Handle LibTIFF errors correctly

fiv-io.c

@@ -3039,7 +3039,8 @@ open_libtiff(
 		// We inform about unsupported directories, but do not fail on them.
 		GError *err = NULL;
 		if (!try_append_page(
-				load_libtiff_directory(tiff, &err), &result, &result_tail)) {
+				load_libtiff_directory(tiff, &err), &result, &result_tail) &&
+			err) {
 			add_warning(ctx, "%s", err->message);
 			g_error_free(err);
 		}
@@ -3107,10 +3108,20 @@ open_gdkpixbuf(
 		gdk_pixbuf_get_bits_per_sample(pixbuf) == 8;
 
 	cairo_surface_t *surface = NULL;
-	if (custom_argb32)
+	if (custom_argb32) {
 		surface = load_gdkpixbuf_argb32_unpremultiplied(pixbuf);
-	else
-		surface = gdk_cairo_surface_create_from_pixbuf(pixbuf, 1, NULL);
+	} else {
+		// Don't depend on GDK being initialized, to speed up thumbnailing
+		// (calling gdk_cairo_surface_create_from_pixbuf() would).
+		cairo_surface_t *dummy =
+			cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 1, 1);
+		cairo_t *cr = cairo_create(dummy);
+		cairo_surface_destroy(dummy);
+		gdk_cairo_set_source_pixbuf(cr, pixbuf, 0, 0);
+		(void) cairo_pattern_get_surface(cairo_get_source(cr), &surface);
+		cairo_surface_reference(surface);
+		cairo_destroy(cr);
+	}
 
 	cairo_status_t surface_status = cairo_surface_status(surface);
 	if (surface_status != CAIRO_STATUS_SUCCESS) {
@@ -3313,6 +3324,8 @@ fiv_io_open_from_data(
 		GError *err = NULL;
 		if ((surface = open_gdkpixbuf(data, len, ctx, &err))) {
 			g_clear_error(error);
+		} else if (!err) {
+			// Contrary to documentation, this is a possible outcome (libheif).
 		} else if (err->code == GDK_PIXBUF_ERROR_UNKNOWN_TYPE) {
 			g_error_free(err);
 		} else {

fiv-thumbnail.c

@@ -332,11 +332,12 @@ extract_libraw_unpack(libraw_data_t *iprc, int *flip, GError **error)
 		sorted[i]->tformat == LIBRAW_INTERNAL_THUMBNAIL_KODAK_THUMB)
 		i++;
 
-	if (i < count)
+	bool found = i != count;
+	if (found)
 		i = sorted[i] - iprc->thumbs_list.thumblist;
 
 	g_free(sorted);
-	if (i == count) {
+	if (!found) {
 		set_error(error, "no suitable thumbnails found");
 		return FALSE;
 	}