netsurf/content/handlers/javascript/duktape/CanvasRenderingContext2D.bnd

/* HTML canvas element rendering context binding using duktape and libdom
 *
 * Copyright 2020 Daniel Silverstone <dsilvers@netsurf-browser.org>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * Released under the terms of the MIT License,
 *         http://www.opensource.org/licenses/mit-license
 */

class CanvasRenderingContext2D {
      private struct dom_html_element *canvas;
      private struct bitmap *bitmap;
      private int width;
      private int height;
      private size_t stride;
      prologue %{
/* prologue */
#include "desktop/gui_internal.h"
#include "desktop/gui_table.h"
#include "netsurf/bitmap.h"
#include "utils/corestrings.h"
/* It's a smidge naughty of us to read
 * this particular header, but we're needing
 * to redraw the node we represent
 */
#include "content/handlers/html/private.h"

static void redraw_node(dom_node *node)
{
	struct box *box = NULL;
	html_content *htmlc = NULL;
	dom_exception exc;
	dom_document *doc;

	exc = dom_node_get_user_data(node,
				     corestring_dom___ns_key_box_node_data,
				     &box);
	if (exc != DOM_NO_ERR || box == NULL) {
		return;
	}

	exc = dom_node_get_owner_document(node, &doc);
	if (exc != DOM_NO_ERR || doc == NULL) {
		return;
	}

	exc = dom_node_get_user_data(doc,
				     corestring_dom___ns_key_html_content_data,
				     &htmlc);
	if (exc != DOM_NO_ERR || htmlc == NULL) {
		dom_node_unref(doc);
		return;
	}

	html__redraw_a_box(htmlc, box);

	dom_node_unref(doc);
}

/* prologue ends */
%};
};

init CanvasRenderingContext2D(struct dom_html_element *canvas)
%{
	struct bitmap *bitmap;
	dom_exception exc;

	assert(canvas != NULL);

	priv->canvas = canvas;
	dom_node_ref(canvas);

	exc = dom_node_get_user_data(canvas,
				     corestring_dom___ns_key_canvas_node_data,
				     &bitmap);
	assert(exc == DOM_NO_ERR);
	assert(bitmap != NULL);

	priv->bitmap = bitmap;
	priv->width = guit->bitmap->get_width(bitmap);
	priv->height = guit->bitmap->get_height(bitmap);
	priv->stride = guit->bitmap->get_rowstride(bitmap);
%}

fini CanvasRenderingContext2D()
%{
	dom_node_unref(priv->canvas);
%}

getter CanvasRenderingContext2D::canvas()
%{
	dukky_push_node(ctx, (dom_node *)priv->canvas);
	return 1;
%}

method CanvasRenderingContext2D::createImageData()
%{
	/* Can be called either with width and height, or with a reference
	 * imagedata object
	 */
	image_data_private_t *idpriv;
	int width, height;

	if (duk_get_top(ctx) == 2) {
		width = duk_to_int(ctx, 0);
		height = duk_to_int(ctx, 1);
	} else if (dukky_instanceof(ctx, 0, PROTO_NAME(IMAGEDATA))) {
		duk_get_prop_string(ctx, 0, dukky_magic_string_private);
		idpriv = duk_get_pointer(ctx, -1);
		width = idpriv->width;
		height = idpriv->height;
		duk_pop(ctx);
	} else {
		duk_push_null(ctx);
		return 1;
	}

	duk_push_int(ctx, width);
	duk_push_int(ctx, height);
	if (dukky_create_object(ctx,
				PROTO_NAME(IMAGEDATA),
				2) != DUK_EXEC_SUCCESS) {
		return duk_error(ctx,
				 DUK_ERR_ERROR,
				 "Unable to create ImageData");
	}
	return 1;
%}

