add CSS variable support

docs/pages/experiments/material-ui/list-item-icon.tsx

@@ -0,0 +1,78 @@
+import * as React from 'react';
+import {
+  Experimental_CssVarsProvider as CssVarsProvider,
+  useColorScheme,
+} from '@mui/material/styles';
+import CssBaseline from '@mui/material/CssBaseline';
+import Box from '@mui/material/Box';
+import Button from '@mui/material/Button';
+import Container from '@mui/material/Container';
+import Moon from '@mui/icons-material/DarkMode';
+import Sun from '@mui/icons-material/LightMode';
+import List from '@mui/material/List';
+import ListItem from '@mui/material/ListItem';
+import ListItemButton from '@mui/material/ListItemButton';
+import ListItemIcon from '@mui/material/ListItemIcon';
+import CommentIcon from '@mui/icons-material/Comment';
+import ListItemText from '@mui/material/ListItemText';
+
+const ColorSchemePicker = () => {
+  const { mode, setMode } = useColorScheme();
+  const [mounted, setMounted] = React.useState(false);
+  React.useEffect(() => {
+    setMounted(true);
+  }, []);
+  if (!mounted) {
+    return null;
+  }
+
+  return (
+    <Button
+      variant="outlined"
+      onClick={() => {
+        if (mode === 'light') {
+          setMode('dark');
+        } else {
+          setMode('light');
+        }
+      }}
+    >
+      {mode === 'light' ? <Moon /> : <Sun />}
+    </Button>
+  );
+};
+
+export default function CssVarsTemplate() {
+  return (
+    <CssVarsProvider>
+      <CssBaseline />
+      <Container sx={{ my: 5 }}>
+        <Box sx={{ pb: 2 }}>
+          <ColorSchemePicker />
+        </Box>
+        <Box
+          sx={{
+            display: 'grid',
+            gridTemplateColumns: 'repeat(auto-fill, minmax(256px, 1fr))',
+            gridAutoRows: 'minmax(160px, auto)',
+            gap: 2,
+            '& > div': {
+              placeSelf: 'center',
+            },
+          }}
+        >
+          <List>
+            <ListItem>
+              <ListItemButton>
+                <ListItemIcon>
+                  <CommentIcon />
+                </ListItemIcon>
+                <ListItemText primary="Test" />
+              </ListItemButton>
+            </ListItem>
+          </List>
+        </Box>
+      </Container>
+    </CssVarsProvider>
+  );
+}

packages/mui-material/src/ListItemIcon/ListItemIcon.js

@@ -27,7 +27,7 @@ const ListItemIconRoot = styled('div', {
   },
 })(({ theme, ownerState }) => ({
   minWidth: 56,
-  color: theme.palette.action.active,
+  color: (theme.vars || theme).palette.action.active,
   flexShrink: 0,
   display: 'inline-flex',
   ...(ownerState.alignItems === 'flex-start' && {