Transitions

CSS transitions let you animate a change from an element’s initial state to an end state

The CSS code demonstrates how to create a smooth transition effect on a button when the user hovers over it.

button {
  border: 1px solid black;
  border-radius: 5px;
  padding: 2% 5% 2% 5%;
  background-color: white;
  color: white;
  transition-property: background-color;
  transition-duration: 1s;
  transition-timing-function: ease-out;
  transition-delay: 0.25s;
}

button:hover {
  background-color: black;
  cursor: pointer;
}

• The button class styles a button element with a black border, rounded corners, and padding.
• The initial background color is set to white, but the color will transition smoothly to black when the user hovers over the button.
• The transition-property specifies that only the background-color will be transitioned.
• The transition-duration sets the duration of the transition to 1 second.
• The transition-timing-function defines how the transition’s speed changes throughout its duration. In this case, it will ease-out, meaning it starts fast and slows down towards the end.
• The transition-delay determines the delay before the transition starts. Here, the color change starts 0.25 seconds after the cursor rests on the button.

A more concise shorthand version of the transition is also provided:

button {
  /* ... other CSS properties ... */
  background-color: white;
  transition: background-color 1s ease-out 0.25s;
}

button:hover {
  background-color: black;
}

• The transition shorthand property includes the same transition properties as above but in a more compact form.

Performance

The notes also highlight two considerations for performance:

1. Stacking Context: When transitioning certain properties, such as transform, a stacking context is formed. This can impact performance, especially if multiple stacking contexts are present, leading to repaints of all elements within each context. Keeping stacking contexts to a minimum can help maintain smooth transitions.

2. Limiting Animations to Opacity and Transform: For the best performance on web pages, it is advised to limit animations to affecting only opacity and transform properties. Even a seemingly simple background-color change, as shown in the example, can be expensive in terms of performance.

Here are the additional notes based on the provided instructions:

Refrences

1. Using CSS Transitions:
   • Read the MDN article for using CSS transitions to learn about CSS transitions and animations.
   • Pay special attention to the Defining transitions section of the article, which provides detailed explanations and examples of how to define transitions in CSS.
   • Code along with the examples to get hands-on experience and become familiar with the syntax used in CSS transitions.
2. Understanding the Stacking Context:
   • To gain a deeper understanding of the stacking context in CSS, read the MDN article about the stacking context.
   • The stacking context is an important concept to grasp, especially when dealing with transitions that may create stacking contexts and affect the performance of rendering elements on the page.
3. Creating Performant CSS Animations:
   • Improve your knowledge of creating efficient CSS animations by reading this article.
   • The article offers useful tips and best practices for optimizing animations to achieve smooth and performant results on web pages.
   • Additionally, explore CSS Triggers to understand how animatable CSS properties can impact other elements. Compare properties like background-color and transform to see their differences in performance.
4. Debugging Repaint Issues with CSS Transitions:
   • Learn how to identify and troubleshoot repaint issues related to CSS transitions by referring to the article from Dzhavat Ushev.
   • Understanding how to catch and debug repaint issues can help you optimize your transitions and ensure smooth rendering on your web pages.