Add and document additional :root CSS variables

- Adds grayscale colors
- Adds root and body variables

Note that some Sass variables default to `null`, so as we generate and use the CSS variable, we'll be potentially adding some lines of code.

2 files changed, 43 insertions, 10 deletions

diff --git a/scss/_reboot.scss b/scss/_reboot.scss
index 3520469883..80bfffb6e6 100644
--- a/scss/_reboot.scss
+++ b/scss/_reboot.scss
@@ -26,7 +26,9 @@
 // null by default, thus nothing is generated.
 
 :root {
-  font-size: $font-size-root;
+  @if $font-size-root != null {
+    font-size: var(--#{$variable-prefix}-root-font-size);
+  }
 
   @if $enable-smooth-scroll {
     @media (prefers-reduced-motion: no-preference) {
@@ -43,18 +45,20 @@
 // 3. Prevent adjustments of font size after orientation changes in iOS.
 // 4. Change the default tap highlight to be completely transparent in iOS.
 
+// scss-docs-start reboot-body-rules
 body {
   margin: 0; // 1
-  font-family: $font-family-base;
-  @include font-size($font-size-base);
-  font-weight: $font-weight-base;
-  line-height: $line-height-base;
-  color: $body-color;
-  text-align: $body-text-align;
-  background-color: $body-bg; // 2
+  font-family: var(--#{$variable-prefix}body-font-family);
+  @include font-size(var(--#{$variable-prefix}body-font-size));
+  font-weight: var(--#{$variable-prefix}body-font-weight);
+  line-height: var(--#{$variable-prefix}body-line-height);
+  color: var(--#{$variable-prefix}body-color);
+  text-align: var(--#{$variable-prefix}body-text-align);
+  background-color: var(--#{$variable-prefix}body-bg); // 2
   -webkit-text-size-adjust: 100%; // 3
   -webkit-tap-highlight-color: rgba($black, 0); // 4
 }
+// scss-docs-end reboot-body-rules
 
 
 // Content grouping
diff --git a/scss/_root.scss b/scss/_root.scss
index 95c7739011..189b2b3bbe 100644
--- a/scss/_root.scss
+++ b/scss/_root.scss
@@ -1,9 +1,18 @@
 :root {
-  // Custom variable values only support SassScript inside `#{}`.
+  // Note: Custom variable values only support SassScript inside `#{}`.
+
+  // Colors
+  //
+  // Generate palettes for full colors, grays, and theme colors.
+
   @each $color, $value in $colors {
     --#{$variable-prefix}#{$color}: #{$value};
   }
 
+  @each $color, $value in $grays {
+    --#{$variable-prefix}gray-#{$color}: #{$value};
+  }
+
   @each $color, $value in $theme-colors {
     --#{$variable-prefix}#{$color}: #{$value};
   }
@@ -16,9 +25,29 @@
   --#{$variable-prefix}black-rgb: #{to-rgb($black)};
   --#{$variable-prefix}body-rgb: #{to-rgb($body-color)};
 
-  // Use `inspect` for lists so that quoted items keep the quotes.
+  // Fonts
+
+  // Note: Use `inspect` for lists so that quoted items keep the quotes.
   // See https://github.com/sass/sass/issues/2383#issuecomment-336349172
   --#{$variable-prefix}font-sans-serif: #{inspect($font-family-sans-serif)};
   --#{$variable-prefix}font-monospace: #{inspect($font-family-monospace)};
   --#{$variable-prefix}gradient: #{$gradient};
+
+  // Root and body
+  // stylelint-disable custom-property-empty-line-before
+  // scss-docs-start root-body-variables
+  @if $font-size-root != null {
+    --#{$variable-prefix}root-font-size: #{$font-size-root};
+  }
+  --#{$variable-prefix}body-font-family: #{$font-family-base};
+  --#{$variable-prefix}body-font-size: #{$font-size-base};
+  --#{$variable-prefix}body-font-weight: #{$font-weight-base};
+  --#{$variable-prefix}body-line-height: #{$line-height-base};
+  --#{$variable-prefix}body-color: #{$body-color};
+  @if $body-text-align != null {
+    --#{$variable-prefix}body-text-align: #{$body-text-align};
+  }
+  --#{$variable-prefix}body-bg: #{$body-bg};
+  // scss-docs-end root-body-variables
+  // stylelint-enable custom-property-empty-line-before
 }