MD Settings: Display: Add snapping and collisions

chrome/browser/resources/settings/device_page/layout_behavior.js

Index: chrome/browser/resources/settings/device_page/layout_behavior.js
diff --git a/chrome/browser/resources/settings/device_page/layout_behavior.js b/chrome/browser/resources/settings/device_page/layout_behavior.js
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+++ b/chrome/browser/resources/settings/device_page/layout_behavior.js
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview Behavior for handling display layout, specifically
+ *     edge snapping and collisions.
+ */
+
+/** @polymerBehavior */
+var LayoutBehavior = {
+  properties: {
+    /**
+     * Array of display layouts.
+     * @type {!Array<!chrome.system.display.DisplayLayout>}
+     */
+    layouts: Array,
+  },
+
+  /** @private {!Map<string, chrome.system.display.Bounds>} */
+  displayBoundsMap_: new Map(),
+
+  /** @private {!Map<string, chrome.system.display.DisplayLayout>} */
+  displayLayoutMap_: new Map(),
+
+  /**
+   * The calculated bounds used for generating the div bounds.
+   * @private {!Map<string, chrome.system.display.Bounds>}
+   */
+  calculatedBoundsMap_: new Map(),
+
+  /** @private {string} */
+  dragLayoutId: '',
+
+  /** @private {string} */
+  dragParentId_: '',
+
+  /** @private {!chrome.system.display.Bounds|undefined} */
+  dragBounds_: undefined,
+
+  /** @private {!chrome.system.display.LayoutPosition|undefined} */
+  dragLayoutPosition_: undefined,
+
+  /**
+   * @param {!Array<!chrome.system.display.DisplayUnitInfo>} displays
+   * @param {!Array<!chrome.system.display.DisplayLayout>} layouts
+   */
+  initializeDisplayLayout: function(displays, layouts) {
+    this.dragLayoutId = '';
+    this.dragParentId_ = '';
+
+    this.displayBoundsMap_.clear();
+    for (let display of displays)
+      this.displayBoundsMap_.set(display.id, display.bounds);
+
+    this.displayLayoutMap_.clear();
+    for (let layout of layouts)
+      this.displayLayoutMap_.set(layout.id, layout);
+
+    this.calculatedBoundsMap_.clear();
+    for (let display of displays) {
+      if (!this.calculatedBoundsMap_.has(display.id)) {
+        let bounds = display.bounds;
+        this.calculateBounds_(display.id, bounds.width, bounds.height);
+      }
+    }
+  },
+
+  /**
+   * Called when a drag event occurs. Checks collisions and updates the layout.
+   * @param {string} id
+   * @param {!chrome.system.display.Bounds} newBounds The new calculated
+   *     bounds for the display.
+   * @return {!chrome.system.display.Bounds}
+   */
+  updateDisplayBounds(id, newBounds) {
+    this.dragLayoutId = id;
+
+    // Find the closest parent.
+    var closestId = this.findClosest_(id, newBounds);
+
+    // Find the closest edge.
+    var layoutPosition = this.getLayoutPositionForBounds_(newBounds, closestId);
+
+    // Snap to the closest edge.
+    this.snapBounds_(closestId, layoutPosition, newBounds);
+
+    // Calculate the new bounds and delta.
+    var oldBounds = this.dragBounds_ || this.getCalculatedDisplayBounds(id);
+    var deltaPos = {
+      x: newBounds.left - oldBounds.left,
+      y: newBounds.top - oldBounds.top
+    };
+
+    // Check for collisions after snapping. This should not collide with the
+    // closest parent.
+    this.collideAndModifyDelta_(id, oldBounds, deltaPos);
+
+    // If the edge changed, update and highlight it.
+    if (layoutPosition != this.dragLayoutPosition_ ||
+        closestId != this.dragParentId_) {
+      this.dragLayoutPosition_ = layoutPosition;
+      this.dragParentId_ = closestId;
+      this.highlightEdge_(closestId, layoutPosition);
+    }
+
+    newBounds.left = oldBounds.left + deltaPos.x;
+    newBounds.top = oldBounds.top + deltaPos.y;
+
+    this.dragBounds_ = newBounds;
+
+    return newBounds;
+  },
+
+  /**
+   * Called when dragging ends. Sends the updated layout to chrome.
