mdb-ui-kit/scss/_forms.scss

// must be broken out for reuse - webkit selector breaks firefox
@mixin label-static($label-top, $static-font-size, $static-line-height) {
  label.control-label {
    top: $label-top;
    left: 0;
    // must repeat because the selector above is more specific than the general label sizing
    //font-size: $static-font-size;
    //line-height: $static-line-height;
  }
}

@mixin label-size-variant($placeholder-font-size, $vertical-padding, $line-height, $static-font-size, $static-line-height, $help-block-font-size) {
  //.form-control {
  //  @include material-placeholder {
  //    font-size: $placeholder-font-size;
  //    line-height: $line-height;
  //    font-weight: 400;
  //  }
  //
  //  // margin-bottom must be specified to give help-block vertical space.
  //  //    $see also form-group padding-bottom (and size variants) re: collapsible margins.  These work together.
  //  margin-bottom: $vertical-padding;
  //}

  // generic labels used anywhere in the form (not control-label)
  .checkbox label,
  .radio label,
  label {
    //font-size: $placeholder-font-size;
    //line-height: $line-height;
    //font-weight: 400;
  }

  // smaller focused or static size
  label.control-label {
    //font-size: $static-font-size;
    //line-height: $static-line-height;
    //margin: 16px 0 0 0; // std and lg
  }

  .help-block {
    //margin-top: 0; // allow the input margin to set-off the top of the help-block
    //font-size: $help-block-font-size;
  }
}

@mixin mdb-form-color($label-color, $border-color) {
  // Use the BS provided mixin for the bulk of the color
  @include form-control-validation($label-color);

  // Set the border and box shadow on specific inputs to match
  .form-control {
    border-color: $border-color;
  }

  // Set validation states also for addons
  .input-group-addon {
    border-color: $border-color;
  }

  label {
    color: $label-color;
  }
}

@mixin mdb-form-control-validation($name, $color) {
  // e.g. has-danger
  &.has-#{$name} {

    // override BS and keep the border-color normal/grey so that focus animation draws attention
    .form-control {
      border-color: $input-border-color;
    }

    &.is-focused {
      // on focus set borders and labels to the validation color
      @include mdb-form-color($color, $color);

      // underline animation color on focus
      .mdb-form-control-decorator {
        &::before,
        &::after {
          @include gradient-vertical($color, $input-border-color);
        }
      }
    }
  }
}

@mixin mdb-form-group-size-variant($parent, $placeholder-font-size, $label-top-margin, $vertical-padding, $line-height, $label-as-placeholder-shim) {
  $static-font-size: ceil(($mdb-label-static-size-ratio * $placeholder-font-size)) !default;
  $static-line-height: ($mdb-label-static-size-ratio * $line-height) !default;

  $label-as-placeholder-top: -1 * ($vertical-padding + $label-as-placeholder-shim) !default;
  $label-top: $label-as-placeholder-top - ($placeholder-font-size + $vertical-padding) !default;

  $help-block-font-size: ceil(($mdb-help-block-size-ratio * $placeholder-font-size)) !default;
  $help-block-line-height: ($mdb-help-block-size-ratio * $line-height) !default;

  // this is outside a form-group
  @if not $parent {
    @include label-size-variant($placeholder-font-size, $vertical-padding, $line-height, $static-font-size, $static-line-height, $help-block-font-size);
  } @else {
    // this is inside a form-group, may be .mdb-form-group.mdb-form-group-sm or .mdb-form-group.mdb-form-group-lg
    #{$parent} {
      @include label-size-variant($placeholder-font-size, $vertical-padding, $line-height, $static-font-size, $static-line-height, $help-block-font-size);

      // form-group padding-bottom
      //  upon collapsing margins, the largest margin is honored which collapses the form-control margin-bottom,
      //  so the form-control margin-bottom must also be expressed as form-group padding
      //padding-bottom: $vertical-padding;

      // FIXME: need to avoid top margin http://v4-alpha.getbootstrap.com/content/reboot/#approach
      // form-group margin-top must be large enough for the label and the label's top padding since label is absolutely positioned
      //margin: ($label-top-margin + $static-font-size) 0 0 0; // old, try padding below
      //padding-top: ($label-top-margin + $static-font-size);

      // larger labels as placeholders
      &.label-floating,
      &.label-placeholder {
        label.control-label {
          top: $label-as-placeholder-top; // place the floating label to look like a placeholder with input padding
          //font-size: $placeholder-font-size;
          //line-height: $line-height;
        }
      }

      // static, focused, or autofill floating labels
      &.label-static,
      &.label-floating.is-focused,
      &.label-floating:not(.is-empty) {
        @include label-static($label-top, $static-font-size, $static-line-height);
      }
      // #559 Fix for webkit/chrome autofill - rule must be separate because it breaks firefox otherwise #731
      &.label-floating input.form-control:-webkit-autofill ~ label.control-label {
        @include label-static($label-top, $static-font-size, $static-line-height);
      }
    }
  }
}

@include mdb-form-color($mdb-label-color, $input-border-color);
@include mdb-form-control-validation(warning, $brand-warning);
@include mdb-form-control-validation(danger, $brand-danger);
@include mdb-form-control-validation(success, $brand-success);
@include mdb-form-control-validation(info, $brand-info);

