libnsgif: Update to latest upstream. (#2706)

libvips/foreign/libnsgif/README.md

@@ -8,7 +8,7 @@ but within the libvips build system.
 Run `./update.sh` to update this copy of libnsgif from the upstream repo. It
 will also patch libnsgif.c to prevent it modifying the input.
 
-Last updated 7 Oct 2021.
+Last updated 3 Mar 2022.
 
 # To do
 

libvips/foreign/libnsgif/gif.c

@@ -625,13 +625,15 @@ static void nsgif__restore_bg(
 		uint32_t offset_x = frame->info.rect.x0;
 		uint32_t offset_y = frame->info.rect.y0;
 
-		width -= gif__clip(offset_x, width, gif->info.width);
+		if (frame->info.display == false ||
-		height -= gif__clip(offset_y, height, gif->info.height);
+		    frame->info.rect.x0 >= gif->info.width ||
-
+		    frame->info.rect.y0 >= gif->info.height) {
-		if (frame->info.display == false || width == 0) {
 			return;
 		}
 
+		width -= gif__clip(offset_x, width, gif->info.width);
+		height -= gif__clip(offset_y, height, gif->info.height);
+
 		if (frame->info.transparency) {
 			for (uint32_t y = 0; y < height; y++) {
 				uint32_t *scanline = bitmap + offset_x +
@@ -1703,7 +1705,7 @@ nsgif_error nsgif_frame_decode(
 	uint32_t start_frame;
 	nsgif_error ret = NSGIF_OK;
 
-	if (frame > gif->info.frame_count) {
+	if (frame >= gif->info.frame_count) {
 		return NSGIF_ERR_BAD_FRAME;
 	}
 
@@ -1742,7 +1744,7 @@ const nsgif_frame_info_t *nsgif_get_frame_info(
 		const nsgif_t *gif,
 		uint32_t frame)
 {
-	if (frame > gif->info.frame_count) {
+	if (frame >= gif->info.frame_count) {
 		return NULL;
 	}
 
@@ -1759,8 +1761,7 @@ const char *nsgif_strerror(nsgif_error err)
 		[NSGIF_ERR_BAD_FRAME]     = "Requested frame does not exist",
 		[NSGIF_ERR_DATA_FRAME]    = "Invalid frame data",
 		[NSGIF_ERR_FRAME_COUNT]   = "Excessive number of frames",
-		[NSGIF_ERR_END_OF_DATA]   = "Insufficient data for first frame",
+		[NSGIF_ERR_END_OF_DATA]   = "Unexpected end of GIF source data",
-		[NSGIF_ERR_END_OF_FRAME]  = "End of data during frame",
 		[NSGIF_ERR_FRAME_DISPLAY] = "Frame can't be displayed",
 		[NSGIF_ERR_ANIMATION_END] = "Animation complete",
 	};

libvips/foreign/libnsgif/nsgif.h

@@ -82,15 +82,10 @@ typedef enum {
 	NSGIF_ERR_FRAME_COUNT,
 
 	/**
-	 * GIF source data ended without one complete frame available.
+	 * Unexpected end of GIF source data.
 	 */
 	NSGIF_ERR_END_OF_DATA,
 
-	/**
-	 * GIF source data ended with incomplete frame.
-	 */
-	NSGIF_ERR_END_OF_FRAME,
-
 	/**
 	 * The current frame cannot be displayed.
 	 */
@@ -215,6 +210,9 @@ void nsgif_destroy(nsgif_t *gif);
  *
  * If an error occurs, all previously scanned frames are retained.
  *
+ * Note that an error returned from this function is purely informational.
+ * So long as at least one frame is available, you can display frames.
+ *
  * \param[in]  gif     The \ref nsgif_t object.
  * \param[in]  size    Number of bytes in data.
  * \param[in]  data    Raw source GIF data.

libvips/foreign/libnsgif/test/nsgif.c

@@ -207,21 +207,21 @@ static void decode(FILE* ppm, const char *name, nsgif_t *gif)
 		}
 		frame_prev = frame_new;
 
-		err = nsgif_frame_decode(gif, frame_new, &bitmap);
-		if (err != NSGIF_OK) {
-			warning("nsgif_decode_frame", err);
-			return;
-		}
-
 		if (nsgif_options.info == true) {
 			const nsgif_frame_info_t *f_info;
 
 			f_info = nsgif_get_frame_info(gif, frame_new);
-			assert(f_info != NULL);
+			if (f_info != NULL) {
 				print_gif_frame_info(f_info);
 			}
+		}
 
-		if (ppm != NULL) {
+		err = nsgif_frame_decode(gif, frame_new, &bitmap);
+		if (err != NSGIF_OK) {
+			warning("nsgif_decode_frame", err);
+			/* Continue decoding the rest of the frames. */
+
+		} else if (ppm != NULL) {
 			fprintf(ppm, "# frame %u:\n", frame_new);
 			image = (const uint8_t *) bitmap;
 			for (uint32_t y = 0; y != info->height; y++) {
@@ -284,10 +284,9 @@ int main(int argc, char *argv[])
 	/* Scan the raw data */
 	err = nsgif_data_scan(gif, size, data);
 	if (err != NSGIF_OK) {
+		/* Not fatal; some GIFs are nasty. Can still try to decode
+		 * any frames that were decoded successfully. */
 		warning("nsgif_data_scan", err);
-		nsgif_destroy(gif);
-		free(data);
-		return EXIT_FAILURE;
 	}
 
 	if (nsgif_options.loops == 0) {