validator: Check screenshot environment property

Author: ximion

src/as-validator-issue-tag.h

@@ -205,6 +205,12 @@ AsValidatorIssueTag as_validator_issue_tag_list[] =  {
 	  N_("The update-contact does not appear to be a valid email address (escaping of `@` is only allowed as `_at_` or `_AT_`).")
 	},
 
+	{ "screenshot-invalid-env-style",
+	  AS_ISSUE_SEVERITY_WARNING,
+	  /* TRANSLATORS: Please do not translate AppStream tag/property names (in backticks). */
+	  N_("The `environment` property is set to an unrecognized graphical environment/style combination.")
+	},
+
 	{ "screenshot-invalid-width",
 	  AS_ISSUE_SEVERITY_WARNING,
 	  /* TRANSLATORS: Please do not translate AppStream tag/property names (in backticks). */

src/as-validator.c

@@ -1448,6 +1448,7 @@ as_validator_check_screenshots (AsValidator *validator, xmlNode *node, AsCompone
 		gboolean caption_found = FALSE;
 		gboolean is_default_screenshot = FALSE;
 		g_autofree gchar *scr_kind_str = NULL;
+		g_autofree gchar *scr_env_style = NULL;
 		gboolean have_source_image = FALSE;
 		g_autoptr(GHashTable) known_source_locale = NULL;
 
@@ -1462,6 +1463,14 @@ as_validator_check_screenshots (AsValidator *validator, xmlNode *node, AsCompone
 			is_default_screenshot = TRUE;
 		}
 
+		scr_env_style = as_xml_get_prop_value (iter, "environment");
+		if (scr_env_style != NULL && !as_utils_is_gui_environment_style (scr_env_style)) {
+			as_validator_add_issue (validator,
+						iter,
+						"screenshot-invalid-env-style",
+						scr_env_style);
+		}
+
 		if (g_strcmp0 ((const gchar *) iter->name, "screenshot") != 0) {
 			as_validator_add_issue (
 			    validator,