+   * @param {string} id
+   */
+  finishUpdateDisplayBounds(id) {
+    this.highlightEdge_('', undefined);  // Remove any highlights.
+    if (id != this.dragLayoutId || !this.dragBounds_ ||
+        !this.dragLayoutPosition_) {
+      return;
+    }
+    var layout = this.displayLayoutMap_.get(id);
+    if (!layout)
+      return;
+    // Note: This updates layout in this.displayLayoutMap_ which is also the
+    // entry in this.layouts.
+    this.updateOffsetAndPosition_(
+        this.dragBounds_, this.dragLayoutPosition_, layout);
+
+    // Send the updated layouts.
+    chrome.system.display.setDisplayLayout(this.layouts, function() {
+      if (chrome.runtime.lastError) {
+        console.error(
+            'setDisplayLayout Error: ' + chrome.runtime.lastError.message);
+      }
+    });
+  },
+
+  /**
+   * @param {string} displayId
+   * @return {!chrome.system.display.Bounds} bounds
+   */
+  getCalculatedDisplayBounds: function(displayId) {
+    var bounds = this.calculatedBoundsMap_.get(displayId);
+    assert(bounds);
+    return bounds;
+  },
+
+  /**
+   * @param {string} displayId
+   * @param {!chrome.system.display.Bounds|undefined} bounds
+   * @private
+   */
+  setCalculatedDisplayBounds_: function(displayId, bounds) {
+    assert(bounds);
+    this.calculatedBoundsMap_.set(
+        displayId,
+        /** @type {!chrome.system.display.Bounds} */ (
+            Object.assign({}, bounds)));
+  },
+
+  /**
+   * Recursively calculate the absolute bounds of a display.
+   * Caches the display bounds so that parent bounds are only calculated once.
+   * @param {string} id
+   * @param {number} width
+   * @param {number} height
+   * @private
+   */
+  calculateBounds_: function(id, width, height) {
+    var left, top;
+    var layout = this.displayLayoutMap_.get(id);
+    if (!layout || !layout.parentId) {
+      left = -width / 2;
+      top = -height / 2;
+    } else {
+      if (!this.calculatedBoundsMap_.has(layout.parentId)) {
+        var pbounds = this.displayBoundsMap_.get(layout.parentId);
+        this.calculateBounds_(layout.parentId, pbounds.width, pbounds.height);
+      }
+      var parentBounds = this.getCalculatedDisplayBounds(layout.parentId);
+      left = parentBounds.left;
+      top = parentBounds.top;
+      switch (layout.position) {
+        case chrome.system.display.LayoutPosition.TOP:
+          left += layout.offset;
+          top -= height;
+          break;
+        case chrome.system.display.LayoutPosition.RIGHT:
+          left += parentBounds.width;
+          top += layout.offset;
+          break;
+        case chrome.system.display.LayoutPosition.BOTTOM:
+          left += layout.offset;
+          top += parentBounds.height;
+          break;
+        case chrome.system.display.LayoutPosition.LEFT:
+          left -= width;
+          top += layout.offset;
+          break;
+      }
+    }
+    var result = {
+      left: left,
+      top: top,
+      width: width,
+      height: height,
+    };
+    this.setCalculatedDisplayBounds_(id, result);
+  },
+
+  /**
+   * Finds the display closest to |bounds| ignoring |opt_ignoreIds|.
+   * @param {string} displayId
+   * @param {!chrome.system.display.Bounds} bounds
+   * @param {Array<string>=} opt_ignoreIds Ids to ignore.
