How Press This Works

If you log into WordPress and navigate to Settings -> Writing you will find a heading for “Press This” which instructs you to drag a link into the bookmarks bar in your browser. What you are bookmarking is not really a link but a small javascript application known as a bookmarklet. You can now navigate to any webpage and when you click your Press This bookmarklet a popup window will open which displays a form allowing you to publish a post about the page. What impressed me here is that certain fields are already filled out:

1. The title tag of the html document is inserted as the value of the post title.
2. If any text was selected, it is inserted into the content box
3. A link to the document is appended to the content box.

What I Need to Do

1. I need to create a bookmark and not a post.
2. I need to automatically set the title.
3. I need all custom taxonomies to display.
4. I need to set the name and value of a custom field.

On my site I have one custom post_type registered (mfields_bookmark) which I use to archive interesting articles about web development that I have read. Unfortunately, Press This only seems to enable you to create “posts”. My initial idea was to create a custom popup window by copying the code from press-this.php into a custom function which would be triggered via admin-ajax.php. Seemed like a good idea, but it also sounded like a lot of work! After thinking about it, I really didn’t need the popup window, I would be happy if my bookmarklet just opened post-new.php in a new tab. So I started hacking post-new.php's query string to see if the post form would recognize any values… And it did!

Post Title

The post title can be injected by setting a value to post_title. Something Like this works rather well: /wp-admin/post-new.php?post_title=TITLE

Although, I will not need to set the content here, I found that it can easily be set in much the same way: /wp-admin/post-new.php?content=CONTENT

Custom Field

I only need one custom field to be defined for a bookmark post to function properly. I couldn’t find any hooks that I could use in core so I decided to try a bit of javascript. I came up with the following code which I added to my theme’s functions.php file:

add_action( 'admin_head-post-new.php', 'mfields_process_bookmark_bookmarklet' );

function mfields_process_bookmark_bookmarklet() {
	global $post;
	if ( isset( $post->post_type ) && 'mfields_bookmark' === $post->post_type && isset( $_GET['mfields_bookmark_url'] ) ) {
		$url = esc_url( $_GET['mfields_bookmark_url'] );
		print <<< EOF
		<script type="text/javascript">
		jQuery( document ).ready( function ( $ ) {
			$( '#metakeyselect' ).val( 'resource_url' );
			$( '#metavalue' ).text( '{$url}' );
		} );
		</script>
EOF;
	}
}

This function will fire during the admin_head action on post-new.php for the mfields_bookmark post_type. If mfields_bookmark_url is defined in the query string, the function will automatically select it as the name from the select box. Likewise, the value of mfields_bookmark_url will be used as the value of the custom field.

Creating the Bookmarklet

Now that WordPress has been configured to recognize this custom information, I needed to create an easy way of sending it. I copied the Press This javascript and reworked it to talk to post-new.php.

javascript:(
	function(){
		var title = encodeURIComponent( document.title ),
		bookmark = encodeURIComponent( document.location.href ),
		url = 'http://example.com/wp-admin/post-new.php?post_type=mfields_bookmark&mfields_bookmark_url=' + bookmark + '&post_title=' + title;
		window.open(url);
	}
)();

Basically when you call this function, it will open post-new.php in a new tab sending the title and url of the document you were just viewing as well as setting the value of post_type to mfields_bookmark.

Adding this code to your browser is simple. In Chrome you can right-click the bookmarks toolbar and select Add Page…. Type “Bookmark This” as the name and use the javascript as the url. It might be a good idea to have the script on one line like this:

javascript:(function(){ var title = encodeURIComponent( document.title ), bookmark = encodeURIComponent( document.location.href ), url = 'http://example.com/wp-admin/post-new.php?post_type=mfields_bookmark&mfields_bookmark_url=' + bookmark + '&post_title=' + title; window.open(url); })();

I hope that someone out there finds this useful. I’m pretty excited about it as it will really cut down the steps involved in posting bookmarks on my site.

The following should illustrate (please change the bold text to reflect the post_name of your post type):

/wp-content/themes/my-active-theme/my-content-type-multiple.php

This code can be placed in your active theme’s functions.php file or added to a plugin.

<?php
add_action( 'template_redirect', 'mfields_redirect_custom_content_multiple' );
function mfields_redirect_custom_content_multiple() {
	global $mfields_template;
	if( $mfields_template ) {
		include_once( $mfields_template );
		exit();
	}
	return false;
}

add_filter( 'status_header', 'mfields_template_404' );
function mfields_template_404( $c ) {
	global $mfields_template;
	$mfields_template = mfields_locate_custom_template();
	if( $mfields_template ) {
		$header = '200';
		$text = get_status_header_desc( $header );
		$protocol = $_SERVER["SERVER_PROTOCOL"];
		if ( 'HTTP/1.1' != $protocol && 'HTTP/1.0' != $protocol )
			$protocol = 'HTTP/1.0';

		return "$protocol $header $text";
	}
	else
		return $c;
}

function mfields_locate_custom_template() {
	global $wp_post_types, $wp;
	if( is_404() ) {
		if( array_key_exists( $wp->request, $wp_post_types ) ) {
			$file = STYLESHEETPATH . '/' . $wp->request . '-multiple.php';
			$file = ( file_exists( $file ) ) ? $file : get_index_template();
			return $file;
		}
	}
	return false;
}
?>