--- /dev/null
+<?php
+
+/**
+ * Plugin default_colors.
+ *
+ * Allow users to easily overrides colors of the default theme.
+ */
+
+use Shaarli\Config\ConfigManager;
+use Shaarli\Plugin\PluginManager;
+
+const DEFAULT_COLORS_PLACEHOLDERS = [
+ 'DEFAULT_COLORS_MAIN',
+ 'DEFAULT_COLORS_BACKGROUND',
+ 'DEFAULT_COLORS_DARK_MAIN',
+];
+
+/**
+ * Display an error if the plugin is active a no color is configured.
+ *
+ * @param $conf ConfigManager instance
+ *
+ * @return array|null The errors array or null of there is none.
+ */
+function default_colors_init($conf)
+{
+ $params = '';
+ foreach (DEFAULT_COLORS_PLACEHOLDERS as $placeholder) {
+ $params .= trim($conf->get('plugins.'. $placeholder, ''));
+ }
+
+ if (empty($params)) {
+ $error = t('Default colors plugin error: '.
+ 'This plugin is active and no custom color is configured.');
+ return array($error);
+ }
+}
+
+/**
+ * When plugin parameters are saved, we regenerate the custom CSS file with provided settings.
+ *
+ * @param array $data $_POST array
+ *
+ * @return array Updated $_POST array
+ */
+function hook_default_colors_save_plugin_parameters($data)
+{
+ $file = PluginManager::$PLUGINS_PATH . '/default_colors/default_colors.css';
+ $template = file_get_contents(PluginManager::$PLUGINS_PATH . '/default_colors/default_colors.css.template');
+ $content = '';
+ foreach (DEFAULT_COLORS_PLACEHOLDERS as $rule) {
+ $content .= ! empty($data[$rule])
+ ? default_colors_format_css_rule($data, $rule) .';'. PHP_EOL
+ : '';
+ }
+
+ if (! empty($content)) {
+ file_put_contents($file, sprintf($template, $content));
+ }
+
+ return $data;
+}
+
+/**
+ * When linklist is displayed, include default_colors CSS file.
+ *
+ * @param array $data - header data.
+ *
+ * @return mixed - header data with default_colors CSS file added.
+ */
+function hook_default_colors_render_includes($data)
+{
+ $file = PluginManager::$PLUGINS_PATH . '/default_colors/default_colors.css';
+ if (file_exists($file )) {
+ $data['css_files'][] = $file ;
+ }
+
+ return $data;
+}
+
+/**
+ * Create a valid CSS rule from parameters settings and plugin parameter.
+ *
+ * @param array $data $_POST array
+ * @param string $parameter Plugin parameter name
+ *
+ * @return string CSS rules for the provided parameter and its matching value.
+ */
+function default_colors_format_css_rule($data, $parameter)
+{
+ if (empty($data[$parameter])) {
+ return '';
+ }
+
+ $key = str_replace('DEFAULT_COLORS_', '', $parameter);
+ $key = str_replace('_', '-', strtolower($key)) .'-color';
+ return ' --'. $key .': '. $data[$parameter];
+}
+
+
+/**
+ * This function is never called, but contains translation calls for GNU gettext extraction.
+ */
+function default_colors_translation()
+{
+ // meta
+ t('Override default theme colors. Use any CSS valid color.');
+ t('Main color (navbar green)');
+ t('Background color (light grey)');
+ t('Dark main color (e.g. visited links)');
+}