Add unit test for wxFont::GetStyle() and special style values

Similarly to the previous commit, verify that wxNORMAL, wxITALIC and
wxSLANT still work for compatibility (note the latter is synonymous with
wxITALIC under MSW).

tests/font/fonttest.cpp

@@ -145,6 +145,39 @@ TEST_CASE("wxFont::Size", "[font][size]")
     }
 }
 
+TEST_CASE("wxFont::Style", "[font][style]")
+{
+#if WXWIN_COMPATIBILITY_3_0
+    // Disable the warning about deprecated wxNORMAL as we use it here
+    // intentionally.
+    #ifdef __VISUALC__
+        #pragma warning(push)
+        #pragma warning(disable:4996)
+    #endif
+
+    wxGCC_WARNING_SUPPRESS(deprecated-declarations)
+
+    wxFont fontNormal(10, wxDEFAULT, wxNORMAL, wxNORMAL);
+    CHECK( fontNormal.GetStyle() == wxFONTSTYLE_NORMAL );
+
+    wxFont fontItalic(10, wxDEFAULT, wxITALIC, wxNORMAL);
+    CHECK( fontItalic.GetStyle() == wxFONTSTYLE_ITALIC );
+
+    wxFont fontSlant(10, wxDEFAULT, wxSLANT, wxNORMAL);
+#ifdef __WXMSW__
+    CHECK( fontSlant.GetStyle() == wxFONTSTYLE_ITALIC );
+#else
+    CHECK( fontSlant.GetStyle() == wxFONTSTYLE_SLANT );
+#endif
+
+    wxGCC_WARNING_RESTORE(deprecated-declarations)
+
+    #ifdef __VISUALC__
+        #pragma warning(pop)
+    #endif
+#endif // WXWIN_COMPATIBILITY_3_0
+}
+
 TEST_CASE("wxFont::Weight", "[font][weight]")
 {
 #if WXWIN_COMPATIBILITY_3_0