netsurf/gtk/thumbnail.c

/*
 * Copyright 2006 Rob Kendrick <rjek@rjek.com>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * NetSurf is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/** \file
 * Page thumbnail creation (implementation).
 *
 * Thumbnails are created by setting the current drawing contexts to the
 * bitmap (a gdk pixbuf) we are passed, and plotting the page at a small
 * scale.
 */

#include <assert.h>
#include <gtk/gtk.h>
#include <gdk/gdk.h>

#include "content/content.h"
#include "content/hlcache.h"
#include "content/urldb.h"
#include "desktop/plotters.h"
#include "desktop/browser.h"
#include "desktop/thumbnail.h"
#include "gtk/scaffolding.h"
#include "gtk/plotters.h"
#include "gtk/bitmap.h"
#include "image/bitmap.h"
#include "render/font.h"
#include "utils/log.h"
#include "utils/utils.h"

/**
 * Create a thumbnail of a page.
 *
 * \param  content  content structure to thumbnail
 * \param  bitmap   the bitmap to draw to
 * \param  url      the URL the thumnail belongs to, or NULL
 */
bool thumbnail_create(hlcache_handle *content, struct bitmap *bitmap,
		const char *url)
{
        GdkPixbuf *pixbuf;
	int cwidth, cheight;
	gint width;
	gint height;
	gint depth;
	GdkPixmap *pixmap;
	GdkPixbuf *big;
	double scale;

	struct redraw_context ctx = {
		.interactive = false,
		.plot = &nsgtk_plotters
	};

	assert(content);
	assert(bitmap);

	/* Get details of required final thumbnail image */
	pixbuf = gtk_bitmap_get_primary(bitmap);
	width = gdk_pixbuf_get_width(pixbuf);
	height = gdk_pixbuf_get_height(pixbuf);
	depth = (gdk_screen_get_system_visual(gdk_screen_get_default()))->depth;

	/* Calculate size of buffer to render the content into */
	/* We get the width from the content width, unless it exceeds 1024,
	 * in which case we use 1024. This means we never create excessively
	 * large render buffers for huge contents, which would eat memory and
	 * cripple performance. */
	cwidth = min(content_get_width(content), 1024);
	/* The height is set in proportion with the width, according to the
	 * aspect ratio of the required thumbnail. */
	cheight = ((cwidth * height) + (width / 2)) / width;

	/*  Create buffer to render into */
	pixmap = gdk_pixmap_new(NULL, cwidth, cheight, depth);
	
	if (pixmap == NULL) {
		/* the creation failed for some reason: most likely because
		 * we've been asked to create with with at least one dimention
		 * as zero.  The RISC OS thumbnail generator returns false
		 * from here when it can't create a bitmap, so we assume it's
		 * safe to do so here too.
		 */
		return false;
	}

	gdk_drawable_set_colormap(pixmap, gdk_colormap_get_system());

	/* set to plot to pixmap */
	current_drawable = pixmap;
	current_gc = gdk_gc_new(current_drawable);
#ifdef CAIRO_VERSION
	current_cr = gdk_cairo_create(current_drawable);
#endif

	/* render the content */
	thumbnail_redraw(content, cwidth, cheight, &ctx);

	/* get the pixbuf we rendered the content into */
	big = gdk_pixbuf_get_from_drawable(NULL, pixmap, NULL, 0, 0, 0, 0,
			cwidth, cheight);

	/* resample the large plot down to the size of our thumbnail */
	scale = (double)width / (double)cwidth;
	gdk_pixbuf_scale(big, pixbuf, 0, 0, width, height, 0, 0,
			scale, scale, GDK_INTERP_TILES);

	/* As a debugging aid, try this to dump out a copy of the thumbnail as
	 * a PNG: gdk_pixbuf_save(pixbuf, "thumbnail.png", "png", NULL, NULL);
	 */

	/* register the thumbnail with the URL */
	if (url)
	  urldb_set_thumbnail(url, bitmap);

	bitmap_modified(bitmap);

	g_object_unref(current_gc);
#ifdef CAIRO_VERSION
	cairo_destroy(current_cr);
#endif
	g_object_unref(pixmap);
	g_object_unref(big);

	return true;
}