Add scale factor in display-monitor-attributes-list.

* lisp/frame.el (display-monitor-attributes-list): Add the comment.
* src/frame.c (make_monitor_attribute_list): Include the scale factor value.
(syms_of_frame): Declare intern'ed scale-factor.
* src/frame.h (struct MonitorInfo): Add scale_factor member.
* src/pgtkfns.c (Fpgtk_display_monitor_attributes_list): Set the value.

3 files changed, 11 insertions, 0 deletions

diff --git a/src/frame.c b/src/frame.c
index daaba2abfec..998ddaabb39 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -5826,6 +5826,10 @@ make_monitor_attribute_list (struct MonitorInfo *monitors,
                           attributes);
       attributes = Fcons (Fcons (Qframes, AREF (monitor_frames, i)),
                           attributes);
+#ifdef HAVE_PGTK
+      attributes = Fcons (Fcons (Qscale_factor, make_float (mi->scale_factor)),
+                          attributes);
+#endif
       attributes = Fcons (Fcons (Qmm_size,
                                  list2i (mi->mm_width, mi->mm_height)),
                           attributes);
@@ -5938,6 +5942,9 @@ syms_of_frame (void)
 
   DEFSYM (Qworkarea, "workarea");
   DEFSYM (Qmm_size, "mm-size");
+#ifdef HAVE_PGTK
+  DEFSYM (Qscale_factor, "scale-factor");
+#endif
   DEFSYM (Qframes, "frames");
   DEFSYM (Qsource, "source");
 
diff --git a/src/frame.h b/src/frame.h
index 10cb3f52e5e..7372e74cfef 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -1746,6 +1746,9 @@ struct MonitorInfo {
   Emacs_Rectangle geom, work;
   int mm_width, mm_height;
   char *name;
+#ifdef HAVE_PGTK
+  double scale_factor;
+#endif
 };
 
 extern void free_monitors (struct MonitorInfo *monitors, int n_monitors);
diff --git a/src/pgtkfns.c b/src/pgtkfns.c
index 63e121f1180..620680fbdaa 100644
--- a/src/pgtkfns.c
+++ b/src/pgtkfns.c
@@ -2647,6 +2647,7 @@ Internal use only, use `display-monitor-attributes-list' instead.  */)
       mi->work.height = work.height;
       mi->mm_width = width_mm;
       mi->mm_height = height_mm;
+      mi->scale_factor = scale;
 
       dupstring (&mi->name, (gdk_monitor_get_model (monitor)));
     }