fontconfig/pattern.scm (make-pattern): Take keyword arguments.

* examples/exmaple.scm: Update accordingly.

examples/example.scm

@@ -1,7 +1,7 @@
 (use-modules (fontconfig))
 
 (let ((pattern (make-pattern
-                '((family "JuliaMono")))))
+                #:family "JuliaMono" #:style "bold")))
   (map
    (lambda (pat)
      (format #t "

fontconfig/pattern.scm

@@ -19,6 +19,7 @@
 
 (define-module (fontconfig pattern)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 optargs)
   #:use-module ((fontconfig bindings) #:prefix ffi:)
   #:use-module (fontconfig object-set)
   #:use-module (rnrs bytevectors)
@@ -67,7 +68,15 @@
   (ffi:fontconfig-pattern-add-bool
    (unwrap-pattern pattern) (symbol->pointer attr) (if value 1 0)))
 
-(define* (make-pattern #:optional (args '()))
+(define* (keywords->symbols args #:optional (out '()))
+  (if (>= (length args) 2)
+      (keywords->symbols
+       (cddr args)
+       (cons (list (keyword->symbol (car args)) (cadr args))
+             out))
+      out))
+
+(define (make-pattern . args)
   (define bool? (cute member <> %bool-attrs))
   (define int? (cute member <> %integer-attrs))
   (define double? (cute member <> %double-attrs))
@@ -85,7 +94,7 @@
                     (((? double? attr) value) pattern-add-double)
                     (((? string? attr) value) pattern-add-string))
                   pattern args))
-         args)
+         (keywords->symbols args))
     pattern))
 
 (define (font-list pattern os)