API Add getContentCSS() / setContentCSS() to allow per-config customisation of content_css

Fixes #7873

docs/en/02_Developer_Guides/15_Customising_the_Admin_Interface/05_Typography.md

@@ -17,6 +17,13 @@ SilverStripe\Forms\HTMLEditor\TinyMCEConfig:
 
 Will load the `mysite/css/editor.css` file.
 
+Alternatively, you can set this on a specific `TinyMCEConfig` instance via `setContentCSS` method.
+
+```php
+$config = new TinyMCEConfig();
+$config->setContentCSS([ '/mysite/client/css/editor.css' ]);
+```
+
 ## Custom style dropdown
 
 The custom style dropdown can be enabled via the `importcss` plugin bundled with admin module. ([Doc](https://www.tinymce.com/docs/plugins/importcss/))  

src/Forms/HTMLEditor/HTMLEditorConfig.php

@@ -20,7 +20,7 @@ use SilverStripe\Core\Injector\Injectable;
  *
  * Typically global config changes should set the active config.
  *
- * The defaut config class can be changed via dependency injection to replace HTMLEditorConfig.
+ * The default config class can be changed via dependency injection to replace HTMLEditorConfig.
  *
  * @author "Hamish Friedlander" <hamish@silverstripe.com>
  */
@@ -59,7 +59,7 @@ abstract class HTMLEditorConfig
      * @var array
      */
     private static $user_themes = [];
-    
+
     /**
      * List of the current themes set for this config
      *
@@ -103,7 +103,7 @@ abstract class HTMLEditorConfig
         }
         return $config;
     }
-    
+
     /**
      * Gets the current themes, if it is not set this will fallback to config
      * @return array
@@ -115,7 +115,7 @@ abstract class HTMLEditorConfig
         }
         return Config::inst()->get(static::class, 'user_themes');
     }
-    
+
     /**
      * Sets the current theme
      *
@@ -125,7 +125,7 @@ abstract class HTMLEditorConfig
     {
         static::$current_themes = $themes;
     }
-    
+
     /**
      * Set the currently active configuration object. Note that the existing active
      * config will not be renamed to the new identifier.

src/Forms/HTMLEditor/TinyMCEConfig.php

@@ -202,6 +202,13 @@ class TinyMCEConfig extends HTMLEditorConfig
      */
     private static $editor_css = [];
 
+    /**
+     * List of content css files to use for this instance, or null to default to editor_css config.
+     *
+     * @var string[]|null
+     */
+    protected $contentCSS = null;
+
     /**
      * TinyMCE JS settings
      *
@@ -621,20 +628,42 @@ class TinyMCEConfig extends HTMLEditorConfig
     }
 
     /**
-     * Get location of all editor.css files
+     * Get location of all editor.css files.
+     * All resource specifiers are resolved to urls.
      *
      * @return array
      */
     protected function getEditorCSS()
     {
-        $editor = array();
+        $editor = [];
+        $resourceLoader = ModuleResourceLoader::singleton();
+        foreach ($this->getContentCSS() as $contentCSS) {
+            $editor[] = $resourceLoader->resolveURL($contentCSS);
+        }
+        return $editor;
+    }
+
+    /**
+     * Get list of resource paths to css files.
+     *
+     * Will default to `editor_css` config, as well as any themed `editor.css` files.
+     * Use setContentCSS() to override.
+     *
+     * @return string[]
+     */
+    public function getContentCSS()
+    {
+        // Prioritise instance specific content
+        if (isset($this->contentCSS)) {
+            return $this->contentCSS;
+        }
 
         // Add standard editor.css
+        $editor = [];
         $editorCSSFiles = $this->config()->get('editor_css');
-        $resourceLoader = ModuleResourceLoader::singleton();
         if ($editorCSSFiles) {
             foreach ($editorCSSFiles as $editorCSS) {
-                $editor[] = $resourceLoader->resolveURL($editorCSS);
+                $editor[] = $editorCSS;
             }
         }
 
@@ -642,12 +671,27 @@ class TinyMCEConfig extends HTMLEditorConfig
         $themes = HTMLEditorConfig::getThemes() ?: SSViewer::get_themes();
         $themedEditor = ThemeResourceLoader::inst()->findThemedCSS('editor', $themes);
         if ($themedEditor) {
-            $editor[] = $resourceLoader->resolveURL($themedEditor);
+            $editor[] = $themedEditor;
         }
-
         return $editor;
     }
 
+    /**
+     * Set explicit set of CSS resources to use for `content_css` option.
+     *
+     * Note: If merging with default paths, you should call getContentCSS() and merge
+     * prior to assignment.
+     *
+     * @param string[] $css Array of resource paths. Supports module prefix,
+     * e.g. `silverstripe/admin:client/dist/styles/editor.css`
+     * @return $this
+     */
+    public function setContentCSS($css)
+    {
+        $this->contentCSS = $css;
+        return $this;
+    }
+
     /**
      * Generate gzipped TinyMCE configuration including plugins and languages.
      * This ends up "pre-loading" TinyMCE bundled with the required plugins

tests/php/Forms/HTMLEditor/TinyMCEConfigTest.php

@@ -37,4 +37,28 @@ class TinyMCEConfigTest extends SapphireTest
             }
         }
     }
+
+    public function testGetContentCSS()
+    {
+        TinyMCEConfig::config()->set('editor_css', [
+            'silverstripe/framework:tests/php/Forms/HTMLEditor.css'
+        ]);
+
+        // Test default config
+        $config = new TinyMCEConfig();
+        $this->assertContains('silverstripe/framework:tests/php/Forms/HTMLEditor.css', $config->getContentCSS());
+
+        // Test manual disable
+        $config->setContentCSS([]);
+        $this->assertEmpty($config->getContentCSS());
+
+        // Test replacement config
+        $config->setContentCSS([
+            'silverstripe/framework:tests/php/Forms/HTMLEditor_another.css'
+        ]);
+        $this->assertEquals(
+            [ 'silverstripe/framework:tests/php/Forms/HTMLEditor_another.css'],
+            $config->getContentCSS()
+        );
+    }
 }