Twitter Bootstrap Question posted in

(Twitter) Bootstrap button input flickering on hover – Twitter bootstrap

Scenario: Chrome v51.0.2704, Bootstrap v2.3.2, Windows 10 v1511. See snippet below. I’ve excluded the Bootstrap CSS that does not apply to this case.

Problem: As can be seen when rapidly moving the mouse on and off of the element, the background appears to randomly “flicker” with light blue horizontal lines appearing for just a moment.

This does not seem to occur on Firefox v46, IE v11, or Edge v25.

button,
input,
select,
textarea {
  margin: 0;
  font-size: 100%;
  vertical-align: middle;
}

button,
input {
  *overflow: visible;
  line-height: normal;
}

button::-moz-focus-inner,
input::-moz-focus-inner {
  padding: 0;
  border: 0;
}

button,
html input[type="button"],
input[type="reset"],
input[type="submit"] {
  cursor: pointer;
  -webkit-appearance: button;
}

label,
select,
button,
input[type="button"],
input[type="reset"],
input[type="submit"],
input[type="radio"],
input[type="checkbox"] {
  cursor: pointer;
}

label,
input,
button,
select,
textarea {
  font-size: 14px;
  font-weight: normal;
  line-height: 20px;
}

input,
button,
select,
textarea {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
}

input,
textarea,
.uneditable-input {
  width: 206px;
}

input[type="file"],
input[type="image"],
input[type="submit"],
input[type="reset"],
input[type="button"],
input[type="radio"],
input[type="checkbox"] {
  width: auto;
}

input:-moz-placeholder,
textarea:-moz-placeholder {
  color: #999999;
}

input:-ms-input-placeholder,
textarea:-ms-input-placeholder {
  color: #999999;
}

input::-webkit-input-placeholder,
textarea::-webkit-input-placeholder {
  color: #999999;
}

input,
textarea,
.uneditable-input {
  margin-left: 0;
}

.btn {
  display: inline-block;
  *display: inline;
  padding: 4px 12px;
  margin-bottom: 0;
  *margin-left: .3em;
  font-size: 14px;
  line-height: 20px;
  color: #333333;
  text-align: center;
  text-shadow: 0 1px 1px rgba(255, 255, 255, 0.75);
  vertical-align: middle;
  cursor: pointer;
  background-color: #f5f5f5;
  *background-color: #e6e6e6;
  background-image: -moz-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#ffffff), to(#e6e6e6));
  background-image: -webkit-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: -o-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: linear-gradient(to bottom, #ffffff, #e6e6e6);
  background-repeat: repeat-x;
  border: 1px solid #cccccc;
  *border: 0;
  border-color: #e6e6e6 #e6e6e6 #bfbfbf;
  border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
  border-bottom-color: #b3b3b3;
  -webkit-border-radius: 4px;
     -moz-border-radius: 4px;
          border-radius: 4px;
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffffff', endColorstr='#ffe6e6e6', GradientType=0);
  filter: progid:DXImageTransform.Microsoft.gradient(enabled=false);
  *zoom: 1;
  -webkit-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
     -moz-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
          box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
}

.btn:hover,
.btn:focus,
.btn:active,
.btn.active,
.btn.disabled,
.btn[disabled] {
  color: #333333;
  background-color: #e6e6e6;
  *background-color: #d9d9d9;
}

.btn:first-child {
  *margin-left: 0;
}

.btn:hover,
.btn:focus {
  color: #333333;
  text-decoration: none;
  background-position: 0 -15px;
  -webkit-transition: background-position 0.1s linear;
     -moz-transition: background-position 0.1s linear;
       -o-transition: background-position 0.1s linear;
          transition: background-position 0.1s linear;
}

.btn-large {
  padding: 11px 19px;
  font-size: 17.5px;
  -webkit-border-radius: 6px;
     -moz-border-radius: 6px;
          border-radius: 6px;
}

.btn-primary {
  color: #ffffff;
  text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.25);
  background-color: #006dcc;
  *background-color: #0044cc;
  background-image: -moz-linear-gradient(top, #0088cc, #0044cc);
  background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#0088cc), to(#0044cc));
  background-image: -webkit-linear-gradient(top, #0088cc, #0044cc);
  background-image: -o-linear-gradient(top, #0088cc, #0044cc);
  background-image: linear-gradient(to bottom, #0088cc, #0044cc);
  background-repeat: repeat-x;
  border-color: #0044cc #0044cc #002a80;
  border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ff0088cc', endColorstr='#ff0044cc', GradientType=0);
  filter: progid:DXImageTransform.Microsoft.gradient(enabled=false);
}

