Reduce color allocation/query traffic in the TrueColor case.

When working with an X visual with TrueColor class, pixel values can
be generated from the RGB values according to mask value provided by
the server on connection.  Some of the image-handling code was already
doing this.

* src/xterm.h (x_make_truecolor_pixel): New function; code taken from
lookup_rgb_color.
(x_mutable_colormap): New function.
* src/image.c (lookup_rgb_color): Move pixel composition code to
x_make_truecolor_pixel.
(x_kill_gs_process): Call x_mutable_colormap.
* src/xfaces.c (x_free_colors, x_free_dpy_colors): Call
x_mutable_colormap.
* src/xftfont.c (xftfont_get_colors): Call x_query_colors.
* src/xterm.c (x_query_colors): For a TrueColor display, decompose the
pixel value into RGB values directly, and don't send a request to the
server.
(x_alloc_nearest_color): For a TrueColor display, construct the pixel
value with x_make_truecolor_pixel.
(x_copy_color): For an immutable color map, just return the provided
pixel value.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/xterm.h b/src/xterm.h
index 300a8b769f2..d8edbc208f4 100644
--- a/src/xterm.h
+++ b/src/xterm.h
@@ -1085,6 +1085,33 @@ x_display_set_last_user_time (struct x_display_info *dpyinfo, Time t)
   dpyinfo->last_user_time = t;
 }
 
+INLINE unsigned long
+x_make_truecolor_pixel (struct x_display_info *dpyinfo, int r, int g, int b)
+{
+  unsigned long pr, pg, pb;
+
+  /* Scale down RGB values to the visual's bits per RGB, and shift
+     them to the right position in the pixel color.  Note that the
+     original RGB values are 16-bit values, as usual in X.  */
+  pr = (r >> (16 - dpyinfo->red_bits))   << dpyinfo->red_offset;
+  pg = (g >> (16 - dpyinfo->green_bits)) << dpyinfo->green_offset;
+  pb = (b >> (16 - dpyinfo->blue_bits))  << dpyinfo->blue_offset;
+
+  /* Assemble the pixel color.  */
+  return pr | pg | pb;
+}
+
+/* If display has an immutable color map, freeing colors is not
+   necessary and some servers don't allow it, so we won't do it.  That
+   also allows us to make other optimizations relating to server-side
+   reference counts.  */
+INLINE bool
+x_mutable_colormap (Visual *visual)
+{
+  int class = visual->class;
+  return (class != StaticColor && class != StaticGray && class != TrueColor);
+}
+
 extern void x_set_sticky (struct frame *, Lisp_Object, Lisp_Object);
 extern bool x_wm_supports (struct frame *, Atom);
 extern void x_wait_for_event (struct frame *, int);