1 files changed, 80 insertions, 0 deletions
diff --git a/apps/web/src/timeline/pixel-utils.ts b/apps/web/src/timeline/pixel-utils.ts
new file mode 100644
index 00000000..71e8466a
--- /dev/null
+++ b/apps/web/src/timeline/pixel-utils.ts
@@ -0,0 +1,80 @@
+import { BASE_TIMELINE_PIXELS_PER_SECOND } from "@/timeline/scale";
+import { TICKS_PER_SECOND } from "@/wasm";
+
+export const TIMELINE_INDICATOR_LINE_WIDTH_PX = 2;
+
+function getDevicePixelRatio({
+	devicePixelRatio,
+}: {
+	devicePixelRatio?: number;
+}): number {
+	if (
+		typeof devicePixelRatio === "number" &&
+		Number.isFinite(devicePixelRatio) &&
+		devicePixelRatio > 0
+	) {
+		return devicePixelRatio;
+	}
+
+	if (typeof window === "undefined") {
+		return 1;
+	}
+
+	if (Number.isFinite(window.devicePixelRatio) && window.devicePixelRatio > 0) {
+		return window.devicePixelRatio;
+	}
+
+	return 1;
+}
+
+export function getTimelinePixelsPerSecond({
+	zoomLevel,
+}: {
+	zoomLevel: number;
+}): number {
+	return BASE_TIMELINE_PIXELS_PER_SECOND * zoomLevel;
+}
+
+export function timelineTimeToPixels({
+	time,
+	zoomLevel,
+}: {
+	time: number;
+	zoomLevel: number;
+}): number {
+	return (time / TICKS_PER_SECOND) * getTimelinePixelsPerSecond({ zoomLevel });
+}
+
+export function snapPixelToDeviceGrid({
+	pixel,
+	devicePixelRatio,
+}: {
+	pixel: number;
+	devicePixelRatio?: number;
+}): number {
+	const safeDevicePixelRatio = getDevicePixelRatio({ devicePixelRatio });
+	return Math.round(pixel * safeDevicePixelRatio) / safeDevicePixelRatio;
+}
+
+export function timelineTimeToSnappedPixels({
+	time,
+	zoomLevel,
+	devicePixelRatio,
+}: {
+	time: number;
+	zoomLevel: number;
+	devicePixelRatio?: number;
+}): number {
+	const rawPixel = timelineTimeToPixels({ time, zoomLevel });
+	return snapPixelToDeviceGrid({ pixel: rawPixel, devicePixelRatio });
+}
+
+export function getCenteredLineLeft({
+	centerPixel,
+	lineWidthPx = TIMELINE_INDICATOR_LINE_WIDTH_PX,
+}: {
+	centerPixel: number;
+	lineWidthPx?: number;
+}): number {
+	return centerPixel - lineWidthPx / 2;
+}