Merge pull request #8376 from Budibase/cheeks-lab-day-grid

Grid component + builder performance improvements

packages/builder/src/builderStore/store/frontend.js

@@ -182,7 +182,70 @@ export const getFrontendStore = () => {
           return state
         })
       },
+      validate: screen => {
+        // Recursive function to find any illegal children in component trees
+        const findIllegalChild = (
+          component,
+          illegalChildren = [],
+          legalDirectChildren = []
+        ) => {
+          const type = component._component
+          if (illegalChildren.includes(type)) {
+            return type
+          }
+          if (
+            legalDirectChildren.length &&
+            !legalDirectChildren.includes(type)
+          ) {
+            return type
+          }
+          if (!component?._children?.length) {
+            return
+          }
+
+          const definition = store.actions.components.getDefinition(
+            component._component
+          )
+
+          // Reset whitelist for direct children
+          legalDirectChildren = []
+          if (definition?.legalDirectChildren?.length) {
+            legalDirectChildren = definition.legalDirectChildren.map(x => {
+              return `@budibase/standard-components/${x}`
+            })
+          }
+
+          // Append blacklisted components and remove duplicates
+          if (definition?.illegalChildren?.length) {
+            const blacklist = definition.illegalChildren.map(x => {
+              return `@budibase/standard-components/${x}`
+            })
+            illegalChildren = [...new Set([...illegalChildren, ...blacklist])]
+          }
+
+          // Recurse on all children
+          for (let child of component._children) {
+            const illegalChild = findIllegalChild(
+              child,
+              illegalChildren,
+              legalDirectChildren
+            )
+            if (illegalChild) {
+              return illegalChild
+            }
+          }
+        }
+
+        // Validate the entire tree and throw an error if an illegal child is
+        // found anywhere
+        const illegalChild = findIllegalChild(screen.props)
+        if (illegalChild) {
+          const def = store.actions.components.getDefinition(illegalChild)
+          throw `You can't place a ${def.name} here`
+        }
+      },
       save: async screen => {
+        store.actions.screens.validate(screen)
         const state = get(store)
         const creatingNewScreen = screen._id === undefined
         const savedScreen = await API.saveScreen(screen)
@@ -445,7 +508,11 @@ export const getFrontendStore = () => {
         return {
           _id: Helpers.uuid(),
           _component: definition.component,
-          _styles: { normal: {}, hover: {}, active: {} },
+          _styles: {
+            normal: {},
+            hover: {},
+            active: {},
+          },
           _instanceName: `New ${definition.friendlyName || definition.name}`,
           ...cloneDeep(props),
           ...extras,
@@ -533,12 +600,11 @@ export const getFrontendStore = () => {
       },
       patch: async (patchFn, componentId, screenId) => {
         // Use selected component by default
-        if (!componentId && !screenId) {
+        if (!componentId || !screenId) {
           const state = get(store)
-          componentId = state.selectedComponentId
+          componentId = componentId || state.selectedComponentId
-          screenId = state.selectedScreenId
+          screenId = screenId || state.selectedScreenId
         }
-        // Invalid if only a screen or component ID provided
         if (!componentId || !screenId || !patchFn) {
           return
         }
@@ -601,18 +667,16 @@ export const getFrontendStore = () => {
         })
 
         // Select the parent if cutting
-        if (cut) {
+        if (cut && selectParent) {
           const screen = get(selectedScreen)
           const parent = findComponentParent(screen?.props, component._id)
           if (parent) {
-            if (selectParent) {
             store.update(state => {
               state.selectedComponentId = parent._id
               return state
             })
           }
         }
-        }
       },
       paste: async (targetComponent, mode, targetScreen) => {
         const state = get(store)
@@ -621,16 +685,24 @@ export const getFrontendStore = () => {
         }
         let newComponentId
 
+        // Remove copied component if cutting, regardless if pasting works
+        let componentToPaste = cloneDeep(state.componentToPaste)
+        if (componentToPaste.isCut) {
+          store.update(state => {
+            delete state.componentToPaste
+            return state
+          })
+        }
+
         // Patch screen
         const patch = screen => {
           // Get up to date ref to target
           targetComponent = findComponent(screen.props, targetComponent._id)
           if (!targetComponent) {
-            return
+            return false
           }
-          const cut = state.componentToPaste.isCut
+          const cut = componentToPaste.isCut
-          const originalId = state.componentToPaste._id
+          const originalId = componentToPaste._id
-          let componentToPaste = cloneDeep(state.componentToPaste)
           delete componentToPaste.isCut
 
           // Make new component unique if copying
@@ -685,11 +757,8 @@ export const getFrontendStore = () => {
         const targetScreenId = targetScreen?._id || state.selectedScreenId
         await store.actions.screens.patch(patch, targetScreenId)
 
+        // Select the new component
         store.update(state => {
-          // Remove copied component if cutting
-          if (state.componentToPaste.isCut) {
-            delete state.componentToPaste
-          }
           state.selectedScreenId = targetScreenId
           state.selectedComponentId = newComponentId
           return state
@@ -893,6 +962,15 @@ export const getFrontendStore = () => {
           }
         })
       },
+      updateStyles: async (styles, id) => {
+        const patchFn = component => {
+          component._styles.normal = {
+            ...component._styles.normal,
+            ...styles,
+          }
+        }
+        await store.actions.components.patch(patchFn, id)
+      },
       updateCustomStyle: async style => {
         await store.actions.components.patch(component => {
           component._styles.custom = style

packages/builder/src/pages/builder/app/[application]/design/[screenId]/_components/AppPreview.svelte

@@ -86,7 +86,11 @@
         : [],
     isBudibaseEvent: true,
     usedPlugins: $store.usedPlugins,
-    location: window.location,
+    location: {
+      protocol: window.location.protocol,
+      hostname: window.location.hostname,
+      port: window.location.port,
+    },
   }
 
   // Refresh the preview when required
@@ -99,7 +103,7 @@
   )
 
   // Register handler to send custom to the preview
-  $: store.actions.preview.registerEventHandler((name, payload) => {
+  $: sendPreviewEvent = (name, payload) => {
     iframe?.contentWindow.postMessage(
       JSON.stringify({
         name,
@@ -108,53 +112,53 @@
         runtimeEvent: true,
       })
     )
-  })
+  }
+  $: store.actions.preview.registerEventHandler(sendPreviewEvent)
 
   // Update the iframe with the builder info to render the correct preview
   const refreshContent = message => {
     iframe?.contentWindow.postMessage(message)
   }
 
-  const receiveMessage = message => {
+  const receiveMessage = async message => {
-    const handlers = {
+    if (!message?.data?.type) {
-      [MessageTypes.READY]: () => {
-        // Initialise the app when mounted
-        if ($store.clientFeatures.messagePassing) {
-          if (!loading) return
-        }
-
-        // Display preview immediately if the intelligent loading feature
-        // is not supported
-        if (!$store.clientFeatures.intelligentLoading) {
-          loading = false
-        }
-        refreshContent(json)
-      },
-      [MessageTypes.ERROR]: event => {
-        // Catch any app errors
-        loading = false
-        error = event.error || "An unknown error occurred"
-      },
-    }
-
-    const messageHandler = handlers[message.data.type] || handleBudibaseEvent
-    messageHandler(message)
-  }
-
-  const handleBudibaseEvent = async event => {
-    const { type, data } = event.data || event.detail
-    if (!type) {
       return
     }
 
