Initial commit of 001code-html Scratch frontend project.

Includes scratch-gui, scratch-vm, scratch-blocks, scratch-render, scratch-l10n, and deployment config.

Co-authored-by: Cursor <cursoragent@cursor.com>

scratch-blocks/core/intersection_observer.js

@@ -0,0 +1,102 @@
+'use strict';
+
+goog.provide('Blockly.IntersectionObserver');
+
+Blockly.IntersectionObserver = function(workspace) {
+  this.workspace = workspace;
+  this.observing = [];
+  this.intersectionCheckQueued = false;
+  this.checkForIntersections = this.checkForIntersections.bind(this);
+};
+
+Blockly.IntersectionObserver.prototype.observe = function(block) {
+  var index = this.observing.indexOf(block);
+  if (index === -1) {
+    this.observing.push(block);
+  }
+};
+
+Blockly.IntersectionObserver.prototype.unobserve = function(block) {
+  var index = this.observing.indexOf(block);
+  if (index !== -1) {
+    this.observing = this.observing.filter(function(i) {
+      return i !== block;
+    });
+  }
+};
+
+Blockly.IntersectionObserver.prototype.dispose = function() {
+  this.observing = [];
+  this.workspace = null;
+};
+
+Blockly.IntersectionObserver.prototype.queueIntersectionCheck = function() {
+  if (this.intersectionCheckQueued) {
+    return;
+  }
+  this.intersectionCheckQueued = true;
+  // Check for intersections on the next microtick
+  // Prefer to use the native method when available, otherwise fallback to a Promise-based polyfill
+  if (window.queueMicrotask) {
+    window.queueMicrotask(this.checkForIntersections);
+  } else {
+    // eslint-disable-next-line no-undef
+    Promise.resolve().then(this.checkForIntersections);
+  }
+};
+
+Blockly.IntersectionObserver.prototype.checkForIntersections = function() {
+  this.intersectionCheckQueued = false;
+
+  if (!this.workspace) {
+    return;
+  }
+
+  var workspace = this.workspace;
+  var workspaceScale = workspace.scale;
+  var RTL = workspace.RTL;
+  var workspaceHeight = workspace.getParentSvg().height.baseVal.value;
+  var workspaceWidth = workspace.getParentSvg().width.baseVal.value;
+  if (workspace.isDragSurfaceActive_) {
+    var canvasPos = Blockly.utils.getRelativeXY(workspace.workspaceDragSurface_.SVG_);
+  } else {
+    var canvasPos = Blockly.utils.getRelativeXY(workspace.getCanvas());
+  }
+
+  // Allow blocks to go slightly offscreen so that effects such as glow do not get cut off.
+  var margin = 12 * workspaceScale;
+
+  for (var i = 0; i < this.observing.length; i++) {
+    var block = this.observing[i];
+    var blockPos = block.getRelativeToSurfaceXY();
+    var blockSize = null;
+    if (RTL) {
+      blockSize = block.getHeightWidth();
+      blockPos.x -= blockSize.width;
+      blockSize.width *= workspaceScale;
+      blockSize.height *= workspaceScale;
+    }
+    blockPos.x *= workspaceScale;
+    blockPos.y *= workspaceScale;
+
+    var visible = true;
+    if (canvasPos.y + blockPos.y - margin > workspaceHeight) {
+      visible = false;
+    } else if (canvasPos.x + blockPos.x - margin > workspaceWidth) {
+      visible = false;
+    } else {
+      if (!blockSize) {
+        blockSize = block.getHeightWidth();
+        blockSize.width *= workspaceScale;
+        blockSize.height *= workspaceScale;
+      }
+      if (canvasPos.x + blockPos.x + blockSize.width + margin < 0) {
+        visible = false;
+      } else if (canvasPos.y + blockPos.y + blockSize.height + margin < 0) {
+        visible = false;
+      }
+    }
+
+    block.setIntersects(visible);
+  }
+};