Silence MuPDF warnings/errors unconditionally (fixes #132)

fitz_cgo.go

@@ -62,6 +62,16 @@ int run_page_contents(fz_context *ctx, fz_page *page, fz_device *dev, fz_matrix
 
 	return 1;
 }
+
+static void go_fitz_silent_cb(void *user, const char *message) {
+	(void)user;
+	(void)message;
+}
+
+void go_fitz_silence(fz_context *ctx) {
+	fz_set_warning_callback(ctx, go_fitz_silent_cb, NULL);
+	fz_set_error_callback(ctx, go_fitz_silent_cb, NULL);
+}
 */
 import "C"
 
@@ -103,6 +113,8 @@ func New(filename string) (f *Document, err error) {
 		return
 	}
 
+	C.go_fitz_silence(f.ctx)
+
 	C.fz_register_document_handlers(f.ctx)
 
 	cfilename := C.CString(filename)
@@ -136,6 +148,8 @@ func NewFromMemory(b []byte) (f *Document, err error) {
 		return
 	}
 
+	C.go_fitz_silence(f.ctx)
+
 	C.fz_register_document_handlers(f.ctx)
 
 	f.stream = C.fz_open_memory(f.ctx, (*C.uchar)(&b[0]), C.size_t(len(b)))

fitz_nocgo.go

@@ -45,6 +45,8 @@ func New(filename string) (f *Document, err error) {
 		return
 	}
 
+	applySilence(f.ctx)
+
 	fzRegisterDocumentHandlers(f.ctx)
 
 	f.doc = fzOpenDocument(f.ctx, filename)
@@ -75,6 +77,8 @@ func NewFromMemory(b []byte) (f *Document, err error) {
 		return
 	}
 
+	applySilence(f.ctx)
+
 	fzRegisterDocumentHandlers(f.ctx)
 
 	f.stream = fzOpenMemory(f.ctx, unsafe.SliceData(b), uint64(len(b)))
@@ -567,8 +571,19 @@ var (
 	fzPrintStextPageAsHTML     func(ctx *fzContext, out *fzOutput, page *fzStextPage, id int)
 	fzPrintStextHeaderAsHTML   func(ctx *fzContext, out *fzOutput)
 	fzPrintStextTrailerAsHTML  func(ctx *fzContext, out *fzOutput)
+	fzSetWarningCallback       func(ctx *fzContext, cb uintptr, user *byte)
+	fzSetErrorCallback         func(ctx *fzContext, cb uintptr, user *byte)
+
+	silentCallback uintptr
 )
 
+// applySilence installs no-op warning/error callbacks on the given context,
+// suppressing MuPDF stderr output.
+func applySilence(ctx *fzContext) {
+	fzSetWarningCallback(ctx, silentCallback, nil)
+	fzSetErrorCallback(ctx, silentCallback, nil)
+}
+
 func init() {
 	libmupdf = loadLibrary()
 
@@ -624,6 +639,10 @@ func init() {
 	purego.RegisterLibFunc(&fzPrintStextPageAsHTML, libmupdf, "fz_print_stext_page_as_html")
 	purego.RegisterLibFunc(&fzPrintStextHeaderAsHTML, libmupdf, "fz_print_stext_header_as_html")
 	purego.RegisterLibFunc(&fzPrintStextTrailerAsHTML, libmupdf, "fz_print_stext_trailer_as_html")
+	purego.RegisterLibFunc(&fzSetWarningCallback, libmupdf, "fz_set_warning_callback")
+	purego.RegisterLibFunc(&fzSetErrorCallback, libmupdf, "fz_set_error_callback")
+
+	silentCallback = purego.NewCallback(func(user *byte, message *byte) {})
 
 	ver := version()
 	if ver != "" {

fitz_test.go

@@ -317,3 +317,18 @@ func TestEmptyBytes(t *testing.T) {
 type emptyReader struct{}
 
 func (emptyReader) Read([]byte) (int, error) { return 0, io.EOF }
+
+// TestSilencedCallbacks verifies that the unconditional silencing of
+// MuPDF warning/error callbacks does not break normal Document creation
+// and text extraction.
+func TestSilencedCallbacks(t *testing.T) {
+	doc, err := fitz.New(filepath.Join("testdata", "test.pdf"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer doc.Close()
+
+	if _, err := doc.Text(0); err != nil {
+		t.Fatal(err)
+	}
+}