+    // Await the event handler
     try {
-      if (type === "select-component" && data.id) {
+      await handleBudibaseEvent(message)
+    } catch (error) {
+      notifications.error(error || "Error handling event from app preview")
+    }
+
+    // Reply that the event has been completed
+    if (message.data?.id) {
+      sendPreviewEvent("event-completed", message.data?.id)
+    }
+  }
+
+  const handleBudibaseEvent = async event => {
+    const { type, data } = event.data
+    if (type === MessageTypes.READY) {
+      // Initialise the app when mounted
+      if (!loading) {
+        return
+      }
+      refreshContent(json)
+    } else if (type === MessageTypes.ERROR) {
+      // Catch any app errors
+      loading = false
+      error = event.error || "An unknown error occurred"
+    } else if (type === "select-component" && data.id) {
       $store.selectedComponentId = data.id
       if (!$isActive("./components")) {
         $goto("./components")
       }
     } else if (type === "update-prop") {
       await store.actions.components.updateSetting(data.prop, data.value)
+    } else if (type === "update-styles") {
+      await store.actions.components.updateStyles(data.styles, data.id)
     } else if (type === "delete-component" && data.id) {
       // Legacy type, can be deleted in future
       confirmDeleteComponent(data.id)
@@ -187,7 +191,7 @@
 
       // Cut and paste the component to the new destination
       if (source && destination) {
-          store.actions.components.copy(source, true)
+        store.actions.components.copy(source, true, false)
         await store.actions.components.paste(destination, data.mode)
       }
     } else if (type === "click-nav") {
@@ -219,10 +223,6 @@
     } else {
       console.warn(`Client sent unknown event type: ${type}`)
     }
-    } catch (error) {
-      console.warn(error)
-      notifications.error("Error handling event from app preview")
-    }
   }
 
   const confirmDeleteComponent = componentId => {
@@ -254,42 +254,10 @@
 
   onMount(() => {
     window.addEventListener("message", receiveMessage)
-    if (!$store.clientFeatures.messagePassing) {
-      // Legacy - remove in later versions of BB
-      iframe.contentWindow.addEventListener(
-        "ready",
-        () => {
-          receiveMessage({ data: { type: MessageTypes.READY } })
-        },
-        { once: true }
-      )
-      iframe.contentWindow.addEventListener(
-        "error",
-        event => {
-          receiveMessage({
-            data: { type: MessageTypes.ERROR, error: event.detail },
-          })
-        },
-        { once: true }
-      )
-      // Add listener for events sent by client library in preview
-      iframe.contentWindow.addEventListener("bb-event", handleBudibaseEvent)
-    }
   })
 
-  // Remove all iframe event listeners on component destroy
   onDestroy(() => {
     window.removeEventListener("message", receiveMessage)
-
-    if (iframe.contentWindow) {
-      if (!$store.clientFeatures.messagePassing) {
-        // Legacy - remove in later versions of BB
-        iframe.contentWindow.removeEventListener(
-          "bb-event",
-          handleBudibaseEvent
-        )
-      }
-    }
   })
 </script>
 

packages/builder/src/pages/builder/app/[application]/design/[screenId]/components/[componentId]/_components/navigation/ComponentKeyHandler.svelte

@@ -80,10 +80,9 @@
         event.preventDefault()
         event.stopPropagation()
       }
-      return handler(component)
+      return await handler(component)
     } catch (error) {
-      console.error(error)
+      notifications.error(error || "Error handling key press")
-      notifications.error("Error handling key press")
     }
   }
 

packages/builder/src/pages/builder/app/[application]/design/[screenId]/components/[componentId]/_components/navigation/ComponentTree.svelte

@@ -70,34 +70,12 @@
     closedNodes = closedNodes
   }
 
-  const onDrop = async (e, component) => {
+  const onDrop = async e => {
     e.stopPropagation()
     try {
-      const compDef = store.actions.components.getDefinition(
-        $dndStore.source?._component
-      )
-      if (!compDef) {
-        return
-      }
-      const compTypeName = compDef.name.toLowerCase()
-      const path = findComponentPath(currentScreen.props, component._id)
-
-      for (let pathComp of path) {
-        const pathCompDef = store.actions.components.getDefinition(
-          pathComp?._component
-        )
-        if (pathCompDef?.illegalChildren?.indexOf(compTypeName) > -1) {
-          notifications.warning(
-            `${compDef.name} cannot be a child of ${pathCompDef.name} (${pathComp._instanceName})`
-          )
-          return
-        }
-      }
-
       await dndStore.actions.drop()
     } catch (error) {
-      console.error(error)
+      notifications.error(error || "Error saving component")
-      notifications.error("Error saving component")
     }
   }
 
@@ -137,9 +115,7 @@
         on:dragstart={() => dndStore.actions.dragstart(component)}
         on:dragover={dragover(component, index)}
         on:iconClick={() => toggleNodeOpen(component._id)}
-        on:drop={e => {
+        on:drop={onDrop}
-          onDrop(e, component)
-        }}
         text={getComponentText(component)}
         icon={getComponentIcon(component)}
         withArrow={componentHasChildren(component)}

packages/builder/src/pages/builder/app/[application]/design/[screenId]/components/[componentId]/new/_components/NewComponentPanel.svelte

@@ -11,9 +11,10 @@
     notifications,
   } from "@budibase/bbui"
   import structure from "./componentStructure.json"
-  import { store, selectedComponent } from "builderStore"
+  import { store, selectedComponent, selectedScreen } from "builderStore"
   import { onMount } from "svelte"
   import { fly } from "svelte/transition"
+  import { findComponentPath } from "builderStore/componentUtils"
 
   let section = "components"
   let searchString
@@ -21,8 +22,10 @@
   let selectedIndex
   let componentList = []
 
-  $: currentDefinition = store.actions.components.getDefinition(
+  $: allowedComponents = getAllowedComponents(
-    $selectedComponent?._component
+    $store.components,
+    $selectedScreen,
+    $selectedComponent
   )
   $: enrichedStructure = enrichStructure(
     structure,
@@ -31,13 +34,50 @@
   )
   $: filteredStructure = filterStructure(
     enrichedStructure,
-    section,
+    allowedComponents,
-    currentDefinition,
     searchString
   )
   $: blocks = enrichedStructure.find(x => x.name === "Blocks").children
   $: orderMap = createComponentOrderMap(componentList)
 
