(Twitter) Bootstrap 悬停时按钮输入闪烁

Question

场景：Chrome v51.0.2704，Bootstrap v2.3.2，Windows 10 v1511。请参阅下面的片段。我排除了不适用于这种情况的 Bootstrap CSS。

问题：正如在元素上快速移动鼠标时所见，背景随机 "flicker" 出现浅蓝色水平线片刻。

这似乎不会发生在 Firefox v46、IE v11 或 Edge v25 上。

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">

Answer 1

问题是悬停时的背景位置。减少第二个值应该可以修复闪烁（从 -8px 到 -14px 的任何值都应该有效）：

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

Answer 2

Fiddle

这里的主要问题是动画 background-position can have bad performance.

解决方案

我没有设置 background-position 的动画，而是使用 transform: translateY(-15px).

设置了单独的 div 动画

为什么这么多 `div`？

您可能想通过仅使用 <button></button> 并使用 transform 动画对 :after 进行动画处理来减少 div 的数量，但是 Chrome 有a bug that doesn't allow you to have transition, overflow: hidden, and border-radiusapplied correctly to an element (covered in this SO question).

为什么要使用 `transform`？

为了帮助体验即将发生的事情，请查看以下 JSFiddles：

（放大真的很有帮助）

More Obvious Flicker - 这个问题的原始闪烁很难发现，因为动画只需要 0.1s 所以我把它放慢到 3s
Color Contrast - 改变蓝色变体的颜色有助于说明动画中存在抖动的原因。在此示例中，您可以看到在红色部分在按钮上向上移动之前有一条黄色。这是我对您在原始问题中看到白色闪烁的原因的猜测。
Fix (with color) - 在此示例中，您可以清楚地看到由于使用了 transform: translateY(-15px)
Final Answer - 这将恢复原始颜色和动画速度

完整代码

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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