Issue 2879 - Move element selection into the content process

lib/child/selection.js

Index: lib/child/selection.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/child/selection.js
@@ -0,0 +1,315 @@
+/*
+ * This Source Code is subject to the terms of the Mozilla Public License
+ * version 2.0 (the "License"). You can obtain a copy of the License at
+ * http://mozilla.org/MPL/2.0/.
+ */
+
+"use strict";
+
+let {Services} = Cu.import("resource://gre/modules/Services.jsm", {});
+
+let messageManager = require("messageManager");
+let {
+  createElement, getWindowSize, getParentElement, getElementPosition
+} = require("./utils");
+
+/**
+ * @typedef State
+ * @type {Object}
+ * @property {Window} window
+ *   The top-level window that we are selecting in.
+ * @property {Element} boxElement
+ *   The element marking the current selection.
+ * @property {Element} anchorElement
+ *   The element that received the last mouse event.
+ * @property {Element} selectedElement
+ *   The element currently selected (usually anchorElement or a parent element
+ *   of it).
+ * @property {boolean} isUserSelected
+ *   Will be true if the user narrowed down the selection to a specific element
+ *   using wider/narrower commands.
+ * @property {Element} lockedAnchor
+ *   When selection is locked, this property will be updated by mouse events
+ *   instead of anchorElement.
+ * @property {number} prevSelectionUpdate
+ *   Time of previous selection update, used for rate limiting.
+ * @property {Object} prevPos
+ *   Position and size of selected element during previous selection update.
+ */
+
+/**
+ * Current selection state. This object will be empty if no selection is
+ * currently in progress.
+ *
+ * @type {State}
+ */
+let state = exports.state = {};
+
+messageManager.addMessageListener("ElemHideHelper:StartSelection", startSelection);
+
+onShutdown.add(() =>
+{
+  messageManager.removeMessageListener("ElemHideHelper:StartSelection", startSelection);
+
+  stopSelection();
+});
+
+function startSelection(message)
+{
+  stopSelection();
+
+  let outerWindowID = message.data;
+  let wnd = Services.wm.getOuterWindowWithId(outerWindowID);
+  if (!wnd || !canSelect(wnd))
+    return;
+
+  state.window = wnd;
+
+  wnd.addEventListener("click", onMouseClick, true);
+  wnd.addEventListener("wheel", onMouseScroll, true);
+  wnd.addEventListener("mousemove", onMouseMove, true);
+  wnd.addEventListener("pagehide", onPageHide, true);
+
+  wnd.focus();
+
+  let doc = wnd.document;
+  let {elementMarkerClass} = require("info");
+  state.boxElement = createElement(doc, "div", {"class": elementMarkerClass}, [
+    createElement(doc, "div", {"class": "ehh-border"}),
+    createElement(doc, "div", {"class": "ehh-label"}, [
+      createElement(doc, "span", {"class": "ehh-labelTag"}),
+      createElement(doc, "span", {"class": "ehh-labelAddition"})
+    ])
+  ]);
+
+  // Make sure to select some element immeditely (whichever is in the center of the browser window)
+  let [wndWidth, wndHeight] = getWindowSize(wnd);
+  state.isUserSelected = false;
+  onMouseMove({clientX: wndWidth / 2, clientY: wndHeight / 2, screenX: -1, screenY: -1, target: null});
+
+  messageManager.sendAsyncMessage("ElemHideHelper:SelectionStarted");
+}
+
+function stopSelection()
+{
+  if (!state.boxElement)
+    return;
+
+  hideSelection();
+
+  let wnd = state.window;
+  wnd.removeEventListener("click", onMouseClick, true);
+  wnd.removeEventListener("wheel", onMouseScroll, true);
+  wnd.removeEventListener("mousemove", onMouseMove, true);
+  wnd.removeEventListener("pagehide", onPageHide, true);
+
+  for (let key of Object.keys(state))
+    delete state[key];
+
+  messageManager.sendAsyncMessage("ElemHideHelper:SelectionStopped");
+}
+exports.stopSelection = stopSelection;
+
+function canSelect(wnd)
+{
+  let acceptLocalFiles;
+  try
+  {
+    let pref = "extensions.elemhidehelper.acceptlocalfiles";
+    acceptLocalFiles = Services.prefs.getBoolPref(pref);
+  }
+  catch (e)
+  {
+    acceptLocalFiles = false;
+  }
+
+  if (!acceptLocalFiles)
+  {
+    let localSchemes;
+    try
+    {
+      localSchemes = new Set(
+        Services.prefs.getCharPref("extensions.adblockplus.whitelistschemes")
+                      .split(/\s+/)
+      );
+    }
+    catch (e)
+    {
+      localSchemes = new Set();
+    }
+
+    if (localSchemes.has(wnd.location.protocol.replace(/:$/, "")))
+      return false;
+  }
+
+  return true;
+}
+
+function getElementLabel(elem)
+{
+  let tagName = elem.localName;
+  let addition = "";
+  if (elem.id != "")
