image: png: Fix completely broken libpng warning/error printing.

Ugh!

Thanks to ArneBab for trying to load a PNG file that exposed this
issue.

1 files changed, 8 insertions, 8 deletions

diff --git a/chickadee/image/png.scm b/chickadee/image/png.scm
index 6cdbc14..938dede 100644
--- a/chickadee/image/png.scm
+++ b/chickadee/image/png.scm
@@ -121,13 +121,13 @@
 (define-wrapped-pointer-type <png-info-struct> png-info-struct?
   wrap-png-info-struct unwrap-png-info-struct display-png-info-struct)
 
-(define (on-error read-struct message)
-  (display (current-error-port) message))
-
-(define (on-warning read-struct message)
-  (display (current-error-port) message))
-
-(define (create-read-struct)
+(define (create-read-struct file-name)
+  (define (on-error read-struct message)
+    (format (current-error-port) "libpng error: ~a: ~a\n"
+            file-name (pointer->string message)))
+  (define (on-warning read-struct message)
+    (format (current-error-port) "libpng warning: ~a: ~a\n"
+            file-name (pointer->string message)))
   (let ((ptr (png-create-read-struct (string->pointer %libpng-version)
                                      %null-pointer
                                      (procedure->pointer void on-error '(* *))
@@ -326,7 +326,7 @@
   (if (file-exists? file-name)
       (call-with-input-file file-name
         (lambda (port)
-          (let* ((read-struct (create-read-struct))
+          (let* ((read-struct (create-read-struct file-name))
                  (info-struct (create-info-struct read-struct)))
             (dynamic-wind
               (lambda () #t)