作者:老葛,北京亚艾元软件有限责任公司,http://www.yaiyuan.com
现在,整个$page数组已经构建完成了,Drupal是怎么把它转为HTML页面的呢?注意这里的这个数组的类型是page,这个和表单元素数组,是一样的。Drupal6里面的表单数组,在Drupal7下,概念上做了进一步的扩充,除了表单元素以外,区块、节点、页面都是以呈现数组的形式出现。所有的呈现数组,经过drupal_render函数处理,就会转换成对应HTML形式。我们来看一下drupal_render的定义。
function drupal_render(&$elements) {
// Early-return nothing if user does not have access.
if (empty($elements) || (isset($elements['#access']) && !$elements['#access'])) {
return;
}
// Do not print elements twice.
if (!empty($elements['#printed'])) {
return;
}
// Try to fetch the element's markup from cache and return.
if (isset($elements['#cache'])) {
$cached_output = drupal_render_cache_get($elements);
if ($cached_output !== FALSE) {
return $cached_output;
}
}
// If #markup is set, ensure #type is set. This allows to specify just #markup
// on an element without setting #type.
if (isset($elements['#markup']) && !isset($elements['#type'])) {
$elements['#type'] = 'markup';
}
// If the default values for this element have not been loaded yet, populate
// them.
if (isset($elements['#type']) && empty($elements['#defaults_loaded'])) {
$elements += element_info($elements['#type']);
}
// Make any final changes to the element before it is rendered. This means
// that the $element or the children can be altered or corrected before the
// element is rendered into the final text.
if (isset($elements['#pre_render'])) {
foreach ($elements['#pre_render'] as $function) {
if (function_exists($function)) {
$elements = $function($elements);
}
}
}
// Allow #pre_render to abort rendering.
if (!empty($elements['#printed'])) {
return;
}
// Get the children of the element, sorted by weight.
$children = element_children($elements, TRUE);
// Initialize this element's #children, unless a #pre_render callback already
// preset #children.
if (!isset($elements['#children'])) {
$elements['#children'] = '';
}
// Call the element's #theme function if it is set. Then any children of the
// element have to be rendered there.
if (isset($elements['#theme'])) {
$elements['#children'] = theme($elements['#theme'], $elements);
}
// If #theme was not set and the element has children, render them now.
// This is the same process as drupal_render_children() but is inlined
// for speed.
if ($elements['#children'] == '') {
foreach ($children as $key) {
$elements['#children'] .= drupal_render($elements[$key]);
}
}
// Let the theme functions in #theme_wrappers add markup around the rendered
// children.
if (isset($elements['#theme_wrappers'])) {
foreach ($elements['#theme_wrappers'] as $theme_wrapper) {
$elements['#children'] = theme($theme_wrapper, $elements);
}
}
// Filter the outputted content and make any last changes before the
// content is sent to the browser. The changes are made on $content
// which allows the output'ed text to be filtered.
if (isset($elements['#post_render'])) {
foreach ($elements['#post_render'] as $function) {
if (function_exists($function)) {
$elements['#children'] = $function($elements['#children'], $elements);
}
}
}
// Add any JavaScript state information associated with the element.
if (!empty($elements['#states'])) {
drupal_process_states($elements);
}
// Add additional libraries, CSS, JavaScript an other custom
// attached data associated with this element.
if (!empty($elements['#attached'])) {
drupal_process_attached($elements);
}
$prefix = isset($elements['#prefix']) ? $elements['#prefix'] : '';
$suffix = isset($elements['#suffix']) ? $elements['#suffix'] : '';
$output = $prefix . $elements['#children'] . $suffix;
// Cache the processed element if #cache is set.
if (isset($elements['#cache'])) {
drupal_render_cache_set($output, $elements);
}
$elements['#printed'] = TRUE;
return $output;
}
这里面注意缓存的相关代码,Drupal缓存无处不在。另外需要注意的是,呈现数组,就是一个树状结构,一个枝干下面会有子枝干,子枝干下面又有子枝干,一直递归下去,最后是树叶。将呈现数组转为HTML的时候,也是这样递归调用的,最先转成HTML的,就是最小的单元组成部分,慢慢地合成,最后整个呈现数组彻底转为HTML。