += -DWITH_GTK=OFF
 endif
 
 ifeq ($(BR2_PACKAGE_OPENCV4_WITH_JPEG),y)