fix preview snapping threshold

4 files changed, 58 insertions, 11 deletions

diff --git a/apps/web/src/hooks/use-preview-interaction.ts b/apps/web/src/hooks/use-preview-interaction.ts
index 2bb33f21..d29f2a4b 100644
--- a/apps/web/src/hooks/use-preview-interaction.ts
+++ b/apps/web/src/hooks/use-preview-interaction.ts
@@ -4,9 +4,16 @@ import { useShiftKey } from "@/hooks/use-shift-key";
 import type { TextElement, Transform } from "@/types/timeline";
 import { getVisibleElementsWithBounds } from "@/lib/preview/element-bounds";
 import { hitTest } from "@/lib/preview/hit-test";
-import { screenToCanvas } from "@/lib/preview/preview-coords";
+import {
+	screenPixelsToLogicalThreshold,
+	screenToCanvas,
+} from "@/lib/preview/preview-coords";
 import { isVisualElement } from "@/lib/timeline/element-utils";
-import { snapPosition, type SnapLine } from "@/lib/preview/preview-snap";
+import {
+	SNAP_THRESHOLD_SCREEN_PIXELS,
+	snapPosition,
+	type SnapLine,
+} from "@/lib/preview/preview-snap";
 
 const MIN_DRAG_DISTANCE = 0.5;
 
@@ -230,11 +237,16 @@ export function usePreviewInteraction({
 			};
 
 			const shouldSnap = !isShiftHeldRef.current;
+			const snapThreshold = screenPixelsToLogicalThreshold({
+				canvas: canvasRef.current,
+				screenPixels: SNAP_THRESHOLD_SCREEN_PIXELS,
+			});
 			const { snappedPosition, activeLines } = shouldSnap
 				? snapPosition({
 						proposedPosition,
 						canvasSize,
 						elementSize: dragStateRef.current.bounds,
+						snapThreshold,
 					})
 				: {
 						snappedPosition: proposedPosition,
diff --git a/apps/web/src/hooks/use-transform-handles.ts b/apps/web/src/hooks/use-transform-handles.ts
index 37ef6d5f..8be6420c 100644
--- a/apps/web/src/hooks/use-transform-handles.ts
+++ b/apps/web/src/hooks/use-transform-handles.ts
@@ -6,9 +6,13 @@ import {
 	getVisibleElementsWithBounds,
 	type ElementWithBounds,
 } from "@/lib/preview/element-bounds";
-import { screenToCanvas } from "@/lib/preview/preview-coords";
+import {
+	screenPixelsToLogicalThreshold,
+	screenToCanvas,
+} from "@/lib/preview/preview-coords";
 import {
 	MIN_SCALE,
+	SNAP_THRESHOLD_SCREEN_PIXELS,
 	snapRotation,
 	snapScale,
 	type SnapLine,
@@ -228,6 +232,10 @@ export function useTransformHandles({
 				);
 
 				const canvasSize = editor.project.getActive().settings.canvasSize;
+				const snapThreshold = screenPixelsToLogicalThreshold({
+					canvas: canvasRef.current,
+					screenPixels: SNAP_THRESHOLD_SCREEN_PIXELS,
+				});
 				const shouldSnap = !isShiftHeldRef.current;
 				const { snappedScale, activeLines } = shouldSnap
 					? snapScale({
@@ -236,6 +244,7 @@ export function useTransformHandles({
 							baseWidth,
 							baseHeight,
 							canvasSize,
+							snapThreshold,
 						})
 					: { snappedScale: proposedScale, activeLines: [] as SnapLine[] };
 
diff --git a/apps/web/src/lib/preview/preview-coords.ts b/apps/web/src/lib/preview/preview-coords.ts
index 08c16735..dcc87282 100644
--- a/apps/web/src/lib/preview/preview-coords.ts
+++ b/apps/web/src/lib/preview/preview-coords.ts
@@ -74,3 +74,17 @@ export function getDisplayScale({
 		y: canvasRect.height / canvasSize.height,
 	};
 }
+
+export function screenPixelsToLogicalThreshold({
+	canvas,
+	screenPixels,
+}: {
+	canvas: HTMLCanvasElement;
+	screenPixels: number;
+}): { x: number; y: number } {
+	const canvasRect = canvas.getBoundingClientRect();
+	return {
+		x: screenPixels * (canvas.width / canvasRect.width),
+		y: screenPixels * (canvas.height / canvasRect.height),
+	};
+}
diff --git a/apps/web/src/lib/preview/preview-snap.ts b/apps/web/src/lib/preview/preview-snap.ts
index bd53f0ca..36efc3ce 100644
--- a/apps/web/src/lib/preview/preview-snap.ts
+++ b/apps/web/src/lib/preview/preview-snap.ts
@@ -3,10 +3,10 @@ export interface SnapLine {
 	position: number;
 }
 
