Summary of new features of CSS3: borders and backgrounds

This series mainly summarizes the understanding of some new features of CSS3, which comes from the book "CSS Revealed".

1. Translucent border

It is best to use hsla instead of rgba for css3. hsla is: h: color value (0~360); s: saturation (0%~100%); l: brightness (0% ~100%); a: Transparency (0~1)

background-clip: clip the background color, the default is border-box (the background color spreads to the border); padding-box (the background color spreads to the padding); content-box (Background color extends to content)

Sample code:

width:200px;
height:200px;
background: rebeccapurple;
border: 10px solid hsla(300, 0%, 50%, 0.5);     
background-clip: padding-box; //去掉和添加上此项可以看出效果

2. Multiple border implementation

box-shadow: Set or retrieve object shadow, format: box-shadow: none | {2, 4} && color? | inset?

length<1>: Horizontal offset, negative value

length<2>: Vertical offset, negative value

length< 3 >: Shadow blur value, non-negative value Value

length<4>: extension length, negative value

: shadow color

inset: expressed as inner shadow, empty means outer shadow

You can set multiple sets of effects, and use between multiple sets Separate by commas (use the box-shadow and overlapping features to set multiple borders, but the border style cannot be striped, dotted, etc.)

If you want to set the search text shadow, use the text-shadow attribute

outline Realize two borders (only two borders can be realized, but the border style is flexible)

3. Background positioning

background-position: background positioning, the value description is as follows

center, left, top, bottom, right etc. all indicate where the background starts to display. If you set repeated tiles, there will be different effects. The value can be a numerical value or a percentage: background-position: right 20px bottom 30px;

background-origin: the positioning parameter of the background image , three-valued context-box, padding-box, border-box, etc.

clac() function to calculate width

The sample code is as follows:

background-image: url('../img/bck.png');
background-repeat: no-repeat;
background-size: 40px 40px;
width:200px;
height:200px;
margin-top:10px;
border: 5px solid red;
--background-position: right 0px bottom 0px;
background-origin: content-box;
background-position: calc(100% - 50px);
padding: 10px;

4. Multiple rounded corners

box-shadow: Its rounded corners will follow the border-radius, but outline does not meeting.

The minimum shadow (box-shadow) calculation formula is: Pythagorean theorem, when setting the shadow, it should be greater than this value

Sample code:

margin: 10px auto;
width: 10em;
height: 8em;
background: tan;
border-radius: .8em;
padding: 1em;
box-shadow: 0 0 0 .6em #655;
outline: .6em solid #556;