+  const getAllowedComponents = (allComponents, screen, component) => {
+    const path = findComponentPath(screen?.props, component?._id)
+    if (!path?.length) {
+      return []
+    }
+
+    // Get initial set of allowed components
+    let allowedComponents = []
+    const definition = store.actions.components.getDefinition(
+      component?._component
+    )
+    if (definition.legalDirectChildren?.length) {
+      allowedComponents = definition.legalDirectChildren.map(x => {
+        return `@budibase/standard-components/${x}`
+      })
+    } else {
+      allowedComponents = Object.keys(allComponents)
+    }
+
+    // Build up list of illegal children from ancestors
+    let illegalChildren = definition.illegalChildren || []
+    path.forEach(ancestor => {
+      const def = store.actions.components.getDefinition(ancestor._component)
+      const blacklist = def?.illegalChildren?.map(x => {
+        return `@budibase/standard-components/${x}`
+      })
+      illegalChildren = [...illegalChildren, ...(blacklist || [])]
+    })
+    illegalChildren = [...new Set(illegalChildren)]
+
+    // Filter out illegal children from allowed components
+    allowedComponents = allowedComponents.filter(x => {
+      return !illegalChildren.includes(x)
+    })
+
+    return allowedComponents
+  }
+
   // Creates a simple lookup map from an array, so we can find the selected
   // component much faster
   const createComponentOrderMap = list => {
@@ -90,7 +130,7 @@
     return enrichedStructure
   }
 
-  const filterStructure = (structure, section, currentDefinition, search) => {
+  const filterStructure = (structure, allowedComponents, search) => {
     selectedIndex = search ? 0 : null
     componentList = []
     if (!structure?.length) {
@@ -114,7 +154,7 @@
         }
 
         // Check if the component is allowed as a child
-        return !currentDefinition?.illegalChildren?.includes(name)
+        return allowedComponents.includes(child.component)
       })
       if (matchedChildren.length) {
         filteredStructure.push({
@@ -138,7 +178,7 @@
       await store.actions.components.create(component)
       $goto("../")
     } catch (error) {
-      notifications.error("Error creating component")
+      notifications.error(error || "Error creating component")
     }
   }
 

packages/builder/src/pages/builder/app/[application]/design/[screenId]/components/[componentId]/new/_components/componentStructure.json

@@ -15,7 +15,8 @@
     "icon": "ClassicGridView",
     "children": [
       "container",
-      "section"
+      "section",
+      "grid"
     ]
   },
   {

packages/client/manifest.json

@@ -87,7 +87,7 @@
     "showSettingsBar": true,
     "size": {
       "width": 400,
-      "height": 100
+      "height": 200
     },
     "styles": [
       "padding",
@@ -5037,6 +5037,45 @@
       }
     ]
   },
+  "grid": {
+    "name": "Grid (Beta)",
+    "icon": "ViewGrid",
+    "hasChildren": true,
+    "styles": [
+      "size"
+    ],
+    "illegalChildren": ["section", "grid"],
+    "legalDirectChildren": [
+      "container",
+      "tableblock",
+      "cardsblock",
+      "repeaterblock",
+      "formblock"
+    ],
+    "size": {
+      "width": 800,
+      "height": 400
+    },
+    "showEmptyState": false,
+    "settings": [
+      {
+        "type": "number",
+        "label": "Rows",
+        "key": "rows",
+        "defaultValue": 12,
+        "min": 1,
+        "max": 32
+      },
+      {
+        "type": "number",
+        "label": "Columns",
+        "key": "cols",
+        "defaultValue": 12,
+        "min": 1,
+        "max": 32
+      }
+    ]
+  },
   "formblock": {
     "name": "Form Block",
     "icon": "Form",

packages/client/src/components/ClientApp.svelte

@@ -30,6 +30,7 @@
   import HoverIndicator from "components/preview/HoverIndicator.svelte"
   import CustomThemeWrapper from "./CustomThemeWrapper.svelte"
   import DNDHandler from "components/preview/DNDHandler.svelte"
+  import GridDNDHandler from "components/preview/GridDNDHandler.svelte"
   import KeyboardManager from "components/preview/KeyboardManager.svelte"
   import DevToolsHeader from "components/devtools/DevToolsHeader.svelte"
   import DevTools from "components/devtools/DevTools.svelte"
@@ -196,6 +197,7 @@
                 {/if}
                 {#if $builderStore.inBuilder}
                   <DNDHandler />
+                  <GridDNDHandler />
                 {/if}
               </div>
             </QueryParamsProvider>

packages/client/src/components/Component.svelte

@@ -21,8 +21,8 @@
     devToolsStore,
     componentStore,
     appStore,
-    dndIsDragging,
     dndComponentPath,
+    dndIsDragging,
   } from "stores"
   import { Helpers } from "@budibase/bbui"
   import { getActiveConditions, reduceConditionActions } from "utils/conditions"
@@ -90,6 +90,10 @@
   let settingsDefinitionMap
   let missingRequiredSettings = false
 
+  // Temporary styles which can be added in the app preview for things like DND.
+  // We clear these whenever a new instance is received.
+  let ephemeralStyles
+
   // Set up initial state for each new component instance
   $: initialise(instance)
 
@@ -171,6 +175,10 @@
     children: children.length,
     styles: {
       ...instance._styles,
+      normal: {
+        ...instance._styles?.normal,
+        ...ephemeralStyles,
+      },
       custom: customCSS,
       id,
       empty: emptyState,
@@ -449,6 +457,7 @@
         getRawSettings: () => ({ ...staticSettings, ...dynamicSettings }),
         getDataContext: () => get(context),
         reload: () => initialise(instance, true),
+        setEphemeralStyles: styles => (ephemeralStyles = styles),
       })
     }
   })

packages/client/src/components/app/Grid.svelte

@@ -0,0 +1,102 @@
+<script>
+  import { getContext } from "svelte"
+
+  const component = getContext("component")
+  const { styleable, builderStore } = getContext("sdk")
+
+  export let cols = 12
+  export let rows = 12
+
+  // Deliberately non-reactive as we want this fixed whenever the grid renders
+  const defaultColSpan = Math.ceil((cols + 1) / 2)
+  const defaultRowSpan = Math.ceil((rows + 1) / 2)
+
+  $: coords = generateCoords(rows, cols)
+
+  const generateCoords = (rows, cols) => {
+    let grid = []
+    for (let row = 0; row < rows; row++) {
+      for (let col = 0; col < cols; col++) {
+        grid.push({ row, col })
+      }
+    }
+    return grid
+  }
+</script>
+
+<div
+  class="grid"
+  use:styleable={{
+    ...$component.styles,
+    normal: {
+      ...$component.styles?.normal,
+      "--cols": cols,
+      "--rows": rows,
+      "--default-col-span": defaultColSpan,
+      "--default-row-span": defaultRowSpan,
+      gap: "0 !important",
+    },
+  }}
+  data-rows={rows}
+  data-cols={cols}
+>
+  {#if $builderStore.inBuilder}
+    <div class="underlay">
+      {#each coords as coord}
+        <div class="placeholder" />
+      {/each}
+    </div>
+  {/if}
+  <slot />
+</div>
+
+<style>
+  /*
+    Ensure all children of containers which are top level children of
+    grids do not overflow
+  */
+  :global(.grid > .component > .valid-container > .component > *) {
+    max-height: 100%;
+    max-width: 100%;
+  }
+
+  /* Ensure all top level children have some grid styles set */
+  :global(.grid > .component > *) {
+    overflow: hidden;
+    width: auto;
+    height: auto;
+    grid-column-start: 1;
+    grid-column-end: var(--default-col-span);
+    grid-row-start: 1;
+    grid-row-end: var(--default-row-span);
+    max-height: 100%;
+    max-width: 100%;
+  }
+
+  .grid {
+    position: relative;
+    height: 400px;
+  }
+  .grid,
+  .underlay {
+    display: grid;
+    grid-template-rows: repeat(var(--rows), 1fr);
+    grid-template-columns: repeat(var(--cols), 1fr);
+  }
+  .underlay {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    grid-gap: 2px;
+    background-color: var(--spectrum-global-color-gray-200);
+    border: 2px solid var(--spectrum-global-color-gray-200);
+  }
+  .underlay {
+    z-index: -1;
+  }
+  .placeholder {
+    background-color: var(--spectrum-global-color-gray-100);
+  }
+</style>

