css skeleton & web app skeleton

css skeleton & web app skeleton

skeleton

https://www.cnblogs.com/xgqfrms/p/10437258.html

https://github.com/dhg/Skeleton/

https://codepen.io/xgqfrms/pen/zQEJWw

https://codepen.io/xgqfrms/details/zQEJWw

https://codepen.io/xgqfrms/full/zQEJWw

https://github.com/dhg/Skeleton/

https://github.com/whatsnewsaes/Skeleton-Sass

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skeleton screens

https://css-tricks.com/building-skeleton-screens-css-custom-properties/

.skeleton {
  background-repeat: no-repeat;
  background-image:
    /* layer 2: avatar */
    /* white circle with 16px radius */
    radial-gradient(circle 16px, white 99%, transparent 0),
    /* layer 1: title */
    /* white rectangle with 40px height */
    linear-gradient(white 40px, transparent 0),
    /* layer 0: card bg */
    /* gray rectangle that covers whole element */
    linear-gradient(gray 100%, transparent 0);
}

.skeleton {
  background-size:
    32px 32px,  /* avatar */
    200px 40px, /* title */
    100% 100%;  /* card bg */
}

.skeleton {
  background-position:
    24px 24px,  /* avatar */
    24px 200px, /* title */
    0 0;        /* card bg */
}

Custom CSS properties & css var

https://www.smashingmagazine.com/2017/04/start-using-css-custom-properties/

.skeleton {
  /*
    define as separate properties
  */
  --card-height: 340px;
  --card-padding:24px;
  --card-skeleton: linear-gradient(gray var(--card-height), transparent 0);

  --title-height: 32px;
  --title-width: 200px;
  --title-position: var(--card-padding) 180px;
  --title-skeleton: linear-gradient(white var(--title-height), transparent 0);

  --avatar-size: 32px;
  --avatar-position: var(--card-padding) var(--card-padding);
  --avatar-skeleton: radial-gradient(
    circle calc(var(--avatar-size) / 2),
    white 99%,
    transparent 0
  );

  /*
    now we can break the background up
    into individual shapes
  */
  background-image:
    var(--avatar-skeleton),
    var(--title-skeleton),
    var(--card-skeleton);

  background-size:
    var(--avatar-size),
    var(--title-width) var(--title-height),
    100% 100%;

  background-position:
    var(--avatar-position),
    var(--title-position),
    0 0;
}

http://caniuse.com/#feat=css-variables

@media screen and (min-width: 47em) {
  :root {
    --card-padding: 32px;
    --card-height: 360px;
  }
}

Animation

<div class="card"></div>

/*
 * Variables
 */

:root {
  --card-padding: 24px;
  --card-height: 340px;
  --card-skeleton: linear-gradient(lightgrey var(--card-height), transparent 0);

  --avatar-size: 32px;
  --avatar-position: var(--card-padding) var(--card-padding);
  --avatar-skeleton: radial-gradient(circle 16px at center, white 99%, transparent 0
  );

  --title-height: 32px;
  --title-width: 200px;
  --title-position: var(--card-padding) 180px;
  --title-skeleton: linear-gradient(white var(--title-height), transparent 0);

  --desc-line-height: 16px;
  --desc-line-skeleton: linear-gradient(white var(--desc-line-height), transparent 0);
  --desc-line-1-width:230px;
  --desc-line-1-position: var(--card-padding) 242px;
  --desc-line-2-width:180px;
  --desc-line-2-position: var(--card-padding) 265px;

  --footer-height: 40px;
  --footer-position: 0 calc(var(--card-height) - var(--footer-height));
  --footer-skeleton: linear-gradient(white var(--footer-height), transparent 0);

  --blur-width: 200px;
  --blur-size: var(--blur-width) calc(var(--card-height) - var(--footer-height));
}

/*
 * Card Skeleton for Loading
 */

.card {
  width: 280px; //demo
  height: var(--card-height);

