CSS overflow:auto is invalid. Is the negative value of the parent element z-index the culprit?

CSS scroll bar failure troubleshooting: overflow: auto failure cause and solution

In CSS, when creating scrollbars using overflow: auto attribute, you sometimes encounter the problem that the scrollbars are displayed but cannot scroll. This article will analyze a case and provide solutions.

Problem description: A container with overflow: auto set, the content height exceeds the container, the scroll bar appears, but it cannot scroll. z-index attribute value of the parent element of the container is negative.

Problem code snippet:

 height: 250px;
box-sizing: border-box;
border-bottom: 1px solid #000;
background-color: #eee;
overflow: auto;
scroll-snap-type: y mandatory;
position: relative;
z-index: 99;

The container has a height of 250px, and overflow: auto is set, but the scrolling is invalid because z-index of the parent element is a negative value.

Cause analysis: z-index controls the stacking order of elements. A negative z-index value indicates that the element is located below other elements. A negative z-index of the parent element may obscure the child element, making it unable to respond to user interactions, even if the child element z-index is a positive value.

Solution: Check the parent element's z-index , set it to a non-negative value, or adjust the parent and child elements' z-index values ​​to ensure that the child elements are visible and interactive.

Sample code that can scroll normally:

<div class="box">
  <div>123</div>
  <div>123</div>
  <!-- ... more divs ... -->
</div>

.box {
  height: 150px;
  box-sizing: border-box;
  border-bottom: 1px solid #000;
  background-color: #eee;
  overflow: auto;
  scroll-snap-type: y mandatory;
  position: relative;
  z-index: 99;
}

In this example, the container can be scrolled normally, and the key is to ensure that z-index of the parent element does not affect the display and interaction of the child element. Ensuring that the parent element's z-index value does not conflict with the child element is the key to solving the problem.

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