feat: Add loading indicator slot and prop

* While the graph is suspended we open up a loading indicator slot
* a prop option has to be passed to enable the indicator
* add some styles for a default loading text
* move loading event to after store has been initialized *and* zoom pane dimensions are present

Signed-off-by: Braks <78412429+bcakmakoglu@users.noreply.github.com>

examples/Stress/StressExample.vue

@@ -49,7 +49,13 @@ const updateElements = () => {
 }
 </script>
 <template>
-  <VueFlow v-model="elements" @load="onLoad" @elementsRemove="onElementsRemove" @connect="onConnect">
+  <VueFlow
+    v-model="elements"
+    :show-loading-indicator="true"
+    @load="onLoad"
+    @elementsRemove="onElementsRemove"
+    @connect="onConnect"
+  >
     <MiniMap />
     <Controls />
     <Background />

src/container/VueFlow/VueFlow.vue

@@ -22,7 +22,7 @@ import SelectionPane from '../../container/SelectionPane/SelectionPane.vue'
 import NodeRenderer from '../../container/NodeRenderer/NodeRenderer.vue'
 import EdgeRenderer from '../../container/EdgeRenderer/EdgeRenderer.vue'
 import { createHooks, initFlow, useZoomPanHelper } from '../../composables'
-import { onLoadGetElements, onLoadProject, onLoadToObject } from '~/utils'
+import { onLoadGetElements, onLoadProject, onLoadToObject } from '../../utils'
 
 export interface FlowProps extends Partial<FlowOptions> {
   id?: string
@@ -62,6 +62,7 @@ export interface FlowProps extends Partial<FlowOptions> {
   zoomOnDoubleClick?: boolean
   edgeUpdaterRadius?: number
   storageKey?: string
+  showLoadingIndicator?: boolean
 }
 
 const emit = defineEmits([...Object.keys(createHooks()), 'update:elements', 'update:modelValue'])
@@ -103,6 +104,7 @@ const props = withDefaults(defineProps<FlowProps>(), {
   panOnScrollMode: PanOnScrollMode.Free,
   paneMoveable: true,
   edgeUpdaterRadius: 10,
+  showLoadingIndicator: false,
 })
 const store = initFlow(emit, typeof props.storageKey === 'string' ? props.storageKey : props.id, props.store)
 const elements = useVModel(props, props.elements.length ? 'elements' : 'modelValue', emit)
@@ -147,10 +149,13 @@ watch(
   },
   { flush: 'post', deep: true },
 )
-const { zoomIn, zoomOut, zoomTo, transform: setTransform, fitView } = useZoomPanHelper(store)
 
 invoke(async () => {
   await init(options)
+  store.isReady = true
+  await until(store.dimensions).toMatch(({ height, width }) => !isNaN(width) && width > 0 && !isNaN(height) && height > 0)
+  const { zoomIn, zoomOut, zoomTo, transform: setTransform, fitView } = useZoomPanHelper(store)
+
   const instance: FlowInstance = {
     fitView: (params = { padding: 0.1 }) => fitView(params),
     zoomIn,
@@ -162,12 +167,12 @@ invoke(async () => {
     toObject: onLoadToObject(store),
   }
   store.hooks.load.trigger(instance)
-  store.isReady = true
   store.instance = instance
 })
 </script>
 <template>
   <div class="vue-flow">
+    <Suspense>
       <ZoomPane
         :selection-key-code="store.selectionKeyCode"
         :zoom-activation-key-code="store.zoomActivationKeyCode"
@@ -209,6 +214,12 @@ invoke(async () => {
           <slot name="zoom-pane" v-bind="zoomPaneProps"></slot>
         </template>
       </ZoomPane>
+      <template v-if="store.showLoadingIndicator" #fallback>
+        <slot name="loading-indicator">
+          <div class="vue-flow__loading-indicator">Almost ready...</div>
+        </slot>
+      </template>
+    </Suspense>
     <slot v-bind="{ store }"></slot>
   </div>
 </template>

src/container/ZoomPane/ZoomPane.vue

@@ -2,9 +2,9 @@
 import { D3ZoomEvent, zoom, zoomIdentity, ZoomTransform } from 'd3-zoom'
 import { get, invoke } from '@vueuse/core'
 import { pointer, select } from 'd3-selection'
-import { FlowInstance, FlowTransform, KeyCode, PanOnScrollMode } from '../../types'
+import { FlowTransform, KeyCode, PanOnScrollMode } from '../../types'
-import { useKeyPress, useStore, useZoomPanHelper } from '../../composables'
+import { useKeyPress, useStore } from '../../composables'
-import { clamp, onLoadGetElements, onLoadProject, onLoadToObject } from '../../utils'
+import { clamp } from '../../utils'
 
 interface ZoomPaneProps {
   selectionKeyCode?: KeyCode
@@ -181,9 +181,7 @@ store.dimensions = {
   height: height.value,
 }
 
-invoke(async () => {
+await until(() => store.isReady).toBe(true)
-  await until(() => !isNaN(width.value) && width.value > 0 && !isNaN(height.value) && height.value > 0).toBeTruthy()
-})
 
 watch(
   [width, height],
@@ -206,13 +204,11 @@ watch(
 </script>
 <template>
   <div ref="zoomPane" class="vue-flow__renderer vue-flow__zoompane">
-    <Suspense>
     <slot
       v-bind="{
         transform,
         dimensions: { width, height },
       }"
     />
-    </Suspense>
   </div>
 </template>

src/store/stateStore.ts

@@ -64,8 +64,8 @@ export default function flowStore(
           workerTerminate('SUCCESS')
         }
         this.elements = elements
-        this.nodes = next.nextNodes
+        this.nodes = next?.nextNodes ?? []
-        this.edges = next.nextEdges
+        this.edges = next?.nextEdges ?? []
       },
       updateNodeDimensions({ id, nodeElement, forceUpdate }) {
         const i = this.nodes.map((x) => x.id).indexOf(id)

src/store/utils.ts

@@ -88,8 +88,7 @@ export const initialState = (): FlowState => ({
 
   isReady: false,
   hooks: createHooks(),
-  storageKey: undefined,
+  showLoadingIndicator: false,
-  instance: undefined,
 
   vueFlowVersion: typeof __VUE_FLOW_VERSION__ !== 'undefined' ? __VUE_FLOW_VERSION__ : '-',
 })

src/style.css

@@ -185,3 +185,10 @@
   bottom: 10px;
   right: 10px;
 }
+
+.vue-flow__loading-indicator {
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  font-size: 16px;
+}

src/types/types.ts

@@ -126,4 +126,5 @@ export interface FlowOptions {
   zoomOnDoubleClick?: boolean
   edgeUpdaterRadius?: number
   storageKey?: string
+  showLoadingIndicator?: boolean
 }