packages/client/src/components/app/index.js

@@ -34,6 +34,7 @@ export { default as spectrumcard } from "./SpectrumCard.svelte"
 export { default as tag } from "./Tag.svelte"
 export { default as markdownviewer } from "./MarkdownViewer.svelte"
 export { default as embeddedmap } from "./embedded-map/EmbeddedMap.svelte"
+export { default as grid } from "./Grid.svelte"
 export * from "./charts"
 export * from "./forms"
 export * from "./table"

packages/client/src/components/preview/DNDHandler.svelte

@@ -22,6 +22,18 @@
   $: target = $dndStore.target
   $: drop = $dndStore.drop
 
+  // Local flag for whether we are awaiting an async drop event
+  let dropping = false
+
+  // Util to check if a DND event originates from a grid (or inside a grid).
+  // This is important as we do not handle grid DND in this handler.
+  const isGridEvent = e => {
+    return e.target
+      ?.closest?.(".component")
+      ?.parentNode?.closest?.(".component")
+      ?.childNodes[0]?.classList.contains("grid")
+  }
+
   // Util to get the inner DOM node by a component ID
   const getDOMNode = id => {
     const component = document.getElementsByClassName(id)[0]
@@ -41,6 +53,10 @@
 
   // Callback when drag stops (whether dropped or not)
   const stopDragging = () => {
+    if (dropping) {
+      return
+    }
+
     // Reset listener
     if (source?.id) {
       const component = document.getElementsByClassName(source?.id)[0]
@@ -55,6 +71,9 @@
 
   // Callback when initially starting a drag on a draggable component
   const onDragStart = e => {
+    if (isGridEvent(e)) {
+      return
+    }
     const component = e.target.closest(".component")
     if (!component?.classList.contains("draggable")) {
       return
@@ -99,9 +118,9 @@
 
   // Core logic for handling drop events and determining where to render the
   // drop target placeholder
-  const processEvent = (mouseX, mouseY) => {
+  const processEvent = Utils.throttle((mouseX, mouseY) => {
     if (!target) {
-      return null
+      return
     }
     let { id, parent, node, acceptsChildren, empty } = target
 
@@ -201,15 +220,15 @@
       parent: id,
       index: idx,
     })
-  }
+  }, ThrottleRate)
-  const throttledProcessEvent = Utils.throttle(processEvent, ThrottleRate)
 
   const handleEvent = e => {
     e.preventDefault()
-    throttledProcessEvent(e.clientX, e.clientY)
+    e.stopPropagation()
+    processEvent(e.clientX, e.clientY)
   }
 
-  // Callback when on top of a component
+  // Callback when on top of a component.
   const onDragOver = e => {
     if (!source || !target) {
       return
@@ -241,18 +260,21 @@
   }
 
   // Callback when dropping a drag on top of some component
-  const onDrop = () => {
+  const onDrop = async () => {
     if (!source || !drop?.parent || drop?.index == null) {
       return
     }
 
     // Check if we're adding a new component rather than moving one
     if (source.newComponentType) {
-      builderStore.actions.dropNewComponent(
+      dropping = true
+      await builderStore.actions.dropNewComponent(
         source.newComponentType,
         drop.parent,
         drop.index
       )
+      dropping = false
+      stopDragging()
       return
     }
 
@@ -289,11 +311,14 @@
     }
 
     if (legacyDropTarget && legacyDropMode) {
-      builderStore.actions.moveComponent(
+      dropping = true
+      await builderStore.actions.moveComponent(
         source.id,
         legacyDropTarget,
         legacyDropMode
       )
+      dropping = false
+      stopDragging()
     }
   }
 

packages/client/src/components/preview/DNDPlaceholder.svelte

@@ -1,33 +0,0 @@
-<script>
-  import { dndBounds } from "stores"
-  import { DNDPlaceholderID } from "constants"
-
-  $: style = getStyle($dndBounds)
-
-  const getStyle = bounds => {
-    if (!bounds) {
-      return null
-    }
-    return `--height: ${bounds.height}px; --width: ${bounds.width}px;`
-  }
-</script>
-
-{#if style}
-  <div class="wrapper">
-    <div class="placeholder" id={DNDPlaceholderID} {style} />
-  </div>
-{/if}
-
-<style>
-  .wrapper {
-    overflow: hidden;
-  }
-  .placeholder {
-    display: block;
-    height: var(--height);
-    width: var(--width);
-    max-height: 100%;
-    max-width: 100%;
-    opacity: 0;
-  }
-</style>

packages/client/src/components/preview/DNDPlaceholderOverlay.svelte

@@ -6,7 +6,8 @@
   let left, top, height, width
 
   const updatePosition = () => {
-    const node = document.getElementById(DNDPlaceholderID)
+    const node =
+      document.getElementsByClassName(DNDPlaceholderID)[0]?.childNodes[0]
     if (!node) {
       height = 0
       width = 0

