From 913f51f15e61a5e6f2a8da799763ad72606f8c22 Mon Sep 17 00:00:00 2001
From: Thilo Molitor <thilo@eightysoft.de>
Date: Mon, 7 Aug 2023 05:19:01 +0200
Subject: [PATCH] Implement css vars

May be a dirty hack, but it works well.
---
 src/Css/Style.php | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/Css/Style.php b/src/Css/Style.php
index 1cd89f42d..ebf0b9768 100644
--- a/src/Css/Style.php
+++ b/src/Css/Style.php
@@ -1248,7 +1248,8 @@ public function set_prop(string $prop, $val, bool $important = false, bool $clea
             $prop = self::$_props_alias[$prop];
         }
 
-        if (!isset(self::$_defaults[$prop])) {
+        // props beginning with "--" (changed above to "__") are css variables --> always allow them
+        if (!isset(self::$_defaults[$prop]) && !substr($prop, 0, 2) == '__') {
             global $_dompdf_warnings;
             $_dompdf_warnings[] = "'$prop' is not a recognized CSS property.";
             return;
@@ -1367,7 +1368,8 @@ public function get_specified(string $prop)
             $prop = self::$_props_alias[$prop];
         }
 
-        if (!isset(self::$_defaults[$prop])) {
+        // props beginning with "--" (changed in set_prop() to "__") are css variables --> always allow them
+        if (!isset(self::$_defaults[$prop]) && !substr($prop, 0, 2) == '__') {
             throw new Exception("'$prop' is not a recognized CSS property.");
         }
 
@@ -1508,6 +1510,12 @@ public function __get(string $prop)
      */
     protected function compute_prop(string $prop, $val)
     {
+        // handle css var() functions as already computed (late binding)
+        // TODO: extend to calc() and other css functons?
+        if(is_string($val) && substr($val, 0, 4) == 'var(') {
+            return $val;
+        }
+
         // During style merge, the parent style is not available yet, so
         // temporarily use the initial value for `inherit` properties. The
         // keyword is properly resolved during inheritance
@@ -1551,6 +1559,23 @@ protected function computed(string $prop)
             $this->_props_computed[$prop] = $computed;
         }
 
+        // now compute value of css var access (late binding)
+        if(isset($this->_props_computed[$prop])) {
+            $value = $this->_props_computed[$prop];
+            if(!is_array($value)) {
+		    $value = [$value];
+            }
+            foreach($value as &$part) {
+                if(is_string($part) && substr($part, 0, 4) == 'var(') {
+                    $css_var = str_replace("-", "_", substr(trim($part), 4, -1));
+                    $part = $this->get_specified($css_var) ?? (isset($this->parent_style) ? $this->parent_style->get_specified($css_var) : null);
+		}
+            }
+            if(!is_array($this->_props_computed[$prop])) {
+                $this->_props_computed[$prop] = $value[0];
+            }
+        }
+
         return $this->_props_computed[$prop];
     }