At each scale, always display a unit that includes MAX_DATEunit-after-max

Without this, with a MAX_DATE of, say 2000/1/1, zooming out to
scale 1e9 won't show events after 1 AD.

1 files changed, 20 insertions, 3 deletions

diff --git a/src/lib.ts b/src/lib.ts
index 3b0bc68..03b443d 100644
--- a/src/lib.ts
+++ b/src/lib.ts
@@ -582,14 +582,31 @@ export function dateToUnit(date: HistDate, scale: number): number {
 		}
 	}
 }
-export function dateToScaleDate(date: HistDate, scale: number): HistDate {
+export function dateToScaleDate(date: HistDate, scale: number, upward=false): HistDate {
 	// Returns a date representing the unit on 'scale' that 'date' is within
 	if (scale == DAY_SCALE){
 		return new CalDate(date.year, date.month, date.day);
 	} else if (scale == MONTH_SCALE){
-		return new CalDate(date.year, date.month, 1);
+		if (upward && date.day > 1){
+			return stepDate(new CalDate(date.year, date.month, 1), MONTH_SCALE);
+		} else {
+			return new CalDate(date.year, date.month, 1);
+		}
+	} else if (scale == 1){
+		if (upward && date.month > 1){
+			return stepDate(new CalDate(date.year, 1, 1), 1);
+		} else {
+			if (date.year < MIN_CAL_YEAR){
+				return new YearDate(date.year);
+			} else {
+				return new CalDate(date.year == 0 ? 1 : date.year, 1, 1);
+			}
+		}
 	} else {
-		const year = Math.floor(date.year / scale) * scale;
+		let year = Math.floor(date.year / scale) * scale;
+		if (upward && moduloPositive(date.year, scale) > 0){
+			year += scale;
+		}
 		if (year < MIN_CAL_YEAR){
 			return new YearDate(year);
 		} else {