Add touchscreen support to the tab bar

* lisp/menu-bar.el (popup-menu-normalize-position): Normalize
`touchscreen-begin' events correctly.
* lisp/tab-bar.el (tab-bar-mouse-context-menu): New argument
POSN.  Use it if specified.
(touch-screen-track-tap, tab-bar-handle-timeout)
(tab-bar-touchscreen-begin): New functions.
(tab-bar-map): Bind [tab-bar touchscreen-begin].
* lisp/touch-screen.el (touch-screen-track-drag): Fix doc
string.
* src/dispextern.h: Export `get_tab_bar_item_kbd'.
* src/keyboard.c (coords_in_tab_bar_window): New function.
(make_lispy_event): Adjust touchscreen begin event mouse
position list for tab bar.
* src/xdisp.c (tab_bar_item_info): Allow CLOSE_P to be NULL.
(get_tab_bar_item): Adjust doc string.
(get_tab_bar_item_kbd): New function.

3 files changed, 121 insertions, 12 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 36e998070a4..402972d33d9 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3528,6 +3528,7 @@ extern void get_glyph_string_clip_rect (struct glyph_string *,
                                         NativeRectangle *nr);
 extern Lisp_Object find_hot_spot (Lisp_Object, int, int);
 
+extern int get_tab_bar_item_kbd (struct frame *, int, int, int *, bool *);
 extern Lisp_Object handle_tab_bar_click (struct frame *,
                                          int, int, bool, int);
 extern void handle_tool_bar_click (struct frame *,
diff --git a/src/keyboard.c b/src/keyboard.c
index 6e63cd71f30..c0d201f72ad 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -5875,6 +5875,25 @@ coords_in_menu_bar_window (struct frame *f, int x, int y)
 
 #endif
 
+/* Return whether or not the coordinates X and Y are inside the
+   tab-bar window of the given frame F.  */
+
+static bool
+coords_in_tab_bar_window (struct frame *f, int x, int y)
+{
+  struct window *window;
+
+  if (!WINDOWP (f->tab_bar_window))
+    return false;
+
+  window = XWINDOW (f->tab_bar_window);
+
+  return (y >= WINDOW_TOP_EDGE_Y (window)
+          && x >= WINDOW_LEFT_EDGE_X (window)
+          && y <= WINDOW_BOTTOM_EDGE_Y (window)
+          && x <= WINDOW_RIGHT_EDGE_X (window));
+}
+
 /* Given a struct input_event, build the lisp event which represents
    it.  If EVENT is 0, build a mouse movement event from the mouse
    movement buffer, which should have a movement event in it.
@@ -6522,11 +6541,14 @@ make_lispy_event (struct input_event *event)
     case TOUCHSCREEN_END_EVENT:
       {
         Lisp_Object x, y, id, position;
-        struct frame *f = XFRAME (event->frame_or_window);
+        struct frame *f;
+        int tab_bar_item;
+        bool close;
 #if defined HAVE_WINDOW_SYSTEM && !defined HAVE_EXT_MENU_BAR
         int column, row, dummy;
-#endif
+#endif /* defined HAVE_WINDOW_SYSTEM && !defined HAVE_EXT_MENU_BAR */
 
+        f = XFRAME (event->frame_or_window);
         id = event->arg;
         x = event->x;
         y = event->y;
@@ -6589,10 +6611,53 @@ make_lispy_event (struct input_event *event)
 
             return Qnil;
           }
-#endif
+#endif /* defined HAVE_WINDOW_SYSTEM && !defined HAVE_EXT_MENU_BAR */
 
         position = make_lispy_position (f, x, y, event->timestamp);
 