+   * @return {string}
+   * @private
+   */
+  findClosest_: function(displayId, bounds, opt_ignoreIds) {
+    var x = bounds.left + bounds.width / 2;
+    var y = bounds.top + bounds.height / 2;
+    var closestId = '';
+    var closestDelta2 = 0;
+    for (let otherId of this.calculatedBoundsMap_.keys()) {
+      if (otherId == displayId)
+        continue;
+      if (opt_ignoreIds && opt_ignoreIds.includes(otherId))
+        continue;
+      var otherBounds = this.getCalculatedDisplayBounds(otherId);
+      var left = otherBounds.left;
+      var top = otherBounds.top;
+      var width = otherBounds.width;
+      var height = otherBounds.height;
+      if (x >= left && x < left + width && y >= top && y < top + height)
+        return otherId;  // point is inside rect
+      var dx, dy;
+      if (x < left)
+        dx = left - x;
+      else if (x > left + width)
+        dx = x - (left + width);
+      else
+        dx = 0;
+      if (y < top)
+        dy = top - y;
+      else if (y > top + height)
+        dy = y - (top + height);
+      else
+        dy = 0;
+      var delta2 = dx * dx + dy * dy;
+      if (closestId == '' || delta2 < closestDelta2) {
+        closestId = otherId;
+        closestDelta2 = delta2;
+      }
+    }
+    return closestId;
+  },
+
+  /**
+   * Calculates the LayoutPosition for |bounds| relative to |parentId|.
+   * @param {!chrome.system.display.Bounds} bounds
+   * @param {string} parentId
+   * @return {!chrome.system.display.LayoutPosition}
+   */
+  getLayoutPositionForBounds_: function(bounds, parentId) {
+    // Translate bounds from top-left to center.
+    var x = bounds.left + bounds.width / 2;
+    var y = bounds.top + bounds.height / 2;
+
+    // Determine the distance from the new bounds to both of the near edges.
+    var parentBounds = this.getCalculatedDisplayBounds(parentId);
+    var left = parentBounds.left;
+    var top = parentBounds.top;
+    var width = parentBounds.width;
+    var height = parentBounds.height;
+
+    // Signed deltas to the center of the div.
+    var dx = x - (left + width / 2);
+    var dy = y - (top + height / 2);
+
+    // Unsigned distance to each edge.
+    var distx = Math.abs(dx) - width / 2;
+    var disty = Math.abs(dy) - height / 2;
+
+    if (distx > disty) {
+      if (dx < 0)
+        return chrome.system.display.LayoutPosition.LEFT;
+      else
+        return chrome.system.display.LayoutPosition.RIGHT;
+    } else {
+      if (dy < 0)
+        return chrome.system.display.LayoutPosition.TOP;
+      else
+        return chrome.system.display.LayoutPosition.BOTTOM;
+    }
+  },
+
+  /**
+   * Modifes |bounds| to the position closest to it along the edge of |parentId|
+   * specified by |layoutPosition|.
+   * @param {string} parentId
+   * @param {!chrome.system.display.LayoutPosition} layoutPosition
+   * @param {!chrome.system.display.Bounds} bounds
+   */
+  snapBounds_: function(parentId, layoutPosition, bounds) {
+    var parentBounds = this.getCalculatedDisplayBounds(parentId);
+
+    var x;
+    if (layoutPosition == chrome.system.display.LayoutPosition.LEFT) {
+      x = parentBounds.left - bounds.width;
+    } else if (layoutPosition == chrome.system.display.LayoutPosition.RIGHT) {
+      x = parentBounds.left + parentBounds.width;
+    } else {
+      x = this.snapToX_(bounds, parentBounds);
+    }
+
+    var y;
+    if (layoutPosition == chrome.system.display.LayoutPosition.TOP) {
+      y = parentBounds.top - bounds.height;
+    } else if (layoutPosition == chrome.system.display.LayoutPosition.BOTTOM) {
+      y = parentBounds.top + parentBounds.height;
+    } else {
+      y = this.snapToY_(bounds, parentBounds);
+    }
+
+    bounds.left = x;
+    bounds.top = y;
+  },
+
+  /**
+   * Snaps a horizontal value, see snapToEdge.
+   * @param {!chrome.system.display.Bounds} newBounds
+   * @param {!chrome.system.display.Bounds} parentBounds
+   * @param {number=} opt_snapDistance Provide to override the snap distance.
+   *     0 means snap from any distance.
