[Complex-Dom] Combine visibility: hidden and display: none for side T…

…reeView hidden elements. (WebKit#327)

resources/todomvc/big-dom-generator/params.js

@@ -16,3 +16,4 @@ export const TARGET_SIZE = 6000;
 // at least MIN_NUMBER_OF_MAX_DEPTH_BRANCHES of depth MAX_GENERATED_DOM_DEPTH.
 export const MIN_NUMBER_OF_MAX_DEPTH_BRANCHES = 2;
 export const MAX_VISIBLE_TREE_VIEW_ITEM_DEPTH = 8;
+export const PERCENTAGE_OF_DISPLAY_NONE_TREEVIEW_ELEMENTS = 0.5;

resources/todomvc/big-dom-generator/src/app.css

@@ -86,6 +86,32 @@ Importing the CSS from the Spectrum CSS library.
     min-width: 30px;
 }
 
+/*
+The visibility of closed spectrum TreeView items is set to hidden
+and the spectrum rule making the open TreeView items visible is
+.spectrum-TreeView-item.is-open > .spectrum-TreeView {
+    visibility: visible;
+}
+This can cause descendants of closed tree view items to be visible.
+Our code only closes the TreeView items at the threshold depth of
+the tree, so we unset the visibility to let the open itmes inherit
+the visibility from their parents.
+*/
+.spectrum-TreeView-item.is-open > .spectrum-TreeView {
+    visibility: unset;
+}
+
+/* 
+We've chosen some items of the side TreeView to be hidden using
+display: none instead of visibility: hidden. We unset their visibility
+and height values set by spectrum CSS.
+*/
+.display-none {
+    display: none;
+    visibility: unset !important;
+    height: auto !important;
+}
+
 /*
 Layout CSS for the UI.
 */

resources/todomvc/big-dom-generator/src/components/tree-area.jsx

@@ -1,5 +1,6 @@
 import { MAX_VISIBLE_TREE_VIEW_ITEM_DEPTH } from "../../params";
 import { generateTreeHead } from "./../tree-generator";
+import classNames from "classnames";
 
 import ChevronRight from "./../assets/Smock_ChevronRight_18_N.svg";
 import TaskListIcon from "./../assets/Smock_TaskList_18_N.svg";
@@ -8,10 +9,14 @@ const TreeItem = (props) => {
     const { treeNode, currentDepth } = props;
 
     const isExpandableItem = treeNode.type === "expandableItem";
-    const treeViewItemIsOpen = isExpandableItem && currentDepth < MAX_VISIBLE_TREE_VIEW_ITEM_DEPTH ? "is-open" : "";
+    /**
+     * Every expandable TreeItem is open by default unless it is at the MAX_VISIBLE_TREE_VIEW_ITEM_DEPTH threshold
+     * or it is marked as display:none.
+     **/
+    const treeViewItemIsOpen = isExpandableItem && currentDepth !== MAX_VISIBLE_TREE_VIEW_ITEM_DEPTH && !treeNode.isDisplayNone;
 
     return (
-        <li className={`spectrum-TreeView-item ${treeViewItemIsOpen} nodetype-${treeNode.type}`}>
+        <li className={classNames("spectrum-TreeView-item", { "display-none": treeNode.isDisplayNone, "is-open": treeViewItemIsOpen }, `nodetype-${treeNode.type}`)}>
             {isExpandableItem
                 ? <>
                     <a className="spectrum-TreeView-itemLink">

resources/todomvc/big-dom-generator/src/tree-generator.js

@@ -1,8 +1,58 @@
 import { LCG } from "random-seedable";
-import { DEFAULT_SEED_FOR_RANDOM_NUMBER_GENERATOR, MAX_GENERATED_DOM_DEPTH, MAX_NUMBER_OF_CHILDREN, PROBABILITY_OF_HAVING_CHILDREN, TARGET_SIZE, MIN_NUMBER_OF_MAX_DEPTH_BRANCHES } from "./../params";
+import { DEFAULT_SEED_FOR_RANDOM_NUMBER_GENERATOR, MAX_GENERATED_DOM_DEPTH, MAX_NUMBER_OF_CHILDREN, PROBABILITY_OF_HAVING_CHILDREN, TARGET_SIZE, MIN_NUMBER_OF_MAX_DEPTH_BRANCHES, PERCENTAGE_OF_DISPLAY_NONE_TREEVIEW_ELEMENTS } from "./../params";
 
 const random = new LCG(DEFAULT_SEED_FOR_RANDOM_NUMBER_GENERATOR);
 
