Gallery.app: Add touch handlers for the zoom/scroll feature.

ui/file_manager/gallery/js/slide_mode.js

Index: ui/file_manager/gallery/js/slide_mode.js
diff --git a/ui/file_manager/gallery/js/slide_mode.js b/ui/file_manager/gallery/js/slide_mode.js
index fdc77f222e6956d1cfaf8f4ff30f92525918213e..4c480f4fdd3f122edf5ebf8864ced53100cb5edb 100644
--- a/ui/file_manager/gallery/js/slide_mode.js
+++ b/ui/file_manager/gallery/js/slide_mode.js
@@ -91,6 +91,11 @@ SlideMode.prototype.getName = function() { return 'slide'; };
 SlideMode.prototype.getTitle = function() { return 'GALLERY_SLIDE'; };
 
 /**
+ * @return {Viewport} Viewport.
+ */
+SlideMode.prototype.getViewport = function() { return this.viewport_; };
+
+/**
  * Initialize the listeners.
  * @private
  */
@@ -232,8 +237,7 @@ SlideMode.prototype.initDom_ = function() {
       this.displayStringFunction_,
       this.onToolsVisibilityChanged_.bind(this));
 
-  this.editor_.getBuffer().addOverlay(
-      new SwipeOverlay(this.advanceManually.bind(this)));
+  this.touchHandlers_ = new TouchHandler(this.imageContainer_, this);
 };
 
 /**
@@ -311,6 +315,7 @@ SlideMode.prototype.enter = function(
     this.selectionModel_.addEventListener('change', this.onSelectionBound_);
     this.dataModel_.addEventListener('splice', this.onSpliceBound_);
     this.dataModel_.addEventListener('content', this.onContentBound_);
+    this.touchHandlers_.enabled = true;
 
     // Wait 1000ms after the animation is done, then prefetch the next image.
     this.requestPrefetch(1, delay + 1000);
@@ -357,6 +362,9 @@ SlideMode.prototype.leave = function(zoomToRect, callback) {
   // Disable the slide-mode only buttons when leaving.
   this.editButton_.setAttribute('disabled', '');
   this.printButton_.setAttribute('disabled', '');
+
+  // Disable touch operation.
+  this.touchHandlers_.enabled = false;
 };
 
 
@@ -860,8 +868,9 @@ SlideMode.prototype.onKeyDown = function(event) {
     case 'U+001B':  // Escape
       if (this.isEditing()) {
         this.toggleEditor(event);
-      } else if (this.viewport_.getZoomIndex() !== 0) {
+      } else if (this.viewport_.isZoomed()) {
         this.viewport_.resetView();
+        this.touchHandlers_.stopOperation();
         this.imageView_.applyViewportChange();
       } else {
         return false;  // Not handled.
@@ -878,14 +887,14 @@ SlideMode.prototype.onKeyDown = function(event) {
     case 'Down':
     case 'Left':
     case 'Right':
-      if (!this.isEditing() && this.viewport_.getZoomIndex() !== 0) {
+      if (!this.isEditing() && this.viewport_.isZoomed()) {
         var delta = SlideMode.KEY_OFFSET_MAP[keyID];
         this.viewport_.setOffset(
             ~~(this.viewport_.getOffsetX() +
                delta[0] * this.viewport_.getZoom()),
             ~~(this.viewport_.getOffsetY() +
-               delta[1] * this.viewport_.getZoom()),
-            true);
+               delta[1] * this.viewport_.getZoom()));
+        this.touchHandlers_.stopOperation();
         this.imageView_.applyViewportChange();
       } else {
         this.advanceWithKeyboard(keyID);
@@ -898,21 +907,24 @@ SlideMode.prototype.onKeyDown = function(event) {
 
     case 'Ctrl-U+00BB':  // Ctrl+'=' zoom in.
       if (!this.isEditing()) {
-        this.viewport_.setZoomIndex(this.viewport_.getZoomIndex() + 1);
+        this.viewport_.zoomIn();
+        this.touchHandlers_.stopOperation();
         this.imageView_.applyViewportChange();
       }
       break;
 
