XEP-0392: get background color from theme

So far we just used -1 (default color). Now we actually check whether
`bkgnd` is set in the theme file and use this if available.

Fix #1255

src/config/color.c

@@ -49,6 +49,7 @@
 #endif
 
 #include "config/color.h"
+#include "config/theme.h"
 #include "log.h"
 
 static
@@ -494,13 +495,19 @@ static int _color_pair_cache_get(int fg, int bg)
  * possible given a 256 colors terminal.
  *
  * hash a string into a color that will be used as fg
- * use default color as bg
+ * check for 'bkgnd' in theme file or use default color as bg
  */
 int color_pair_cache_hash_str(const char *str, color_profile profile)
 {
     int fg = color_hash(str, profile);
     int bg = -1;
 
+    char *bkgnd = theme_get_bkgnd();
+    if (bkgnd) {
+        bg = find_col(bkgnd, strlen(bkgnd));
+        free(bkgnd);
+    }
+
     return _color_pair_cache_get(fg, bg);
 }
 

src/config/theme.c

@@ -618,6 +618,14 @@ _theme_prep_bgnd(char *setting, char *def, GString *lookup_str)
     g_free(val);
 }
 
+/* return value needs to be freed */
+char*
+theme_get_bkgnd(void)
+{
+    char *val = g_key_file_get_string(theme, "colours", "bkgnd", NULL);
+    return val;
+}
+
 static void
 _theme_prep_fgnd(char *setting, GString *lookup_str, gboolean *bold)
 {

src/config/theme.h

@@ -155,5 +155,6 @@ theme_item_t theme_main_presence_attrs(const char *const presence);
 theme_item_t theme_roster_unread_presence_attrs(const char *const presence);
 theme_item_t theme_roster_active_presence_attrs(const char *const presence);
 theme_item_t theme_roster_presence_attrs(const char *const presence);
+char* theme_get_bkgnd(void);
 
 #endif