114 lines
3.6 KiB
Ruby
114 lines
3.6 KiB
Ruby
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#!/usr/bin/env ruby
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=begin
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composited-windows.rb - Sample script translated from http://library.gnome.org/devel/gdk/unstable/gdk-Windows.html#composited-window-example
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Copyright (c) 2008 Ruby-GNOME2 Project Team
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This program is licenced under the same licence as Ruby-GNOME2.
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=end
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require 'gtk2'
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if str = Gtk.check_version(2, 12, 0)
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puts "This sample requires GTK+ 2.12.0 or later."
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puts str
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exit
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end
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unless Gdk.cairo_available?
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puts "This sample requires Cairo support."
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exit
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end
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Gtk.init
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# Make the widgets
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button = Gtk::Button.new("A Button")
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event = Gtk::EventBox.new
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window = Gtk::Window.new(Gtk::Window::TOPLEVEL)
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# Put a red background on the window
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window.modify_bg(Gtk::STATE_NORMAL, Gdk::Color.parse("red"))
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# Set the colourmap for the event box. Must be done before the event box is realised.
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event.colormap = event.screen.rgba_colormap
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# Set our event box to have a fully-transparent background
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# drawn on it. Currently there is no way to simply tell GTK+
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# that "transparency" is the background colour for a widget.
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event.app_paintable = true
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event.signal_connect('expose-event') do |widget, event|
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# This function simply draws a transparency onto a widget on the area
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# for which it receives expose events. This is intended to give the
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# event box a "transparent" background.
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#
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# In order for this to work properly, the widget must have an RGBA
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# colourmap. The widget should also be set as app-paintable since it
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# doesn't make sense for GTK+ to draw a background if we are drawing it
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# (and because GTK+ might actually replace our transparency with its
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# default background colour).
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#
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cr = widget.window.create_cairo_context
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cr.operator = Cairo::OPERATOR_CLEAR
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cr.gdk_region(event.region)
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cr.fill
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false
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end
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# Put them inside one another
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window.border_width = 10
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window.add(event)
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event.add(button)
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# Realize and show everything
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window.show_all
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# Set the event box GdkWindow to be composited.
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# Obviously must be performed after event box is realised.
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event.window.composited = true
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# Set up the compositing handler.
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# Note that we do _after_ so that the normal (red) background is drawn
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# by gtk before our compositing occurs.
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#
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window.signal_connect_after('expose-event') do |widget, event|
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# This function performs the actual compositing of the event box onto
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# the already-existing background of the window at 50% normal opacity.
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#
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# In this case we do not want app-paintable to be set on the widget
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# since we want it to draw its own (red) background. Because of this,
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# however, we must ensure that we use #signal_connect_after so that
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# this handler is called after the red has been drawn. If it was
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# called before then GTK would just blindly paint over our work.
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#
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# Note: if the child window has children, then you need a cairo 1.16
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# feature to make this work correctly.
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#
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# get our child (in this case, the event box)
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child = widget.child
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# create a cairo context to draw to the window
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cr = widget.window.create_cairo_context
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# the source data is the (composited) event box
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# NOTICE: next line generates a GTK warning, it is maybe a GTK problem, it is tracked
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# at http://bugzilla.gnome.org/show_bug.cgi?id=526965
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cr.set_source_pixmap(child.window, child.allocation.x, child.allocation.y)
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# draw no more than our expose event intersects our child
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region = Gdk::Region.new(Gdk::Rectangle.new(child.allocation.x, child.allocation.y, child.allocation.width, child.allocation.height))
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region.intersect(event.region)
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cr.gdk_region(region)
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cr.clip
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# composite, with a 50% opacity
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cr.operator = Cairo::OPERATOR_OVER
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cr.paint(0.5)
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false
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end
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Gtk.main
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