Follow-up to #19099 for grid fixes

- Restores two-mixin approach to generating semantic grid columns (now with 'make-col-ready' and 'make-col')
- Removes need for .col-xs-12 by restoring the mass list of all grid tier classes to set position, min-height, and padding
- Adds an initial 'width: 100%' to flexbox grid column prep (later overridden by the column sizing in 'flex' shorthand or 'width') to prevent flexbox columns from collapsing in lower viewports

2 files changed, 32 insertions, 13 deletions

diff --git a/scss/mixins/_grid-framework.scss b/scss/mixins/_grid-framework.scss
index cb25be92a..4b69c2761 100644
--- a/scss/mixins/_grid-framework.scss
+++ b/scss/mixins/_grid-framework.scss
@@ -4,22 +4,32 @@
 // any value of `$grid-columns`.
 
 @mixin make-grid-columns($columns: $grid-columns, $gutter: $grid-gutter-width, $breakpoints: $grid-breakpoints) {
+
+  // Common properties for all breakpoints
+  %grid-column {
+    position: relative;
+    // Prevent columns from collapsing when empty
+    min-height: 1px;
+    // Inner gutter via padding
+    padding-left: ($gutter / 2);
+    padding-right: ($gutter / 2);
+
+    @if $enable-flex {
+      width: 100%;
+    }
+  }
+
   $breakpoint-counter: 0;
   @each $breakpoint in map-keys($breakpoints) {
     $breakpoint-counter: ($breakpoint-counter + 1);
-    @include media-breakpoint-up($breakpoint, $breakpoints) {
-      @if $enable-flex {
-        .col-#{$breakpoint} {
-          position: relative;
-          flex-basis: 0;
-          flex-grow: 1;
-          max-width: 100%;
-          min-height: 1px;
-          padding-right: ($gutter / 2);
-          padding-left:  ($gutter / 2);
-        }
+
+    @for $i from 1 through $columns {
+      .col-#{$breakpoint}-#{$i} {
+        @extend %grid-column;
       }
+    }
 
+    @include media-breakpoint-up($breakpoint, $breakpoints) {
       @for $i from 1 through $columns {
         .col-#{$breakpoint}-#{$i} {
           @include make-col($i, $columns, $gutter);
diff --git a/scss/mixins/_grid.scss b/scss/mixins/_grid.scss
index 3ba4f43bc..87f112278 100644
--- a/scss/mixins/_grid.scss
+++ b/scss/mixins/_grid.scss
@@ -33,12 +33,21 @@
   margin-right: ($gutter / -2);
 }
 
-@mixin make-col($size, $columns: $grid-columns, $gutter: $grid-gutter-width) {
+@mixin make-col-ready($size, $columns: $grid-columns, $gutter: $grid-gutter-width) {
   position: relative;
-  min-height: 1px;
+  min-height: 1px; // Prevent collapsing
   padding-right: ($gutter / 2);
   padding-left:  ($gutter / 2);
 
+  // Prevent columns from becoming too narrow when at smaller grid tiers by
+  // always setting `width: 100%;`. This works because we use `flex` values
+  // later on to override this initial width.
+  @if $enable-flex {
+    width: 100%;
+  }
+}
+
+@mixin make-col($size, $columns: $grid-columns, $gutter: $grid-gutter-width) {
   @if $enable-flex {
     flex: 0 0 percentage($size / $columns);
     // Add a `max-width` to ensure content within each column does not blow out