-const SNAP_THRESHOLD = 10;
 const ROTATION_SNAP_STEP_DEGREES = 90;
 const ROTATION_SNAP_THRESHOLD_DEGREES = 5;
 export const MIN_SCALE = 0.01;
+export const SNAP_THRESHOLD_SCREEN_PIXELS = 8;
 
 export interface SnapResult {
 	snappedPosition: { x: number; y: number };
@@ -17,10 +17,12 @@ export function snapPosition({
 	proposedPosition,
 	canvasSize,
 	elementSize,
+	snapThreshold,
 }: {
 	proposedPosition: { x: number; y: number };
 	canvasSize: { width: number; height: number };
 	elementSize: { width: number; height: number };
+	snapThreshold: { x: number; y: number };
 }): SnapResult {
 	const centerX = 0;
 	const centerY = 0;
@@ -41,11 +43,13 @@ export function snapPosition({
 
 	function getClosestAxisSnap({
 		candidates,
+		threshold,
 	}: {
 		candidates: AxisSnapCandidate[];
+		threshold: number;
 	}): AxisSnapCandidate | null {
 		const snapCandidatesWithinThreshold = candidates.filter(
-			(candidate) => candidate.distance <= SNAP_THRESHOLD,
+			(candidate) => candidate.distance <= threshold,
 		);
 		if (snapCandidatesWithinThreshold.length === 0) {
 			return null;
@@ -95,8 +99,14 @@ export function snapPosition({
 		});
 	}
 
-	const closestX = getClosestAxisSnap({ candidates: xCandidates });
-	const closestY = getClosestAxisSnap({ candidates: yCandidates });
+	const closestX = getClosestAxisSnap({
+		candidates: xCandidates,
+		threshold: snapThreshold.x,
+	});
+	const closestY = getClosestAxisSnap({
+		candidates: yCandidates,
+		threshold: snapThreshold.y,
+	});
 
 	const x = closestX?.snappedPosition ?? proposedPosition.x;
 	const y = closestY?.snappedPosition ?? proposedPosition.y;
@@ -124,12 +134,14 @@ export function snapScale({
 	baseWidth,
 	baseHeight,
 	canvasSize,
+	snapThreshold,
 }: {
 	proposedScale: number;
 	position: { x: number; y: number };
 	baseWidth: number;
 	baseHeight: number;
 	canvasSize: { width: number; height: number };
+	snapThreshold: { x: number; y: number };
 }): ScaleSnapResult {
 	const centerX = 0;
 	const centerY = 0;
@@ -162,7 +174,7 @@ export function snapScale({
 
 	for (const target of verticalTargets) {
 		const distanceLeft = Math.abs(leftEdge - target.position);
-		if (distanceLeft <= SNAP_THRESHOLD) {
+		if (distanceLeft <= snapThreshold.x) {
 			const scale = (2 * (position.x - target.position)) / baseWidth;
 			if (scale > MIN_SCALE) {
 				candidates.push({
@@ -173,7 +185,7 @@ export function snapScale({
 			}
 		}
 		const distanceRight = Math.abs(rightEdge - target.position);
-		if (distanceRight <= SNAP_THRESHOLD) {
+		if (distanceRight <= snapThreshold.x) {
 			const scale = (2 * (target.position - position.x)) / baseWidth;
 			if (scale > MIN_SCALE) {
 				candidates.push({
@@ -199,7 +211,7 @@ export function snapScale({
 
 	for (const target of horizontalTargets) {
 		const distanceTop = Math.abs(topEdge - target.position);
-		if (distanceTop <= SNAP_THRESHOLD) {
+		if (distanceTop <= snapThreshold.y) {
 			const scale = (2 * (position.y - target.position)) / baseHeight;
 			if (scale > MIN_SCALE) {
 				candidates.push({
@@ -210,7 +222,7 @@ export function snapScale({
 			}
 		}
 		const distanceBottom = Math.abs(bottomEdge - target.position);
-		if (distanceBottom <= SNAP_THRESHOLD) {
+		if (distanceBottom <= snapThreshold.y) {
 			const scale = (2 * (target.position - position.y)) / baseHeight;
 			if (scale > MIN_SCALE) {
 				candidates.push({