method CanvasRenderingContext2D::getImageData()
%{
	/* called with x, y, width, height */
	int x = duk_get_int(ctx, 0);
	int y = duk_get_int(ctx, 1);
	int width = duk_get_int(ctx, 2);
	int height = duk_get_int(ctx, 3);
	image_data_private_t *idpriv;
	uint8_t *bitmap_base;

	if (width < 1 || height < 1 ||
	    (x + width) > priv->width || (y + height) > priv->height) {
		return duk_error(ctx, DUK_ERR_RANGE_ERROR, "invalid (%d,%d) (%dx%d)", x, y, width, height);
	}

	duk_push_int(ctx, width);
	duk_push_int(ctx, height);
	if (dukky_create_object(ctx,
				PROTO_NAME(IMAGEDATA),
				2) != DUK_EXEC_SUCCESS) {
		return duk_error(ctx,
				 DUK_ERR_ERROR,
				 "Unable to create ImageData");
	}

	/* ... imgdata */
	duk_get_prop_string(ctx, -1, dukky_magic_string_private);
	idpriv = duk_get_pointer(ctx, -1);
	duk_pop(ctx);

	/* We now have access to the imagedata private, so we need to copy
	 * the pixel range out of ourselves
	 */
	bitmap_base = guit->bitmap->get_buffer(priv->bitmap);
	for (int yy = y; yy < (y+height); ++yy) {
		uint8_t *src_base = bitmap_base + (priv->stride * yy);
		uint8_t *dst_base = idpriv->data + (width * 4);
		memcpy(dst_base + (x * 4), src_base + (x * 4), width * 4);
	}
	return 1;
%}

method CanvasRenderingContext2D::putImageData()
%{
	/* imgdata, x, y[, clipx, clipy, clipw, cliph] */
	/* If provided, the clip coordinates are within the input image data */
	/* We pretend the image is placed at x,y within ourselves, and then we
	 * copy the clip rectangle (defaults to whole image)
	 */
	image_data_private_t *idpriv;
	int x = duk_to_int(ctx, 1);
	int y = duk_to_int(ctx, 2);
	int clipx = 0;
	int clipy = 0;
	int clipw = 0;
	int cliph = 0;
	uint8_t *bitmap_base;

	if (!dukky_instanceof(ctx, 0, PROTO_NAME(IMAGEDATA))) {
		return duk_generic_error(ctx, "Expected ImageData as first argument");
	}

	duk_get_prop_string(ctx, 0, dukky_magic_string_private);
	idpriv = duk_get_pointer(ctx, -1);
	duk_pop(ctx);

	if (duk_get_top(ctx) < 7) {
		/* Clipping data not provided */
		clipw = idpriv->width;
		cliph = idpriv->height;
	} else {
		clipx = duk_to_int(ctx, 3);
		clipy = duk_to_int(ctx, 4);
		clipw = duk_to_int(ctx, 5);
		cliph = duk_to_int(ctx, 6);
	}

	if (x < 0 || y < 0 ||  /* Not positioning negative */
	    (x + clipx + clipw) > priv->width || /* RHS not beyond bounds */
	    (y + clipy + cliph) > priv->height || /* bottom not beyond bounds */
	    clipx < 0 || clipy < 0 || /* Input in range */
	    (clipx + clipw) > idpriv->width || /* Input in range */
	    (clipy + cliph) > idpriv->height) { /* Input in range */
		return duk_error(ctx, DUK_ERR_RANGE_ERROR, "invalid inputs");
	}

	bitmap_base = guit->bitmap->get_buffer(priv->bitmap);

	for (int yy = clipy; yy < (clipy + cliph); yy++) {
		uint8_t *dst_row = bitmap_base + ((y + yy) * priv->stride);
		uint8_t *src_row = idpriv->data + (yy * idpriv->width * 4);
		memcpy(dst_row + ((x + clipx) * 4),
		       src_row + (clipx * 4),
		       clipw * 4);
	}
	guit->bitmap->modified(priv->bitmap);

	redraw_node((dom_node *)(priv->canvas));

	return 0;
%}