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src/utils/calcTextareaHeight.js 2.89 KB
0f822c9b   梁灏   add Input component
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  // Thanks to
  // https://github.com/andreypopp/react-textarea-autosize/
  // https://github.com/ElemeFE/element/blob/master/packages/input/src/calcTextareaHeight.js
  
  let hiddenTextarea;
  
  const HIDDEN_STYLE = `
      height:0 !important;
      min-height:0 !important;
      max-height:none !important;
      visibility:hidden !important;
      overflow:hidden !important;
      position:absolute !important;
      z-index:-1000 !important;
      top:0 !important;
      right:0 !important
  `;
  
  const CONTEXT_STYLE = [
      'letter-spacing',
      'line-height',
      'padding-top',
      'padding-bottom',
      'font-family',
      'font-weight',
      'font-size',
      'text-rendering',
      'text-transform',
      'width',
      'text-indent',
      'padding-left',
      'padding-right',
      'border-width',
      'box-sizing'
  ];
  
  function calculateNodeStyling(node) {
      const style = window.getComputedStyle(node);
  
      const boxSizing = style.getPropertyValue('box-sizing');
  
      const paddingSize = (
          parseFloat(style.getPropertyValue('padding-bottom')) +
          parseFloat(style.getPropertyValue('padding-top'))
      );
  
      const borderSize = (
          parseFloat(style.getPropertyValue('border-bottom-width')) +
          parseFloat(style.getPropertyValue('border-top-width'))
      );
  
      const contextStyle = CONTEXT_STYLE
          .map(name => `${name}:${style.getPropertyValue(name)}`)
          .join(';');
  
      return {contextStyle, paddingSize, borderSize, boxSizing};
  }
  
  export default function calcTextareaHeight(targetNode, minRows = null, maxRows = null) {
      if (!hiddenTextarea) {
          hiddenTextarea = document.createElement('textarea');
          document.body.appendChild(hiddenTextarea);
      }
  
      let {
          paddingSize,
          borderSize,
          boxSizing,
          contextStyle
      } = calculateNodeStyling(targetNode);
  
      hiddenTextarea.setAttribute('style', `${contextStyle};${HIDDEN_STYLE}`);
      hiddenTextarea.value = targetNode.value || targetNode.placeholder || '';
  
      let height = hiddenTextarea.scrollHeight;
      let minHeight = -Infinity;
      let maxHeight = Infinity;
  
      if (boxSizing === 'border-box') {
          height = height + borderSize;
      } else if (boxSizing === 'content-box') {
          height = height - paddingSize;
      }
  
      hiddenTextarea.value = '';
      let singleRowHeight = hiddenTextarea.scrollHeight - paddingSize;
  
      if (minRows !== null) {
          minHeight = singleRowHeight * minRows;
          if (boxSizing === 'border-box') {
              minHeight = minHeight + paddingSize + borderSize;
          }
          height = Math.max(minHeight, height);
      }
      if (maxRows !== null) {
          maxHeight = singleRowHeight * maxRows;
          if (boxSizing === 'border-box') {
              maxHeight = maxHeight + paddingSize + borderSize;
          }
          height = Math.min(maxHeight, height);
      }
  
      return {
          height: `${height}px`,
          minHeight: `${minHeight}px`,
          maxHeight: `${maxHeight}px`
      };
  };