Enable pixel-precision scrolling on pgtk port

* src/pgtkterm.c (scroll_event): Generate enhanced wheel
events.
(x_coalesce_scroll_events): New variable.

1 files changed, 55 insertions, 11 deletions

diff --git a/src/pgtkterm.c b/src/pgtkterm.c
index f7aadec321c..8353a9ca4dc 100644
--- a/src/pgtkterm.c
+++ b/src/pgtkterm.c
@@ -6032,37 +6032,77 @@ scroll_event (GtkWidget * widget, GdkEvent * event, gpointer * user_data)
     {
       dpyinfo->scroll.acc_x += delta_x;
       dpyinfo->scroll.acc_y += delta_y;
-      if (dpyinfo->scroll.acc_y >= dpyinfo->scroll.y_per_line)
+      if (dpyinfo->scroll.acc_y >= dpyinfo->scroll.y_per_line
+          || !x_coalesce_scroll_events)
         {
           int nlines = dpyinfo->scroll.acc_y / dpyinfo->scroll.y_per_line;
           inev.ie.kind = WHEEL_EVENT;
           inev.ie.modifiers |= down_modifier;
-          inev.ie.arg = make_fixnum (nlines);
-          dpyinfo->scroll.acc_y -= dpyinfo->scroll.y_per_line * nlines;
+          inev.ie.arg = list3 (make_fixnum (nlines),
+                               make_float (-dpyinfo->scroll.acc_x * 10),
+                               make_float (-dpyinfo->scroll.acc_y * 10));
+          if (!x_coalesce_scroll_events)
+            {
+              dpyinfo->scroll.acc_y = 0;
+              dpyinfo->scroll.acc_x = 0;
+            }
+          else
+            {
+              dpyinfo->scroll.acc_y -= dpyinfo->scroll.y_per_line * nlines;
+            }
         }
-      else if (dpyinfo->scroll.acc_y <= -dpyinfo->scroll.y_per_line)
+      else if (dpyinfo->scroll.acc_y <= -dpyinfo->scroll.y_per_line
+               || !x_coalesce_scroll_events)
         {
           int nlines = -dpyinfo->scroll.acc_y / dpyinfo->scroll.y_per_line;
           inev.ie.kind = WHEEL_EVENT;
           inev.ie.modifiers |= up_modifier;
-          inev.ie.arg = make_fixnum (nlines);
-          dpyinfo->scroll.acc_y -= -dpyinfo->scroll.y_per_line * nlines;
+          inev.ie.arg = list3 (make_fixnum (nlines),
+                               make_float (-dpyinfo->scroll.acc_x * 10),
+                               make_float (-dpyinfo->scroll.acc_y * 10));
+
+          if (!x_coalesce_scroll_events)
+            {
+              dpyinfo->scroll.acc_y = 0;
+              dpyinfo->scroll.acc_x = 0;
+            }
+          else
+            dpyinfo->scroll.acc_y -= -dpyinfo->scroll.y_per_line * nlines;
         }
-      else if (dpyinfo->scroll.acc_x >= dpyinfo->scroll.x_per_char)
+      else if (dpyinfo->scroll.acc_x >= dpyinfo->scroll.x_per_char
+               || !x_coalesce_scroll_events)
         {
           int nchars = dpyinfo->scroll.acc_x / dpyinfo->scroll.x_per_char;
           inev.ie.kind = HORIZ_WHEEL_EVENT;
           inev.ie.modifiers |= up_modifier;
-          inev.ie.arg = make_fixnum (nchars);
-          dpyinfo->scroll.acc_x -= dpyinfo->scroll.x_per_char * nchars;
+          inev.ie.arg = list3 (make_fixnum (nchars),
+                               make_float (-dpyinfo->scroll.acc_x * 10),
+                               make_float (-dpyinfo->scroll.acc_y * 10));
+
+          if (x_coalesce_scroll_events)
+            dpyinfo->scroll.acc_x -= dpyinfo->scroll.x_per_char * nchars;
+          else
+            {
+              dpyinfo->scroll.acc_x = 0;
+              dpyinfo->scroll.acc_y = 0;
+            }
         }
       else if (dpyinfo->scroll.acc_x <= -dpyinfo->scroll.x_per_char)
         {
           int nchars = -dpyinfo->scroll.acc_x / dpyinfo->scroll.x_per_char;
           inev.ie.kind = HORIZ_WHEEL_EVENT;
           inev.ie.modifiers |= down_modifier;
-          inev.ie.arg = make_fixnum (nchars);
-          dpyinfo->scroll.acc_x -= -dpyinfo->scroll.x_per_char * nchars;
+          inev.ie.arg = list3 (make_fixnum (nchars),
+                               make_float (-dpyinfo->scroll.acc_x * 10),
+                               make_float (-dpyinfo->scroll.acc_y * 10));
+
+          if (x_coalesce_scroll_events)
+            dpyinfo->scroll.acc_x -= -dpyinfo->scroll.x_per_char * nchars;
+          else
+            {
+              dpyinfo->scroll.acc_x = 0;
+              dpyinfo->scroll.acc_y = 0;
+            }
         }
     }
 
@@ -6711,6 +6751,10 @@ If set to a non-float value, there will be no wait at all.  */);
   window_being_scrolled = Qnil;
   staticpro (&window_being_scrolled);
 
+  DEFVAR_BOOL ("x-coalesce-scroll-events", x_coalesce_scroll_events,
+               doc: /* SKIP: real doc in xterm.c.  */);
+  x_coalesce_scroll_events = true;
+
   /* Tell Emacs about this window system.  */
   Fprovide (Qpgtk, Qnil);
 }