.btn-primary:hover,
.btn-primary:focus,
.btn-primary:active,
.btn-primary.active,
.btn-primary.disabled,
.btn-primary[disabled] {
  color: #ffffff;
  background-color: #0044cc;
  *background-color: #003bb3;
}

button.btn,
input[type="submit"].btn {
  *padding-top: 3px;
  *padding-bottom: 3px;
}

button.btn::-moz-focus-inner,
input[type="submit"].btn::-moz-focus-inner {
  padding: 0;
  border: 0;
}

button.btn.btn-large,
input[type="submit"].btn.btn-large {
  *padding-top: 7px;
  *padding-bottom: 7px;
}
<input type="submit" name="submit" class="btn btn-primary btn-lg">
Tags:

2

Answers


  1. 0

    The problem is the background-position on hover. Reducing the second value should fix the flickering (any value from -8px to -14px should work):

    .btn:hover,
.btn:focus {
  background-position: 0 -14px;
}
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  2. 0

    Fiddle

    The main issue here is that animating background-position can have bad performance.

    Solution

    Instead of animating the background-position I setup a separate div that is animated using transform: translateY(-15px).

    Why so many divs?

    You might think to reduce the number of divs by just using <button></button> and animating :after with a transform animation, but Chrome has a bug that doesn’t allow you to have transition, overflow: hidden, and border-radiusapplied correctly to an element (covered in this SO question).

    Why use transform?

    To help experience what’s going check out the following JSFiddles:

    (Zooming in really helps)

    • More Obvious Flicker – the original flicker from this question can be difficult to spot because the animation only takes 0.1s so I slowed it down to 3s
    • Color Contrast – changing the colors from variants of blue can help show why there is a jitter in the animation. With this example you can see that just before the red portion moves up on the button there is a sliver of yellow. This is my guess as to why you see the white flicker in the original question.
    • Fix (with color) – in this example you can clearly see that the animation is moving smoothly because of using transform: translateY(-15px)
    • Final Answer – this restores the original colors and animation speed

    Full Code

    button,
input,
select,
textarea {
  margin: 0;
  font-size: 100%;
  vertical-align: middle;
}

button,
input {
  *overflow: visible;
  line-height: normal;
}

button::-moz-focus-inner,
input::-moz-focus-inner {
  padding: 0;
  border: 0;
}

button,
html input[type="button"],
input[type="reset"],
input[type="submit"] {
  cursor: pointer;
  -webkit-appearance: button;
}

label,
select,
button,
input[type="button"],
input[type="reset"],
input[type="submit"],
input[type="radio"],
input[type="checkbox"] {
  cursor: pointer;
}

label,
input,
button,
select,
textarea {
  font-size: 14px;
  font-weight: normal;
  line-height: 20px;
}

input,
button,
select,
textarea {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
}

input,
textarea,
.uneditable-input {
  width: 206px;
}

input[type="file"],
input[type="image"],
input[type="submit"],
input[type="reset"],
input[type="button"],
input[type="radio"],
input[type="checkbox"] {
  width: auto;
}

input:-moz-placeholder,
textarea:-moz-placeholder {
  color: #999999;
}

input:-ms-input-placeholder,
textarea:-ms-input-placeholder {
  color: #999999;
}

input::-webkit-input-placeholder,
textarea::-webkit-input-placeholder {
  color: #999999;
}

