Handle negative coordinates in ‘x_calc_absolute_position’

* src/w32term.c (x_calc_absolute_position): Find display origin to
allow for negative coordinates.

1 files changed, 33 insertions, 0 deletions

diff --git a/src/w32term.c b/src/w32term.c
index 83178672679..f764e250aa8 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -5913,16 +5913,49 @@ x_calc_absolute_position (struct frame *f)
       top_bottom_borders_height = 32;
     }
 
+  /* With multiple monitors, we can legitimately get negative
+     coordinates (for monitors above or to the left of the primary
+     monitor).  Find the display origin to ensure negative positions
+     are computed correctly (Bug#21173).  */
+  int display_left = 0;
+  int display_top = 0;
+  if (flags & (XNegative | YNegative))
+    {
+      Lisp_Object list;
+
+      list = Fw32_display_monitor_attributes_list (Qnil);
+      while (CONSP (list))
+        {
+          Lisp_Object attributes = CAR(list);
+          Lisp_Object geometry;
+          Lisp_Object monitor_left, monitor_top;
+
+          list = CDR(list);
+
+          geometry = Fassoc (Qgeometry, attributes);
+          if (!NILP (geometry))
+            {
+              monitor_left = Fnth (make_number (1), geometry);
+              monitor_top  = Fnth (make_number (2), geometry);
+
+              display_left = min (display_left, XINT (monitor_left));
+              display_top  = min (display_top,  XINT (monitor_top));
+            }
+        }
+    }
+
   /* Treat negative positions as relative to the rightmost bottommost
      position that fits on the screen.  */
   if (flags & XNegative)
     f->left_pos = (x_display_pixel_width (FRAME_DISPLAY_INFO (f))
+                   + display_left
                    - FRAME_PIXEL_WIDTH (f)
                    + f->left_pos
                    - (left_right_borders_width - 1));
 
   if (flags & YNegative)
     f->top_pos = (x_display_pixel_height (FRAME_DISPLAY_INFO (f))
+                  + display_top
                   - FRAME_PIXEL_HEIGHT (f)
                   + f->top_pos
                   - (top_bottom_borders_height - 1));