Screenshot: Add an 'type' option

This option allows to select the type (screen, window, area) of screenshot
to be taken. Useful for apps that want to do the interactive parts
themselves but still allow the user these different types of screenshots.
This is only a hint, backends may not implement all of these.

data/org.freedesktop.impl.portal.Screenshot.xml

@@ -25,7 +25,7 @@
 
       This screenshot portal lets sandboxed applications request a screenshot.
 
-      This documentation describes version 2 of this interface.
+      This documentation describes version 3 of this interface.
   -->
   <interface name="org.freedesktop.impl.portal.Screenshot">
     <!--
@@ -50,6 +50,17 @@
           Hint whether the dialog should offer customization before taking a screenshot.
           Defaults to no.
 
+        * ``type`` (``u``)
+
+          Hints what type of screenshot should be taken. May preselect the type if combined with interactive.
+          Default is 0. Accepted values are:
+
+          - ``0``: Entire screen (default)
+          - ``1``: A window to be selected by the user
+          - ``2``: An area to be selected by the user
+
+          **Since version 3.**
+
         * ``permission_store_checked`` (``b``)
 
           Hint whether the screenshot portal has checked the 'screenshot' permission for

data/org.freedesktop.portal.Screenshot.xml

@@ -29,7 +29,7 @@
       may involve adding it to the :ref:`Documents
       portal<org.freedesktop.portal.Documents>`).
 
-      This documentation describes **version 2** of this interface.
+      This documentation describes **version 3** of this interface.
   -->
   <interface name="org.freedesktop.portal.Screenshot">
     <!--
@@ -57,6 +57,17 @@
           Hint whether the dialog should offer customization before taking a screenshot.
           Default is no.  **Since version 2.**
 
+        * ``type`` (``u``)
+
+          Hints what type of screenshot should be taken. May preselect the type if combined with interactive.
+          Default is 0. Accepted values are:
+
+          - ``0``: Entire screen (default)
+          - ``1``: A window to be selected by the user
+          - ``2``: An area to be selected by the user
+
+          **Since version 3.**
+
         The following results get returned via the :ref:`org.freedesktop.portal.Request::Response`
         signal:
 

src/screenshot.c

@@ -20,6 +20,7 @@
 
 #include "config.h"
 
+#include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
@@ -178,9 +179,28 @@ screenshot_done (GObject *source,
   g_task_run_in_thread (task, send_response_in_thread_func);
 }
 
+static gboolean
+validate_type (const char *key,
+               GVariant *value,
+               GVariant *options,
+               GError **error)
+{
+  uint32_t type = g_variant_get_uint32 (value);
+
+  if (type > 2)
+    {
+      g_set_error (error, XDG_DESKTOP_PORTAL_ERROR, XDG_DESKTOP_PORTAL_ERROR_INVALID_ARGUMENT,
+                   "Invalid screenshot type: %x", type);
+      return FALSE;
+    }
+
+  return TRUE;
+}
+
 static XdpOptionKey screenshot_options[] = {
   { "modal", G_VARIANT_TYPE_BOOLEAN, NULL },
-  { "interactive", G_VARIANT_TYPE_BOOLEAN, NULL }
+  { "interactive", G_VARIANT_TYPE_BOOLEAN, NULL },
+  { "type", G_VARIANT_TYPE_UINT32, validate_type }
 };
 
 static void