Add distinct controls for child frames' borders (Bug#45620)

The background of the 'child-frame-border' face instead of the
'internal-border' face now controls the color of child frames'
borders.

The 'child-frame-border-width' frame parameter is now used for the
width of child frames' borders instead of internal-border-width',
though we still fall back on using the latter if the former is not
set.

* doc/lispref/frames.texi (Frame Layout): Mention
'child-frame-border' and 'child-frame-border-width'.
(Layout Parameters): Mention 'child-frame-border-width'.
* etc/NEWS: Mention new face 'child-frame-border' and frame
parameter 'child-frame-border-width'.
* lisp/faces.el (child-frame-border): New face.
* src/dispextern.h (enum face_id): Add CHILD_FRAME_BORDER_FACE_ID.
* src/frame.c (Fframe_child_frame_border_width): New function.
(gui_report_frame_params): Add entry for Qchild_frame_border_width.
* src/frame.h (struct frame): New slot child_frame_border_width.
(FRAME_CHILD_FRAME_BORDER_WIDTH): New inlined function.
* src/nsfns.m (ns_set_child_frame_border_width): New function.
(Fx_create_frame): Handle Qchild_frame_border_width parameter.
(ns_frame_parm_handlers): Add ns_set_child_frame_border_width.
* src/nsterm.m (ns_clear_under_internal_border): Handle
CHILD_FRAME_BORDER_FACE_ID.
* src/w32fns.c (w32_clear_under_internal_border): Handle
CHILD_FRAME_BORDER_FACE_ID.
(w32_set_internal_border_width): New function.
(Fx_create_frame): Handle Qchild_frame_border_width parameter.
(w32_frame_parm_handlers): Add w32_set_child_frame_border_width.
* src/xfaces.c (lookup_basic_face, realize_basic_faces): Handle
CHILD_FRAME_BORDER_FACE_ID.
* src/xfns.c (x_set_child_frame_border_width): New function.
(Fx_create_frame): Handle Qchild_frame_border_width parameter.
(x_frame_parm_handlers): Add x_set_child_frame_border_width.
* src/xterm.c (x_clear_under_internal_border)
(x_after_update_window_line): Handle CHILD_FRAME_BORDER_FACE_ID.

9 files changed, 180 insertions, 14 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 3ad98b8344e..f4e872644db 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1826,6 +1826,7 @@ enum face_id
   WINDOW_DIVIDER_FIRST_PIXEL_FACE_ID,
   WINDOW_DIVIDER_LAST_PIXEL_FACE_ID,
   INTERNAL_BORDER_FACE_ID,
+  CHILD_FRAME_BORDER_FACE_ID,
   TAB_BAR_FACE_ID,
   TAB_LINE_FACE_ID,
   BASIC_FACE_ID_SENTINEL
diff --git a/src/frame.c b/src/frame.c
index 599c4075f88..a2167ce1e49 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -3543,6 +3543,13 @@ DEFUN ("frame-fringe-width", Ffringe_width, Sfringe_width, 0, 1, 0,
   return make_fixnum (FRAME_TOTAL_FRINGE_WIDTH (decode_any_frame (frame)));
 }
 
+DEFUN ("frame-child-frame-border-width", Fframe_child_frame_border_width, Sframe_child_frame_border_width, 0, 1, 0,
+       doc: /* Return width of FRAME's child-frame border in pixels.  */)
+  (Lisp_Object frame)
+{
+  return make_fixnum (FRAME_CHILD_FRAME_BORDER_WIDTH (decode_any_frame (frame)));
+}
+
 DEFUN ("frame-internal-border-width", Fframe_internal_border_width, Sframe_internal_border_width, 0, 1, 0,
        doc: /* Return width of FRAME's internal border in pixels.  */)
   (Lisp_Object frame)
@@ -3759,6 +3766,7 @@ static const struct frame_parm_table frame_parms[] =
   {"foreground-color",          -1},
   {"icon-name",                 SYMBOL_INDEX (Qicon_name)},
   {"icon-type",                 SYMBOL_INDEX (Qicon_type)},
+  {"child-frame-border-width",  SYMBOL_INDEX (Qchild_frame_border_width)},
   {"internal-border-width",     SYMBOL_INDEX (Qinternal_border_width)},
   {"right-divider-width",       SYMBOL_INDEX (Qright_divider_width)},
   {"bottom-divider-width",      SYMBOL_INDEX (Qbottom_divider_width)},
@@ -4302,6 +4310,8 @@ gui_report_frame_params (struct frame *f, Lisp_Object *alistptr)
 
