85 lines
3.1 KiB
Ruby
85 lines
3.1 KiB
Ruby
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# Copyright (c) 2005 Ruby-GNOME2 Project Team
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# This program is licenced under the same licence as Ruby-GNOME2.
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#
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# $Id: rotated_text.rb,v 1.2 2005/03/05 15:01:16 mutoh Exp $
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=begin
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= Rotated Text
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This demo shows how to use GDK and Pango to draw rotated and transformed text.
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The use of Gdk::PangoRenderer in this example is a somewhat advanced technique; most applications can simply use Gdk::Drawable#draw_layout.
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We use it here mostly because that allows us to work in user coordinates - that is, coordinates prior to the application of the transformation matrix, rather than device coordinates.
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As of GTK+-2.6, the ability to draw transformed and anti-aliased graphics as shown in this example is only present for text.
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With GTK+-2.8, a new graphics system called "Cairo" will be introduced that provides these capabilities and many more for all types of graphics.
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=end
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require 'common'
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module Demo
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class RotatedText < BasicWindow
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RADIUS = 150
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N_WORDS = 10
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FONT = "Sans Bold 27"
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def initialize
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super('Rotated Text')
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unless Gtk.check_version?(2, 6, 0)
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add(Gtk::Label.new("This sample requires GTK+ 2.6.0 or later"))
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return
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end
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drawing_area = Gtk::DrawingArea.new
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add(drawing_area)
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drawing_area.modify_bg(Gtk::STATE_NORMAL, Gdk::Color.new(65535, 65535, 65535))
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drawing_area.signal_connect("expose_event") do
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matrix = Pango::Matrix.new
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# Get the default renderer for the screen, and set it up for drawing
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renderer = Gdk::PangoRenderer.get_default(drawing_area.screen)
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renderer.drawable = drawing_area.window
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renderer.gc = style.black_gc
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width = drawing_area.allocation.width
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height = drawing_area.allocation.height
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# Set up a transformation matrix so that the user space coordinates for
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# the centered square where we draw are [-RADIUS, RADIUS], [-RADIUS, RADIUS]
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# We first center, then change the scale
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device_radius = [width, height].min / 2.0
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matrix.translate!(device_radius + (width - 2 * device_radius) / 2.0,
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device_radius + (height - 2 * device_radius) / 2.0)
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matrix.scale!(device_radius / RADIUS, device_radius / RADIUS)
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# Create a PangoLayout, set the font and text
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context = Gdk::Pango.context
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layout = Pango::Layout.new(context)
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layout.text = "Text"
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layout.font_description = Pango::FontDescription.new(FONT)
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# Draw the layout N_WORDS times in a circle
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(0...N_WORDS).each do |i|
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rotated_matrix = matrix.dup
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angle = 360 * i / N_WORDS.to_f
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# Gradient from red at angle == 60 to blue at angle == 300
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red = 65535 * (1 + Math.cos((angle - 60) * Math::PI / 180.0)) / 2
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color = Gdk::Color.new(red, 0, 65535 - red)
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renderer.set_override_color(Pango::Renderer::PART_FOREGROUND, color)
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rotated_matrix.rotate!(angle)
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context.matrix = rotated_matrix
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# Inform Pango to re-layout the text with the new transformation matrix
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layout.context_changed
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width, height = layout.size
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renderer.draw_layout(layout, - width / 2, - RADIUS * Pango::SCALE)
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end
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# Clean up default renderer, since it is shared
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renderer.set_override_color(Gdk::PangoRenderer::PART_FOREGROUND, nil)
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renderer.drawable = nil
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renderer.gc = nil
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end
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end
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end
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end
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