add gtk+3

packages/g/gtk+3/xmake.lua

@@ -0,0 +1,14 @@
+package("gtk+3")
+
+    set_homepage("https://gtk.org/")
+    set_description("Toolkit for creating graphical user interfaces")
+    set_license("LGPL-2.0-or-later")
+
+    if on_fetch then
+        on_fetch("linux", function (package, opt)
+            if opt.system and package.find_package then
+                return package:find_package("pkgconfig::gtk+-3.0")
+            end
+        end)
+    end
+

packages/o/opencv/xmake.lua

@@ -85,6 +85,11 @@ package("opencv")
         if package:config("cuda") then
             package:add("deps", "cuda", {system = true, configs = {utils = {"cudnn", "cufft", "cublas"}}})
         end
+        if package:is_plat("linux") then
+            if package:config("gtk") then
+                package:add("deps", "gtk+3", {optional = true})
+            end
+        end
         if not package.is_built or package:is_built() then
             package:add("deps", "cmake", "python 3.x", {kind = "binary"})
         end