1 | /**
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2 | * @license
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3 | * Copyright 2019 Google Inc.
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4 | *
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5 | * Permission is hereby granted, free of charge, to any person obtaining a copy
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6 | * of this software and associated documentation files (the "Software"), to deal
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7 | * in the Software without restriction, including without limitation the rights
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8 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 | * copies of the Software, and to permit persons to whom the Software is
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10 | * furnished to do so, subject to the following conditions:
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11 | *
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12 | * The above copyright notice and this permission notice shall be included in
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13 | * all copies or substantial portions of the Software.
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14 | *
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15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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18 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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19 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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20 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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21 | * THE SOFTWARE.
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22 | */
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23 | /**
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24 | * Determine whether the current browser supports passive event listeners, and
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25 | * if so, use them.
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26 | */
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27 | export function applyPassive(globalObj) {
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28 | if (globalObj === void 0) { globalObj = window; }
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29 | return supportsPassiveOption(globalObj) ?
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30 | { passive: true } :
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31 | false;
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32 | }
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33 | function supportsPassiveOption(globalObj) {
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34 | if (globalObj === void 0) { globalObj = window; }
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35 | // See
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36 | // https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener
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37 | var passiveSupported = false;
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38 | try {
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39 | var options = {
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40 | // This function will be called when the browser
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41 | // attempts to access the passive property.
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42 | get passive() {
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43 | passiveSupported = true;
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44 | return false;
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45 | }
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46 | };
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47 | var handler = function () { };
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48 | globalObj.document.addEventListener('test', handler, options);
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49 | globalObj.document.removeEventListener('test', handler, options);
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50 | }
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51 | catch (err) {
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52 | passiveSupported = false;
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53 | }
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54 | return passiveSupported;
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55 | }
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56 | //# sourceMappingURL=events.js.map |
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