-webkit-background-origin

`-webkit-background-origin` 是一个 CSS 属性，用于指定背景图片的起始位置。它是 WebKit 浏览器引擎私有的属性，在其他浏览器中不被支持。该属性可支持的值有 `padding-box`、`border-box` 和 `content-box`。其中，`padding-box` 表示背景图片从 padding 区域开始显示；`border-box` 表示背景图片从 border 区域开始显示；`content-box` 表示背景图片从 content 区域开始显示。

相关问题

如何让IOS富文本支持background: linear-gradient(90deg, black 50%, #D3D3D3 50%);-webkit-background-clip: text;-webkit-text-fill-color: transparent;

要让iOS富文本支持该样式，你可以使用Core Text框架来实现。下面是一个示例代码：

import UIKit
import CoreText

extension NSMutableAttributedString {
    func applyLinearGradient(colors: [CGColor], startPoint: CGPoint, endPoint: CGPoint) {
        let gradient = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: colors as CFArray, locations: nil)!
        
        let stringRange = NSRange(location: 0, length: self.length)
        let line = CTLineCreateWithAttributedString(self)
        let runs = CTLineGetGlyphRuns(line)
        
        for runIndex in 0..<CFArrayGetCount(runs) {
            let run = CFArrayGetValueAtIndex(runs, runIndex)!
            let runRange = CTRunGetStringRange(run)
            
            var runRect = CGRect.zero
            CTRunGetTypographicBounds(run, CFRangeMake(0, 0), &runRect.origin, &runRect.size, nil)
            
            let glyphCount = CTRunGetGlyphCount(run)
            var glyphPositions = Array<CGPoint>(repeating: .zero, count: glyphCount)
            CTRunGetPositions(run, CFRangeMake(0, 0), &glyphPositions)
            
            for glyphIndex in 0..<glyphCount {
                let glyphRange = CFRangeMake(glyphIndex, 1)
                let position = glyphPositions[glyphIndex]
                let glyphRect = CGRect(x: runRect.origin.x + position.x, y: runRect.origin.y + position.y, width: runRect.size.width, height: runRect.size.height)
                
                let glyphLocation = runRange.location + glyphRange.location
                let characterRange = CFRangeMake(glyphLocation, glyphRange.length)
                let tokenRange = CTLineGetStringRange(line)
                let adjustedRange = CFRangeMake(characterRange.location - tokenRange.location, characterRange.length)
                
                self.enumerateAttribute(.font, in: adjustedRange, options: []) { (value, range, stop) in
                    let font = value as! UIFont
                    let fontSize = font.pointSize
                    
                    let glyphPath = CTFontCreatePathForGlyph(font, glyphRange.location, nil)!
                    let glyphBoundingBox = glyphPath.boundingBox
                    
                    let textMatrix = CGAffineTransform(scaleX: 1, y: -1).translatedBy(x: 0, y: -runRect.size.height)
                    let glyphTransform = glyphBoundingBox.applying(textMatrix)
                    
                    let startPoint = CGPoint(x: startPoint.x + glyphRect.origin.x, y: startPoint.y + glyphRect.origin.y)
                    let endPoint = CGPoint(x: endPoint.x + glyphRect.origin.x, y: endPoint.y + glyphRect.origin.y)
                    let gradientTransform = CGAffineTransform(translationX: startPoint.x, y: startPoint.y).scaledBy(x: (endPoint.x - startPoint.x) / glyphBoundingBox.width, y: (endPoint.y - startPoint.y) / glyphBoundingBox.height)
                    
                    let gradientPath = glyphPath.copy(using: &gradientTransform)!
                    let gradientBoundingBox = gradientPath.boundingBox
                    let boundingBoxTransform = CGAffineTransform(translationX: -gradientBoundingBox.origin.x, y: -gradientBoundingBox.origin.y)
                    
                    let transformedGradientPath = gradientPath.copy(using: &boundingBoxTransform)!
                    