packages/client/src/components/preview/GridDNDHandler.svelte

@@ -0,0 +1,227 @@
+<script>
+  import { onMount, onDestroy } from "svelte"
+  import { builderStore, componentStore } from "stores"
+  import { Utils } from "@budibase/frontend-core"
+
+  let dragInfo
+  let gridStyles
+  let id
+
+  // Some memoisation of primitive types for performance
+  $: jsonStyles = JSON.stringify(gridStyles)
+  $: id = dragInfo?.id || id
+
+  // Set ephemeral grid styles on the dragged component
+  $: componentStore.actions.getComponentInstance(id)?.setEphemeralStyles({
+    ...gridStyles,
+    ...(gridStyles ? { "z-index": 999 } : null),
+  })
+
+  // Util to check if a DND event originates from a grid (or inside a grid).
+  // This is important as we do not handle grid DND in this handler.
+  const isGridEvent = e => {
+    return (
+      e.target
+        .closest?.(".component")
+        ?.parentNode.closest(".component")
+        ?.childNodes[0].classList.contains("grid") ||
+      e.target.classList.contains("anchor")
+    )
+  }
+
+  // Util to get the inner DOM node by a component ID
+  const getDOMNode = id => {
+    const component = document.getElementsByClassName(id)[0]
+    return [...component.children][0]
+  }
+
+  const processEvent = Utils.throttle((mouseX, mouseY) => {
+    if (!dragInfo?.grid) {
+      return
+    }
+
+    const { mode, side, gridId, grid } = dragInfo
+    const {
+      startX,
+      startY,
+      rowStart,
+      rowEnd,
+      colStart,
+      colEnd,
+      rowDeltaMin,
+      rowDeltaMax,
+      colDeltaMin,
+      colDeltaMax,
+    } = grid
+
+    const domGrid = getDOMNode(gridId)
+    const cols = parseInt(domGrid.dataset.cols)
+    const rows = parseInt(domGrid.dataset.rows)
+    const { width, height } = domGrid.getBoundingClientRect()
+
+    const colWidth = width / cols
+    const diffX = mouseX - startX
+    let deltaX = Math.round(diffX / colWidth)
+    const rowHeight = height / rows
+    const diffY = mouseY - startY
+    let deltaY = Math.round(diffY / rowHeight)
+
+    if (mode === "move") {
+      deltaY = Math.min(Math.max(deltaY, rowDeltaMin), rowDeltaMax)
+      deltaX = Math.min(Math.max(deltaX, colDeltaMin), colDeltaMax)
+      const newStyles = {
+        "grid-row-start": rowStart + deltaY,
+        "grid-row-end": rowEnd + deltaY,
+        "grid-column-start": colStart + deltaX,
+        "grid-column-end": colEnd + deltaX,
+      }
+      if (JSON.stringify(newStyles) !== jsonStyles) {
+        gridStyles = newStyles
+      }
+    } else if (mode === "resize") {
+      let newStyles = {}
+      if (side === "right") {
+        newStyles["grid-column-end"] = Math.max(colEnd + deltaX, colStart + 1)
+      } else if (side === "left") {
+        newStyles["grid-column-start"] = Math.min(colStart + deltaX, colEnd - 1)
+      } else if (side === "top") {
+        newStyles["grid-row-start"] = Math.min(rowStart + deltaY, rowEnd - 1)
+      } else if (side === "bottom") {
+        newStyles["grid-row-end"] = Math.max(rowEnd + deltaY, rowStart + 1)
+      } else if (side === "bottom-right") {
+        newStyles["grid-column-end"] = Math.max(colEnd + deltaX, colStart + 1)
+        newStyles["grid-row-end"] = Math.max(rowEnd + deltaY, rowStart + 1)
+      } else if (side === "bottom-left") {
+        newStyles["grid-column-start"] = Math.min(colStart + deltaX, colEnd - 1)
+        newStyles["grid-row-end"] = Math.max(rowEnd + deltaY, rowStart + 1)
+      } else if (side === "top-right") {
+        newStyles["grid-column-end"] = Math.max(colEnd + deltaX, colStart + 1)
+        newStyles["grid-row-start"] = Math.min(rowStart + deltaY, rowEnd - 1)
+      } else if (side === "top-left") {
+        newStyles["grid-column-start"] = Math.min(colStart + deltaX, colEnd - 1)
+        newStyles["grid-row-start"] = Math.min(rowStart + deltaY, rowEnd - 1)
+      }
+      if (JSON.stringify(newStyles) !== jsonStyles) {
+        gridStyles = newStyles
+      }
+    }
+  }, 100)
+
+  const handleEvent = e => {
+    e.preventDefault()
+    e.stopPropagation()
+    processEvent(e.clientX, e.clientY)
+  }
+
+  // Callback when initially starting a drag on a draggable component
+  const onDragStart = e => {
+    if (!isGridEvent(e)) {
+      return
+    }
+
+    // Hide drag ghost image
+    e.dataTransfer.setDragImage(new Image(), 0, 0)
+
+    // Extract state
+    let mode, id, side
+    if (e.target.classList.contains("anchor")) {
+      // Handle resize
+      mode = "resize"
+      id = e.target.dataset.id
+      side = e.target.dataset.side
+    } else {
+      // Handle move
+      mode = "move"
+      const component = e.target.closest(".component")
+      id = component.dataset.id
+    }
+
+    // Find grid parent
+    const domComponent = getDOMNode(id)
+    const gridId = domComponent?.closest(".grid")?.parentNode.dataset.id
+    if (!gridId) {
+      return
+    }
+
+    // Update state
+    dragInfo = {
+      domTarget: e.target,
+      id,
+      gridId,
+      mode,
+      side,
+    }
+
+    // Add event handler to clear all drag state when dragging ends
+    dragInfo.domTarget.addEventListener("dragend", stopDragging)
+  }
+
+  // Callback when entering a potential drop target
+  const onDragEnter = e => {
+    // Skip if we aren't validly dragging currently
+    if (!dragInfo || dragInfo.grid) {
+      return
+    }
+
+    const domGrid = getDOMNode(dragInfo.gridId)
+    const gridCols = parseInt(domGrid.dataset.cols)
+    const gridRows = parseInt(domGrid.dataset.rows)
+    const domNode = getDOMNode(dragInfo.id)
+    const styles = window.getComputedStyle(domNode)
+    if (domGrid) {
+      const minMax = (value, min, max) => Math.min(max, Math.max(min, value))
+      const getStyle = x => parseInt(styles?.[x] || "0")
+      const getColStyle = x => minMax(getStyle(x), 1, gridCols + 1)
+      const getRowStyle = x => minMax(getStyle(x), 1, gridRows + 1)
+      dragInfo.grid = {
+        startX: e.clientX,
+        startY: e.clientY,
+        rowStart: getRowStyle("grid-row-start"),
+        rowEnd: getRowStyle("grid-row-end"),
+        colStart: getColStyle("grid-column-start"),
+        colEnd: getColStyle("grid-column-end"),
+        rowDeltaMin: 1 - getRowStyle("grid-row-start"),
+        rowDeltaMax: gridRows + 1 - getRowStyle("grid-row-end"),
+        colDeltaMin: 1 - getColStyle("grid-column-start"),
+        colDeltaMax: gridCols + 1 - getColStyle("grid-column-end"),
+      }
+      handleEvent(e)
+    }
+  }
+
+  const onDragOver = e => {
+    if (!dragInfo?.grid) {
+      return
+    }
+    handleEvent(e)
+  }
+
+  // Callback when drag stops (whether dropped or not)
+  const stopDragging = async () => {
+    // Save changes
+    if (gridStyles) {
+      await builderStore.actions.updateStyles(gridStyles, dragInfo.id)
+    }
+
+    // Reset listener
+    if (dragInfo?.domTarget) {
+      dragInfo.domTarget.removeEventListener("dragend", stopDragging)
+    }
+
+    // Reset state
+    dragInfo = null
+    gridStyles = null
+  }
+
+  onMount(() => {
+    document.addEventListener("dragstart", onDragStart, false)
+    document.addEventListener("dragenter", onDragEnter, false)
+    document.addEventListener("dragover", onDragOver, false)
+  })
+
+  onDestroy(() => {
+    document.removeEventListener("dragstart", onDragStart, false)
+    document.removeEventListener("dragenter", onDragEnter, false)
+    document.removeEventListener("dragover", onDragOver, false)
+  })
+</script>

packages/client/src/components/preview/HoverIndicator.svelte

@@ -4,11 +4,25 @@
   import { builderStore, dndIsDragging } from "stores"
 
   let componentId
+
   $: zIndex = componentId === $builderStore.selectedComponentId ? 900 : 920
 
   const onMouseOver = e => {
+    // Ignore if dragging
+    if (e.buttons > 0) {
+      return
+    }
+
+    let newId
+    if (e.target.classList.contains("anchor")) {
+      // Handle resize anchors
+      newId = e.target.dataset.id
+    } else {
+      // Handle normal components
       const element = e.target.closest(".interactive.component")
-    const newId = element?.dataset?.id
+      newId = element?.dataset?.id
+    }
+
     if (newId !== componentId) {
       componentId = newId
     }
@@ -34,4 +48,5 @@
   color="var(--spectrum-global-color-static-blue-200)"
   transition
   {zIndex}
+  allowResizeAnchors
 />

packages/client/src/components/preview/Indicator.svelte

@@ -10,9 +10,22 @@
   export let icon
   export let color
   export let zIndex
+  export let componentId
   export let transition = false
   export let line = false
   export let alignRight = false
+  export let showResizeAnchors = false
+
+  const AnchorSides = [
+    "right",
+    "left",
+    "top",
+    "bottom",
+    "bottom-right",
+    "bottom-left",
+    "top-right",
+    "top-left",
+  ]
 
