前端代码

node_modules/bootstrap/scss/forms/_floating-labels.scss

@@ -0,0 +1,97 @@
+.form-floating {
+  position: relative;
+
+  > .form-control,
+  > .form-control-plaintext,
+  > .form-select {
+    height: $form-floating-height;
+    min-height: $form-floating-height;
+    line-height: $form-floating-line-height;
+  }
+
+  > label {
+    position: absolute;
+    top: 0;
+    left: 0;
+    z-index: 2;
+    max-width: 100%;
+    height: 100%; // allow textareas
+    padding: $form-floating-padding-y $form-floating-padding-x;
+    overflow: hidden;
+    color: rgba(var(--#{$prefix}body-color-rgb), #{$form-floating-label-opacity});
+    text-align: start;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+    pointer-events: none;
+    border: $input-border-width solid transparent; // Required for aligning label's text with the input as it affects inner box model
+    transform-origin: 0 0;
+    @include transition($form-floating-transition);
+  }
+
+  > .form-control,
+  > .form-control-plaintext {
+    padding: $form-floating-padding-y $form-floating-padding-x;
+
+    &::placeholder {
+      color: transparent;
+    }
+
+    &:focus,
+    &:not(:placeholder-shown) {
+      padding-top: $form-floating-input-padding-t;
+      padding-bottom: $form-floating-input-padding-b;
+    }
+    // Duplicated because `:-webkit-autofill` invalidates other selectors when grouped
+    &:-webkit-autofill {
+      padding-top: $form-floating-input-padding-t;
+      padding-bottom: $form-floating-input-padding-b;
+    }
+  }
+
+  > .form-select {
+    padding-top: $form-floating-input-padding-t;
+    padding-bottom: $form-floating-input-padding-b;
+    padding-left: $form-floating-padding-x;
+  }
+
+  > .form-control:focus,
+  > .form-control:not(:placeholder-shown),
+  > .form-control-plaintext,
+  > .form-select {
+    ~ label {
+      transform: $form-floating-label-transform;
+    }
+  }
+  // Duplicated because `:-webkit-autofill` invalidates other selectors when grouped
+  > .form-control:-webkit-autofill {
+    ~ label {
+      transform: $form-floating-label-transform;
+    }
+  }
+  > textarea:focus,
+  > textarea:not(:placeholder-shown) {
+    ~ label::after {
+      position: absolute;
+      inset: $form-floating-padding-y ($form-floating-padding-x * .5);
+      z-index: -1;
+      height: $form-floating-label-height;
+      content: "";
+      background-color: $input-bg;
+      @include border-radius($input-border-radius);
+    }
+  }
+  > textarea:disabled ~ label::after {
+    background-color: $input-disabled-bg;
+  }
+
+  > .form-control-plaintext {
+    ~ label {
+      border-width: $input-border-width 0; // Required to properly position label text - as explained above
+    }
+  }
+
+  > :disabled ~ label,
+  > .form-control:disabled ~ label { // Required for `.form-control`s because of specificity
+    color: $form-floating-label-disabled-color;
+  }
+}