+#ifdef HAVE_WINDOW_SYSTEM
+
+        /* Now check if POSITION lies on the tab bar.  If so, look up
+           the corresponding tab bar item's propertized string as the
+           OBJECT.  */
+
+        if (coords_in_tab_bar_window (f, XFIXNUM (event->x),
+                                      XFIXNUM (event->y))
+            /* `get_tab_bar_item_kbd' returns 0 if the item was
+               previously highlighted, 1 otherwise, and -1 if there is
+               no tab bar item.  */
+            && get_tab_bar_item_kbd (f, XFIXNUM (event->x),
+                                     XFIXNUM (event->y), &tab_bar_item,
+                                     &close) >= 0)
+          {
+            /* First, obtain the propertized string.  */
+            x = Fcopy_sequence (AREF (f->tab_bar_items,
+                                      (tab_bar_item
+                                       + TAB_BAR_ITEM_CAPTION)));
+
+            /* Next, add the key binding.  */
+            AUTO_LIST2 (y, Qmenu_item, list3 (AREF (f->tab_bar_items,
+                                                    (tab_bar_item
+                                                     + TAB_BAR_ITEM_KEY)),
+                                              AREF (f->tab_bar_items,
+                                                    (tab_bar_item
+                                                     + TAB_BAR_ITEM_BINDING)),
+                                              close ? Qt : Qnil));
+
+            /* And add the new properties to the propertized string.  */
+            Fadd_text_properties (make_fixnum (0),
+                                  make_fixnum (SCHARS (x)),
+                                  y, x);
+
+            /* Set the position to 0.  */
+            x = Fcons (x, make_fixnum (0));
+
+            /* Finally, add the OBJECT.  */
+            position = nconc2 (position, Fcons (x, Qnil));
+          }
+
+#endif /* HAVE_WINDOW_SYSTEM */
+
         return list2 (((event->kind
                         == TOUCHSCREEN_BEGIN_EVENT)
                        ? Qtouchscreen_begin
diff --git a/src/xdisp.c b/src/xdisp.c
index 89b1ae77e6f..09b1cc616f2 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -14584,21 +14584,32 @@ tab_bar_item_info (struct frame *f, struct glyph *glyph,
                              Qmenu_item, f->current_tab_bar_string);
   if (! FIXNUMP (prop))
     return false;
+
   *prop_idx = XFIXNUM (prop);
 
-  *close_p = !NILP (Fget_text_property (make_fixnum (charpos),
-                                        Qclose_tab,
-                                        f->current_tab_bar_string));
+  if (close_p)
+    *close_p = !NILP (Fget_text_property (make_fixnum (charpos),
+                                          Qclose_tab,
+                                          f->current_tab_bar_string));
 
   return true;
 }
 
 
-/* Get information about the tab-bar item at position X/Y on frame F.
-   Return in *GLYPH a pointer to the glyph of the tab-bar item in
-   the current matrix of the tab-bar window of F, or NULL if not
-   on a tab-bar item.  Return in *PROP_IDX the index of the tab-bar
-   item in F->tab_bar_items.  Value is
+/* Get information about the tab-bar item at position X/Y on frame F's
+   tab bar window.
+
+   Set *GLYPH to a pointer to the glyph of the tab-bar item in the
+   current matrix of the tab-bar window of F, or NULL if not on a
+   tab-bar item.  Return in *PROP_IDX the index of the tab-bar item in
+   F->tab_bar_items.
+
+   Place the window-relative vpos of Y in *VPOS, and the
+   window-relative hpos of X in *HPOS.  If CLOSE_P, set it to whether
+   or not the tab bar item represents a button that should close a
+   tab.
+
+   Value is
 
    -1   if X/Y is not on a tab-bar item
    0    if X/Y is on the same item that was highlighted before.
@@ -14606,7 +14617,7 @@ tab_bar_item_info (struct frame *f, struct glyph *glyph,
 
 static int
 get_tab_bar_item (struct frame *f, int x, int y, struct glyph **glyph,
-                   int *hpos, int *vpos, int *prop_idx, bool *close_p)
+                  int *hpos, int *vpos, int *prop_idx, bool *close_p)
 {
   struct window *w = XWINDOW (f->tab_bar_window);
   int area;
@@ -14624,6 +14635,38 @@ get_tab_bar_item (struct frame *f, int x, int y, struct glyph **glyph,
   return *prop_idx == f->last_tab_bar_item ? 0 : 1;
 }
 
+/* EXPORT:
+
+   Like `get_tab_bar_item'.  However, don't return anything for GLYPH,
+   HPOS, or VPOS, and treat X and Y as relative to F itself, as
+   opposed to its tab bar window.  */
+
+int
+get_tab_bar_item_kbd (struct frame *f, int x, int y, int *prop_idx,
+                      bool *close_p)
+{
+  struct window *w;
+  int area, vpos, hpos;
+  struct glyph *glyph;
+
+  w = XWINDOW (f->tab_bar_window);
+
+  /* Convert X and Y to window coordinates.  */
+  frame_to_window_pixel_xy (w, &x, &y);
+
+  /* Find the glyph under X/Y.  */
+  glyph = x_y_to_hpos_vpos (w, x, y, &hpos, &vpos, 0,
+                            0, &area);
+  if (glyph == NULL)
+    return -1;
+
+  /* Get the start of this tab-bar item's properties in
+     f->tab_bar_items.  */
+  if (!tab_bar_item_info (f, glyph, prop_idx, close_p))
+    return -1;
+
+  return *prop_idx == f->last_tab_bar_item ? 0 : 1;
+}
 
 /* EXPORT:
    Handle mouse button event on the tab-bar of frame F, at