Sv: Sv: Support for background transparency

["Håkon Flatval" <hkon20@hotmail.com>]

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Hi again,

At long last the copyright assignment process is finished.

I have attached a final patch. The only changes from the last one is a small conflict resolution I did while rebasing today.

Is everything ready to have it merged? And also, how does that happen? Is the ball in your court, or does it require action on my end?

Best,
Håkon

________________________________
Fra: Lars Ingebrigtsen <larsi@gnus.org>
Sendt: fredag 10. desember 2021 01:40
Til: Håkon Flatval <hkon20@hotmail.com>
Kopi: Eli Zaretskii <eliz@gnu.org>; emacs-devel@gnu.org <emacs-devel@gnu.org>
Emne: Re: Sv: Support for background transparency

Håkon Flatval <hkon20@hotmail.com> writes:

> I eventually decided that it makes sense for the fringe to be
> considered background, i.e. be rendered transparent as well. I've
> included it in this patch.

I tried the patch here (Debian/bookworm), and it works great.  So I
guess we just have to wait until the copyright assignment process has
completed?

--
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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diff --git a/src/frame.c b/src/frame.c
index 8aaff949ba..c331cff32b 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -3907,6 +3907,7 @@ DEFUN ("frame-scale-factor", Fframe_scale_factor, Sframe_scale_factor,
   {"z-group",			SYMBOL_INDEX (Qz_group)},
   {"override-redirect",		SYMBOL_INDEX (Qoverride_redirect)},
   {"no-special-glyphs",		SYMBOL_INDEX (Qno_special_glyphs)},
+  {"alpha-background",          SYMBOL_INDEX (Qalpha_background)},
 #ifdef NS_IMPL_COCOA
   {"ns-appearance",		SYMBOL_INDEX (Qns_appearance)},
   {"ns-transparent-titlebar",	SYMBOL_INDEX (Qns_transparent_titlebar)},
@@ -5024,6 +5025,33 @@ gui_set_alpha (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
     }
 }
 
+void
+gui_set_alpha_background (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
+{
+  double alpha = 1.0;
+
+  if (NILP (arg))
+    alpha = 1.0;
+  else if (FLOATP (arg))
+    {
+      alpha = XFLOAT_DATA (arg);
+      if (! (0 <= alpha && alpha <= 1.0))
+	args_out_of_range (make_float (0.0), make_float (1.0));
+    }
+  else if (FIXNUMP (arg))
+    {
+      EMACS_INT ialpha = XFIXNUM (arg);
+      if (! (0 <= ialpha && ialpha <= 100))
+	args_out_of_range (make_fixnum (0), make_fixnum (100));
+      alpha = ialpha / 100.0;
+    }
+  else
+    wrong_type_argument (Qnumberp, arg);
+
+  f->alpha_background = alpha;
+
+  SET_FRAME_GARBAGED (f);
+}
 
 /**
  * gui_set_no_special_glyphs:
@@ -6100,6 +6128,7 @@ syms_of_frame (void)
 #endif
 
   DEFSYM (Qalpha, "alpha");
+  DEFSYM (Qalpha_background, "alpha-background");
   DEFSYM (Qauto_lower, "auto-lower");
   DEFSYM (Qauto_raise, "auto-raise");
   DEFSYM (Qborder_color, "border-color");
diff --git a/src/frame.h b/src/frame.h
index cb2f58e261..5d5f2122fb 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -637,6 +637,9 @@ #define EMACS_FRAME_H
      Negative values mean not to change alpha.  */
   double alpha[2];
 
+  /* Background opacity */
+  double alpha_background;
+
   /* Exponent for gamma correction of colors.  1/(VIEWING_GAMMA *
      SCREEN_GAMMA) where viewing_gamma is 0.4545 and SCREEN_GAMMA is a
      frame parameter.  0 means don't do gamma correction.  */
@@ -1669,6 +1672,7 @@ #define EMACS_CLASS "Emacs"
 extern long gui_figure_window_size (struct frame *, Lisp_Object, bool, bool);
 
 extern void gui_set_alpha (struct frame *, Lisp_Object, Lisp_Object);
+extern void gui_set_alpha_background (struct frame *, Lisp_Object, Lisp_Object);
 extern void gui_set_no_special_glyphs (struct frame *, Lisp_Object, Lisp_Object);
 
 extern void validate_x_resource_name (void);
diff --git a/src/gtkutil.c b/src/gtkutil.c
index 3cb8cd1533..ab3b3cc8d8 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -231,6 +231,27 @@ xg_get_scale (struct frame *f)
   return xg_get_gdk_scale ();
 }
 