     case 'Ctrl-U+00BD':  // Ctrl+'-' zoom out.
       if (!this.isEditing()) {
-        this.viewport_.setZoomIndex(this.viewport_.getZoomIndex() - 1);
+        this.viewport_.zoomOut();
+        this.touchHandlers_.stopOperation();
         this.imageView_.applyViewportChange();
       }
       break;
 
     case 'Ctrl-U+0030': // Ctrl+'0' zoom reset.
       if (!this.isEditing()) {
-        this.viewport_.resetView();
+        this.viewport_.setZoom(1.0);
+        this.touchHandlers_.stopOperation();
         this.imageView_.applyViewportChange();
       }
       break;
@@ -928,6 +940,7 @@ SlideMode.prototype.onKeyDown = function(event) {
 SlideMode.prototype.onResize_ = function() {
   this.viewport_.setScreenSize(
       this.container_.clientWidth, this.container_.clientHeight);
+  this.touchHandlers_.stopOperation();
   this.editor_.getBuffer().draw();
 };
 
@@ -1077,7 +1090,7 @@ SlideMode.prototype.isSlideshowOn_ = function() {
 };
 
 /**
- * Start the slideshow.
+ * Starts the slideshow.
  * @param {number=} opt_interval First interval in ms.
  * @param {Event=} opt_event Event.
  */
@@ -1086,6 +1099,9 @@ SlideMode.prototype.startSlideshow = function(opt_interval, opt_event) {
   this.viewport_.resetView();
   this.imageView_.applyViewportChange();
 
+  // Disable touch operation.
+  this.touchHandlers_.enabled = false;
+
   // Set the attribute early to prevent the toolbar from flashing when
   // the slideshow is being started from the mosaic view.
   this.container_.setAttribute('slideshow', 'playing');
@@ -1116,7 +1132,7 @@ SlideMode.prototype.startSlideshow = function(opt_interval, opt_event) {
 };
 
 /**
- * Stop the slideshow.
+ * Stops the slideshow.
  * @param {Event=} opt_event Event.
  * @private
  */
@@ -1141,6 +1157,9 @@ SlideMode.prototype.stopSlideshow_ = function(opt_event) {
     this.leaveAfterSlideshow_ = false;
     setTimeout(this.toggleMode_.bind(this), toggleModeDelay);
   }
+
+  // Re-enable touch operation.
+  this.touchHandlers_.enabled = true;
 };
 
 /**
@@ -1152,7 +1171,7 @@ SlideMode.prototype.isSlideshowPlaying_ = function() {
 };
 
 /**
- * Pause/resume the slideshow.
+ * Pauses/resumes the slideshow.
  * @private
  */
 SlideMode.prototype.toggleSlideshowPause_ = function() {
@@ -1182,7 +1201,7 @@ SlideMode.prototype.scheduleNextSlide_ = function(opt_interval) {
 };
 
 /**
- * Resume the slideshow.
+ * Resumes the slideshow.
  * @param {number=} opt_interval Slideshow interval in ms.
  * @private
  */
@@ -1192,7 +1211,7 @@ SlideMode.prototype.resumeSlideshow_ = function(opt_interval) {
 };
 
 /**
- * Pause the slideshow.
+ * Pauses the slideshow.
  * @private
  */
 SlideMode.prototype.pauseSlideshow_ = function() {
@@ -1211,7 +1230,7 @@ SlideMode.prototype.isEditing = function() {
 };
 
 /**
- * Stop editing.
+ * Stops editing.
  * @private
  */
 SlideMode.prototype.stopEditing_ = function() {
@@ -1244,9 +1263,11 @@ SlideMode.prototype.toggleEditor = function(opt_event) {
       this.editor_.getPrompt().showAt(
           'top', 'GALLERY_READONLY_WARNING', 0, this.context_.readonlyDirName);
     }
+    this.touchHandlers_.enabled = false;
   } else {
     this.editor_.getPrompt().hide();
     this.editor_.leaveModeGently();
+    this.touchHandlers_.enabled = true;
   }
 };
 
