% PLcairo port of 'image pattern' sample code at http://cairographics.org/samples/.
% The original C code snippets are considered to be part of the public domain.
% Keri Harris <keri.harris@gentoo.org>, 2015.



:- use_module(library(plgi)).
:- use_module(library(plcairo)).

:- plgi_use_namespace('Gtk').

on_draw_event(DrawingArea, CairoContext, _UserData, false) :-
	gtk_widget_get_allocated_width(DrawingArea, Width),
	gtk_widget_get_allocated_height(DrawingArea, Height),

	XC is Width/2,
	YC is Height/2,
	Angle45 is 45.0 * pi/180.0,

	predicate_property(user:main, file(File)),
	file_directory_name(File, Directory),
	atom_concat(Directory, '/vermeer.png', ImageFile),

	cairo_image_surface_create_from_png(ImageFile, Image),
	cairo_image_surface_get_width(Image, ImageWidth),
	cairo_image_surface_get_height(Image, ImageHeight),

	XI is -ImageWidth/2, YI is -ImageHeight/2,
	Scale is 1/sqrt(2),

	cairo_pattern_create_for_surface(Image, Pattern),
	cairo_pattern_set_extend(Pattern, 'CAIRO_EXTEND_REPEAT'),

	cairo_translate(CairoContext, XC, YC),
	cairo_rotate(CairoContext, Angle45),
	cairo_scale(CairoContext, Scale, Scale),
	cairo_translate(CairoContext, XI, YI),

	SX is ImageWidth/256.0*5.0, SY is ImageHeight/256.0*5.0,
	plgi_struct_new('CairoMatrix'(), Matrix),
	cairo_matrix_init_scale(Matrix, SX, SY),
	cairo_pattern_set_matrix(Pattern, Matrix),
	cairo_set_source(CairoContext, Pattern),

	cairo_rectangle(CairoContext, 0, 0, 256, 256),
	cairo_fill(CairoContext).

main :-
	gtk_window_new('GTK_WINDOW_TOPLEVEL', Window),
	gtk_window_set_title(Window, 'Image Pattern'),
	gtk_window_set_default_size(Window, 256, 256),

	gtk_drawing_area_new(DrawingArea),
	gtk_container_add(Window, DrawingArea),
	g_signal_connect(DrawingArea, 'draw', on_draw_event/4, {null}, _),

	g_signal_connect(Window, 'destroy', gtk_main_quit/0, {null}, _),
	gtk_widget_show_all(Window),
	gtk_main,
	halt.

:- main.