                    let context = UIGraphicsGetCurrentContext()!
                    context.addPath(transformedGradientPath)
                    context.clip()
                    context.drawLinearGradient(gradient, start: startPoint, end: endPoint, options: [.drawsBeforeStartLocation, .drawsAfterEndLocation])
                }
            }
        }
    }
}

// 使用示例
let label = UILabel()
let attributedText = NSMutableAttributedString(string: "Your text here")
let colors = [UIColor.black.cgColor, UIColor(red: 211/255, green: 211/255, blue: 211/255, alpha: 1).cgColor]
let startPoint = CGPoint(x: 0, y: 0)
let endPoint = CGPoint(x: label.bounds.width, y: 0)

attributedText.addAttribute(.foregroundColor, value: UIColor.clear, range: NSRange(location: 0, length: attributedText.length))
label.attributedText = attributedText

label.applyLinearGradient(colors: colors, startPoint: startPoint, endPoint: endPoint)

通过上述代码，你可以将UILabel的文本设置为富文本，并应用线性渐变背景效果。请注意，这个代码示例是使用Swift编写的，所以你需要在你的iOS项目中创建一个适当的代码文件，并将其添加到你的项目中。

<main-content :ifDetail="true"> <div class="two-side"> <div class="main-left"> <el-form :model="form" :rules="rules" ref="form" label-width="120px"> <el-form-item label="选择下载模块" prop="accountName"> <el-input v-model.trim="form.accountName" :maxlength="50"></el-input> </el-form-item> <el-form-item label="倾斜度"> <el-slider v-model.number="form.rotate" :min="-180" :max="180"></el-slider> </el-form-item> <el-form-item label="文字"> <el-input type="textarea" v-model="form.text"></el-input> </el-form-item> <el-form-item label="文字大小"> <el-input-number v-model.number="form.fontSize" :min="10" :max="50"></el-input-number> px </el-form-item> <el-form-item label="位置"> <el-select placeholder="请选择位置" v-model="form.alignment"> <el-option v-for="item in options" :key="item.value" :label="item.label" :value="item.value"></el-option> </el-select> </el-form-item> <el-form-item> <el-select v-if="form.alignment === 2" placeholder="请选择位置" v-model="form.textPosition"> <el-option v-for="item in textPositionOptions" :key="item.value" :label="item.label" :value="item.value" ></el-option> </el-select> </el-form-item> </el-form> {{ watermarkStyle }} </div> <div class="main-right" id="show"> <div class="watermark"> <span :style="watermarkStyle" ref="showText" style="word-break:break-all;display: inline-block">{{ form.text }}</span> </div> </div> </div> </main-content> 左边来控制右边div里水印展示，代码怎么写

您可以在 `<el-form>` 标签上绑定 `@input` 事件，当表单数据发生改变时，触发该事件，然后在事件处理函数中计算出水印的样式，并将样式绑定到 `<span>` 标签上。具体实现代码如下：

<template>
  <main-content :ifDetail="true">
    <div class="two-side">
      <div class="main-left">
        <el-form :model="form" :rules="rules" ref="form" label-width="120px" @input="handleInput">
          <!-- 表单项省略 -->
        </el-form>
      </div>
      <div class="main-right" id="show">
        <div class="watermark">
          <span :style="watermarkStyle" ref="showText" style="word-break:break-all;display: inline-block">{{ form.text }}</span>
        </div>
      </div>
    </div>
  </main-content>
</template>