+// Recursively depth-first computing subTreeWeight.
+const fillSubtreeWeights = (node, expandableItemWeight, nonExpandableItemWeight) => {
+    if (node.type === "expandableItem")
+        node.subTreeWeight = node.children.reduce((acc, child) => acc + fillSubtreeWeights(child, expandableItemWeight, nonExpandableItemWeight), expandableItemWeight);
+    else
+        node.subTreeWeight = nonExpandableItemWeight;
+
+    return node.subTreeWeight;
+};
+
+/*
+ * Iterate over the exapandableItem nodes in a breadth-first manner until the
+ * sum of weights of the subtrees with root nodes in the queue is less than
+ * the target number of elements we want to have display none. Mark the
+ * nodes in the queue as display none.
+ * Consider the following example with the weights as displayed in the figure
+ * and 10 as the target number of display none elements. The iteration will
+ * stop with the nodes with weights 7 and 2 marked with *.
+ *             20
+ *          /      \
+ *         12       8
+ *        /  \     / \
+ *       5   *7* *2*   6
+ *           /   / \
+ *          7   1   1
+ */
+const markDisplayNoneNodes = (node, expandableItemWeight, nonExpandableItemWeight) => {
+    let currentSubTreesWeights = node.subTreeWeight;
+    let currentIndex = 0;
+    let nodeQueue = [node];
+    while (currentSubTreesWeights >= TARGET_SIZE * PERCENTAGE_OF_DISPLAY_NONE_TREEVIEW_ELEMENTS) {
+        const currentNode = nodeQueue[currentIndex];
+        nodeQueue[currentIndex] = null;
+        const expandableChildren = currentNode.children.filter((child) => child.type === "expandableItem");
+        if (expandableChildren.length) {
+            nodeQueue.push(...expandableChildren);
+            currentSubTreesWeights -= expandableItemWeight;
+            let numberOfNonExpandableChildren = currentNode.children.length - expandableChildren.length;
+            currentSubTreesWeights -= numberOfNonExpandableChildren * nonExpandableItemWeight;
+        } else {
+            currentSubTreesWeights -= currentNode.subTreeWeight;
+        }
+        currentIndex++;
+    }
+    nodeQueue.forEach((node) => {
+        if (node)
+            node.isDisplayNone = true;
+    });
+};
+
 /**
  * Generates the blueprint of the tree-view side panel for the complex DOM shell with expandable and non-expandable items.
  * It starts with the minimum number of maximum-depth branches and randomly adds
@@ -21,15 +71,21 @@ const random = new LCG(DEFAULT_SEED_FOR_RANDOM_NUMBER_GENERATOR);
  *         children: [
  *           {
  *             type: "nonExpandableItem",
- *             children: []
+ *             children: [],
+ *             isDisplayNone: false,
+ *             subTreeWeight: 0,
  *           }
- *         ]
+ *         ],
+ *         isDisplayNone: false,
+ *        subTreeWeight: 0,
  *      }
- *    ]
+ *    ],
+ *    isDisplayNone: false,
+ *    subTreeWeight: 0,
  * }
  **/
 export const generateTreeHead = ({ expandableItemWeight, nonExpandableItemWeight }) => {
-    const treeHead = { type: "expandableItem", children: [] };
+    const treeHead = { type: "expandableItem", children: [], isDisplayNone: false, subTreeWeight: 0 };
     const nodeWeight = { expandableItem: expandableItemWeight, nonExpandableItem: nonExpandableItemWeight };
 
     let totalNodes = expandableItemWeight;
@@ -85,5 +141,7 @@ export const generateTreeHead = ({ expandableItemWeight, nonExpandableItemWeight
         }
     }
 
+    fillSubtreeWeights(treeHead, expandableItemWeight, nonExpandableItemWeight);
+    markDisplayNoneNodes(treeHead, expandableItemWeight, nonExpandableItemWeight);
     return treeHead;
 };