From c37538d61125734a32aeb0a178843c61f5b63e25 Mon Sep 17 00:00:00 2001
From: Andrew Kingston <andrew@kingston.dev>
Date: Tue, 17 Oct 2023 11:51:42 +0100
Subject: [PATCH] Use CSS content-visibility to improve rendering performance
 by hiding offscreen grid cells

---
 .../src/components/grid/cells/DataCell.svelte |  2 +
 .../src/components/grid/cells/GridCell.svelte |  5 +++
 .../src/components/grid/layout/GridRow.svelte |  2 +
 .../src/components/grid/layout/NewRow.svelte  |  2 +
 .../src/components/grid/stores/viewport.js    | 45 ++++++++++++++++++-
 5 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/packages/frontend-core/src/components/grid/cells/DataCell.svelte b/packages/frontend-core/src/components/grid/cells/DataCell.svelte
index f9cdef3756..cdaf28978a 100644
--- a/packages/frontend-core/src/components/grid/cells/DataCell.svelte
+++ b/packages/frontend-core/src/components/grid/cells/DataCell.svelte
@@ -21,6 +21,7 @@
   export let invertX = false
   export let invertY = false
   export let contentLines = 1
+  export let hidden = false
 
   const emptyError = writable(null)
 
@@ -78,6 +79,7 @@
   {focused}
   {selectedUser}
   {readonly}
+  {hidden}
   error={$error}
   on:click={() => focusedCellId.set(cellId)}
   on:contextmenu={e => menu.actions.open(cellId, e)}
diff --git a/packages/frontend-core/src/components/grid/cells/GridCell.svelte b/packages/frontend-core/src/components/grid/cells/GridCell.svelte
index fe4bd70ba4..dcc76b9c75 100644
--- a/packages/frontend-core/src/components/grid/cells/GridCell.svelte
+++ b/packages/frontend-core/src/components/grid/cells/GridCell.svelte
@@ -10,6 +10,7 @@
   export let defaultHeight = false
   export let center = false
   export let readonly = false
+  export let hidden = false
 
   $: style = getStyle(width, selectedUser)
 
@@ -30,6 +31,7 @@
   class:error
   class:center
   class:readonly
+  class:hidden
   class:default-height={defaultHeight}
   class:selected-other={selectedUser != null}
   class:alt={rowIdx % 2 === 1}
@@ -81,6 +83,9 @@
   .cell.center {
     align-items: center;
   }
+  .cell.hidden {
+    content-visibility: hidden;
+  }
 
   /* Cell border */
   .cell.focused:after,
diff --git a/packages/frontend-core/src/components/grid/layout/GridRow.svelte b/packages/frontend-core/src/components/grid/layout/GridRow.svelte
index 93dc11f6ed..4a0db40ee8 100644
--- a/packages/frontend-core/src/components/grid/layout/GridRow.svelte
+++ b/packages/frontend-core/src/components/grid/layout/GridRow.svelte
@@ -19,6 +19,7 @@
     isDragging,
     dispatch,
     rows,
+    columnRenderMap,
   } = getContext("grid")
 
   $: rowSelected = !!$selectedRows[row._id]
@@ -51,6 +52,7 @@
       selectedUser={$selectedCellMap[cellId]}
       width={column.width}
       contentLines={$contentLines}
+      hidden={!$columnRenderMap[column.name]}
     />
   {/each}
 </div>
diff --git a/packages/frontend-core/src/components/grid/layout/NewRow.svelte b/packages/frontend-core/src/components/grid/layout/NewRow.svelte
index cc2d76f536..980f86326d 100644
--- a/packages/frontend-core/src/components/grid/layout/NewRow.svelte
+++ b/packages/frontend-core/src/components/grid/layout/NewRow.svelte
@@ -31,6 +31,7 @@
     refreshing,
     config,
     filter,
+    columnRenderMap,
   } = getContext("grid")
 
   let visible = false
@@ -224,6 +225,7 @@
               topRow={offset === 0}
               invertX={columnIdx >= $columnHorizontalInversionIndex}
               {invertY}
+              hidden={!$columnRenderMap[column.name]}
             >
               {#if column?.schema?.autocolumn}
                 <div class="readonly-overlay">Can't edit auto column</div>
diff --git a/packages/frontend-core/src/components/grid/stores/viewport.js b/packages/frontend-core/src/components/grid/stores/viewport.js
index 3a1b65e2b9..0890792989 100644
--- a/packages/frontend-core/src/components/grid/stores/viewport.js
+++ b/packages/frontend-core/src/components/grid/stores/viewport.js
@@ -1,7 +1,8 @@
-import { derived } from "svelte/store"
+import { derived, get } from "svelte/store"
 import {
   MaxCellRenderHeight,
   MaxCellRenderWidthOverflow,
+  MinColumnWidth,
   ScrollBarSize,
 } from "../lib/constants"
 
@@ -44,6 +45,47 @@ export const deriveStores = context => {
     []
   )
 
+  // Derive visible columns
+  const scrollLeftRounded = derived(scrollLeft, $scrollLeft => {
+    const interval = MinColumnWidth
+    return Math.round($scrollLeft / interval) * interval
+  })
+  const columnRenderMap = derived(
+    [visibleColumns, scrollLeftRounded, width],
+    ([$visibleColumns, $scrollLeft, $width]) => {
+      if (!$visibleColumns.length) {
+        return {}
+      }
+      let startColIdx = 0
+      let rightEdge = $visibleColumns[0].width
+      while (
+        rightEdge < $scrollLeft &&
+        startColIdx < $visibleColumns.length - 1
+      ) {
+        startColIdx++
+        rightEdge += $visibleColumns[startColIdx].width
+      }
+      let endColIdx = startColIdx + 1
+      let leftEdge = rightEdge
+      while (
+        leftEdge < $width + $scrollLeft &&
+        endColIdx < $visibleColumns.length
+      ) {
+        leftEdge += $visibleColumns[endColIdx].width
+        endColIdx++
+      }
+
+      // Only update the store if different
+      let next = {}
+      $visibleColumns
+        .slice(Math.max(0, startColIdx), endColIdx)
+        .forEach(col => {
+          next[col.name] = true
+        })
+      return next
+    }
+  )
+
   // Determine the row index at which we should start vertically inverting cell
   // dropdowns
   const rowVerticalInversionIndex = derived(
@@ -87,6 +129,7 @@ export const deriveStores = context => {
     scrolledRowCount,
     visualRowCapacity,
     renderedRows,
+    columnRenderMap,
     rowVerticalInversionIndex,
     columnHorizontalInversionIndex,
   }