   $: flipped = top < 24
 </script>
@@ -40,6 +53,18 @@
       {/if}
     </div>
   {/if}
+  {#if showResizeAnchors}
+    {#each AnchorSides as side}
+      <div
+        draggable="true"
+        class="anchor {side}"
+        data-side={side}
+        data-id={componentId}
+      >
+        <div class="anchor-inner" />
+      </div>
+    {/each}
+  {/if}
 </div>
 
 <style>
@@ -105,4 +130,64 @@
   /* Icon styles */
   .label :global(.spectrum-Icon + .text) {
   }
+
+  /* Anchor */
+  .anchor {
+    --size: 24px;
+    position: absolute;
+    width: var(--size);
+    height: var(--size);
+    pointer-events: all;
+    display: grid;
+    place-items: center;
+    border-radius: 50%;
+  }
+  .anchor-inner {
+    width: 12px;
+    height: 12px;
+    background: white;
+    border: 2px solid var(--color);
+    pointer-events: none;
+  }
+  .anchor.right {
+    right: calc(var(--size) / -2 - 1px);
+    top: calc(50% - var(--size) / 2);
+    cursor: e-resize;
+  }
+  .anchor.left {
+    left: calc(var(--size) / -2 - 1px);
+    top: calc(50% - var(--size) / 2);
+    cursor: w-resize;
+  }
+  .anchor.bottom {
+    left: calc(50% - var(--size) / 2 + 1px);
+    bottom: calc(var(--size) / -2 - 1px);
+    cursor: s-resize;
+  }
+  .anchor.top {
+    left: calc(50% - var(--size) / 2 + 1px);
+    top: calc(var(--size) / -2 - 1px);
+    cursor: n-resize;
+  }
+
+  .anchor.bottom-right {
+    right: calc(var(--size) / -2 - 1px);
+    bottom: calc(var(--size) / -2 - 1px);
+    cursor: se-resize;
+  }
+  .anchor.bottom-left {
+    left: calc(var(--size) / -2 - 1px);
+    bottom: calc(var(--size) / -2 - 1px);
+    cursor: sw-resize;
+  }
+  .anchor.top-right {
+    right: calc(var(--size) / -2 - 1px);
+    top: calc(var(--size) / -2 - 1px);
+    cursor: ne-resize;
+  }
+  .anchor.top-left {
+    left: calc(var(--size) / -2 - 1px);
+    top: calc(var(--size) / -2 - 1px);
+    cursor: nw-resize;
+  }
 </style>

packages/client/src/components/preview/IndicatorSet.svelte

@@ -9,11 +9,13 @@
   export let transition
   export let zIndex
   export let prefix = null
+  export let allowResizeAnchors = false
 
   let indicators = []
   let interval
   let text
   let icon
+  let insideGrid = false
 
   $: visibleIndicators = indicators.filter(x => x.visible)
   $: offset = $builderStore.inBuilder ? 0 : 2
@@ -23,6 +25,20 @@
   let callbackCount = 0
   let nextIndicators = []
 
+  const checkInsideGrid = id => {
+    const component = document.getElementsByClassName(id)[0]
+    const domNode = component?.children[0]
+
+    // Ignore grid itself
+    if (domNode?.classList.contains("grid")) {
+      return false
+    }
+
+    return component?.parentNode
+      ?.closest?.(".component")
+      ?.childNodes[0]?.classList.contains("grid")
+  }
+
   const createIntersectionCallback = idx => entries => {
     if (callbackCount >= observers.length) {
       return
@@ -52,6 +68,11 @@
     observers = []
     nextIndicators = []
 
+    // Check if we're inside a grid
+    if (allowResizeAnchors) {
+      insideGrid = checkInsideGrid(componentId)
+    }
+
     // Determine next set of indicators
     const parents = document.getElementsByClassName(componentId)
     if (parents.length) {
@@ -127,6 +148,8 @@
       height={indicator.height}
       text={idx === 0 ? text : null}
       icon={idx === 0 ? icon : null}
+      showResizeAnchors={allowResizeAnchors && insideGrid}
+      {componentId}
       {transition}
       {zIndex}
       {color}

packages/client/src/components/preview/SelectionIndicator.svelte

@@ -1,5 +1,5 @@
 <script>
-  import { builderStore, dndIsDragging } from "stores"
+  import { builderStore } from "stores"
   import IndicatorSet from "./IndicatorSet.svelte"
 
   $: color = $builderStore.editMode
@@ -8,8 +8,9 @@
 </script>
 
 <IndicatorSet
-  componentId={$dndIsDragging ? null : $builderStore.selectedComponentId}
+  componentId={$builderStore.selectedComponentId}
   {color}
   zIndex="910"
   transition
+  allowResizeAnchors
 />

packages/client/src/components/preview/SettingsBar.svelte

@@ -17,6 +17,11 @@
 
   $: definition = $componentStore.selectedComponentDefinition
   $: showBar = definition?.showSettingsBar && !$dndIsDragging
+  $: {
+    if (!showBar) {
+      measured = false
+    }
+  }
   $: settings = getBarSettings(definition)
 
   const getBarSettings = definition => {

packages/client/src/constants.js

@@ -32,5 +32,4 @@ export const ActionTypes = {
 }
 
 export const DNDPlaceholderID = "dnd-placeholder"
-export const DNDPlaceholderType = "dnd-placeholder"
 export const ScreenslotType = "screenslot"

packages/client/src/index.js

@@ -7,6 +7,7 @@ import {
   componentStore,
   environmentStore,
   dndStore,
+  eventStore,
 } from "./stores"
 import loadSpectrumIcons from "@budibase/bbui/spectrum-icons-rollup.js"
 import { get } from "svelte/store"
@@ -46,7 +47,9 @@ const loadBudibase = async () => {
   appStore.actions.setAppId(window["##BUDIBASE_APP_ID##"])
 
   // Fetch environment info
+  if (!get(environmentStore)?.loaded) {
     await environmentStore.actions.fetchEnvironment()
+  }
 
   // Enable dev tools or not. We need to be using a dev app and not inside
   // the builder preview to enable them.
@@ -54,15 +57,17 @@ const loadBudibase = async () => {
   devToolsStore.actions.setEnabled(enableDevTools)
 