@@ -1260,7 +1281,7 @@ SlideMode.prototype.print_ = function() {
 };
 
 /**
- * Display the error banner.
+ * Displays the error banner.
  * @param {string} message Message.
  * @private
  */
@@ -1272,7 +1293,7 @@ SlideMode.prototype.showErrorBanner_ = function(message) {
 };
 
 /**
- * Show/hide the busy spinner.
+ * Shows/hides the busy spinner.
  *
  * @param {boolean} on True if show, false if hide.
  * @private
@@ -1294,45 +1315,203 @@ SlideMode.prototype.showSpinner_ = function(on) {
 };
 
 /**
- * Overlay that handles swipe gestures. Changes to the next or previous file.
- * @param {function(number)} callback A callback accepting the swipe direction
- *    (1 means left, -1 right).
+ * Apply the change of viewport.
+ */
+SlideMode.prototype.applyViewportChange = function() {
+  this.imageView_.applyViewportChange();
+};
+
+/**
+ * Touch handlers of the slide mode.
+ * @param {DOMElement} targetElement Event source.
+ * @param {SlideMode} slideMode Slide mode to be operated by the handler.
  * @constructor
- * @implements {ImageBuffer.Overlay}
  */
-function SwipeOverlay(callback) {
-  this.callback_ = callback;
+function TouchHandler(targetElement, slideMode) {
+  /**
+   * Event source.
+   * @type {DOMElement}
+   */
+  this.targetElement_ = targetElement;
+
+  /**
+   * Target of touch operations.
+   * @type {SlideMode}
+   * @private
+   */
+  this.slideMode_ = slideMode;
+
+  /**
+   * Flag to enable/disable touch operation.
+   * @type {boolean}
+   */
+  this.enabled_ = true;
+
+  /**
+   * Whether it is in a touch operation that is started from targetElement or
+   * not.
+   * @type {boolean}
+   * @private
+   */
+  this.touchStarted_ = false;
+
+  /**
+   * The swipe action that should happen only once in an operation is already
+   * done or not.
+   * @type {boolean}
+   * @private
+   */
+  this.done_ = false;
+
+  /**
+   * Event on beginning of the current gesture.
+   * The variable is updated when the number of touch finger changed.
+   * @type {TouchEvent}
+   * @private
+   */
+  this.gestureStartEvent_ = null;
+
+  /**
+   * Last touch event.
+   * @type {TouchEvent}
+   * @private
+   */
+  this.lastEvent_ = null;
+
+  /**
+   * Zoom value just after last touch event.
+   * @type {number}
+   * @private
+   */
+  this.lastZoom_ = 1.0;
+
+  targetElement.addEventListener('touchstart', this.onTouchStart_.bind(this));
+  var onTouchEventBound = this.onTouchEvent_.bind(this);
+  targetElement.ownerDocument.addEventListener('touchmove', onTouchEventBound);
+  targetElement.ownerDocument.addEventListener('touchend', onTouchEventBound);
 }
 
 /**
- * Inherit ImageBuffer.Overlay.
+ * If the user touched the image and moved the finger more than SWIPE_THRESHOLD
+ * horizontally it's considered as a swipe gesture (change the current image).
+ * @type {number}
+ * @const
  */
-SwipeOverlay.prototype.__proto__ = ImageBuffer.Overlay.prototype;
+TouchHandler.SWIPE_THRESHOLD = 100;
 
