Stable element placement in relation to its container

Question

Stable element placement in relation to its container

While dragging an element, it obtains a position: fixed. This particular element is located within a modal that is directly nested inside the body element.

In the image below, the modal appears in gray, while the rest of the body is black, and the button stands out in blue. The issue arises when I apply the following styles to the button:

position: fixed;
top: xxxpx;
left: -100px;

Interestingly, the button gets positioned in relation to the modal rather than the viewport. It seems as though an element with position: fixed behaves like an absolutely positioned element instead. Is this scenario even plausible?

https://i.sstatic.net/8pu7m.png

html css

Answer 1

Answer №1

'Usually' when an element has a position fixed, it is positioned relative to the viewport.

However, there are exceptions to this rule. For more information, visit MDN

In some cases, when an element has a position fixed, it is removed from the normal document flow and no space is allocated for it in the page layout. Instead, it is positioned based on the initial containing block established by the viewport. This changes if any of its ancestors have a transform, perspective, or filter property set to something other than none. In that case, the ancestor behaves as the containing block instead. Please note that browser inconsistencies may arise with perspective and filter affecting containing block formation. The final position of the element is determined by the values of top, right, bottom, and left properties.

Here's a simple example:

body {}

.parent {
  position: relative;
  margin: 100px;
  transform: scale(1);
  width: 50vw;
  height: 10vw;
  background: black;
  rfilter: blur(1);
}

.child {
  position: fixed;
  top: 0px;
  left: 0px;
  width: 100px;
  height: 100px;
  background-color: blue;
}

<body>
  <div class="parent">
    <div class="child"></div>
  </div>
</body>

As you can see in the example above, the blue child element is positioned at the top left corner of its parent. Even though the parent has a transform property (scale(1)), it still serves as the containing block.

It seems like the issue might be related to the transform applied to the parent element.

Answer 2

'Usually' when an element has a position fixed, it is positioned relative to the viewport.

However, there are exceptions to this rule. For more information, visit MDN

In some cases, when an element has a position fixed, it is removed from the normal document flow and no space is allocated for it in the page layout. Instead, it is positioned based on the initial containing block established by the viewport. This changes if any of its ancestors have a transform, perspective, or filter property set to something other than none. In that case, the ancestor behaves as the containing block instead. Please note that browser inconsistencies may arise with perspective and filter affecting containing block formation. The final position of the element is determined by the values of top, right, bottom, and left properties.

Here's a simple example:

body {}

.parent {
  position: relative;
  margin: 100px;
  transform: scale(1);
  width: 50vw;
  height: 10vw;
  background: black;
  rfilter: blur(1);
}

.child {
  position: fixed;
  top: 0px;
  left: 0px;
  width: 100px;
  height: 100px;
  background-color: blue;
}

<body>
  <div class="parent">
    <div class="child"></div>
  </div>
</body>

As you can see in the example above, the blue child element is positioned at the top left corner of its parent. Even though the parent has a transform property (scale(1)), it still serves as the containing block.

It seems like the issue might be related to the transform applied to the parent element.

Answer 3

Answer №2

For those working with React (and perhaps there is a comparable method in other frameworks), the createPortal feature from 'react-dom' can be utilized as shown below:

createPortal(<YourComponent/>, document.body)

By using this approach, there is no need to remove transformations from parent elements - they can simply be disregarded.

Answer 4

For those working with React (and perhaps there is a comparable method in other frameworks), the createPortal feature from 'react-dom' can be utilized as shown below:

createPortal(<YourComponent/>, document.body)

By using this approach, there is no need to remove transformations from parent elements - they can simply be disregarded.

Stable element placement in relation to its container

Answer №1

Answer №2

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