input,
textarea,
.uneditable-input {
  margin-left: 0;
}




.btn {
  display: inline-block;
  *display: inline;
  padding: 4px 12px;
  margin-bottom: 0;
  *margin-left: .3em;
  font-size: 14px;
  line-height: 20px;
  color: #333333;
  text-align: center;
  text-shadow: 0 1px 1px rgba(255, 255, 255, 0.75);
  vertical-align: middle;
  cursor: pointer;
  /*
  background-color: #f5f5f5;
  *background-color: #e6e6e6;
  background-image: -moz-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#ffffff), to(#e6e6e6));
  background-image: -webkit-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: -o-linear-gradient(top, #ffffff, #e6e6e6);
  background-image: linear-gradient(to bottom, #ffffff, #e6e6e6);
  background-repeat: repeat-x;
  */
  border: 1px solid #cccccc;
  *border: 0;
  border-color: #e6e6e6 #e6e6e6 #bfbfbf;
  border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
  border-bottom-color: #b3b3b3;
  -webkit-border-radius: 4px;
  -moz-border-radius: 4px;
  border-radius: 4px;
  filter: progid: DXImageTransform.Microsoft.gradient(startColorstr='#ffffffff', endColorstr='#ffe6e6e6', GradientType=0);
  filter: progid: DXImageTransform.Microsoft.gradient(enabled=false);
  *zoom: 1;
  -webkit-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
  -moz-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
}

.btn:hover,
.btn:focus,
.btn:active,
.btn.active,
.btn.disabled,
.btn[disabled] {
  color: #333333;
  /*
  background-color: #e6e6e6;
  *background-color: #d9d9d9;
  */
}

.btn:first-child {
  *margin-left: 0;
}

.btn:hover,
.btn:focus {
  color: #333333;
  text-decoration: none;
  /* Removed
  background-position: 0 -15px;
  -webkit-transition: background-position 3s linear;
     -moz-transition: background-position 3s linear;
       -o-transition: background-position 3s linear;
          transition: background-position 3s linear;
   */
}

.btn-large {
  padding: 11px 19px;
  font-size: 17.5px;
  -webkit-border-radius: 6px;
  -moz-border-radius: 6px;
  border-radius: 6px;
}

.btn-primary {
  color: #ffffff;
  text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.25);
  /*
  background-color: #006dcc;
  *background-color: #0044cc;
  background-image: -moz-linear-gradient(top, #0088cc, #0044cc);
  background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#0088cc), to(#0044cc));
  background-image: -webkit-linear-gradient(top, #0088cc, #0044cc);
  background-image: -o-linear-gradient(top, #0088cc, #0044cc);
  background-image: linear-gradient(to bottom, #0088cc, #0044cc);
  background-repeat: repeat-x;
  */
  border-color: #0044cc #0044cc #002a80;
  border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
  filter: progid: DXImageTransform.Microsoft.gradient(startColorstr='#ff0088cc', endColorstr='#ff0044cc', GradientType=0);
  filter: progid: DXImageTransform.Microsoft.gradient(enabled=false);
}

.btn-primary:hover,
.btn-primary:focus,
.btn-primary:active,
.btn-primary.active,
.btn-primary.disabled,
.btn-primary[disabled] {
  color: #ffffff;
  /*background-color: #0044cc;
  *background-color: #003bb3;
  */
}

button.btn,
input[type="submit"].btn {
  *padding-top: 3px;
  *padding-bottom: 3px;
}

button.btn::-moz-focus-inner,
input[type="submit"].btn::-moz-focus-inner {
  padding: 0;
  border: 0;
}

button.btn.btn-large,
input[type="submit"].btn.btn-large {
  *padding-top: 7px;
  *padding-bottom: 7px;
}


/* New Styles  */
.btn-container {
  overflow: hidden;
  display: inline-block;
  position: relative;
}

.background {
  content: "";
  background-color: #0044cc;
  position: absolute;
  bottom: -15px;
  left: 0;
  right: 0;
  width: 100%;
  height: 45px;
  z-index: -1;
  background-image: linear-gradient(to bottom, #0088cc 0%, #0044cc 66%, #0044cc 66%, #0044cc 100%);
  background-repeat: repeat-x;
}

.btn-container:hover .background {
  transform: translateY(-15px);
  -webkit-transition: transform 0.1s linear;
  -moz-transition: transform 0.1s linear;
  -o-transition: transform 0.1s linear;
  transition: transform 0.1s linear;
}

.btn {
  background-color: transparent;
}

.mask {
  position: absolute;
  margin: 0 auto;
  overflow: hidden;
  height: 30px;
  z-index: 9;
  top: 0px;
  left: 0;
  right: 0;
  width: 100%;
}

.mask:after {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  border-radius: 4px;
  width: 100%;
  height: 100%;
  box-shadow: 0px 0px 0px 2000px #f3f5f6;
}
    <div class="btn-container">
  <button class="btn btn-primary btn-lg">
    Submit
  </button>
  <div class="mask">
  </div>
  <div class="background">
  </div>
</div>
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