   store_in_alist (alistptr, Qborder_width,
                   make_fixnum (f->border_width));
+  store_in_alist (alistptr, Qchild_frame_border_width,
+                  make_fixnum (FRAME_CHILD_FRAME_BORDER_WIDTH (f)));
   store_in_alist (alistptr, Qinternal_border_width,
                   make_fixnum (FRAME_INTERNAL_BORDER_WIDTH (f)));
   store_in_alist (alistptr, Qright_divider_width,
@@ -5999,6 +6009,7 @@ syms_of_frame (void)
   DEFSYM (Qhorizontal_scroll_bars, "horizontal-scroll-bars");
   DEFSYM (Qicon_name, "icon-name");
   DEFSYM (Qicon_type, "icon-type");
+  DEFSYM (Qchild_frame_border_width, "child-frame-border-width");
   DEFSYM (Qinternal_border_width, "internal-border-width");
   DEFSYM (Qleft_fringe, "left-fringe");
   DEFSYM (Qline_spacing, "line-spacing");
@@ -6423,6 +6434,7 @@ iconify the top level frame instead.  */);
   defsubr (&Sscroll_bar_width);
   defsubr (&Sscroll_bar_height);
   defsubr (&Sfringe_width);
+  defsubr (&Sframe_child_frame_border_width);
   defsubr (&Sframe_internal_border_width);
   defsubr (&Sright_divider_width);
   defsubr (&Sbottom_divider_width);
diff --git a/src/frame.h b/src/frame.h
index 8cf41dc0046..7b3bf20a241 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -534,6 +534,10 @@ struct frame
   /* Border width of the frame window as known by the (X) window system.  */
   int border_width;
 
+  /* Width of child frames' internal border. Acts as
+     internal_border_width for child frames.  */
+  int child_frame_border_width;
+
   /* Width of the internal border.  This is a line of background color
      just inside the window's border.  When the frame is selected,
      a highlighting is displayed inside the internal border.  */
@@ -1432,11 +1436,27 @@ FRAME_TOTAL_FRINGE_WIDTH (struct frame *f)
   return FRAME_LEFT_FRINGE_WIDTH (f) + FRAME_RIGHT_FRINGE_WIDTH (f);
 }
 
-/* Pixel-width of internal border lines.  */
+INLINE int
+FRAME_CHILD_FRAME_BORDER_WIDTH (struct frame *f)
+{
+  return frame_dimension (f->child_frame_border_width);
+}
+
+/* Pixel-width of internal border.  Uses child_frame_border_width for
+   child frames if possible and falls back on internal_border_width
+   otherwise.  */
 INLINE int
 FRAME_INTERNAL_BORDER_WIDTH (struct frame *f)
 {
-  return frame_dimension (f->internal_border_width);
+#ifdef HAVE_WINDOW_SYSTEM
+  return FRAME_PARENT_FRAME(f)
+    ? (f->child_frame_border_width
+       ? FRAME_CHILD_FRAME_BORDER_WIDTH(f)
+       : frame_dimension (f->internal_border_width))
+    : frame_dimension (f->internal_border_width);
+#else
+  return frame_dimension (f->internal_border_width)
+#endif
 }
 
 /* Pixel-size of window divider lines.  */
diff --git a/src/nsfns.m b/src/nsfns.m
index 24ea7d7f63b..c383e2f7ecf 100644
--- a/src/nsfns.m
+++ b/src/nsfns.m
@@ -687,6 +687,21 @@ ns_set_tool_bar_lines (struct frame *f, Lisp_Object value, Lisp_Object oldval)
   }
 }
 