+static unsigned int
+x_get_bit_depth (struct frame *f)
+{
+  Visual *visual = FRAME_X_VISUAL (f);
+  VisualID visual_id = XVisualIDFromVisual (visual);
+
+  XVisualInfo vinfo_template;
+  vinfo_template.visualid = visual_id;
+
+  int num_items;
+
+  XVisualInfo *visual_infos = XGetVisualInfo (FRAME_X_DISPLAY (f),
+					      VisualIDMask,
+					      &vinfo_template,
+					      &num_items);
+
+  eassert (num_items > 0);
+
+  return visual_infos[0].depth;
+}
+
 /* Close display DPY.  */
 
 void
@@ -1469,6 +1490,10 @@ xg_create_frame_widgets (struct frame *f)
   gtk_widget_add_events (wtop, GDK_ALL_EVENTS_MASK);
 #endif
 
+  /* This prevents GTK from painting the window's background, which
+     would interfere with transparent background in some environments */
+  gtk_widget_set_app_paintable (wtop, TRUE);
+
   /* gtk_window_set_has_resize_grip is a Gtk+ 3.0 function but Ubuntu
      has backported it to Gtk+ 2.0 and they add the resize grip for
      Gtk+ 2.0 applications also.  But it has a bug that makes Emacs loop
@@ -1587,6 +1612,15 @@ xg_create_frame_widgets (struct frame *f)
 #endif
                          | GDK_VISIBILITY_NOTIFY_MASK);
 
+  GdkScreen *screen = gtk_widget_get_screen (wtop);
+
+  if (x_get_bit_depth (f) == 32)
+    {
+      GdkVisual *visual = gdk_screen_get_rgba_visual (screen);
+      gtk_widget_set_visual (wtop, visual);
+      gtk_widget_set_visual (wfixed, visual);
+    }
+
 #ifndef HAVE_PGTK
   /* Must realize the windows so the X window gets created.  It is used
      by callers of this function.  */
@@ -1651,7 +1685,6 @@ xg_create_frame_widgets (struct frame *f)
 #endif
 
   {
-    GdkScreen *screen = gtk_widget_get_screen (wtop);
     GtkSettings *gs = gtk_settings_get_for_screen (screen);
     /* Only connect this signal once per screen.  */
     if (! g_signal_handler_find (G_OBJECT (gs),
diff --git a/src/xfns.c b/src/xfns.c
index a1435d5351..7fcc5e2c3f 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -4569,6 +4569,8 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
                          RES_TYPE_NUMBER);
   gui_default_parameter (f, parms, Qalpha, Qnil,
                          "alpha", "Alpha", RES_TYPE_NUMBER);
+  gui_default_parameter (f, parms, Qalpha_background, Qnil,
+			 "alpha_background", "AlphaBackground", RES_TYPE_NUMBER);
 
   if (!NILP (parent_frame))
     {
@@ -6342,14 +6344,35 @@ select_visual (struct x_display_info *dpyinfo)
       int n_visuals;
       XVisualInfo *vinfo, vinfo_template;
 
-      dpyinfo->visual = DefaultVisualOfScreen (screen);
+      vinfo_template.screen = XScreenNumberOfScreen (screen);
+
+#if defined (USE_GTK) && defined (USE_CAIRO)
+      /* First attempt to use 32-bit visual if available */
+
+      vinfo_template.depth = 32;
+
+      vinfo = XGetVisualInfo (dpy, VisualScreenMask | VisualDepthMask,
+			      &vinfo_template, &n_visuals);
+
+      if (n_visuals > 0)
+	{
+	  dpyinfo->n_planes = vinfo->depth;
+	  dpyinfo->visual = vinfo->visual;
+	  XFree (vinfo);
+	  return;
+	}
 
