fix: stabilise modal chart render after transition

app/components/Modal.client.vue

@@ -5,6 +5,10 @@ const props = defineProps<{
 
 const dialogRef = useTemplateRef('dialogRef')
 
+const emit = defineEmits<{
+  (e: 'transitioned'): void
+}>()
+
 const modalTitleId = computed(() => {
   const id = getCurrentInstance()?.attrs.id
   return id ? `${id}-title` : undefined
@@ -14,6 +18,20 @@ function handleModalClose() {
   dialogRef.value?.close()
 }
 
+/**
+ * Emits `transitioned` once the dialog has finished its open opacity transition.
+ * This is used by consumers that need to run layout-sensitive logic (for example
+ * dispatching a resize) only after the modal is fully displayed.
+ */
+function onDialogTransitionEnd(event: TransitionEvent) {
+  const el = dialogRef.value
+  if (!el) return
+  if (!el.open) return
+  if (event.target !== el) return
+  if (event.propertyName !== 'opacity') return
+  emit('transitioned')
+}
+
 defineExpose({
   showModal: () => dialogRef.value?.showModal(),
   close: () => dialogRef.value?.close(),
@@ -28,6 +46,7 @@ defineExpose({
       class="w-full bg-bg border border-border rounded-lg shadow-xl max-h-[90vh] overflow-y-auto overscroll-contain m-0 m-auto p-6 text-fg focus-visible:outline focus-visible:outline-accent/70"
       :aria-labelledby="modalTitleId"
       v-bind="$attrs"
+      @transitionend="onDialogTransitionEnd"
     >
       <!-- Modal top header section -->
       <div class="flex items-center justify-between mb-6">

app/components/Package/WeeklyDownloadStats.vue

@@ -9,16 +9,27 @@ const props = defineProps<{
 }>()
 
 const chartModal = useModal('chart-modal')
-
+const hasChartModalTransitioned = shallowRef(false)
 const isChartModalOpen = shallowRef(false)
+
 async function openChartModal() {
   isChartModalOpen.value = true
+  hasChartModalTransitioned.value = false
   // ensure the component renders before opening the dialog
   await nextTick()
   await nextTick()
   chartModal.open()
 }
 
+function handleModalClose() {
+  isChartModalOpen.value = false
+  hasChartModalTransitioned.value = false
+}
+
+function handleModalTransitioned() {
+  hasChartModalTransitioned.value = true
+}
+
 const { fetchPackageDownloadEvolution } = useCharts()
 
 const { accentColors, selectedAccentColor } = useAccentColor()
@@ -249,16 +260,45 @@ const config = computed(() => {
     </CollapsibleSection>
   </div>
 
-  <PackageChartModal v-if="isChartModalOpen" @close="isChartModalOpen = false">
-    <PackageDownloadAnalytics
-      :weeklyDownloads="weeklyDownloads"
-      :inModal="true"
-      :packageName="props.packageName"
-      :createdIso="createdIso"
+  <PackageChartModal @close="handleModalClose" @transitioned="handleModalTransitioned">
+    <!-- The Chart is mounted after the dialog has transitioned -->
+    <!-- This avoids flaky behavior that hides the chart's minimap half of the time -->
+    <Transition name="opacity" mode="out-in">
+      <PackageDownloadAnalytics
+        v-if="hasChartModalTransitioned"
+        :weeklyDownloads="weeklyDownloads"
+        :inModal="true"
+        :packageName="props.packageName"
+        :createdIso="createdIso"
+      />
+    </Transition>
+
+    <!-- This placeholder bears the same dimensions as the PackageDownloadAnalytics component -->
+    <!-- Avoids CLS when the dialog has transitioned -->
+    <div
+      v-if="!hasChartModalTransitioned"
+      class="w-full aspect-[390/634.5] sm:aspect-[718/622.797]"
     />
   </PackageChartModal>
 </template>
 
+<style scoped>
+.opacity-enter-active,
+.opacity-leave-active {
+  transition: opacity 200ms ease;
+}
+
+.opacity-enter-from,
+.opacity-leave-to {
+  opacity: 0;
+}
+
+.opacity-enter-to,
+.opacity-leave-from {
+  opacity: 1;
+}
+</style>
+
 <style>
 /** Overrides */
 .vue-ui-sparkline-title span {