fix calendar flickering on move for non-aligned entries

this is a trade-off where for non grid aligned entries, the cursor position is a bit off, but data and visual are stil in sync. otherwise fc overrides height on drag, causing flickers.

resources/js/packages/ui/src/FullCalendar/TimeEntryCalendar.vue

@@ -235,8 +235,8 @@ function handleDateSelect(arg: { start: Date; end: Date }) {
         .utc()
         .tz(getUserTimezone(), true);
     const endLocal = getDayJsInstance()(arg.end.toISOString()).utc().tz(getUserTimezone(), true);
-    const snappedStart = snapToGrid(startLocal, snap);
-    let snappedEnd = snapToGrid(endLocal, snap);
+    const snappedStart = snapStartToGrid(startLocal, snap);
+    let snappedEnd = snapEndToGrid(endLocal, snap);
     if (!snappedEnd.isAfter(snappedStart)) {
         snappedEnd = snappedStart.add(snap, 'minute');
     }
@@ -255,10 +255,17 @@ function handleEventClick(arg: EventClickArg) {
     showEditTimeEntryModal.value = true;
 }
 
-// Snap a dayjs time to the nearest snap interval boundary
-function snapToGrid(time: Dayjs, snapMinutes: number): Dayjs {
+// Snap a dayjs time down to the previous snap boundary (for start times)
+function snapStartToGrid(time: Dayjs, snapMinutes: number): Dayjs {
     const minutes = time.hour() * 60 + time.minute();
-    const snapped = Math.round(minutes / snapMinutes) * snapMinutes;
+    const snapped = Math.floor(minutes / snapMinutes) * snapMinutes;
+    return time.startOf('day').add(snapped, 'minute');
+}
+
+// Snap a dayjs time up to the next snap boundary (for end times)
+function snapEndToGrid(time: Dayjs, snapMinutes: number): Dayjs {
+    const minutes = time.hour() * 60 + time.minute();
+    const snapped = Math.ceil(minutes / snapMinutes) * snapMinutes;
     return time.startOf('day').add(snapped, 'minute');
 }
 
@@ -291,7 +298,7 @@ async function handleEventDrop(arg: EventDropArg) {
         .utc()
         .tz(getUserTimezone(), true)
         .second(0);
-    const snappedStart = snapToGrid(startLocal, snap);
+    const snappedStart = snapStartToGrid(startLocal, snap);
     const durationMs = getLocalizedDayJs(timeEntry.end).diff(getLocalizedDayJs(timeEntry.start));
     const snappedEnd = snappedStart.add(durationMs, 'millisecond');
     // Set FC event to snapped position immediately to avoid flash
@@ -325,8 +332,8 @@ async function handleEventResize(arg: EventChangeArg) {
     const startChanged = !newStartLocal.isSame(origStartLocal, 'minute');
 
     // Snap only the changed edge once, reuse for both setDates and API update
-    const snappedStart = startChanged ? snapToGrid(newStartLocal, snap) : null;
-    const snappedEnd = !startChanged && !ext.isRunning ? snapToGrid(newEndLocal, snap) : null;
+    const snappedStart = startChanged ? snapStartToGrid(newStartLocal, snap) : null;
+    const snappedEnd = !startChanged && !ext.isRunning ? snapEndToGrid(newEndLocal, snap) : null;
 
     // Set FC event to snapped position immediately to avoid flash.
     // Use the original event date for the edge that wasn't resized.
@@ -361,7 +368,7 @@ const calendarOptions = computed(() => {
         slotDuration: formatDuration(s.slotMinutes * 60),
         slotLabelInterval: '01:00:00',
         slotLabelFormat: getSlotLabelFormat(),
-        snapDuration: '00:01:00',
+        snapDuration: formatDuration(s.snapMinutes * 60),
         firstDay: getFirstDay(),
         allDaySlot: false,
         nowIndicator: true,
@@ -747,6 +754,10 @@ onUnmounted(() => {
     border: 1px solid var(--primary);
 }
 
+.fullcalendar :deep(.fc-event-mirror) {
+    pointer-events: none;
+}
+
 .fullcalendar :deep(.fc-scrollgrid) {
     border: 1px solid var(--border);
     border-left: 1px solid transparent;

resources/js/packages/ui/src/FullCalendar/useVisualSnap.ts

@@ -32,6 +32,9 @@ export function useVisualSnap({
     function findMirrorHarness(calendarEl: HTMLElement) {
         const mirror = calendarEl.querySelector('.fc-event-mirror') as HTMLElement | null;
         const harness = mirror?.closest('.fc-timegrid-event-harness') as HTMLElement | null;
+        if (harness) {
+            harness.style.pointerEvents = 'none';
+        }
         return { mirror, harness };
     }
 
@@ -81,8 +84,8 @@ export function useVisualSnap({
 
             const top = parseFloat(harness.style.top) || 0;
             const endPos = -(parseFloat(harness.style.bottom) || 0);
-            const snappedTop = Math.round(top / snapPx) * snapPx;
-            const snappedEnd = Math.round(endPos / snapPx) * snapPx;
+            const snappedTop = Math.floor(top / snapPx) * snapPx;
+            const snappedEnd = Math.ceil(endPos / snapPx) * snapPx;
             const clampedEnd = Math.max(snappedTop + snapPx, snappedEnd);
             harness.style.top = snappedTop + 'px';
             harness.style.bottom = -clampedEnd + 'px';
@@ -99,7 +102,7 @@ export function useVisualSnap({
             const top = parseFloat(harness.style.top) || 0;
             const endPos = -(parseFloat(harness.style.bottom) || 0);
             const height = endPos - top;
-            const snappedTop = Math.round(top / snapPx) * snapPx;
+            const snappedTop = Math.floor(top / snapPx) * snapPx;
             harness.style.top = snappedTop + 'px';
             harness.style.bottom = -(snappedTop + height) + 'px';
         });
@@ -135,12 +138,12 @@ export function useVisualSnap({
             }
 
             if (resizeEdge === 'bottom') {
-                const snappedEnd = Math.round(endPos / snapPx) * snapPx;
+                const snappedEnd = Math.ceil(endPos / snapPx) * snapPx;
                 const clampedEnd = Math.max(top + snapPx, snappedEnd);
                 harness.style.bottom = -clampedEnd + 'px';
                 if (mirror) updateMirrorDurationLabel(mirror, top, clampedEnd, snapPx);
             } else if (resizeEdge === 'top') {
-                const snappedTop = Math.round(top / snapPx) * snapPx;
+                const snappedTop = Math.floor(top / snapPx) * snapPx;
                 const clampedTop = Math.min(endPos - snapPx, snappedTop);
                 harness.style.top = clampedTop + 'px';
                 if (mirror) updateMirrorDurationLabel(mirror, clampedTop, endPos, snapPx);