Add frame parameter which allows border transparency

The new 'borders-respect-alpha-background' frame parameter, when
set to 't', will make window dividers and internal borders
respect the 'alpha-background' frame parameter. This allows
transparent gaps between windows.
* doc/lispref/frames.texi (Font and Color Parameters):
Document the change.
* src/frame.c (frame_parm_table, syms_of_frame)
(gui_set_borders_respect_alpha_background):
* src/frame.h (struct frame): Add frame parameter.
* src/androidfns.c (x_create_frame, android_create_tip_frame)
(android_frame_parm_handlers):
* src/haikufns.c (haiku_create_frame, haiku_create_tip_frame)
(haiku_frame_parm_handlers):
* src/nsfns.m (ns_frame_parm_handlers, x_create_frame):
* src/w32fns.c (x_create_frame, w32_create_tip_frame)
(w32_frame_parm_handlers): Add dummy parameters for backends
that don't support opacity.
* src/pgtkfns.c (pgtk_frame_parm_handlers, x_create_frame)
(pgtk_create_tip_frame):
* src/pgtkterm.c (pgtk_draw_window_divider):
* src/xfns.c (x_create_frame, x_create_tip_frame)
(x_frame_parm_handlers)
* src/xterm.c (x_draw_window_divider)
(x_clear_under_internal_border): Implement parameter on backends
that support opacity.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/pgtkfns.c b/src/pgtkfns.c
index b55728b579c..917c9e7ab67 100644
--- a/src/pgtkfns.c
+++ b/src/pgtkfns.c
@@ -985,6 +985,7 @@ frame_parm_handler pgtk_frame_parm_handlers[] =
     pgtk_set_override_redirect,
     gui_set_no_special_glyphs,
     pgtk_set_alpha_background,
+    gui_set_borders_respect_alpha_background,
     NULL,
   };
 
@@ -1571,6 +1572,9 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame, 1, 1, 0,
                          "alpha", "Alpha", RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qalpha_background, Qnil,
                          "alphaBackground", "AlphaBackground", RES_TYPE_NUMBER);
+  gui_default_parameter (f, parms, Qborders_respect_alpha_background, Qnil,
+                         "bordersRespectAlphaBackground",
+                         "BordersRespectAlphaBackground", RES_TYPE_NUMBER);
 
   if (!NILP (parent_frame))
     {
@@ -2730,6 +2734,9 @@ pgtk_create_tip_frame (struct pgtk_display_info *dpyinfo, Lisp_Object parms, str
                          "alpha", "Alpha", RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qalpha_background, Qnil,
                          "alphaBackground", "AlphaBackground", RES_TYPE_NUMBER);
+  gui_default_parameter (f, parms, Qborders_respect_alpha_background, Qnil,
+                         "bordersRespectAlphaBackground",
+                         "BordersRespectAlphaBackground", RES_TYPE_NUMBER);
 
   /* Add `tooltip' frame parameter's default value. */
   if (NILP (Fframe_parameter (frame, Qtooltip)))