Optional btn & input font sizes (#28068)

scss/_buttons.scss

@@ -6,6 +6,7 @@
 
 .btn {
   display: inline-block;
+  font-family: $btn-font-family;
   font-weight: $btn-font-weight;
   color: $body-color;
   text-align: center;

scss/_custom-forms.scss

@@ -214,6 +214,7 @@
   width: 100%;
   height: $custom-select-height;
   padding: $custom-select-padding-y ($custom-select-padding-x + $custom-select-indicator-padding) $custom-select-padding-y $custom-select-padding-x;
+  font-family: $custom-select-font-family;
   font-size: $custom-select-font-size;
   font-weight: $custom-select-font-weight;
   line-height: $custom-select-line-height;
@@ -329,6 +330,7 @@
   z-index: 1;
   height: $custom-file-height;
   padding: $custom-file-padding-y $custom-file-padding-x;
+  font-family: $custom-file-font-family;
   font-weight: $custom-file-font-weight;
   line-height: $custom-file-line-height;
   color: $custom-file-color;

scss/_forms.scss

@@ -9,6 +9,7 @@
   width: 100%;
   height: $input-height;
   padding: $input-padding-y $input-padding-x;
+  font-family: $input-font-family;
   font-size: $input-font-size;
   font-weight: $input-font-weight;
   line-height: $input-line-height;

scss/_variables.scss

@@ -381,6 +381,7 @@ $table-border-level:          -6 !default;
 
 $input-btn-padding-y:         .375rem !default;
 $input-btn-padding-x:         .75rem !default;
+$input-btn-font-family:       null !default;
 $input-btn-font-size:         $font-size-base !default;
 $input-btn-line-height:       $line-height-base !default;
 
@@ -407,6 +408,7 @@ $input-btn-border-width:      $border-width !default;
 
 $btn-padding-y:               $input-btn-padding-y !default;
 $btn-padding-x:               $input-btn-padding-x !default;
+$btn-font-family:             $input-btn-font-family !default;
 $btn-font-size:               $input-btn-font-size !default;
 $btn-line-height:             $input-btn-line-height !default;
 
@@ -447,6 +449,7 @@ $label-margin-bottom:                   .5rem !default;
 
 $input-padding-y:                       $input-btn-padding-y !default;
 $input-padding-x:                       $input-btn-padding-x !default;
+$input-font-family:                     $input-btn-font-family !default;
 $input-font-size:                       $input-btn-font-size !default;
 $input-font-weight:                     $font-weight-base !default;
 $input-line-height:                     $input-btn-line-height !default;
@@ -559,6 +562,7 @@ $custom-switch-indicator-size:                  calc(#{$custom-control-indicator
 
 $custom-select-padding-y:           $input-padding-y !default;
 $custom-select-padding-x:           $input-padding-x !default;
+$custom-select-font-family:         $input-font-family !default;
 $custom-select-font-size:           $input-font-size !default;
 $custom-select-height:              $input-height !default;
 $custom-select-indicator-padding:   1rem !default; // Extra padding to account for the presence of the background-image based indicator
@@ -623,6 +627,7 @@ $custom-file-disabled-bg:           $input-disabled-bg !default;
 $custom-file-padding-y:             $input-padding-y !default;
 $custom-file-padding-x:             $input-padding-x !default;
 $custom-file-line-height:           $input-line-height !default;
+$custom-file-font-family:           $input-font-family !default;
 $custom-file-font-weight:           $input-font-weight !default;
 $custom-file-color:                 $input-color !default;
 $custom-file-bg:                    $input-bg !default;