// -----
// Inputs
//
// Reference http://www.google.com/design/spec/components/text-fields.html
// MDL implementation: http://www.getmdl.io/components/index.html#textfields-section
.form-control {
  // The border bottom should be static in all states, the decorator will be animated over this.
  &,
  &:focus,
  .mdb-form-group.is-focused & {
    border: 0;
    border-bottom: $input-border-width solid $input-border-color;
  }

  &[disabled],
  fieldset[disabled] & {
    border-bottom: $input-border-width dotted $input-border-color;
  }
}

// Focus underline animation =================================
.mdb-form-control-decorator {
  position: relative;
  top: (-1 * $input-border-width); // move the top up enough to overlay the border from the input
  display: block;
  &::before,
  &::after {
    position: absolute;
    width: 0;
    height: $input-border-width;
    content: "";
    @include gradient-vertical($brand-primary, $input-border-color);
    transition: 0.3s ease all;

    // focused state - it transitions the width of each (before and after) to 50% creating the center out effect
    .form-control:focus ~ &,
    .mdb-form-group.is-focused .form-control ~ & {
      width: 50%;
    }
  }
  &::before {
    left: 50%;
  }
  &::after {
    right: 50%;
  }
}

// End: Focus underline animation =================================

// -----
// Labels with mdb-form-group signalled state
//
// Reference http://www.google.com/design/spec/components/text-fields.html
// MDL implementation: http://www.getmdl.io/components/index.html#textfields-section
//.variations(unquote(" label.control-label"), color, $mdb-input-placeholder-color);  // default label color variations

.mdb-form-group {
  position: relative;

  // -----
  // Labels with form-group signalled state
  //
  // Reference http://www.google.com/design/spec/components/text-fields.html
  // MDL implementation: http://www.getmdl.io/components/index.html#textfields-section
  &.label-static,
  &.label-placeholder,
  &.label-floating {
    label.control-label {
      //position: absolute;
      //pointer-events: none;
      //transition: 0.3s ease all;
    }
  }

  // hint to browser for optimization
  //    TODO: evaluate effectiveness - looking for community feedback
  &.label-floating label.control-label {
    //will-change: left, top, contents;
  }

  // hide label-placeholders when the field is not empty
  &.label-placeholder:not(.is-empty) {
    label.control-label {
      display: none;
    }
  }

  // Help blocks - position: absolute approach - uses no vertical space, text wrapping - not so good.
  .help-block {
    //position: absolute; // do not use position: absolute because width/wrapping isn't automatic and overflows occur
    //display: none;
  }

  // form-group is-focused display
  &.is-focused {

    label,
    label.control-label {
      color: $brand-primary;
    }

    &.label-placeholder {
      label,
      label.control-label {
        //color: $mdb-input-placeholder-color;
      }
    }

    //.help-block {
    //  display: block;
    //}
  }

  //textarea {
  //  resize: none;
  //}
}

select {
  &,
  &.form-control {
    // Use vendor prefixes as `appearance` isn't part of the CSS spec. OSX doesn't obey the border-radius: 0 without this.
    -moz-appearance: none;
    -webkit-appearance: none;
  }
}

// default floating size/location without a form-group (will skip form-group styles, and just render default sizing variation)
@include mdb-form-group-size-variant(null, $font-size-base, $mdb-label-top-margin-base, $mdb-input-padding-y-base, $line-height, $mdb-label-as-placeholder-shim-base);

// default floating size/location with a form-group (need margin etc from a default form-group)
@include mdb-form-group-size-variant(unquote(".mdb-form-group"), $font-size-base, $mdb-label-top-margin-base, $mdb-input-padding-y-base, $line-height, $mdb-label-as-placeholder-shim-base);

// sm floating size/location
@include mdb-form-group-size-variant(unquote(".mdb-form-group.mdb-form-group-sm"), $font-size-sm, $mdb-label-top-margin-sm, $mdb-input-padding-y-sm, $line-height-sm, $mdb-label-as-placeholder-shim-sm);

// lg floating size/location
@include mdb-form-group-size-variant(unquote(".mdb-form-group.mdb-form-group-lg"), $font-size-lg, $mdb-label-top-margin-lg, $mdb-input-padding-y-lg, $line-height-lg, $mdb-label-as-placeholder-shim-lg);


// Input files - hide actual input - requires specific markup in the sample.
//.mdb-form-group input[type=file] {
//  opacity: 0;
//  position: absolute;
//  top: 0;
//  right: 0;
//  bottom: 0;
//  left: 0;
//  width: 100%;
//  height: 100%;
//  z-index: 100;
//}

//  I don't think this was in use...
//legend {
//  border-bottom: 0;
//}
//
//
//.form-horizontal {
//
//  // Consistent vertical alignment of radios and checkboxes
//  .radio,
//  .checkbox,
//  .radio-inline,
//  .checkbox-inline {
//    padding-top: 0;
//  }
//
//  .radio {
//    margin-bottom: 10px;
//  }
//
//  label {
//    text-align: right;
//  }
//
//  label.control-label {
//    margin: 0;
//  }
//}