Move client/{base, observable, layout, touch, util, view} to samples/ui_lib .

client/touch/ClickBuster.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-/**
- * Click buster implementation, which is a behavior that prevents native clicks
- * from firing at undesirable times. There are two scenarios where we may want
- * to 'bust' a click.
- *
- * Buttons implemented with touch events usually have click handlers as well.
- * This is because sometimes touch events stop working, and the click handler
- * serves as a fallback. Here we use a click buster to prevent the native click
- * from firing if the touchend event was succesfully handled.
- *
- * When native scrolling behavior is disabled (see Scroller), click events will
- * fire after the touchend event when the drag sequence is complete. The click
- * event also happens to fire at the location of the touchstart event which can
- * lead to some very strange behavior.
- *
- * This class puts a single click handler on the body, and calls preventDefault
- * on the click event if we detect that there was a touchend event that already
- * fired in the same spot recently.
- */
-class ClickBuster {
-  /**
-   * The threshold for how long we allow a click to occur after a touchstart.
-   */
-  static final _TIME_THRESHOLD = 2500;
-
-  /**
-   * The threshold for how close a click has to be to the saved coordinate for
-   * us to allow it.
-   */
-  static final _DISTANCE_THRESHOLD = 25;
-
-  /**
-   * The list of coordinates that we use to measure the distance of clicks from.
-   * If a click is within the distance threshold of any of these coordinates
-   * then we allow the click.
-   * TODO(ngeoffray): Should be DoubleLinkedQueue<num>
-   */
-  static var _coordinates;
-
-  /** The last time preventGhostClick was called. */
-  static int _lastPreventedTime;
-
-  /**
-   * This handler will prevent the default behavior for any clicks unless the
-   * click is within the distance threshold of one of the temporary allowed
-   * coordinates.
-   */
-  static void _onClick(Event e) {
-    if (TimeUtil.now() - _lastPreventedTime > _TIME_THRESHOLD) {
-      return;
-    }
-    final coord = new Coordinate.fromClient(e);
-    // TODO(rnystrom): On Android, we get spurious click events at (0, 0). We
-    // *do* want those clicks to be busted, so commenting this out fixes it.
-    // Leaving it commented out instead of just deleting it because I'm not sure
-    // what this code was intended to do to begin with.
-    /*
-    if (coord.x < 1 && coord.y < 1) {
-      // TODO(jacobr): implement a configurable logging framework.
-      // _logger.warning(
-      //     "Not busting click on label elem at(${coord.x}, ${coord.y})");
-      return;
-    }
-    */
-    var entry = _coordinates.firstEntry();
-    while (entry != null) {
-      if (_hitTest(entry.element,
-                   entry.nextEntry().element,
-                   coord.x,
-                   coord.y)) {
-        entry.nextEntry().remove();
-        entry.remove();
-        return;
-      } else {
-        entry = entry.nextEntry().nextEntry();
-      }
-    }
-
-    // TODO(jacobr): implement a configurable logging framework.
-    // _logger.warning("busting click at ${coord.x}, ${coord.y}");
-    e.stopPropagation();
-    e.preventDefault();
-  }
-
-  /**
-   * This handler will temporarily allow a click to occur near the touch event's
-   * coordinates.
-   */
-  static void _onTouchStart(Event e) {
-    TouchEvent te = e;
-    final coord = new Coordinate.fromClient(te.touches[0]);
-    _coordinates.add(coord.x);
-    _coordinates.add(coord.y);
-    window.setTimeout(() {
-      _removeCoordinate(coord.x, coord.y);
-    }, _TIME_THRESHOLD);
-    _toggleTapHighlights(true);
-  }
-
-  /**
-   * Hit test for whether a coordinate is within the distance threshold of an
-   * event.
-   */
-  static bool _hitTest(num x, num y, num eventX, num eventY) {
-    return (eventX - x).abs() < _DISTANCE_THRESHOLD &&
-        (eventY - y).abs() < _DISTANCE_THRESHOLD;
-  }
-
-  /**
-   * Remove one specified coordinate from the coordinates list.
