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#!/usr/bin/env ruby
1		#!/usr/bin/env ruby
2
3		require 'gtk2'
4		require 'rational'
5
6		=begin
7		A drawing area, which can be panned and zoomed.
8		(requires rational)
9		Panning is done with middle mouse drag, zooming is with the scrollwheel.
10		To zoom only into x or y axis, hold down the shift or ctrl keys respectively.
11		You must create the following method:
12		expose_event event, cairo, coordinates
13		where
14		event is the expose event
15		cairo is the cairo context
16		coordinates is an array with the [xstart, ystart, xend, yend] coordinates
17		=end
18		class DragZoomDrawingArea < Gtk::DrawingArea
19		type_register
20
21		def initialize
22		super
23
24		@xscale = @yscale = 1.to_r
25		@xoffset = @yoffset = 0.to_r
26		@xscalestep = @yscalestep = 2.to_r
27		@drag_sig_handlers = []
28
29		signal_connect('expose-event') {\|widget, event\|
30		cairo = window.create_cairo_context
31		cairo.scale(@xscale, @yscale)
32		cairo.translate(@xoffset, @yoffset)
33
34		alloc = allocation
35		width, height = alloc.width, alloc.height
36
37		xstart = (0.to_r - @xoffset) / @xscale
38		xend = (width.to_r - @xoffset) / @xscale
39
40		ystart = (0.to_r - @yoffset) / @yscale
41		yend = (height.to_r - @yoffset) / @yscale
42
43		expose_event widget, event, cairo, [xstart, ystart, xend, yend]
44		true
45		}
46
47		signal_connect('scroll-event') {\|widget, event\|
48		do_xscale = do_yscale = true
49
50		if event.state & Gdk::Window::ModifierType::SHIFT_MASK != 0
51		do_yscale = false
52		end
53		if event.state & Gdk::Window::ModifierType::CONTROL_MASK != 0
54		do_xscale = false
55		end
56
57		xscale_old, yscale_old = @xscale, @yscale
58		case event.direction
59		when Gdk::EventScroll::DOWN
60		@xscale /= @xscalestep if do_xscale
61		@yscale /= @yscalestep if do_yscale
62		when Gdk::EventScroll::UP
63		@xscale *= @xscalestep if do_xscale
64		@yscale *= @yscalestep if do_yscale
65		end
66
67		@xoffset = event.x.to_i.to_r / @xscale - (event.x.to_i / xscale_old - @xoffset)
68		@yoffset = event.y.to_i.to_r / @yscale - (event.y.to_i / yscale_old - @yoffset)
69		queue_draw
70		}
71
72		@motion_cb = proc {\|widget, event\|
73		deltax, deltay = event.x.to_i.to_r - @startx.to_i, event.y.to_i.to_r - @starty.to_i
74		@xoffset += deltax / @xscale
75		@yoffset += deltay / @yscale
76		@startx, @starty = event.x, event.y
77		queue_draw
78		}
79
80		signal_connect('button-press-event') {\|widget, event\|
81		if(event.button == 2)
82		@startx, @starty = event.x, event.y
83		@drag_sig_handlers << signal_connect('motion-notify-event', &@motion_cb)
84		end
85		}
86
87		signal_connect('button-release-event') {\|widget, event\|
88		if(event.button == 2)
89		@drag_sig_handlers.reject!{\|s\| signal_handler_disconnect(s); true}
90		end
91		}
92
93		add_events(Gdk::Event::SCROLL_MASK \|
94		Gdk::Event::BUTTON_PRESS_MASK \|
95		Gdk::Event::BUTTON_RELEASE_MASK \|
96		Gdk::Event::POINTER_MOTION_MASK)
97		end
98		end
99
100		class MyWindow < Gtk::Window
101		def initialize
102		super('interactive graph')
103		set_size_request(500,500)
104		signal_connect("delete-event") { Gtk.main_quit;true }
105
106
107		drawing_area = DragZoomDrawingArea.new
108		def drawing_area.expose_event widget, event, cairo, disp
109		cairo.set_source_rgb(1,0,0)
110		cairo.rectangle(100, 100, 50, 50)
111		cairo.stroke
112		end
113		add(drawing_area)
114		show_all
115		end
116		end
117
118		app = MyWindow.new
119
120		Gtk.main
121
122