CSS Tips: Overlay content and implement responsive scaling on SVG animations

This article aims to solve the problem of superimposing content on the background of SVG animation in CSS and implementing SVG animation adapting to the screen width while maintaining the content proportion. We will explore two ways to overlay elements: traditional absolute positioning and modern Grid layouts, and provide SVG scaling to suit containers, helping developers create more attractive web interfaces.

Element Overlay: Absolute Positioning vs. Grid Layout

In web development, placing one element over another is a common requirement, especially when creating complex UI interfaces. This article will introduce two ways to implement element superposition: traditional position: absolute and modern CSS Grid layout.

1. Absolute positioning

Absolute positioning is a common method that allows us to position an element relative to its nearest positioned ancestor element. If there is no positioned ancestor element, it is positioned relative to the initial containing block (usually the element).

Implementation steps:

1. Set the parent element to position: relative. This creates a positioning context relative to which child elements can be positioned.
2. Set the child element to be superimposed to position: absolute.
3. Use the top, right, bottom, and left attributes to precisely control the position of the child elements.

Sample code:

 .parent {
  position: relative;
  width: 200px;
  height: 150px;
}

.child-one {
  display: block;
}

.child-two {
  position: absolute;
  top: 0;
  left: 0; /* Optional: Adjust as needed*/
}

 <div class="parent">
  <svg class="child-one" width="200" height="150">
    <rect x="0" y="0" width="200" height="150" fill="linen"></rect>
    <circle cx="50" cy="50" r="40" fill="red"></circle>
  </svg>

  <div class="child-two">
    Some text.<br>
    Some more text.<br>
    Etcetera.
  </div>
</div>

Notes:

• An absolutely positioned element will detach from the document stream, meaning it will not affect the position of other elements.
• The top, right, bottom, and left attributes need to be carefully adjusted to ensure that the elements are properly superimposed.

2. Grid layout

CSS Grid layout is a powerful two-dimensional layout system that allows us to place elements in a grid and control their size and position. Using Grid layouts to overlay elements is more concise and flexible.

Implementation steps:

1. Set the parent element to display: grid.
2. Use the grid-template-columns and grid-template-rows properties to define the columns and rows of the grid.
3. Place all the child elements to be superimposed in the same grid cell.

Sample code:

 .parent {
  display: grid;
  grid-template-columns: 200px;
  grid-template-rows: 150px;
}

.child-one, .child-two {
  grid-column: 1 / 1;
  grid-row: 1 / 1;
}

 <div class="parent">
  <svg class="child-one" width="200" height="150">
    <rect x="0" y="0" width="200" height="150" fill="linen"></rect>
    <circle cx="50" cy="50" r="40" fill="red"></circle>
  </svg>

  <div class="child-two">
    Some text.<br>
    Some more text.<br>
    Etcetera.
  </div>
</div>

Notes:

• Grid layouts support well for modern browsers, but may require Polyfill in older browsers.
• Use the z-index attribute to control the stacking order of overlay elements.

SVG scaling to fit containers

In order for SVG animation to adapt to screen width while maintaining its content proportions, we need to make sure that the SVG elements are scaled correctly to fill their containers.

Solution:

The key is to correctly set the viewBox attribute and CSS style of the SVG element.

1. viewBox property: The viewBox property defines the coordinate system of the SVG content. It accepts four values: min-x, min-y, width, height. These values define the visible area of the SVG content.
2. CSS style: Use width: 100% and height: auto to ensure that the SVG element can fill the width of its container and automatically adjust the height to maintain its content proportions.

Sample code:

 <svg width="100%" height="30rem" id="svg" viewbox="0 70 1440 700" xmlns="http://www.w3.org/2000/svg">
  </svg>

explain:

• width="100%": Make sure that the SVG element fills the width of its parent container.
• height="30rem": Set the height of the SVG element to 30rem.
• viewBox="0 70 1440 700": Defines the visible area of the SVG content. 0 70 is the coordinates of the upper left corner, and 1440 700 is the width and height of the visible area.

Summarize:

By combining the position: absolute or Grid layout for element overlay and correctly setting the viewBox attribute and CSS style of the SVG element, we can easily overlay content on SVG animations and implement responsive scaling of SVG animations, creating a more attractive and adaptable web interface.

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