+static void
+ns_set_child_frame_border_width (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
+{
+  int old_width = FRAME_CHILD_FRAME_BORDER_WIDTH (f);
+  int new_width = check_int_nonnegative (arg);
+
+  if (new_width == old_width)
+    return;
+  f->child_frame_border_width = new_width;
+
+  if (FRAME_NATIVE_WINDOW (f) != 0)
+    adjust_frame_size (f, -1, -1, 3, 0, Qchild_frame_border_width);
+
+  SET_FRAME_GARBAGED (f);
+}
 
 static void
 ns_set_internal_border_width (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
@@ -912,6 +927,7 @@ frame_parm_handler ns_frame_parm_handlers[] =
   ns_set_foreground_color,
   ns_set_icon_name,
   ns_set_icon_type,
+  ns_set_child_frame_border_width,
   ns_set_internal_border_width,
   gui_set_right_divider_width, /* generic OK */
   gui_set_bottom_divider_width, /* generic OK */
@@ -1197,6 +1213,9 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
   gui_default_parameter (f, parms, Qinternal_border_width, make_fixnum (2),
                          "internalBorderWidth", "InternalBorderWidth",
                          RES_TYPE_NUMBER);
+  gui_default_parameter (f, parms, Qchild_frame_border_width, make_fixnum (2),
+                         "childFrameBorderWidth", "childFrameBorderWidth",
+                         RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qright_divider_width, make_fixnum (0),
                        NULL, NULL, RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qbottom_divider_width, make_fixnum (0),
diff --git a/src/nsterm.m b/src/nsterm.m
index df3934c5c34..1b2328628ee 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3037,9 +3037,13 @@ ns_clear_under_internal_border (struct frame *f)
       NSRectEdge edge[] = {NSMinXEdge, NSMinYEdge, NSMaxXEdge, NSMaxYEdge};
 
       int face_id =
-        !NILP (Vface_remapping_alist)
-        ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
-        : INTERNAL_BORDER_FACE_ID;
+        (FRAME_PARENT_FRAME (f)
+         ? (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, CHILD_FRAME_BORDER_FACE_ID)
+            : CHILD_FRAME_BORDER_FACE_ID)
+         : (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
+            : INTERNAL_BORDER_FACE_ID));
       struct face *face = FACE_FROM_ID_OR_NULL (f, face_id);
 
       if (!face)
diff --git a/src/w32fns.c b/src/w32fns.c
index c1e18ff7fad..29d2e3d75f9 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -1519,9 +1519,13 @@ w32_clear_under_internal_border (struct frame *f)
       int width = FRAME_PIXEL_WIDTH (f);
       int height = FRAME_PIXEL_HEIGHT (f);
       int face_id =
-        !NILP (Vface_remapping_alist)
-        ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
-        : INTERNAL_BORDER_FACE_ID;
+        (FRAME_PARENT_FRAME (f)
+         ? (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, CHILD_FRAME_BORDER_FACE_ID)
+            : CHILD_FRAME_BORDER_FACE_ID)
+         : (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
+            : INTERNAL_BORDER_FACE_ID));
       struct face *face = FACE_FROM_ID_OR_NULL (f, face_id);
 
       block_input ();
@@ -1548,6 +1552,32 @@ w32_clear_under_internal_border (struct frame *f)
     }
 }
 
+/**
+ * w32_set_child_frame_border_width:
+ *
+ * Set width of child frame F's internal border to ARG pixels.
+ * ARG < 0 is * treated like ARG = 0.
+ */
+static void
+w32_set_child_frame_border_width (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
+{
+  int argval = check_integer_range (arg, INT_MIN, INT_MAX);
+  int border = max (argval, 0);
+
+  if (border != FRAME_CHILD_FRAME_BORDER_WIDTH (f))
+    {
+      f->child_frame_border_width = border;
+
+      if (FRAME_NATIVE_WINDOW (f) != 0)
+        {
+          adjust_frame_size (f, -1, -1, 3, false, Qchild_frame_border_width);
+
+          if (FRAME_VISIBLE_P (f))
+            w32_clear_under_internal_border (f);
+        }
+    }
+}
+
 
