103 lines
2.8 KiB
JavaScript
103 lines
2.8 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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* @providesModule StyleSheet
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* @flow
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*/
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'use strict';
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var PixelRatio = require('PixelRatio');
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var StyleSheetRegistry = require('StyleSheetRegistry');
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var StyleSheetValidation = require('StyleSheetValidation');
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var flatten = require('flattenStyle');
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var hairlineWidth = PixelRatio.roundToNearestPixel(0.4);
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if (hairlineWidth === 0) {
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hairlineWidth = 1 / PixelRatio.get();
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}
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/**
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* A StyleSheet is an abstraction similar to CSS StyleSheets
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*
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* Create a new StyleSheet:
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*
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* ```
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* var styles = StyleSheet.create({
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* container: {
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* borderRadius: 4,
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* borderWidth: 0.5,
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* borderColor: '#d6d7da',
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* },
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* title: {
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* fontSize: 19,
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* fontWeight: 'bold',
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* },
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* activeTitle: {
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* color: 'red',
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* },
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* });
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* ```
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*
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* Use a StyleSheet:
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*
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* ```
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* <View style={styles.container}>
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* <Text style={[styles.title, this.props.isActive && styles.activeTitle]} />
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* </View>
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* ```
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*
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* Code quality:
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*
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* - By moving styles away from the render function, you're making the code
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* easier to understand.
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* - Naming the styles is a good way to add meaning to the low level components
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* in the render function.
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*
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* Performance:
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*
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* - Making a stylesheet from a style object makes it possible to refer to it
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* by ID instead of creating a new style object every time.
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* - It also allows to send the style only once through the bridge. All
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* subsequent uses are going to refer an id (not implemented yet).
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*/
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module.exports = {
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/**
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* This is defined as the width of a thin line on the platform. It can be
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* used as the thickness of a border or division between two elements.
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* Example:
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* ```
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* {
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* borderBottomColor: '#bbb',
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* borderBottomWidth: StyleSheet.hairlineWidth
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* }
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* ```
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*
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* This constant will always be a round number of pixels (so a line defined
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* by it look crisp) and will try to match the standard width of a thin line
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* on the underlying platform. However, you should not rely on it being a
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* constant size, because on different platforms and screen densities its
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* value may be calculated differently.
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*/
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hairlineWidth,
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flatten,
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/**
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* Creates a StyleSheet style reference from the given object.
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*/
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create(obj: {[key: string]: any}): {[key: string]: number} {
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var result = {};
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for (var key in obj) {
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StyleSheetValidation.validateStyle(key, obj);
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result[key] = StyleSheetRegistry.registerStyle(obj[key]);
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}
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return result;
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}
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};
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