+   * @return {number}
+   */
+  snapToX_: function(newBounds, parentBounds, opt_snapDistance) {
+    return this.snapToEdge_(
+        newBounds.left, newBounds.width, parentBounds.left, parentBounds.width,
+        opt_snapDistance);
+  },
+
+  /**
+   * Snaps a vertical value, see snapToEdge.
+   * @param {!chrome.system.display.Bounds} newBounds
+   * @param {!chrome.system.display.Bounds} parentBounds
+   * @param {number=} opt_snapDistance Provide to override the snap distance.
+   *     0 means snap from any distance.
+   * @return {number}
+   */
+  snapToY_: function(newBounds, parentBounds, opt_snapDistance) {
+    return this.snapToEdge_(
+        newBounds.top, newBounds.height, parentBounds.top, parentBounds.height,
+        opt_snapDistance);
+  },
+
+  /**
+   * Snaps the region [point, width] to [basePoint, baseWidth] if
+   * the [point, width] is close enough to the base's edge.
+   * @param {number} point The starting point of the region.
+   * @param {number} width The width of the region.
+   * @param {number} basePoint The starting point of the base region.
+   * @param {number} baseWidth The width of the base region.
+   * @param {number=} opt_snapDistance Provide to override the snap distance.
+   *     0 means snap at any distance.
+   * @return {number} The moved point. Returns the point itself if it doesn't
+   *     need to snap to the edge.
+   * @private
+   */
+  snapToEdge_: function(point, width, basePoint, baseWidth, opt_snapDistance) {
+    // If the edge of the region is smaller than this, it will snap to the
+    // base's edge.
+    /** @const */ var SNAP_DISTANCE_PX = 16;
+    var snapDist =
+        (opt_snapDistance !== undefined) ? opt_snapDistance : SNAP_DISTANCE_PX;
+
+    var startDiff = Math.abs(point - basePoint);
+    var endDiff = Math.abs(point + width - (basePoint + baseWidth));
+    // Prefer the closer one if both edges are close enough.
+    if ((!snapDist || startDiff < snapDist) && startDiff < endDiff)
+      return basePoint;
+    else if (!snapDist || endDiff < snapDist)
+      return basePoint + baseWidth - width;
+
+    return point;
+  },
+
+  /**
+   * Intersects |layout| with each other layout and reduces |deltaPos| to
+   * avoid any collisions (or sets it to [0,0] if the display can not be moved
+   * in the direction of |deltaPos|).
+   * Note: this assumes that deltaPos is already 'snapped' to the parent edge,
+   * and therefore will not collide with the parent, i.e. this is to prevent
+   * overlapping with displays other than the parent.
+   * @param {string} id
+   * @param {!chrome.system.display.Bounds} bounds
+   * @param {!{x: number, y: number}} deltaPos
+   */
+  collideAndModifyDelta_: function(id, bounds, deltaPos) {
+    var keys = this.calculatedBoundsMap_.keys();
+    var others = new Set(keys);
+    others.delete(id);
+    var checkCollisions = true;
+    while (checkCollisions) {
+      checkCollisions = false;
+      for (let otherId of others) {
+        var otherBounds = this.getCalculatedDisplayBounds(otherId);
+        if (this.collideWithBoundsAndModifyDelta_(
+                bounds, otherBounds, deltaPos)) {
+          if (deltaPos.x == 0 && deltaPos.y == 0)
+            return;
+          others.delete(otherId);
+          checkCollisions = true;
+          break;
+        }
+      }
+    }
+  },
+
+  /**
+   * Intersects |bounds| with |otherBounds|. If there is a collision, modifies
+   * |deltaPos| to limit movement to a single axis and avoid the collision
+   * and returns true. See note for |collideAndModifyDelta_|.
+   * @param {!chrome.system.display.Bounds} bounds
+   * @param {!chrome.system.display.Bounds} otherBounds
+   * @param {!{x: number, y: number}} deltaPos
+   * @return {boolean} Whether there was a collision.