 /**
  * w32_set_internal_border_width:
@@ -5873,6 +5903,28 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
                             parameters);
     }
 
+  /* Same for child frames.  */
+  if (NILP (Fassq (Qchild_frame_border_width, parameters)))
+    {
+      Lisp_Object value;
+
+      value = gui_display_get_arg (dpyinfo, parameters, Qchild_frame_border_width,
+                                   "childFrameBorderWidth", "childFrameBorderWidth",
+                                   RES_TYPE_NUMBER);
+      if (! EQ (value, Qunbound))
+        parameters = Fcons (Fcons (Qchild_frame_border_width, value),
+                       parameters);
+
+    }
+
+  gui_default_parameter (f, parameters, Qchild_frame_border_width,
+#ifdef USE_GTK /* We used to impose 0 in xg_create_frame_widgets.  */
+                         make_fixnum (0),
+#else
+                         make_fixnum (1),
+#endif
+                         "childFrameBorderWidth", "childFrameBorderWidth",
+                         RES_TYPE_NUMBER);
   gui_default_parameter (f, parameters, Qinternal_border_width, make_fixnum (0),
                          "internalBorderWidth", "InternalBorder", RES_TYPE_NUMBER);
   gui_default_parameter (f, parameters, Qright_divider_width, make_fixnum (0),
@@ -10232,6 +10284,7 @@ frame_parm_handler w32_frame_parm_handlers[] =
   w32_set_foreground_color,
   w32_set_icon_name,
   w32_set_icon_type,
+  w32_set_child_frame_border_width,
   w32_set_internal_border_width,
   gui_set_right_divider_width,
   gui_set_bottom_divider_width,
diff --git a/src/xfaces.c b/src/xfaces.c
index 258b365eda3..12087138e51 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -4914,6 +4914,7 @@ lookup_basic_face (struct window *w, struct frame *f, int face_id)
     case WINDOW_DIVIDER_FIRST_PIXEL_FACE_ID:    name = Qwindow_divider_first_pixel;     break;
     case WINDOW_DIVIDER_LAST_PIXEL_FACE_ID:     name = Qwindow_divider_last_pixel;      break;
     case INTERNAL_BORDER_FACE_ID:       name = Qinternal_border;        break;
+    case CHILD_FRAME_BORDER_FACE_ID:    name = Qchild_frame_border;     break;
 
     default:
       emacs_abort (); /* the caller is supposed to pass us a basic face id */
@@ -5620,6 +5621,7 @@ realize_basic_faces (struct frame *f)
       realize_named_face (f, Qwindow_divider_last_pixel,
                           WINDOW_DIVIDER_LAST_PIXEL_FACE_ID);
       realize_named_face (f, Qinternal_border, INTERNAL_BORDER_FACE_ID);
+      realize_named_face (f, Qchild_frame_border, CHILD_FRAME_BORDER_FACE_ID);
       realize_named_face (f, Qtab_bar, TAB_BAR_FACE_ID);
       realize_named_face (f, Qtab_line, TAB_LINE_FACE_ID);
 
@@ -6973,6 +6975,7 @@ syms_of_xfaces (void)
   DEFSYM (Qwindow_divider_first_pixel, "window-divider-first-pixel");
   DEFSYM (Qwindow_divider_last_pixel, "window-divider-last-pixel");
   DEFSYM (Qinternal_border, "internal-border");
+  DEFSYM (Qchild_frame_border, "child-frame-border");
 
   /* TTY color-related functions (defined in tty-colors.el).  */
   DEFSYM (Qtty_color_desc, "tty-color-desc");
diff --git a/src/xfns.c b/src/xfns.c
index 9ab537ca8d9..cac41ee4856 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -1800,6 +1800,28 @@ x_change_tool_bar_height (struct frame *f, int height)
 #endif /* USE_GTK */
 }
 
