nemo-mime-actions.c: Only add entire view file list to an image

viewer launch if its commandline supports multiple files.

As a result of #2705, when
a single image file is selected and launched, the full file list
for the current directory is appended for certain viewers.

This is a problem if the viewer's desktop file  Exec line doesn't
support multiple files, as it can cause multiple instances of
a program to launch when that was not the intent.

Only apply this new behavior if the Exec line accepts multiple
files (%U and %F).

ref: #2771

Author: mtwebster

libnemo-private/org.nemo.gschema.xml

@@ -210,7 +210,7 @@
     <key name="image-viewers-with-external-sort" type="as">
       <default>['xviewer','feh','sxiv']</default>
       <summary>Image viewer executables to pass sort order to</summary>
-      <description>When opening a single image with an application in this list, allow that viewer to display other images in the current nemo view, in the presented order (including searches). Other image viewers can be added, but are likely to ignore the order.</description>
+      <description>When opening a single image with an application in this list, allow that viewer to display other images in the current nemo view, in the presented order (including searches). Other image viewers can be added, but are likely to ignore the order. The viewer Exec line must accept a list of files (either %U or %F).</description>
     </key>
     <key name="mouse-use-extra-buttons" type="b">
       <default>true</default>

src/nemo-mime-actions.c

@@ -1491,9 +1491,12 @@ launch_application (GAppInfo *application,
 {
 	NemoFile *single_file;
 	char **sortable_image_viewers;
+    gboolean accepts_uri_list;
 
-	if (uris != NULL && uris->next == NULL) {
+    accepts_uri_list = g_strstr_len (g_app_info_get_commandline (application), -1, "%F") ||
+                       g_strstr_len (g_app_info_get_commandline (application), -1, "%U");
 
+	if (uris != NULL && uris->next == NULL && accepts_uri_list) {
 		sortable_image_viewers = g_settings_get_strv (nemo_preferences,
 													  NEMO_PREFERENCES_IMAGE_VIEWERS_WITH_EXTERNAL_SORT);