Why Doesn't CSS Transition Work With the `display` Property?

CSS3 Transition Not Working with display Property

Problem Description:

Attempting to use a CSS transition to fade in a hidden div on hover is not yielding the desired result; no easing transitions are observed.

Analysis of Code:

Upon examination of the provided code, it is apparent that the problem stems from the use of the display property. The display property in CSS controls the presence and visibility of elements on a page. When set to none, as it is in the initial state of the hidden div, the element is removed from the page's document flow and effectively rendered invisible.

Transition Applicability:

CSS transitions only apply to properties that affect the element's geometry or appearance. In the case of the display property, it toggles the element's visibility status rather than altering its geometry or appearance. As a result, transitions cannot be applied to the display property.

Alternative Solution Using Opacity:

Instead of using the display property, consider using the opacity property to achieve the desired fade-in effect. Opacity controls the transparency of an element, allowing it to fade in smoothly by adjusting its opacity from 0 to 1.

Updated CSS Code:

The following updated CSS code employs the opacity property to create a smooth fade-in transition:

#header #button:hover > .content {
    opacity: 1;
    height: 150px;
    padding: 8px;    
}

#header #button .content {
    opacity: 0;
    height: 0;
    padding: 0 8px;
    overflow: hidden;
    transition: all .3s ease .15s;
}

Advantages of Opacity-Based Transition:

• Allows for fine-grained control over the fade-in effect by adjusting the opacity value.
• Preserves the element's position and dimensions during the transition, unlike display which removes the element from the document flow.
• Compatible with CSS transitions, enabling smooth and animated transformations.

Conclusion:

While CSS transitions cannot be applied to the display property, the opacity property provides a viable and effective solution for creating smooth fade-in effects on hover. By adjusting the opacity value, you can control the visibility and appearance of hidden elements, achieving the desired transitions seamlessly.

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