Fix picture loading

Signed vs unsigned comparisons are such a pain. Since we want offsets to
be +/- 30 minutes around the dive we need to allow negative offsets - but
duration_t was defined as uint32_t.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

dive.c

@@ -2389,7 +2389,7 @@ void dive_create_picture(struct dive *d, char *filename, int shift_time)
 	picture_load_exif_data(p, &timestamp);
 	if (timestamp) {
 		p->offset.seconds = timestamp - d->when + shift_time;
-		if (p->offset.seconds < -D30MIN || p->offset.seconds > d->duration.seconds + D30MIN) {
+		if (p->offset.seconds < -D30MIN || p->offset.seconds > (int)d->duration.seconds + D30MIN) {
 			// this picture doesn't belong to this dive
 			free(p);
 			return;

dive.h

@@ -292,7 +292,7 @@ struct dive {
 /* picture list and methods related to dive picture handling */
 struct picture {
 	char *filename;
-	duration_t offset;
+	offset_t offset;
 	degrees_t latitude;
 	degrees_t longitude;
 	struct picture *next;

parse-xml.c

@@ -412,6 +412,20 @@ static void sampletime(char *buffer, duration_t *time)
 	}
 }
 
+static void offsettime(char *buffer, offset_t *time)
+{
+	duration_t uoffset;
+	int sign = 1;
+	if (*buffer == '-') {
+		sign = -1;
+		buffer++;
+	}
+	/* yes, this could indeed fail if we have an offset > 34yrs
+	 * - too bad */
+	sampletime(buffer, &uoffset);
+	time->seconds = sign * uoffset.seconds;
+}
+
 static void duration(char *buffer, duration_t *time)
 {
 	/* DivingLog 5.08 (and maybe other versions) appear to sometimes
@@ -1106,7 +1120,7 @@ static void try_to_fill_dive(struct dive *dive, const char *name, char *buf)
 
 	if (MATCH("filename.picture", utf8_string, &cur_picture->filename))
 		return;
-	if (MATCH("offset.picture", sampletime, &cur_picture->offset))
+	if (MATCH("offset.picture", offsettime, &cur_picture->offset))
 		return;
 	if (MATCH("gps.picture", gps_picture_location, cur_picture))
 		return;
@@ -1317,7 +1331,8 @@ static void event_end(void)
 			if (cur_event.type == 123) {
 				struct picture *pic = alloc_picture();
 				pic->filename = strdup(cur_event.name);
-				pic->offset = cur_event.time;
+				/* theoretically this could fail - but we didn't support multi year offsets */
+				pic->offset.seconds = cur_event.time.seconds;
 				dive_add_picture(cur_dive, pic);
 			} else {
 				add_event(dc, cur_event.time.seconds,

save-xml.c

@@ -333,8 +333,15 @@ static void save_picture(struct membuffer *b, struct picture *pic)
 	put_string(b, "  <picture filename='");
 	put_string(b, pic->filename);
 	put_string(b, "'");
-	if (pic->offset.seconds)
-		put_format(b, " offset='%u:%02u min'", FRACTION(pic->offset.seconds, 60));
+	if (pic->offset.seconds) {
+		int offset = pic->offset.seconds;
+		char sign = '+';
+		if (offset < 0) {
+			sign = '-';
+			offset = -offset;
+		}
+		put_format(b, " offset='%c%u:%02u min'", sign, FRACTION(offset, 60));
+	}
 	if (pic->latitude.udeg || pic->longitude.udeg) {
 		put_degrees(b, pic->latitude, " gps='", " ");
 		put_degrees(b, pic->longitude, "", "'");

units.h

@@ -69,6 +69,11 @@ typedef struct
 	uint32_t seconds; // durations up to 68 yrs
 } duration_t;
 
+typedef struct
+{
+	int32_t seconds; // offsets up to +/- 34 yrs
+} offset_t;
+
 typedef struct
 {
 	int32_t mm;