From b176909995eea600d99354be2127469f472ce4bb Mon Sep 17 00:00:00 2001
From: Alexander Miller <alexanderm@web.de>
Date: Tue, 5 Jan 2021 13:31:09 +0100
Subject: [PATCH 2/2] WIP child-frame-border-width

---
 src/frame.c |  4 ++++
 src/frame.h | 14 +++++++++++++-
 src/xfns.c  | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/src/frame.c b/src/frame.c
index 45ee96e962..d5040dfae6 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -3744,6 +3744,7 @@ DEFUN ("set-frame-window-state-change", Fset_frame_window_state_change,
   {"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)},
@@ -4287,6 +4288,8 @@ 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 (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,
@@ -5984,6 +5987,7 @@ 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");
diff --git a/src/frame.h b/src/frame.h
index 8cf41dc004..7d816f2516 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -534,6 +534,10 @@ #define EMACS_FRAME_H
   /* Border width of the frame window as known by the (X) window system.  */
   int border_width;

+  /* Width of child frames' internal border.  Acts exactly like
+     internal_border_width below and will fall back on it when not set.*/
+  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 +1436,19 @@ FRAME_TOTAL_FRINGE_WIDTH (struct frame *f)
   return FRAME_LEFT_FRINGE_WIDTH (f) + FRAME_RIGHT_FRINGE_WIDTH (f);
 }

+INLINE int
+CHILD_FRAME_BORDER_WIDTH (struct frame *f)
+{
+  return frame_dimension (f->child_frame_border_width);
+}
+
 /* Pixel-width of internal border lines.  */
 INLINE int
 FRAME_INTERNAL_BORDER_WIDTH (struct frame *f)
 {
-  return frame_dimension (f->internal_border_width);
+  return f->child_frame_border_width
+    ? CHILD_FRAME_BORDER_WIDTH(f)
+    : frame_dimension (f->internal_border_width);
 }

 /* Pixel-size of window divider lines.  */
diff --git a/src/xfns.c b/src/xfns.c
index 9ab537ca8d..663146d7f2 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 != 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)
@@ -3897,14 +3919,37 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
 	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,
+                                   "internalBorder", "internalBorder",
+                                   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),
+			 make_fixnum (0),
 #else
-                         make_fixnum (1),
+			 make_fixnum (1),
 #endif
-                         "internalBorderWidth", "internalBorderWidth",
-                         RES_TYPE_NUMBER);
+			 "internalBorderWidth", "internalBorderWidth",
+			 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),
@@ -7762,6 +7807,7 @@ DEFUN ("x-gtk-debug", Fx_gtk_debug, Sx_gtk_debug, 1, 1, 0,
   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,
--
2.29.2