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<?php

/**
 * Google Slides embed shortcode
 * The slideshow must be set to public!
 */

add_shortcode( 'googleslideshow','google_slideshow' );
function google_slideshow( $atts, $content = '' ) {
	$atts = shortcode_atts( array(
		'id' => NULL,
		'height' => '550',
		'start' => false,
		'loop' => false
	), $atts);
	ob_start();

	/**
	 * Shortened slideshow ID
	 * (for use as an element ID)
	 */
	$trimmedID = strtolower( substr( $atts['id'], 0, 10 ) );
	?>

	<?php if( $atts['id'] != NULL ) : ?>
	<!-- [start] Google Slides - ID: <?php echo $atts['id']; ?> -->
	<iframe
		class="google-slideshow-iframe"
		id="google-slideshow-<?php echo $trimmedID; ?>"
		src="https://docs.google.com/presentation/embed?id=<?php echo $atts['id']; ?>&amp;start=<?php echo $atts['start']; ?>&amp;loop=<?php $atts['loop'];?>&amp;"
		frameborder="0"
		width="100%"
		height="<?php echo $atts['height']; ?>">
	</iframe>
	<!-- [end] Google Slides - ID: <?php echo $atts['id']; ?> -->
	<?php else : ?>
	<p style="font-weight:bold;color:red;padding:10px;margin:20px 0;background:#eee;">You did not specify a Google Slideshow ID!</p>
	<?php endif; ?>

	<?php
	$output = ob_get_contents();
	ob_end_clean();
	return $output;
}

?>