Use scaled coordinates when calling into GTK

This is part two of a two part fix for the GTK scaling
problems.  See the thread starting at
http://lists.gnu.org/archive/html/emacs-devel/2018-01/msg00372.html
for an explanation of why it has been added to Emacs 26.

* src/gtkutil.c (xg_set_geometry): Scale down the coordinates that we
pass to gtk_window_move and to gtk_window_parse_geometry.
* src/xterm.c (x_set_offset): Likewise.

2 files changed, 13 insertions, 7 deletions

diff --git a/src/gtkutil.c b/src/gtkutil.c
index 123236f5f08..83b306a730a 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -823,6 +823,7 @@ xg_set_geometry (struct frame *f)
 {
   if (f->size_hint_flags & (USPosition | PPosition))
     {
+      int scale = xg_get_scale (f);
 #if ! GTK_CHECK_VERSION (3, 22, 0)
       if (x_gtk_use_window_move)
         {
@@ -838,8 +839,9 @@ xg_set_geometry (struct frame *f)
             f->top_pos = (x_display_pixel_height (FRAME_DISPLAY_INFO (f))
                           - FRAME_PIXEL_HEIGHT (f) + f->top_pos);
 
+          /* GTK works in scaled pixels, so convert from X pixels.  */
           gtk_window_move (GTK_WINDOW (FRAME_GTK_OUTER_WIDGET (f)),
-                           f->left_pos, f->top_pos);
+                           f->left_pos / scale, f->top_pos / scale);
 
           /* Reset size hint flags.  */
           f->size_hint_flags &= ~ (XNegative | YNegative);
@@ -847,9 +849,10 @@ xg_set_geometry (struct frame *f)
         }
       else
         {
-          int left = f->left_pos;
+          /* GTK works in scaled pixels, so convert from X pixels.  */
+          int left = f->left_pos / scale;
           int xneg = f->size_hint_flags & XNegative;
-          int top = f->top_pos;
+          int top = f->top_pos / scale;
           int yneg = f->size_hint_flags & YNegative;
           char geom_str[sizeof "=x--" + 4 * INT_STRLEN_BOUND (int)];
           guint id;
diff --git a/src/xterm.c b/src/xterm.c
index f771631dafa..f05ac6147eb 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -10310,6 +10310,7 @@ void
 x_set_offset (struct frame *f, register int xoff, register int yoff, int change_gravity)
 {
   int modified_top, modified_left;
+  int scale = xg_get_scale (f);
 
   if (change_gravity > 0)
     {
@@ -10332,11 +10333,12 @@ x_set_offset (struct frame *f, register int xoff, register int yoff, int change_
   if (x_gtk_use_window_move)
     {
       /* When a position change was requested and the outer GTK widget
-         has been realized already, leave it to gtk_window_move to DTRT
-         and return.  Used for Bug#25851 and Bug#25943.  */
+         has been realized already, leave it to gtk_window_move to
+         DTRT and return.  Used for Bug#25851 and Bug#25943.  Convert
+         from X pixels to GTK scaled pixels.  */
       if (change_gravity != 0 && FRAME_GTK_OUTER_WIDGET (f))
         gtk_window_move (GTK_WINDOW (FRAME_GTK_OUTER_WIDGET (f)),
-                         f->left_pos, f->top_pos);
+                         f->left_pos / scale, f->top_pos / scale);
       unblock_input ();
       return;
     }
@@ -10355,8 +10357,9 @@ x_set_offset (struct frame *f, register int xoff, register int yoff, int change_
     }
 
 #ifdef USE_GTK
+  /* Make sure we adjust for possible scaling.  */
   gtk_window_move (GTK_WINDOW (FRAME_GTK_OUTER_WIDGET (f)),
-                   modified_left, modified_top);
+                   modified_left / scale, modified_top / scale);
 #else
   XMoveWindow (FRAME_X_DISPLAY (f), FRAME_OUTER_WINDOW (f),
                modified_left, modified_top);