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Implement amp-story dynamic page scaling
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| /** | ||
| * Copyright 2018 The AMP HTML Authors. All Rights Reserved. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS-IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| import {Services} from '../../../src/services'; | ||
| import {dev, user} from '../../../src/log'; | ||
| import {dict} from '../../../src/utils/object'; | ||
| import {isExperimentOn} from '../../../src/experiments'; | ||
| import {childElementsByTag, matches} from '../../../src/dom'; | ||
| import {px, setImportantStyles} from '../../../src/style'; | ||
| import {renderAsElement} from './simple-template'; | ||
| import {throttle} from '../../../src/utils/rate-limit'; | ||
| import {toArray} from '../../../src/types'; | ||
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| /** @private @const {number} */ | ||
| const MIN_LAYER_WIDTH_PX = 380; | ||
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| /** @private @const {number} */ | ||
| const MAX_LAYER_WIDTH_PX = 520; | ||
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| /** @private @const {string} */ | ||
| const SCALING_APPLIED_CLASSNAME = 'i-amphtml-story-scaled'; | ||
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| /** @private @const {!./simple-template.ElementDef} */ | ||
| const SIZER_TEMPLATE = { | ||
| tag: 'div', | ||
| attrs: dict({'class': 'i-amphtml-story-page-sizer'}), | ||
| }; | ||
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| /** @struct @typedef {{factor: number, width: number, height: number}} */ | ||
| let DimensionsDef; | ||
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| /** @typedef {{scale: function(!Element):!Promise}} */ | ||
| let PageScalingServiceInterface; | ||
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| /** | ||
| * @param {!Element} sizer | ||
| * @return {!DimensionsDef} | ||
| */ | ||
| function targetDimensionsFor(sizer) { | ||
| const {width, height} = sizer./*OK*/getBoundingClientRect(); | ||
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| const ratio = width / height; | ||
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| const targetWidth = Math.min(MAX_LAYER_WIDTH_PX, | ||
| Math.max(width, Math.max(1, ratio) * MIN_LAYER_WIDTH_PX)); | ||
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| const targetHeight = (targetWidth / ratio); | ||
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| const factor = width / targetWidth; | ||
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| return {width: targetWidth, height: targetHeight, factor}; | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @param {!DimensionsDef} dimensions | ||
| */ | ||
| function applyScaling(page, dimensions) { | ||
| const {width, height, factor} = dimensions; | ||
| // TODO(alanorozco): Calculate relative layer dimensions for cases where | ||
| // they won't fill the entire page. | ||
| const style = { | ||
| 'width': px(width), | ||
| 'height': px(height), | ||
| 'zoom': `${factor * 100}%`, | ||
| 'box-sizing': 'border-box', | ||
| }; | ||
| scalableChildren(page).forEach(el => { | ||
| setImportantStyles(el, style); | ||
| }); | ||
| markScalingApplied(page); | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @return {!Array<!Element>} | ||
| */ | ||
| function scalableChildren(page) { | ||
| return toArray(childElementsByTag(page, 'amp-story-grid-layer')); | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @return {boolean} | ||
| */ | ||
| function isScalingEnabled(page) { | ||
| return page.getAttribute('scaling') != 'disabled'; | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @return {boolean} | ||
| */ | ||
| function isScalingApplied(page) { | ||
| return page.classList.contains(SCALING_APPLIED_CLASSNAME); | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @param {boolean} isApplied | ||
| */ | ||
| function markScalingApplied(page, isApplied = true) { | ||
| page.classList.toggle(SCALING_APPLIED_CLASSNAME, isApplied); | ||
| } | ||
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| /** | ||