+#endif // defined (USE_GTK) && defined (USE_CAIRO)
+
+      /* 32-bit visual not available, fallback to default visual */
+      dpyinfo->visual = DefaultVisualOfScreen (screen);
       vinfo_template.visualid = XVisualIDFromVisual (dpyinfo->visual);
-      vinfo_template.screen = XScreenNumberOfScreen (screen);
+
       vinfo = XGetVisualInfo (dpy, VisualIDMask | VisualScreenMask,
 			      &vinfo_template, &n_visuals);
+
       if (n_visuals <= 0)
-	fatal ("Can't get proper X visual info");
+	  fatal ("Can't get proper X visual info");
 
       dpyinfo->n_planes = vinfo->depth;
       XFree (vinfo);
@@ -7203,6 +7226,8 @@ x_create_tip_frame (struct x_display_info *dpyinfo, Lisp_Object parms)
                          "cursorType", "CursorType", RES_TYPE_SYMBOL);
   gui_default_parameter (f, parms, Qalpha, Qnil,
                          "alpha", "Alpha", RES_TYPE_NUMBER);
+  gui_default_parameter (f, parms, Qalpha_background, Qnil,
+			 "alpha_background", "AlphaBackground", RES_TYPE_NUMBER);
 
   /* Add `tooltip' frame parameter's default value. */
   if (NILP (Fframe_parameter (frame, Qtooltip)))
@@ -8531,6 +8556,7 @@ DEFUN ("x-gtk-debug", Fx_gtk_debug, Sx_gtk_debug, 1, 1, 0,
   x_set_z_group,
   x_set_override_redirect,
   gui_set_no_special_glyphs,
+  gui_set_alpha_background,
 };
 
 void
diff --git a/src/xterm.c b/src/xterm.c
index d3619f5b5e..7df20daff8 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -837,9 +837,12 @@ x_set_cr_source_with_gc_background (struct frame *f, GC gc)
 
   XGetGCValues (FRAME_X_DISPLAY (f), gc, GCBackground, &xgcv);
   color.pixel = xgcv.background;
+
   x_query_colors (f, &color, 1);
-  cairo_set_source_rgb (FRAME_CR_CONTEXT (f), color.red / 65535.0,
-			color.green / 65535.0, color.blue / 65535.0);
+  cairo_set_source_rgba (FRAME_CR_CONTEXT (f), color.red / 65535.0,
+                         color.green / 65535.0, color.blue / 65535.0, f->alpha_background);
+
+  cairo_set_operator (FRAME_CR_CONTEXT (f), CAIRO_OPERATOR_SOURCE);
 }
 
 static const cairo_user_data_key_t xlib_surface_key, saved_drawable_key;
@@ -1252,6 +1255,29 @@ x_fill_rectangle (struct frame *f, GC gc, int x, int y, int width, int height)
 #endif
 }
 
+
+static void
+x_clear_rectangle (struct frame *f, GC gc, int x, int y, int width, int height)
+{
+#ifdef USE_CAIRO
+  cairo_t *cr;
+
+  cr = x_begin_cr_clip (f, gc);
+  x_set_cr_source_with_gc_background (f, gc);
+  cairo_rectangle (cr, x, y, width, height);
+  cairo_fill (cr);
+  x_end_cr_clip (f);
+#else
+  XGCValues xgcv;
+  Display *dpy = FRAME_X_DISPLAY (f);
+  XGetGCValues (dpy, gc, GCBackground | GCForeground, &xgcv);
+  XSetForeground (dpy, gc, xgcv.background);
+  XFillRectangle (dpy, FRAME_X_DRAWABLE (f),
+		  gc, x, y, width, height);
+  XSetForeground (dpy, gc, xgcv.foreground);
+#endif
+}
+
 static void
 x_draw_rectangle (struct frame *f, GC gc, int x, int y, int width, int height)
 {
@@ -1828,9 +1854,9 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row, struct draw_fring
       if (face->stipple)
 	XSetFillStyle (display, face->gc, FillOpaqueStippled);
       else
-	XSetForeground (display, face->gc, face->background);
+	XSetBackground (display, face->gc, face->background);
 
-      x_fill_rectangle (f, face->gc, p->bx, p->by, p->nx, p->ny);
+      x_clear_rectangle (f, face->gc, p->bx, p->by, p->nx, p->ny);
 
       if (!face->stipple)
 	XSetForeground (display, face->gc, face->foreground);
@@ -2131,12 +2157,7 @@ x_compute_glyph_string_overhangs (struct glyph_string *s)
 static void
 x_clear_glyph_string_rect (struct glyph_string *s, int x, int y, int w, int h)
 {
-  Display *display = FRAME_X_DISPLAY (s->f);
-  XGCValues xgcv;
-  XGetGCValues (display, s->gc, GCForeground | GCBackground, &xgcv);
-  XSetForeground (display, s->gc, xgcv.background);
-  x_fill_rectangle (s->f, s->gc, x, y, w, h);
-  XSetForeground (display, s->gc, xgcv.foreground);
+  x_clear_rectangle (s->f, s->gc, x, y, w, h);
 }