+static void
+x_set_child_frame_border_width (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
+{
+  int border = check_int_nonnegative (arg);
+
+  if (border != FRAME_CHILD_FRAME_BORDER_WIDTH (f))
+    {
+      f->child_frame_border_width = border;
+
+#ifdef USE_X_TOOLKIT
+      if (FRAME_X_OUTPUT (f)->edit_widget)
+        widget_store_internal_border (FRAME_X_OUTPUT (f)->edit_widget);
+#endif
+
+      if (FRAME_X_WINDOW (f))
+        {
+          adjust_frame_size (f, -1, -1, 3, false, Qchild_frame_border_width);
+          x_clear_under_internal_border (f);
+        }
+    }
+
+}
 
 static void
 x_set_internal_border_width (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
@@ -3897,6 +3919,29 @@ This function is an internal primitive--use `make-frame' instead.  */)
         parms = Fcons (Fcons (Qinternal_border_width, value),
                        parms);
     }
+
+  /* Same for child frames.  */
+  if (NILP (Fassq (Qchild_frame_border_width, parms)))
+    {
+      Lisp_Object value;
+
+      value = gui_display_get_arg (dpyinfo, parms, Qchild_frame_border_width,
+                                   "childFrameBorderWidth", "childFrameBorderWidth",
+                                   RES_TYPE_NUMBER);
+      if (! EQ (value, Qunbound))
+        parms = Fcons (Fcons (Qchild_frame_border_width, value),
+                       parms);
+
+    }
+
+  gui_default_parameter (f, parms, Qchild_frame_border_width,
+#ifdef USE_GTK /* We used to impose 0 in xg_create_frame_widgets.  */
+                         make_fixnum (0),
+#else
+                         make_fixnum (1),
+#endif
+                         "childFrameBorderWidth", "childFrameBorderWidth",
+                         RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qinternal_border_width,
 #ifdef USE_GTK /* We used to impose 0 in xg_create_frame_widgets.  */
                          make_fixnum (0),
@@ -7762,6 +7807,7 @@ frame_parm_handler x_frame_parm_handlers[] =
   x_set_foreground_color,
   x_set_icon_name,
   x_set_icon_type,
+  x_set_child_frame_border_width,
   x_set_internal_border_width,
   gui_set_right_divider_width,
   gui_set_bottom_divider_width,
diff --git a/src/xterm.c b/src/xterm.c
index b8374fed8b1..a855d2d67aa 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1293,9 +1293,13 @@ x_clear_under_internal_border (struct frame *f)
       int height = FRAME_PIXEL_HEIGHT (f);
       int margin = FRAME_TOP_MARGIN_HEIGHT (f);
       int face_id =
-        !NILP (Vface_remapping_alist)
-        ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
-        : INTERNAL_BORDER_FACE_ID;
+        (FRAME_PARENT_FRAME (f)
+         ? (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, CHILD_FRAME_BORDER_FACE_ID)
+            : CHILD_FRAME_BORDER_FACE_ID)
+         : (!NILP (Vface_remapping_alist)
+            ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
+            : INTERNAL_BORDER_FACE_ID));
       struct face *face = FACE_FROM_ID_OR_NULL (f, face_id);
 
       block_input ();
@@ -1360,9 +1364,13 @@ x_after_update_window_line (struct window *w, struct glyph_row *desired_row)
       {
         int y = WINDOW_TO_FRAME_PIXEL_Y (w, max (0, desired_row->y));
         int face_id =
-          !NILP (Vface_remapping_alist)
-          ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
-          : INTERNAL_BORDER_FACE_ID;
+          (FRAME_PARENT_FRAME (f)
+           ? (!NILP (Vface_remapping_alist)
+              ? lookup_basic_face (NULL, f, CHILD_FRAME_BORDER_FACE_ID)
+              : CHILD_FRAME_BORDER_FACE_ID)
+           : (!NILP (Vface_remapping_alist)
+              ? lookup_basic_face (NULL, f, INTERNAL_BORDER_FACE_ID)
+              : INTERNAL_BORDER_FACE_ID));
         struct face *face = FACE_FROM_ID_OR_NULL (f, face_id);
 
         block_input ();