When the grandfather element background obscures pseudo-elements, how to solve the effect of adding shadows to text gradients?

Solve the gradient and shadow effects of pseudo-element text occlusion in grandfather element background

When creating text gradients and shadow effects, we often use pseudo-elements and absolute positioning. However, when the grandfather element (e.g.<header></header> ) When you have a background, the pseudo-element may be obscured, causing the shadow to disappear. This article analyzes this problem and provides solutions.

Usually, we implement text gradients and shadows like this:

<div class="header">
  <p class="text" data-text="示例文本">Sample text</p>
</div>

.header {
  width: 100%;
  height: 100px;
  /* Add background color, pseudo-elements will be blocked here*/
  background-color: #f0f0f0; 
}

.text {
  -webkit-text-fill-color: transparent;
  background-image: linear-gradient(to bottom, red 0%, green 100%);
  -webkit-background-clip: text;
  background-clip: text;
  font-size: 40px;
  font-weight: bold;
  letter-spacing: 9px;
  position: relative; /* Add relative positioning to the parent element*/
}

.text::before {
  content: attr(data-text);
  position: absolute;
  color: transparent;
  text-shadow: 0 4px 2px blue;
  z-index: 1; /* Set z-index to a positive value*/
}

Although this allows gradients and shadows, pseudo-elements are obscured when .header has a background. Simply adjusting z-index of .header does not solve the problem, because the cascaded context of the pseudo-element is related to its parent element.

The root of the problem: the hierarchical relationship between the stacked context and pseudo-elements

z-index attribute is only valid in the same stacking context. A pseudo-element belongs to the cascade context of its parent element, so z-index of the parent element does not directly affect the pseudo-element. The key is that the rendering order of the pseudo-element is related to other elements in its parent element, and by default it may be behind the parent element background.

Solution: Adjust the positioning of z-index and parent elements of the pseudo-element

To solve this problem, we need:

1. Add position: relative; for the parent .text : This will create a new local cascade context that makes z-index take effect in that context.

2. Set z-index of the pseudo-element.text .text::before to a positive value : This ensures that the pseudo-element is above the parent element background.

Through the above adjustments, text gradients and shadow effects can be displayed correctly even if the grandfather element has a background. Understanding the rendering order of cascaded contexts and pseudo-elements is crucial to solving such problems.

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