Fix #234 pick up images from inline style background image.

classes/local/controllers/maintenance_static_page_generator.php

@@ -43,6 +43,15 @@ defined('MOODLE_INTERNAL') || die();
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class maintenance_static_page_generator {
+    /** PATTERN
+     * The pattern should match the attribute values that
+     * go as 'url(xxxxx)', but make sure 'url(data:xxxxx)' is not
+     * rewritten. Must be case insensitive to match 'URL(xxxxx)'.
+     * It should be possible to specify other background attributes as
+     * 'background: color url(xxxxx) no-repeat'.
+     */
+    protected const PATTERN = '/url\s*\(\s*[\'"]?(?![\'"]?data:)([^\s\'"]+)[\'"]?\s*\)/i';
+
     /** @var DOMDocument */
     protected $dom;
 
@@ -83,6 +92,7 @@ class maintenance_static_page_generator {
             $this->update_link_favicon();
             $this->update_images();
             $this->remove_configured_css_selectors();
+            $this->update_inline_background_images();
 
             $html = $this->dom->saveHTML();
             if (trim($html) == '') {
@@ -150,6 +160,18 @@ class maintenance_static_page_generator {
         return $matches;
     }
 
+    /**
+     * Retrieves a URL from inline style using regular expressions.
+     *
+     * @param string $style Content of the style attribute
+     * @return array Array containing match
+     */
+    public function get_url_from_inline_style($style) {
+        preg_match(self::PATTERN, $style, $match);
+        return $match;
+    }
+
+
     /**
      * Checks for urls inside filename.
      *
@@ -218,6 +240,31 @@ class maintenance_static_page_generator {
         }
     }
 
+    /**
+     * Fetch and fixes all inline background images.
+     */
+    private function update_inline_background_images() {
+        global $CFG;
+        $xpath = new \DOMXPath($this->dom);
+        $elements = $xpath->query("//*[@style]");
+
+        foreach ($elements as $element) {
+            $style = $element->getAttribute("style");
+            $matches = $this->get_url_from_inline_style($style);
+            if (isset($matches[1])) {
+                // Allow incomplete URLs in style, assume it is from moodle root.
+                if (maintenance_static_page_io::is_url($matches[1])) {
+                    $fullurl = $matches[1];
+                } else {
+                    $fullurl = (string) new moodle_url($matches[1]);
+                }
+                $newurl = $this->io->generate_file_url($fullurl);
+                $updated = preg_replace(self::PATTERN, ' url('.$newurl.') ', $style);
+                $element->setAttribute('style', $updated);
+            }
+        }
+    }
+
     /**
      * Remove from DOM the CSS selectores defined in the plugin settings.
      */

tests/phpunit/local/controllers/maintenance_static_page_test.php

@@ -193,6 +193,60 @@ class maintenance_static_page_test extends auth_outage_base_testcase {
         self::assertStringContainsString('www.example.com/moodle/auth/outage/file.php?file=', $generated);
     }
 
+
+    /**
+     * Data provider for test_update_inline_background_images
+     * @return array
+     */
+    public function test_update_inline_background_images_provider() {
+        return [
+            // Empty string.
+            ["", false],
+            // URLs that should be retrieved.
+            ["color: #FF00FF; background: lightblue url(/pluginfile.php/1/theme_custom/banner/251298630/0001.png) no-repeat", true],
+            ["background: lightblue url(https://www.example.com/moodle/pluginfile.php/1/theme_custom/banner/251298630/0001.png) no-repeat", true],
+            ["background:url('https://www.example.com/moodle/pluginfile.php/1/theme_custom/banner/251298630/0001.png')", true],
+            ["background-image : url( /pix/help.png);", true],
+            ["background-image: url ('/pix/help.png')", true],
+            // URLs that should not be retrieved.
+            ["background-image:url(data:image/gif;base64,R0lGODlhYADIAP=)", false],
+            ["background-image:url('data:image/gif;base64,R0lGODlhYADIAP=')", false]
+        ];
+    }
+
+    /**
+     * Tests update_inline_background_images() method to update the background images.
+     *
+     * @dataProvider test_update_inline_background_images_provider
+     * @param string $stylecontent Content of the style to test
+     * @param bool $rewrite Flag if URL should be rewritten
+     * @throws coding_exception
+     */
+    public function test_update_inline_background_images($stylecontent, $rewrite) {
+        global $CFG;
+        $this->resetAfterTest(true);
+        $generator = new maintenance_static_page_generator(new DOMDocument(), new maintenance_static_page_io());
+
+        $html = '<!DOCTYPE html>\n'.
+            '<html><head><title>Title</title></head>'.
+            '<body><div style="'.$stylecontent.'">Content</div></body></html>';
+
+        // Temporarily disable debugging to prevent errors because file does not exist
+        $debuglevel = $CFG->debug;
+        $CFG->debug = '';
+        $generated = $this->generated_page_html($html);
+        // Restore debugging level
+        $CFG->debug = $debuglevel;
+        $matches = $generator->get_url_from_inline_style($stylecontent);
+        if ($rewrite) {
+            self::assertStringNotContainsString($matches[1], $generated);
+            self::assertStringContainsString('www.example.com/moodle/auth/outage/file.php?file=', $generated);
+            self::assertIsArray($matches);
+        } else {
+            self::assertStringContainsString($stylecontent, $generated);
+        }
+    }
+
      /**
       * Test update preview path to file.php style link.
       */