   // Register handler for runtime events from the builder
-  window.handleBuilderRuntimeEvent = (name, payload) => {
+  window.handleBuilderRuntimeEvent = (type, data) => {
     if (!window["##BUDIBASE_IN_BUILDER##"]) {
       return
     }
-    if (name === "eject-block") {
+    if (type === "event-completed") {
-      const block = blockStore.actions.getBlock(payload)
+      eventStore.actions.resolveEvent(data)
+    } else if (type === "eject-block") {
+      const block = blockStore.actions.getBlock(data)
       block?.eject()
-    } else if (name === "dragging-new-component") {
+    } else if (type === "dragging-new-component") {
-      const { dragging, component } = payload
+      const { dragging, component } = data
       if (dragging) {
         const definition =
           componentStore.actions.getComponentDefinition(component)

packages/client/src/stores/builder.js

@@ -1,10 +1,7 @@
 import { writable, get } from "svelte/store"
 import { API } from "api"
 import { devToolsStore } from "./devTools.js"
-
+import { eventStore } from "./events.js"
-const dispatchEvent = (type, data = {}) => {
-  window.parent.postMessage({ type, data })
-}
 
 const createBuilderStore = () => {
   const initialState = {
@@ -19,6 +16,7 @@ const createBuilderStore = () => {
     navigation: null,
     hiddenComponentIds: [],
     usedPlugins: null,
+    eventResolvers: {},
 
     // Legacy - allow the builder to specify a layout
     layout: null,
@@ -35,22 +33,25 @@ const createBuilderStore = () => {
         selectedComponentId: id,
       }))
       devToolsStore.actions.setAllowSelection(false)
-      dispatchEvent("select-component", { id })
+      eventStore.actions.dispatchEvent("select-component", { id })
     },
     updateProp: (prop, value) => {
-      dispatchEvent("update-prop", { prop, value })
+      eventStore.actions.dispatchEvent("update-prop", { prop, value })
+    },
+    updateStyles: async (styles, id) => {
+      await eventStore.actions.dispatchEvent("update-styles", { styles, id })
     },
     keyDown: (key, ctrlKey) => {
-      dispatchEvent("key-down", { key, ctrlKey })
+      eventStore.actions.dispatchEvent("key-down", { key, ctrlKey })
     },
     duplicateComponent: id => {
-      dispatchEvent("duplicate-component", { id })
+      eventStore.actions.dispatchEvent("duplicate-component", { id })
     },
     deleteComponent: id => {
-      dispatchEvent("delete-component", { id })
+      eventStore.actions.dispatchEvent("delete-component", { id })
     },
     notifyLoaded: () => {
-      dispatchEvent("preview-loaded")
+      eventStore.actions.dispatchEvent("preview-loaded")
     },
     analyticsPing: async () => {
       try {
@@ -59,15 +60,15 @@ const createBuilderStore = () => {
         // Do nothing
       }
     },
-    moveComponent: (componentId, destinationComponentId, mode) => {
+    moveComponent: async (componentId, destinationComponentId, mode) => {
-      dispatchEvent("move-component", {
+      await eventStore.actions.dispatchEvent("move-component", {
         componentId,
         destinationComponentId,
         mode,
       })
     },
     dropNewComponent: (component, parent, index) => {
-      dispatchEvent("drop-new-component", {
+      eventStore.actions.dispatchEvent("drop-new-component", {
         component,
         parent,
         index,
@@ -80,16 +81,16 @@ const createBuilderStore = () => {
       store.update(state => ({ ...state, editMode: enabled }))
     },
     clickNav: () => {
-      dispatchEvent("click-nav")
+      eventStore.actions.dispatchEvent("click-nav")
     },
     requestAddComponent: () => {
-      dispatchEvent("request-add-component")
+      eventStore.actions.dispatchEvent("request-add-component")
     },
     highlightSetting: setting => {
-      dispatchEvent("highlight-setting", { setting })
+      eventStore.actions.dispatchEvent("highlight-setting", { setting })
     },
     ejectBlock: (id, definition) => {
-      dispatchEvent("eject-block", { id, definition })
+      eventStore.actions.dispatchEvent("eject-block", { id, definition })
     },
     updateUsedPlugin: (name, hash) => {
       // Check if we used this plugin
@@ -106,7 +107,7 @@ const createBuilderStore = () => {
       }
 
       // Notify the builder so we can reload component definitions
-      dispatchEvent("reload-plugin")
+      eventStore.actions.dispatchEvent("reload-plugin")
     },
   }
   return {

packages/client/src/stores/components.js

@@ -5,9 +5,8 @@ import { devToolsStore } from "./devTools"
 import { screenStore } from "./screens"
 import { builderStore } from "./builder"
 import Router from "../components/Router.svelte"
-import DNDPlaceholder from "../components/preview/DNDPlaceholder.svelte"
 import * as AppComponents from "../components/app/index.js"
-import { DNDPlaceholderType, ScreenslotType } from "../constants.js"
+import { ScreenslotType } from "../constants.js"
 
 const budibasePrefix = "@budibase/standard-components/"
 
@@ -49,6 +48,9 @@ const createComponentStore = () => {
   )
 
   const registerInstance = (id, instance) => {
+    if (!id) {
+      return
+    }
     store.update(state => {
       // If this is a custom component, flag it so we can reload this component
       // later if required
@@ -68,6 +70,9 @@ const createComponentStore = () => {
   }
 
   const unregisterInstance = id => {
+    if (!id) {
+      return
+    }
     store.update(state => {
       // Remove from custom component map if required
       const component = state.mountedComponents[id]?.instance?.component
@@ -103,8 +108,6 @@ const createComponentStore = () => {
     // Screenslot is an edge case
     if (type === ScreenslotType) {
       type = `${budibasePrefix}${type}`
-    } else if (type === DNDPlaceholderType) {
-      return {}
     }
 
     // Handle built-in components
@@ -124,8 +127,6 @@ const createComponentStore = () => {
     }
     if (type === ScreenslotType) {
       return Router
-    } else if (type === DNDPlaceholderType) {
-      return DNDPlaceholder
     }
 
     // Handle budibase components
@@ -140,6 +141,13 @@ const createComponentStore = () => {
     return customComponentManifest?.[type]?.Component
   }
 