<script>
export default {
  data() {
    return {
      form: {
        accountName: '',
        rotate: 0,
        text: '',
        fontSize: 16,
        alignment: 1,
        textPosition: 1
      },
      options: [
        { label: '左上', value: 1 },
        { label: '居中', value: 2 },
        { label: '右下', value: 3 }
      ],
      textPositionOptions: [
        { label: '正常', value: 1 },
        { label: '斜体', value: 2 }
      ]
    }
  },
  computed: {
    watermarkStyle() {
      const { rotate, fontSize, alignment, textPosition } = this.form
      const deg = rotate + (textPosition === 2 ? -45 : 0)
      const translateX =
        alignment === 1 ? '-10%' : alignment === 2 ? '-50%' : '90%'
      const translateY =
        alignment === 1 ? '-10%' : alignment === 2 ? '-50%' : '90%'
      const transform = `rotate(${deg}deg)`
      const style = {
        position: 'absolute',
        top: 0,
        left: 0,
        bottom: 0,
        right: 0,
        fontSize: `${fontSize}px`,
        transform: transform,
        '-webkit-transform': transform,
        '-ms-transform': transform,
        '-moz-transform': transform,
        '-o-transform': transform,
        opacity: '0.2',
        'pointer-events': 'none',
        'text-align': 'center',
        'z-index': 9999,
        transformOrigin: '50% 50%',
        '-webkit-transform-origin': '50% 50%',
        '-ms-transform-origin': '50% 50%',
        '-moz-transform-origin': '50% 50%',
        '-o-transform-origin': '50% 50%',
        color: '#000',
        'word-break': 'break-all',
        'white-space': 'pre-wrap',
        'max-height': '100%',
        'max-width': '100%',
        overflow: 'hidden',
        'text-overflow': 'ellipsis',
        '-webkit-text-fill-color': 'transparent',
        '-webkit-background-clip': 'text',
        'background-clip': 'text',
        '-webkit-user-select': 'none',
        '-moz-user-select': 'none',
        '-ms-user-select': 'none',
        userSelect: 'none',
        '-webkit-line-clamp': '1',
        display: 'flex',
        'align-items': 'center',
        'justify-content': 'center',
        'transform-style': 'preserve-3d'
      }
      if (textPosition === 2) {
        style.padding = '0.5rem'
        style.background =
          'linear-gradient(to right bottom, rgba(255, 255, 255, 0.2) 0%, rgba(255, 255, 255, 0.2) 45%, rgba(255, 255, 255, 0) 50%, rgba(255, 255, 255, 0.2) 55%, rgba(255, 255, 255, 0.2) 100%)'
      }
      style.transform += ` translate(${translateX}, ${translateY})`
      style['-webkit-transform'] += ` translate(${translateX}, ${translateY})`
      style['-moz-transform'] += ` translate(${translateX}, ${translateY})`
      style['-ms-transform'] += ` translate(${translateX}, ${translateY})`
      style['-o-transform'] += ` translate(${translateX}, ${translateY})`
      return style
    }
  },
  methods: {
    handleInput() {
      this.$nextTick(() => {
        const { width, height } = this.$refs.show.getBoundingClientRect()
        const { offsetWidth, offsetHeight } = this.$refs.showText
        if (width === 0 || height === 0 || offsetWidth === 0 || offsetHeight === 0) {
          return
        }
        const scaleX = width / offsetWidth
        const scaleY = height / offsetHeight
        const scale = Math.min(scaleX, scaleY)
        this.$refs.showText.style.transform += `scale(${scale})`
        this.$refs.showText.style['-webkit-transform'] += `scale(${scale})`
        this.$refs.showText.style['-moz-transform'] += `scale(${scale})`
        this.$refs.showText.style['-ms-transform'] += `scale(${scale})`
        this.$refs.showText.style['-o-transform'] += `scale(${scale})`
      })
    }
  }
}
</script>

代码中的 `watermarkStyle` 计算属性用于计算水印的样式，`handleInput` 方法用于在计算出水印样式后，将水印按照比例缩小并居中显示。注意，为了保证水印样式的正确性，需要在表单项加载完成之后计算水印样式，因此需要在 `handleInput` 方法中使用 `$nextTick` 方法等待表单项加载完成再进行计算。