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      1 // Copyright 2015 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 var Selection = function(handler) {
      6   this.handler = handler;
      7   this.selectionBase = null;
      8   this.lastSelection = null;
      9   this.selection = new Set();
     10 }
     11 
     12 
     13 Selection.prototype.isEmpty = function() {
     14   return this.selection.size == 0;
     15 }
     16 
     17 
     18 Selection.prototype.clear = function() {
     19   var handler = this.handler;
     20   this.selectionBase = null;
     21   this.lastSelection = null;
     22   handler.select(this.selection, false);
     23   handler.clear();
     24   this.selection = new Set();
     25 }
     26 
     27 
     28 count = 0;
     29 
     30 Selection.prototype.select = function(s, isSelected) {
     31   var handler = this.handler;
     32   if (!(Symbol.iterator in Object(s))) { s = [s]; }
     33   if (isSelected) {
     34     let first = true;
     35     for (let i of s) {
     36       if (first) {
     37         this.selectionBase = i;
     38         this.lastSelection = i;
     39         first = false;
     40       }
     41       this.selection.add(i);
     42     }
     43     handler.select(this.selection, true);
     44   } else {
     45     let unselectSet = new Set();
     46     for (let i of s) {
     47       if (this.selection.has(i)) {
     48         unselectSet.add(i);
     49         this.selection.delete(i);
     50       }
     51     }
     52     handler.select(unselectSet, false);
     53   }
     54 }
     55 
     56 
     57 Selection.prototype.extendTo = function(pos) {
     58   if (pos == this.lastSelection || this.lastSelection === null) return;
     59 
     60   var handler = this.handler;
     61   var pos_diff = handler.selectionDifference(pos, true, this.lastSelection, false);
     62   var unselect_diff = [];
     63   if (pos_diff.length == 0) {
     64     pos_diff = handler.selectionDifference(this.selectionBase, false, pos, true);
     65     if (pos_diff.length != 0) {
     66       unselect_diff = handler.selectionDifference(this.lastSelection, true, this.selectionBase, false);
     67       this.selection = new Set();
     68       this.selection.add(this.selectionBase);
     69       for (var d of pos_diff) {
     70         this.selection.add(d);
     71       }
     72     } else {
     73       unselect_diff = handler.selectionDifference(this.lastSelection, true, pos, false);
     74       for (var d of unselect_diff) {
     75         this.selection.delete(d);
     76       }
     77     }
     78   } else {
     79     unselect_diff = handler.selectionDifference(this.selectionBase, false, this.lastSelection, true);
     80     if (unselect_diff != 0) {
     81       pos_diff = handler.selectionDifference(pos, true, this.selectionBase, false);
     82       if (pos_diff.length == 0) {
     83         unselect_diff = handler.selectionDifference(pos, false, this.lastSelection, true);
     84       }
     85       for (var d of unselect_diff) {
     86         this.selection.delete(d);
     87       }
     88     }
     89     if (pos_diff.length != 0) {
     90       for (var d of pos_diff) {
     91         this.selection.add(d);
     92       }
     93     }
     94   }
     95   handler.select(unselect_diff, false);
     96   handler.select(pos_diff, true);
     97   this.lastSelection = pos;
     98 }
     99 
    100 
    101 Selection.prototype.detachSelection = function() {
    102   var result = new Set();
    103   for (var i of this.selection) {
    104     result.add(i);
    105   }
    106   this.clear();
    107   return result;
    108 }
    109