+   */
+  collideWithBoundsAndModifyDelta_: function(bounds, otherBounds, deltaPos) {
+    var newX = bounds.left + deltaPos.x;
+    var newY = bounds.top + deltaPos.y;
+
+    if ((newX + bounds.width <= otherBounds.left) ||
+        (newX >= otherBounds.left + otherBounds.width) ||
+        (newY + bounds.height <= otherBounds.top) ||
+        (newY >= otherBounds.top + otherBounds.height)) {
+      return false;
+    }
+
+    // |deltaPos| should already be restricted to X or Y. This shortens the
+    // delta to stay outside the bounds, however it does not change the sign of
+    // the delta, i.e. it does not "push" the point outside the bounds if
+    // the point is already inside.
+    if (Math.abs(deltaPos.x) > Math.abs(deltaPos.y)) {
+      deltaPos.y = 0;
+      let snapDeltaX;
+      if (deltaPos.x > 0) {
+        let x = otherBounds.left - bounds.width;
+        snapDeltaX = Math.max(0, x - bounds.left);
+      } else {
+        let x = otherBounds.left + otherBounds.width;
+        snapDeltaX = Math.min(x - bounds.left, 0);
+      }
+      deltaPos.x = snapDeltaX;
+    } else {
+      deltaPos.x = 0;
+      let snapDeltaY;
+      if (deltaPos.y > 0) {
+        let y = otherBounds.top - bounds.height;
+        snapDeltaY = Math.min(0, y - bounds.top);
+      } else if (deltaPos.y < 0) {
+        let y = otherBounds.top + otherBounds.height;
+        snapDeltaY = Math.max(y - bounds.top, 0);
+      } else {
+        snapDeltaY = 0;
+      }
+      deltaPos.y = snapDeltaY;
+    }
+
+    return true;
+  },
+
+  /**
+   * Updates the offset for |layout| from |bounds|.
+   * @param {!chrome.system.display.Bounds} bounds
+   * @param {!chrome.system.display.LayoutPosition} position
+   * @param {!chrome.system.display.DisplayLayout} layout
+   */
+  updateOffsetAndPosition_: function(bounds, position, layout) {
+    layout.position = position;
+    if (!layout.parentId) {
+      layout.offset = 0;
+      return;
+    }
+
+    // Offset is calculated from top or left edge.
+    var parentBounds = this.getCalculatedDisplayBounds(layout.parentId);
+    var offset, minOffset, maxOffset;
+    if (position == chrome.system.display.LayoutPosition.LEFT ||
+        position == chrome.system.display.LayoutPosition.RIGHT) {
+      offset = bounds.top - parentBounds.top;
+      minOffset = -bounds.height;
+      maxOffset = parentBounds.height;
+    } else {
+      offset = bounds.left - parentBounds.left;
+      minOffset = -bounds.width;
+      maxOffset = parentBounds.width;
+    }
+    /** @const */ var MIN_OFFSET_OVERLAP = 50;
+    minOffset += MIN_OFFSET_OVERLAP;
+    maxOffset -= MIN_OFFSET_OVERLAP;
+    layout.offset = Math.max(minOffset, Math.min(offset, maxOffset));
+
+    // Update the calculated bounds to match the new offset.
+    this.calculateBounds_(layout.id, bounds.width, bounds.height);
+  },
+
+  /**
+   * Highlights the edge of the div associated with |id| based on
+   * |layoutPosition| and removes any other highlights. If |layoutPosition| is
+   * undefined, removes all highlights.
+   * @param {string} id
+   * @param {chrome.system.display.LayoutPosition|undefined} layoutPosition
+   * @private
+   */
+  highlightEdge_: function(id, layoutPosition) {
+    for (let layout of this.layouts) {
+      var highlight = (layout.id == id) ? layoutPosition : undefined;
+      var div = this.$$('#_' + layout.id);
+      div.classList.toggle(
+          'highlight-right',
+          highlight == chrome.system.display.LayoutPosition.RIGHT);
+      div.classList.toggle(
+          'highlight-left',
+          highlight == chrome.system.display.LayoutPosition.LEFT);
+      div.classList.toggle(
+          'highlight-top',
+          highlight == chrome.system.display.LayoutPosition.TOP);
+      div.classList.toggle(
+          'highlight-bottom',
+          highlight == chrome.system.display.LayoutPosition.BOTTOM);
+    }
+  },
+};