mdb-ui-kit/scss/mixins/_forms.scss

@mixin mdb-form-color($label-color, $label-color-focus, $border-color) {

  label[class^='mdb-label'],
  label[class*=' mdb-label'] {
    color: $label-color;
  }

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

  .is-focused, // may or may not be a form-group or mdb-form-group
  &.is-focused {
    // on focus set borders and labels to the validation color

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

    label[class^='mdb-label'],
    label[class*=' mdb-label'] {
      color: $label-color-focus;
    }

    // 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;
    }

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

    .mdb-help {
      color: $mdb-label-color-inner-focus;
    }
  }
}


// must be broken out for reuse - webkit selector breaks firefox
@mixin mdb-label-static($label-top, $static-font-size, $static-line-height) {
  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 mdb-form-size-variant($font-size, $label-top-margin, $vertical-padding, $line-height, $label-as-placeholder-shim, $form-group-context: null) {
  $static-font-size: ($mdb-mdb-label-static-size-ratio * $font-size);
  $static-line-height: ($mdb-mdb-label-static-size-ratio * $line-height);

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

  $help-font-size: ($mdb-help-size-ratio * $font-size);
  $help-line-height: ($mdb-help-size-ratio * $line-height);

  @debug "font-size: #{$font-size} static-font-size: #{$static-font-size} help-font-size: #{$help-font-size} form-group-context: #{$form-group-context} ";

  // this may be inside or outside a form-group, may be .mdb-form-group.mdb-form-group-sm or .mdb-form-group.mdb-form-group-lg
  //@include label-size-variant($font-size, $vertical-padding, $line-height, $static-font-size, $static-line-height, $help-font-size);
  .form-control {
    //
    //  // 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;
  }

  input::placeholder {
    font-size: $font-size;
    line-height: $line-height;
  }

  // generic labels used anywhere in the form
  .checkbox label,
  .radio label,
  label {
    font-size: $font-size;
    line-height: $line-height;
  }

  // smaller focused or static size
  //label[class^='mdb-label'],
  //label[class*=' mdb-label'] {
  //  //font-size: $static-font-size;
  //  //line-height: $static-line-height;
  //  //margin: 16px 0 0 0; // std and lg
  //}

  // floating/placeholder default
  .mdb-label-floating,
  .mdb-label-placeholder {
    @debug "top: #{$label-as-placeholder-top}";
    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;
  }

  // floating focused/filled will look like static
  &.is-focused,
  .is-focused,
  &.is-filled,
  .is-filled {
    .mdb-label-floating {
      @include mdb-label-static($label-top, $static-font-size, $static-line-height);
    }
  }

  // static
  .mdb-label-static {
    @include mdb-label-static($label-top, $static-font-size, $static-line-height);
  }
  // #559 Fix for webkit/chrome autofill - rule must be separate because it breaks firefox otherwise #731
  //input:-webkit-autofill ~ .mdb-label-floating {  FIXME: confirm that the autofill js generation of change event makes this unnecessary
  //  @include mdb-label-static($label-top, $static-font-size, $static-line-height);
  //}

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

  @if $form-group-context {

    // 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);
  }
}

@mixin mdb-label-color-inner-focus() {
  // override bootstrap focus and keep all the standard color (could be multiple radios in the form group)
  .mdb-form-group.is-focused & {
    color: $mdb-label-color;

    // on focus just darken the specific labels, do not turn them to the brand-primary
    &:hover,
    &:focus {
      color: $mdb-label-color-inner-focus;
    }

    // correct the above focus color for disabled items
    fieldset[disabled] & {
      color: $mdb-label-color;
    }
  }
}