qwt: Added check for cppstd

recipes/qwt/all/conanfile.py

@@ -1,6 +1,6 @@
 from conan import ConanFile
 from conan.errors import ConanInvalidConfiguration
-from conan.tools.build import cross_building
+from conan.tools.build import cross_building, check_min_cppstd
 from conan.tools.cmake import CMake, CMakeToolchain, CMakeDeps, cmake_layout
 from conan.tools.env import VirtualBuildEnv, VirtualRunEnv
 from conan.tools.files import apply_conandata_patches, copy, export_conandata_patches, get, rmdir
@@ -48,6 +48,10 @@ class QwtConan(ConanFile):
     def _is_legacy_one_profile(self):
         return not hasattr(self, "settings_build")
 
+    @property
+    def _min_cppstd(self):
+        return  17 if self.dependencies["qt"].ref.version >= 6 else 11
+
     def export_sources(self):
         export_conandata_patches(self)
 
@@ -68,6 +72,8 @@ def requirements(self):
     def validate(self):
         if hasattr(self, "settings_build") and cross_building(self):
             raise ConanInvalidConfiguration("Qwt recipe does not support cross-compilation yet")
+        if self.settings.compiler.get_safe("cppstd"):
+            check_min_cppstd(self, self._min_cppstd)
         qt_options = self.dependencies["qt"].options
         if self.options.widgets and not qt_options.widgets:
             raise ConanInvalidConfiguration("qwt:widgets=True requires qt:widgets=True")