-   */
-  static void _removeCoordinate(num x, num y) {
-    var entry = _coordinates.firstEntry();
-    while (entry != null) {
-      if (entry.element == x && entry.nextEntry().element == y) {
-        entry.nextEntry().remove();
-        entry.remove();
-        return;
-      } else {
-        entry = entry.nextEntry().nextEntry();
-      }
-    }
-  }
-
-  /**
-   * Enable or disable tap highlights. They are disabled when preventGhostClick
-   * is called so that the flicker on links is not invoked when the ghost click
-   * does fire. This is due to a bug: links get highlighted even if the click
-   * event has preventDefault called on it.
-   */
-  static void _toggleTapHighlights(bool enable) {
-    document.body.style.setProperty(
-        "-webkit-tap-highlight-color", enable ? "" : "rgba(0,0,0,0)", "");
-  }
-
-  /**
-   * Registers new touches to create temporary "allowable zones" and registers
-   * new clicks to be prevented unless they fall in one of the current
-   * "allowable zones". Note that if the touchstart and touchend locations are
-   * different, it is still possible for a ghost click to be fired if you
-   * called preventDefault on all touchmove events. In this case the ghost
-   * click will be fired at the location of the touchstart event, so the
-   * coordinate you pass in should be the coordinate of the touchstart.
-   */
-  static void preventGhostClick(num x, num y) {
-    // First time this is called the following occurs:
-    //   1) Attaches a handler to touchstart events so that each touch will
-    //      temporarily create an "allowable zone" for clicks to occur in.
-    //   2) Attaches a handler to click events so that each click will be
-    //      prevented unless it is in an "allowable zone".
-    //
-    // Every time this is called (including the first) the following occurs:
-    //   1) Removes an allowable zone that contains the specified coordinate.
-    //
-    // How this enables click busting:
-    //   1) User performs first click.
-    //     - No attached touchstart handler yet.
-    //     - preventGhostClick is called before the click event occurs, it
-    //       attaches the touchstart and click handlers.
-    //     - The click handler captures the user's click event and prevents it
-    //       from propagating since there is no "allowable zone".
-    //
-    //   2) User performs subsequent, to-be-busted click.
-    //     - touchstart event triggers the attached handler and creates a
-    //       temporary "allowable zone".
-    //     - preventGhostClick is called and removes the "allowable zone".
-    //     - The click handler captures the user's click event and prevents it
-    //       from propagating since there is no "allowable zone".
-    //
-    //   3) User performs a should-not-be-busted click.
-    //     - touchstart event triggers the attached handler and creates a
-    //       temporary "allowable zone".
-    //     - The click handler captures the user's click event and allows it to
-    //       propagate since the click falls in the "allowable zone".
-    if (_coordinates === null) {
-      // Listen to clicks on capture phase so they can be busted before anything
-      // else gets a chance to handle them.
-      document.on.click.add((e) { _onClick(e); }, true);
-      document.on.focus.add((e) { _lastPreventedTime = 0; }, true);
-
-      // Listen to touchstart on capture phase since it must be called prior to
-      // every click or else we will accidentally prevent the click even if we
-      // don't call preventGhostClick.
-      Function startFn = (e) { _onTouchStart(e); };
-      if (!Device.supportsTouch) {
-        startFn = mouseToTouchCallback(startFn);
-      }
-      EventUtil.observe(document,
-          Device.supportsTouch ? document.on.touchStart : document.on.mouseDown,
-          startFn, true, true);
-      _coordinates = new Queue<num>();
-    }
-
-    // Turn tap highlights off until we know the ghost click has fired.
-    _toggleTapHighlights(false);
-
-    // Above all other rules, we won't bust any clicks if there wasn't some call
-    // to preventGhostClick in the last time threshold.
-    _lastPreventedTime = TimeUtil.now();
-    var entry = _coordinates.firstEntry();
-    while (entry != null) {
-      if (_hitTest(entry.element, entry.nextEntry().element, x, y)) {
-        entry.nextEntry().remove();
-        entry.remove();
-        return;
-      } else {
-        entry = entry.nextEntry().nextEntry();
-      }
-    }
-  }
-}