* termhooks.h (enum scroll_bar_part): Begin from 0 to allow...

(struct input_event): ...unsigned bitfields.  Likewise for
`event_kind' member.  Prefer unsigned for `code' and 'modifiers'.
Use `timestamp' for HELP_EVENT position.  Add compile-time assert.
* keyboard.c (gen_help_event, kbd_buffer_store_help_event)
(kbd_buffer_get_event): Adjust users.
(scroll_bar_parts): Add Qnil to match scroll_bar_nowhere.
(make_scroll_bar_position): New function, refactored out of...
(make_lispy_event): ...adjusted user.
* nsterm.h (EmacsScroller): Use enum for `last_hit_part' member.
* nsterm.m (ns_mouse_position, mouseUp):
* term.c (term_mouse_position):
* w32inevt.c (w32_console_mouse_position):
* w32term.c (w32_mouse_position):
* xterm.c (XTmouse_position): Use scroll_bar_above_handle.
(x_send_scroll_bar_event, xm_scroll_callback, xg_scroll_callback):
Prefer enum and explicit enum members to integers and numeric values.

1 files changed, 21 insertions, 10 deletions

diff --git a/src/termhooks.h b/src/termhooks.h
index 04104eb41e9..6412f0da6ca 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -28,7 +28,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 INLINE_HEADER_BEGIN
 
 enum scroll_bar_part {
-  scroll_bar_nowhere = -1,
+  scroll_bar_nowhere,
   scroll_bar_above_handle,
   scroll_bar_handle,
   scroll_bar_below_handle,
@@ -255,31 +255,42 @@ enum event_kind
 struct input_event
 {
   /* What kind of event was this?  */
-  enum event_kind kind;
+  ENUM_BF (event_kind) kind : 16;
+
+  /* Used in scroll back click events.  */
+  ENUM_BF (scroll_bar_part) part : 16;
 
   /* For an ASCII_KEYSTROKE_EVENT and MULTIBYTE_CHAR_KEYSTROKE_EVENT,
      this is the character.
      For a NON_ASCII_KEYSTROKE_EVENT, this is the keysym code.
-     For a mouse event, this is the button number.
-     For a HELP_EVENT, this is the position within the object
-      (stored in ARG below) where the help was found.  */
-  ptrdiff_t code;
-  enum scroll_bar_part part;
+     For a mouse event, this is the button number.  */
+  unsigned code;
 
-  int modifiers;                /* See enum below for interpretation.  */
+  /* See enum below for interpretation.  */
+  unsigned modifiers;
 
+  /* One would prefer C integers, but HELP_EVENT uses these to
+     record frame or window object and a help form, respectively.  */
   Lisp_Object x, y;
+
+  /* Usually a time as reported by window system-specific event loop.
+     For a HELP_EVENT, this is the position within the object (stored
+     in ARG below) where the help was found.  */
   Time timestamp;
 
   /* This field is copied into a vector while the event is in
      the queue, so that garbage collections won't kill it.  */
   Lisp_Object frame_or_window;
 
-  /* Additional event argument.  This is used for TOOL_BAR_EVENTs and
-     HELP_EVENTs and avoids calling Fcons during signal handling.  */
+  /* This additional argument is used in attempt to avoid extra consing
+     when building events.  Unfortunately some events have to pass much
+     more data than it's reasonable to pack directly into this structure.  */
   Lisp_Object arg;
 };
 
+/* To make sure we don't break HELP_EVENT.  */
+verify (sizeof (Time) == sizeof (ptrdiff_t));
+
 #define EVENT_INIT(event) memset (&(event), 0, sizeof (struct input_event))
 
 /* Bits in the modifiers member of the input_event structure.