+    addition += ", id: " + elem.id;
+  if (elem.className != "")
+    addition += ", class: " + elem.className;
+  if (elem.style.cssText != "")
+    addition += ", style: " + elem.style.cssText;
+
+  return [tagName, addition];
+}
+
+function setAnchorElement(anchor)
+{
+  state.anchorElement = anchor;
+
+  let newSelection = anchor;
+  if (state.isUserSelected)
+  {
+    // User chose an element via wider/narrower commands, keep the selection if
+    // our new anchor is still a child of that element
+    let e = newSelection;
+    while (e && e != state.selectedElement)
+      e = getParentElement(e);
+
+    if (e)
+      newSelection = state.selectedElement;
+    else
+      state.isUserSelected = false;
+  }
+
+  selectElement(newSelection);
+}
+exports.setAnchorElement = setAnchorElement;
+
+function selectElement(elem)
+{
+  state.selectedElement = elem;
+  state.prevSelectionUpdate = Date.now();
+
+  let border = state.boxElement.querySelector(".ehh-border");
+  let label = state.boxElement.querySelector(".ehh-label");
+  let labelTag = state.boxElement.querySelector(".ehh-labelTag");
+  let labelAddition = state.boxElement.querySelector(".ehh-labelAddition");
+
+  let doc = state.window.document;
+  let [wndWidth, wndHeight] = getWindowSize(state.window);
+
+  let pos = getElementPosition(elem);
+  state.boxElement.style.left = Math.min(pos.left - 1, wndWidth - 2) + "px";
+  state.boxElement.style.top = Math.min(pos.top - 1, wndHeight - 2) + "px";
+  border.style.width = Math.max(pos.right - pos.left - 2, 0) + "px";
+  border.style.height = Math.max(pos.bottom - pos.top - 2, 0) + "px";
+
+  [labelTag.textContent, labelAddition.textContent] = getElementLabel(elem);
+
+  // If there is not enough space to show the label move it up a little
+  if (pos.bottom < wndHeight - 25)
+    label.className = "ehh-label";
+  else
+    label.className = "ehh-label onTop";
+
+  doc.documentElement.appendChild(state.boxElement);
+
+  state.prevPos = pos;
+  state.window.addEventListener("MozAfterPaint", onAfterPaint, false);
+}
+exports.selectElement = selectElement;
+
+function hideSelection()
+{
+  if (!Cu.isDeadWrapper(state.boxElement) && state.boxElement.parentNode)
+    state.boxElement.parentNode.removeChild(state.boxElement);
+
+  if (!Cu.isDeadWrapper(state.window))
+    state.window.removeEventListener("MozAfterPaint", onAfterPaint, false);
+}
+
+/******************
+ * Event handlers *
+ ******************/
+
+function onMouseClick(event)
+{
+  if (event.button != 0 || event.shiftKey || event.altKey || event.ctrlKey || event.metaKey)
+    return;
+
+  require("./commands").select();
+  event.preventDefault();
+}
+
+function onMouseScroll(event)
+{
+  if (!event.shiftKey || event.altKey || event.ctrlKey || event.metaKey)
+    return;
+
+  let delta = event.deltaY || event.deltaX;
+  if (!delta)
+    return;
+
+  let commands = require("./commands");
+  if (delta > 0)
+    commands.wider();
+  else
+    commands.narrower();
+  event.preventDefault();
+}
+
+function onMouseMove(event)
+{
+  hideSelection();
+
+  let x = event.clientX;
+  let y = event.clientY;
+
+  // We might have coordinates relative to a frame, recalculate relative to top window
+  let node = event.target;
+  while (node && node.ownerDocument && node.ownerDocument.defaultView && node.ownerDocument.defaultView.frameElement)
+  {
+    node = node.ownerDocument.defaultView.frameElement;
+    let rect = node.getBoundingClientRect();
+    x += rect.left;
+    y += rect.top;
+  }
+
+  // Get the element matching the coordinates, probably within a frame
+  let elem = state.window.document.elementFromPoint(x, y);
+  while (elem && "contentWindow" in elem && canSelect(elem.contentWindow))
+  {
+    let rect = elem.getBoundingClientRect();
+    x -= rect.left;
+    y -= rect.top;
+    elem = elem.contentWindow.document.elementFromPoint(x, y);
+  }
+
+  if (elem)
+  {
+    if (!state.lockedAnchor)
+      setAnchorElement(elem);
+    else
+    {
+      state.lockedAnchor = elem;
+      selectElement(state.selectedElement);
+    }
+  }
+}
+
+function onPageHide(event)
+{
+  stopSelection();
+}
+
+function onAfterPaint(event)
+{
+  // Don't update position too often
+  if (state.selectedElement && Date.now() - state.prevSelectionUpdate > 20)
+  {
+    let pos = getElementPosition(state.selectedElement);
+    if (!state.prevPos || state.prevPos.left != pos.left ||
+        state.prevPos.right != pos.right || state.prevPos.top != pos.top ||
+        state.prevPos.bottom != pos.bottom)
+    {
+      selectElement(state.selectedElement);
+    }
+  }
+}