 /**
- * @param {number} x X pointer position.
- * @param {number} y Y pointer position.
- * @param {boolean} touch True if dragging caused by touch.
- * @return {function} The closure to call on drag.
+ * Obtains distance between fingers.
+ * @param {TouchEvent} event Touch event. It should include more than two
+ *     touches.
+ * @return {boolean} Distance between touch[0] and touch[1].
  */
-SwipeOverlay.prototype.getDragHandler = function(x, y, touch) {
-  if (!touch)
-    return null;
-  var origin = x;
-  var done = false;
-  return function(x, y) {
-    if (!done && origin - x > SwipeOverlay.SWIPE_THRESHOLD) {
-      this.callback_(1);
-      done = true;
-    } else if (!done && x - origin > SwipeOverlay.SWIPE_THRESHOLD) {
-      this.callback_(-1);
-      done = true;
-    }
-  }.bind(this);
+TouchHandler.getDistance = function(event) {
+  var touch1 = event.touches[0];
+  var touch2 = event.touches[1];
+  var dx = touch1.clientX - touch2.clientX;
+  var dy = touch1.clientY - touch2.clientY;
+  return Math.sqrt(dx * dx + dy * dy);
+};
+
+TouchHandler.prototype = {
+  /**
+   * @param {boolean} flag New value.
+   */
+  set enabled(flag) {
+    this.enabled_ = flag;
+    if (!this.enabled_)
+      this.stopOperation();
+  }
 };
 
 /**
- * If the user touched the image and moved the finger more than SWIPE_THRESHOLD
- * horizontally it's considered as a swipe gesture (change the current image).
+ * Stops the current touch operation.
  */
-SwipeOverlay.SWIPE_THRESHOLD = 100;
+TouchHandler.prototype.stopOperation = function() {
+  this.touchStarted_ = false;
+  this.done_ = false;
+  this.gestureStartEvent_ = null;
+  this.lastEvent_ = null;
+  this.lastZoom_ = 1.0;
+};
+
+TouchHandler.prototype.onTouchStart_ = function(event) {
+  if (this.enabled_ && event.touches.length === 1)
+    this.touchStarted_ = true;
+};
+
+/**
+ * @param {event} event Touch event.
+ */
+TouchHandler.prototype.onTouchEvent_ = function(event) {
+  // Check if the current touch operation started from the target element or
+  // not.
+  if (!this.touchStarted_)
+    return;
+
+  // Check if the current touch operation ends with the event.
+  if (event.touches.length === 0) {
+    this.stopOperation();
+    return;
+  }
+
+  // Check if a new gesture started or not.
+  if (!this.lastEvent_ ||
+      this.lastEvent_.touches.length !== event.touches.length) {
+    if (event.touches.length === 2 ||
+        event.touches.length === 1) {
+      this.gestureStartEvent_ = event;
+      this.lastEvent_ = event;
+      this.lastZoom_ = this.slideMode_.getViewport().getZoom();
+    } else {
+      this.gestureStartEvent_ = null;
+      this.lastEvent_ = null;
+      this.lastZoom_ = 1.0;
+    }
+    return;
+  }
+
+  // Handle the gesture movement.
+  var viewport = this.slideMode_.getViewport();
+  switch (event.touches.length) {
+    case 1:
+      if (viewport.isZoomed()) {
+        // Scrolling an image by swipe.
+        var dx = event.touches[0].screenX - this.lastEvent_.touches[0].screenX;
+        var dy = event.touches[0].screenY - this.lastEvent_.touches[0].screenY;
+        viewport.setOffset(
+            viewport.getOffsetX() + dx, viewport.getOffsetY() + dy);
+        this.slideMode_.applyViewportChange();
+      } else {
+        // Traversing images by swipe.
+        if (this.done_)
+          break;
+        var dx =
+            event.touches[0].clientX -
+            this.gestureStartEvent_.touches[0].clientX;
+        if (dx > TouchHandler.SWIPE_THRESHOLD) {
+          this.slideMode_.advanceManually(-1);
+          this.done_ = true;
+        } else if (dx < -TouchHandler.SWIPE_THRESHOLD) {
+          this.slideMode_.advanceManually(1);
+          this.done_ = true;
+        }
+      }
+      break;
+
+    case 2:
+      // Pinch zoom.
+      var distance1 = TouchHandler.getDistance(this.lastEvent_);
+      var distance2 = TouchHandler.getDistance(event);
+      if (distance1 === 0)
+        break;
+      var zoom = distance2 / distance1 * this.lastZoom_;
+      viewport.setZoom(zoom);
+      this.slideMode_.applyViewportChange();
+      break;
+  }
+
+  // Update the last event.
+  this.lastEvent_ = event;
+  this.lastZoom_ = viewport.getZoom();
+};