  &:empty::after {
    content:"";
    display:block;
    width: 100%;
    height: 100%;
    border-radius:6px;
    box-shadow: 0 10px 45px rgba(0,0,0, .1);

    background-image:
      linear-gradient(
        90deg,
        rgba(lightgrey, 0) 0,
        rgba(lightgrey, .8) 50%,
        rgba(lightgrey, 0) 100%
      ),                          //animation blur
      var(--title-skeleton),      //title
      var(--desc-line-skeleton),  //desc1
      var(--desc-line-skeleton),  //desc2
      var(--avatar-skeleton),     //avatar
      var(--footer-skeleton),     //footer bar
      var(--card-skeleton)        //card
    ;

    background-size:
      var(--blur-size),
      var(--title-width) var(--title-height),
      var(--desc-line-1-width) var(--desc-line-height),
      var(--desc-line-2-width) var(--desc-line-height),
      var(--avatar-size) var(--avatar-size),
      100% var(--footer-height),
      100% 100%
    ;

    background-position:
      -150% 0,                      //animation
      var(--title-position),        //title
      var(--desc-line-1-position),  //desc1
      var(--desc-line-2-position),  //desc2
      var(--avatar-position),       //avatar
      var(--footer-position),       //footer bar
      0 0                           //card
    ;

    background-repeat: no-repeat;
    animation: loading 1.5s infinite;
  }
}

@keyframes loading {
  to {
    background-position:
      350% 0,
      var(--title-position),
      var(--desc-line-1-position),
      var(--desc-line-2-position),
      var(--avatar-position),
      var(--footer-position),
      0 0
    ;
  }
}

/*
 * Demo Stuff
 */

body {
  min-height:100vh;
  background-color:#FFF;
  display:flex;
  justify-content:center;
  align-items:center;
}

:empty selector & pseudo element

CSS & Card Skeleton

https://codepen.io/xgqfrms/pen/KLXrob

https://codepen.io/xgqfrms/pen/gJGQeX

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web app demos

https://cangdu.org/elm/#/shop?geohash=31.278702,121.465513&id=3276

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CSS Pseudo Selectors

::slotted & :empty

https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements

https://developer.mozilla.org/en-US/docs/Web/CSS/pseudo-classes

https://developer.mozilla.org/en-US/docs/Web/CSS/::slotted

https://developer.mozilla.org/en-US/docs/Web/CSS/:empty

/* Selects any element placed inside a slot */
::slotted(*) {
  font-weight: bold;
}

/* Selects any <span> placed inside a slot */
::slotted(span) {
  font-weight: bold;
}

https://css-tricks.com/building-skeleton-screens-css-custom-properties/

1. You can use the :empty selector and a pseudo element to draw the skeleton, so it only applies to empty card elements.

   Once the content is injected, the skeleton screen will automatically disappear.

/* css skeleton */

/*
 * Card Skeleton for Loading
 */

.card {
  width: 280px; //demo
  height: var(--card-height);

  &:empty::after {
    content:"";
    display:block;
    width: 100%;
    height: 100%;
    border-radius:6px;
    box-shadow: 0 10px 45px rgba(0,0,0, .1);

    background-image:
      linear-gradient(
        90deg,
        rgba(lightgrey, 0) 0,
        rgba(lightgrey, .8) 50%,
        rgba(lightgrey, 0) 100%
      ),                          //animation blur
      var(--title-skeleton),      //title
      var(--desc-line-skeleton),  //desc1
      var(--desc-line-skeleton),  //desc2
      var(--avatar-skeleton),     //avatar
      var(--footer-skeleton),     //footer bar
      var(--card-skeleton)        //card
    ;

    background-size:
      var(--blur-size),
      var(--title-width) var(--title-height),
      var(--desc-line-1-width) var(--desc-line-height),
      var(--desc-line-2-width) var(--desc-line-height),
      var(--avatar-size) var(--avatar-size),
      100% var(--footer-height),
      100% 100%
    ;

    background-position:
      -150% 0,                      //animation
      var(--title-position),        //title
      var(--desc-line-1-position),  //desc1
      var(--desc-line-2-position),  //desc2
      var(--avatar-position),       //avatar
      var(--footer-position),       //footer bar
      0 0                           //card
    ;

    background-repeat: no-repeat;
    animation: loading 1.5s infinite;
  }
}

@keyframes loading {
  to {
    background-position:
      350% 0,
      var(--title-position),
      var(--desc-line-1-position),
      var(--desc-line-2-position),
      var(--avatar-position),
      var(--footer-position),
      0 0
    ;
  }
}

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