| * Required for lazy evaluation after resize. | ||
| * @param {!Element} page | ||
| * @return {boolean} | ||
| */ | ||
| function withinRange(page) { | ||
| return matches(page, '[active], [distance="1"], [desktop] > [distance="2"]'); | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @return {boolean} | ||
| */ | ||
| function needsScaling(page) { | ||
| return isScalingEnabled(page) && !isScalingApplied(page) && withinRange(page); | ||
| } | ||
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| /** | ||
| * @param {!Document} doc | ||
| * @param {!Element} container | ||
| */ | ||
| function createSizer(doc, container) { | ||
| const element = renderAsElement(doc, SIZER_TEMPLATE); | ||
| container.appendChild(element); | ||
| return element; | ||
| } | ||
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| /** @private @const {!PageScalingServiceInterface} */ | ||
| const MOCK_PAGE_SCALING_SERVICE = { | ||
| scale(unusedPage) { | ||
| return Promise.resolve(); | ||
| }, | ||
| }; | ||
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| /** @private {?PageScalingServiceInterface} */ | ||
| let pageScalingService = null; | ||
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| /** | ||
| * Service for scaling pages dynamically so their layers will be sized within a | ||
| * certain pixel range independent of visual dimensions. | ||
| */ | ||
| // TODO(alanorozco): Make this part of the runtime layout system to prevent | ||
| // FOUC-like jump and allow for SSR. | ||
| export class PageScalingService { | ||
| constructor(win, story) { | ||
| /** @private @const {!Element} */ | ||
| this.story_ = story; | ||
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| /** @private @const */ | ||
| this.vsync_ = Services.vsyncFor(win); | ||
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| /** @private @const {!Element} */ | ||
| this.sizer_ = createSizer(win.document, story); | ||
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| /** @private {?DimensionsDef} */ | ||
| this.dimensions_ = null; | ||
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| Services.viewportForDoc(story).onResize( | ||
| throttle(win, () => this.onViewportResize_(), 100)); | ||
| } | ||
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| /** | ||
| * @param {!Window} win | ||
| * @param {!Element} story | ||
| * @return {!PageScalingServiceInterface} | ||
| */ | ||
| static for(win, story) { | ||
| // Implemented as singleton for now, should be mapped to story element. | ||
| // TODO(alanorozco): Implement mapping to support multiple <amp-story> | ||
| // instances in one doc. | ||
| if (!pageScalingService) { | ||
| if (!isExperimentOn(win, 'amp-story-scaling')) { | ||
| pageScalingService = MOCK_PAGE_SCALING_SERVICE; | ||
| } else if (Services.platformFor(win).isFirefox()) { | ||
| // Firefox does not support `zoom`. | ||
| // TODO(alanorozco): Use `scale` on Firefox. | ||
| user().warn('`amp-story-scaling` ignored: Firefox is not supported.'); | ||
| pageScalingService = MOCK_PAGE_SCALING_SERVICE; | ||
| } else { | ||
| pageScalingService = new PageScalingService(win, story); | ||
| } | ||
| } | ||
| return pageScalingService; | ||
| } | ||
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| /** | ||
| * @param {!Element} page | ||
| * @return {!Promise} | ||
| */ | ||
| scale(page) { | ||
| if (!needsScaling(page)) { | ||
| return Promise.resolve(); | ||
| } | ||
| return this.vsync_.runPromise({ | ||
| measure: () => { | ||
| if (!this.dimensions_) { | ||
| this.dimensions_ = targetDimensionsFor(this.sizer_); | ||
| } | ||
| }, | ||
| mutate: () => { | ||
| const dimensions = | ||
| /** @type {!DimensionsDef} */ (dev().assert(this.dimensions_)); | ||
| applyScaling(page, dimensions); | ||
| }, | ||
| }); | ||
| } | ||
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| /** @private */ | ||
| onViewportResize_() { | ||
| const pages = toArray(childElementsByTag(this.story_, 'amp-story-page')); | ||
| this.dimensions_ = null; | ||
| pages.forEach(page => { | ||
| markScalingApplied(page, false); | ||
| this.scale(page); | ||
| }); | ||
| } | ||
| } |