master 028fae96614 03/18: Simplify building of color names in image.c

[Paul Eggert]

branch: master
commit 028fae966142b6e2330b9250fb4cdf2cbd8e1446
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Simplify building of color names in image.c
    
    * src/image.c (make_color_name): New function.
    (image_background, image_build_heuristic_mask, png_load_body): Use it.
---
 src/image.c | 41 ++++++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 23 deletions(-)

diff --git a/src/image.c b/src/image.c
index 4350c415d9c..901063c9bde 100644
--- a/src/image.c
+++ b/src/image.c
@@ -1971,6 +1971,12 @@ four_corners_best (Emacs_Pix_Context pimg, int *corners,
   return best;
 }
 
+static Lisp_Object
+make_color_name (unsigned int red, unsigned int green, unsigned int blue)
+{
+  return make_formatted_string ("#%04x%04x%04x", red, green, blue);
+}
+
 /* Return the `background' field of IMG.  If IMG doesn't have one yet,
    it is guessed heuristically.  If non-zero, XIMG is an existing
    Emacs_Pix_Context object (device context with the image selected on
@@ -1993,14 +1999,10 @@ image_background (struct image *img, struct frame *f, 
Emacs_Pix_Context pimg)
       RGB_PIXEL_COLOR bg
        = four_corners_best (pimg, img->corners, img->width, img->height);
 #ifdef USE_CAIRO
-      {
-       char color_name[30];
-       snprintf (color_name, sizeof color_name, "#%04x%04x%04x",
-                 (unsigned int) RED16_FROM_ULONG (bg),
-                 (unsigned int) GREEN16_FROM_ULONG (bg),
-                 (unsigned int) BLUE16_FROM_ULONG (bg));
-       bg = image_alloc_image_color (f, img, build_string (color_name), 0);
-      }
+      Lisp_Object color_name = make_color_name (RED16_FROM_ULONG (bg),
+                                               GREEN16_FROM_ULONG (bg),
+                                               BLUE16_FROM_ULONG (bg));
+      bg = image_alloc_image_color (f, img, color_name, 0);
 #endif
       img->background = bg;
 
@@ -7383,15 +7385,11 @@ image_build_heuristic_mask (struct frame *f, struct 
image *img,
       if (i == 3 && NILP (how))
        {
 #ifndef USE_CAIRO
-         char color_name[30];
-         int len = snprintf (color_name, sizeof color_name, "#%04x%04x%04x",
-                             rgb[0] + 0u, rgb[1] + 0u, rgb[2] + 0u);
-         eassert (len < sizeof color_name);
-         bg = (
-#ifdef HAVE_NTGUI
-               0x00ffffff & /* Filter out palette info.  */
-#endif /* HAVE_NTGUI */
-               image_alloc_image_color (f, img, build_string (color_name), 0));
+         Lisp_Object color_name = make_color_name (rgb[0], rgb[1], rgb[2]);
+         bg = image_alloc_image_color (f, img, color_name, 0);
+# ifdef HAVE_NTGUI
+         bg &= 0x00ffffff; /* Filter out palette info.  */
+# endif
 #else  /* USE_CAIRO */
          bg = lookup_rgb_color (f, rgb[0], rgb[1], rgb[2]);
 #endif /* USE_CAIRO */
@@ -8535,12 +8533,9 @@ png_load_body (struct frame *f, struct image *img, 
struct png_load_context *c)
 #ifndef USE_CAIRO
          img->background = lookup_rgb_color (f, bg->red, bg->green, bg->blue);
 #else  /* USE_CAIRO */
-         char color_name[30];
-         int len = snprintf (color_name, sizeof color_name, "#%04x%04x%04x",
-                             bg->red, bg->green, bg->blue);
-         eassert (len < sizeof color_name);
-         img->background
-           = image_alloc_image_color (f, img, build_string (color_name), 0);
+         Lisp_Object color_name
+           = make_color_name (bg->red, bg->green, bg->blue);
+         img->background = image_alloc_image_color (f, img, color_name, 0);
 #endif /* USE_CAIRO */
          img->background_valid = 1;
        }