+  const getComponentInstance = id => {
+    if (!id) {
+      return null
+    }
+    return get(store).mountedComponents[id]
+  }
+
   const registerCustomComponent = ({ Component, schema, version }) => {
     if (!Component || !schema?.schema?.name || !version) {
       return
@@ -171,6 +179,7 @@ const createComponentStore = () => {
       getComponentById,
       getComponentDefinition,
       getComponentConstructor,
+      getComponentInstance,
       registerCustomComponent,
     },
   }

packages/client/src/stores/dnd.js

@@ -1,4 +1,5 @@
-import { writable, derived } from "svelte/store"
+import { writable } from "svelte/store"
+import { computed } from "../utils/computed.js"
 
 const createDndStore = () => {
   const initialState = {
@@ -77,14 +78,11 @@ export const dndStore = createDndStore()
 // performance by deriving any state that needs to be externally observed.
 // By doing this and using primitives, we can avoid invalidating other stores
 // or components which depend on DND state unless values actually change.
-export const dndIsDragging = derived(dndStore, $dndStore => !!$dndStore.source)
+export const dndParent = computed(dndStore, x => x.drop?.parent)
-export const dndParent = derived(dndStore, $dndStore => $dndStore.drop?.parent)
+export const dndIndex = computed(dndStore, x => x.drop?.index)
-export const dndIndex = derived(dndStore, $dndStore => $dndStore.drop?.index)
+export const dndBounds = computed(dndStore, x => x.source?.bounds)
-export const dndBounds = derived(
+export const dndIsDragging = computed(dndStore, x => !!x.source)
+export const dndIsNewComponent = computed(
   dndStore,
-  $dndStore => $dndStore.source?.bounds
+  x => x.source?.newComponentType != null
-)
-export const dndIsNewComponent = derived(
-  dndStore,
-  $dndStore => $dndStore.source?.newComponentType != null
 )

packages/client/src/stores/environment.js

@@ -2,6 +2,7 @@ import { API } from "api"
 import { writable } from "svelte/store"
 
 const initialState = {
+  loaded: false,
   cloud: false,
 }
 
@@ -15,6 +16,7 @@ const createEnvironmentStore = () => {
         store.set({
           ...initialState,
           ...environment,
+          loaded: true,
         })
       } catch (error) {
         store.set(initialState)

packages/client/src/stores/events.js

@@ -0,0 +1,31 @@
+import { writable, get } from "svelte/store"
+
+const createEventStore = () => {
+  const initialState = {
+    eventResolvers: {},
+  }
+  const store = writable(initialState)
+
+  const actions = {
+    dispatchEvent: (type, data) => {
+      const id = Math.random()
+      return new Promise(resolve => {
+        window.parent.postMessage({ type, data, id })
+        store.update(state => {
+          state.eventResolvers[id] = resolve
+          return state
+        })
+      })
+    },
+    resolveEvent: data => {
+      get(store).eventResolvers[data]?.()
+    },
+  }
+
+  return {
+    subscribe: store.subscribe,
+    actions,
+  }
+}
+
+export const eventStore = createEventStore()

packages/client/src/stores/index.js

@@ -15,6 +15,7 @@ export { uploadStore } from "./uploads.js"
 export { rowSelectionStore } from "./rowSelection.js"
 export { blockStore } from "./blocks.js"
 export { environmentStore } from "./environment"
+export { eventStore } from "./events.js"
 export {
   dndStore,
   dndIndex,

packages/client/src/stores/screens.js

@@ -2,11 +2,11 @@ import { derived } from "svelte/store"
 import { routeStore } from "./routes"
 import { builderStore } from "./builder"
 import { appStore } from "./app"
-import { dndIndex, dndParent, dndIsNewComponent } from "./dnd.js"
+import { dndIndex, dndParent, dndIsNewComponent, dndBounds } from "./dnd.js"
 import { RoleUtils } from "@budibase/frontend-core"
 import { findComponentById, findComponentParent } from "../utils/components.js"
 import { Helpers } from "@budibase/bbui"
-import { DNDPlaceholderID, DNDPlaceholderType } from "constants"
+import { DNDPlaceholderID } from "constants"
 
 const createScreenStore = () => {
   const store = derived(
@@ -17,6 +17,7 @@ const createScreenStore = () => {
       dndParent,
       dndIndex,
       dndIsNewComponent,
+      dndBounds,
     ],
     ([
       $appStore,
@@ -25,6 +26,7 @@ const createScreenStore = () => {
       $dndParent,
       $dndIndex,
       $dndIsNewComponent,
+      $dndBounds,
     ]) => {
       let activeLayout, activeScreen
       let screens
@@ -62,32 +64,43 @@ const createScreenStore = () => {
 
       // Insert DND placeholder if required
       if (activeScreen && $dndParent && $dndIndex != null) {
-        // Remove selected component from tree if we are moving an existing
-        // component
         const { selectedComponentId } = $builderStore
-        if (!$dndIsNewComponent) {
+
+        // Extract and save the selected component as we need a reference to it
+        // later, and we may be removing it
         let selectedParent = findComponentParent(
           activeScreen.props,
           selectedComponentId
         )
-          if (selectedParent) {
+
+        // Remove selected component from tree if we are moving an existing
+        // component
+        if (!$dndIsNewComponent && selectedParent) {
           selectedParent._children = selectedParent._children?.filter(
             x => x._id !== selectedComponentId
           )
         }
-        }
 
         // Insert placeholder component
-        const placeholder = {
+        const componentToInsert = {
-          _component: DNDPlaceholderID,
+          _component: "@budibase/standard-components/container",
-          _id: DNDPlaceholderType,
+          _id: DNDPlaceholderID,
+          _styles: {
+            normal: {
+              width: `${$dndBounds?.width || 400}px`,
+              height: `${$dndBounds?.height || 200}px`,
+              opacity: 0,
+            },
+          },
           static: true,
         }
         let parent = findComponentById(activeScreen.props, $dndParent)
+        if (parent) {
           if (!parent._children?.length) {
-          parent._children = [placeholder]
+            parent._children = [componentToInsert]
           } else {
-          parent._children.splice($dndIndex, 0, placeholder)
+            parent._children.splice($dndIndex, 0, componentToInsert)
+          }
         }
       }
 

packages/client/src/utils/computed.js

@@ -0,0 +1,38 @@
+import { writable } from "svelte/store"
+
+/**
+ * Extension of Svelte's built in "derived" stores, which the addition of deep
+ * comparison of non-primitives. Falls back to using shallow comparison for
+ * primitive types to avoid performance penalties.
+ * Useful for instances where a deep comparison is cheaper than an additional
+ * store invalidation.
+ * @param store the store to observer
+ * @param deriveValue the derivation function
+ * @returns {Writable<*>} a derived svelte store containing just the derived value
+ */
+export const computed = (store, deriveValue) => {
+  const initialValue = deriveValue(store)
+  const computedStore = writable(initialValue)
+  let lastKey = getKey(initialValue)
+
+  store.subscribe(state => {
+    const value = deriveValue(state)
+    const key = getKey(value)
+    if (key !== lastKey) {
+      lastKey = key
+      computedStore.set(value)
+    }
+  })
+
+  return computedStore
+}
+
+// Helper function to serialise any value into a primitive which can be cheaply
+// and shallowly compared
+const getKey = value => {
+  if (value == null || typeof value !== "object") {
+    return value
+  } else {
+    return JSON.stringify(value)
+  }
+}

packages/frontend-core/src/utils/utils.js

@@ -6,17 +6,29 @@
  */
 export const sequential = fn => {
   let queue = []
-  return async (...params) => {
+  return (...params) => {
+    return new Promise((resolve, reject) => {
       queue.push(async () => {
-      await fn(...params)
+        let data, error
+        try {
+          data = await fn(...params)
+        } catch (err) {
+          error = err
+        }
         queue.shift()
         if (queue.length) {
-        await queue[0]()
+          queue[0]()
+        }
+        if (error) {
+          reject(error)
+        } else {
+          resolve(data)
         }
       })
       if (queue.length === 1) {
-      await queue[0]()
+        queue[0]()
       }
+    })
   }
 }