Why does 'transform:rotate(Xdeg)' cause the animation to stop?-CodePudding

I tried to rotate an animated font arrow when the window reached a min/max size, but when the rotate takes place the animation stops, also just for testing I tried replacing transform: rotate(90deg) to transform: rotate(0deg) which maintains the same arrow's direction but it causes to stop the animation too. The issue is with transform: rotate() and it can be easily tested by inspecting the element and activating/deactivating it in the browsers developer tools.

An easy way to bypass this can be using two <p> each one with an arrow in different direction and with vertical and horizontal animation each, and using display: none; to alternate between them when the min/max size switches, but what I want is to know why this is happening and how to solve this using this approach

.text-center {
  text-align: center;
}

.lnr-x3 {
  font-size: 2.4rem;
}

@media (max-width: 991px) {
  #catalogArrow_h {
    transform: rotate(90deg) !important;
    transform-origin: center !important;
  }
}

.animated-h {
  text-decoration: none;
  outline-style: none;
  -webkit-animation: movingHorizontally 1.7s ease-in-out infinite;
  animation: movingHorizontally 1.7s ease-in-out infinite;
}

@keyframes movingHorizontally {
  0% {
    transform: translateX(0px);
    -webkit-transform: translateX(0px);
  }
  50% {
    transform: translateX(-10px);
    -webkit-transform: translateX(-10px);
  }
  100% {
    transform: translateX(0px);
    -webkit-transform: translateX(0px);
  }
}

@-webkit-keyframes movingHorizontally {
  0% {
    transform: translateX(0px);
    -webkit-transform: translateX(0px);
  }
  50% {
    transform: translateX(-10px);
    -webkit-transform: translateX(-10px);
  }
  100% {
    transform: translateX(0px);
    -webkit-transform: translateX(0px);
  }
}

<!-- Font Icons -->
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.3/css/all.css" type="text/css">
<link rel="stylesheet" href="https://cdn.linearicons.com/free/1.0.0/icon-font.min.css">

<div >
  <p >
    <span id="catalogArrow_h" ></span>
  </p>
</div>

CodePudding user response：

Why does this happen

The transform property is "shared" for many transform functions and css doesn't combine any property's values.

Because your animation is made with transform: translateX(..), adding transform: rotate(..) will overwrite the property's value, not combine them. I.e. the resulting style is transform: rotate(..), not transform: translateX(..) rotate(..).

It would be the same if you were animating the box-shadow and then wanted an inset box-shadow too, it would overwrite one with the other. Or more simply - if you have .box { color: red; color: blue; } css will choose the last value (blue) to apply to the color property.

If there were css properties rotate: 90deg and translate: 4px (there are but not widely supported), then your animation would work, because the translate animation would be applying to a different property than the rotation, not overwriting one that is essentially shared amongst many transform functions.

Ways around it

There are many ways around this problem.

You can set the translate or rotate on the parent element

<div >
  <span ></span>
</div>

You can add the rotate to your translate animation properties:

@keyframes movingHorizontallyRotated {
  0%, 100% { transform: translateX(0px)   rotate(90deg); }
  50%      { transform: translateX(-10px) rotate(90deg); }
}

You can animate a different property to translate the element:

@keyframes movingHorizontally {
  0%, 100% { padding: 5px 10px 5px 0px; }
  50%      { padding: 5px 0px 5px 10px; }
}

You can use/make an already rotated arrow if your framework/ assets provides one.