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using System;
using Gtk;
using Cairo;
class Knockout : DrawingArea
{
static void Main ()
{
Application.Init ();
new Knockout ();
Application.Run ();
}
Knockout ()
{
Window win = new Window ("Cairo with Gtk#");
win.SetDefaultSize (400, 400);
win.DeleteEvent += new DeleteEventHandler (OnQuit);
win.Add (this);
win.ShowAll ();
}
void OvalPath (Context cr, double xc, double yc, double xr, double yr)
{
Matrix m = cr.Matrix;
cr.Translate (xc, yc);
cr.Scale (1.0, yr / xr);
cr.MoveTo (xr, 0.0);
cr.Arc (0, 0, xr, 0, 2 * Math.PI);
cr.ClosePath ();
cr.Matrix = m;
}
void FillChecks (Context cr, int x, int y, int width, int height)
{
int CHECK_SIZE = 32;
cr.Save ();
Surface check = cr.Target.CreateSimilar (Content.Color, 2 * CHECK_SIZE, 2 * CHECK_SIZE);
// draw the check
using (Context cr2 = new Context (check)) {
cr2.Operator = Operator.Source;
cr2.Color = new Color (0.4, 0.4, 0.4);
cr2.Rectangle (0, 0, 2 * CHECK_SIZE, 2 * CHECK_SIZE);
cr2.Fill ();
cr2.Color = new Color (0.7, 0.7, 0.7);
cr2.Rectangle (x, y, CHECK_SIZE, CHECK_SIZE);
cr2.Fill ();
cr2.Rectangle (x + CHECK_SIZE, y + CHECK_SIZE, CHECK_SIZE, CHECK_SIZE);
cr2.Fill ();
}
// Fill the whole surface with the check
SurfacePattern check_pattern = new SurfacePattern (check);
check_pattern.Extend = Extend.Repeat;
cr.Source = check_pattern;
cr.Rectangle (0, 0, width, height);
cr.Fill ();
check_pattern.Destroy ();
check.Destroy ();
cr.Restore ();
}
void Draw3Circles (Context cr, int xc, int yc, double radius, double alpha)
{
double subradius = radius * (2 / 3.0 - 0.1);
cr.Color = new Color (1.0, 0.0, 0.0, alpha);
OvalPath (cr, xc + radius / 3.0 * Math.Cos (Math.PI * 0.5), yc - radius / 3.0 * Math.Sin (Math.PI * 0.5), subradius, subradius);
cr.Fill ();
cr.Color = new Color (0.0, 1.0, 0.0, alpha);
OvalPath (cr, xc + radius / 3.0 * Math.Cos (Math.PI * (0.5 + 2 / 0.3)), yc - radius / 3.0 * Math.Sin (Math.PI * (0.5 + 2 / 0.3)), subradius, subradius);
cr.Fill ();
cr.Color = new Color (0.0, 0.0, 1.0, alpha);
OvalPath (cr, xc + radius / 3.0 * Math.Cos (Math.PI * (0.5 + 4 / 0.3)), yc - radius / 3.0 * Math.Sin (Math.PI * (0.5 + 4 / 0.3)), subradius, subradius);
cr.Fill ();
}
void Draw (Context cr, int width, int height)
{
double radius = 0.5 * Math.Min (width, height) - 10;
int xc = width / 2;
int yc = height / 2;
Surface overlay = cr.Target.CreateSimilar (Content.ColorAlpha, width, height);
Surface punch = cr.Target.CreateSimilar (Content.Alpha, width, height);
Surface circles = cr.Target.CreateSimilar (Content.ColorAlpha, width, height);
FillChecks (cr, 0, 0, width, height);
cr.Save ();
// Draw a black circle on the overlay
using (Context cr_overlay = new Context (overlay)) {
cr_overlay.Color = new Color (0.0, 0.0, 0.0);
OvalPath (cr_overlay, xc, yc, radius, radius);
cr_overlay.Fill ();
// Draw 3 circles to the punch surface, then cut
// that out of the main circle in the overlay
using (Context cr_tmp = new Context (punch))
Draw3Circles (cr_tmp, xc, yc, radius, 1.0);
cr_overlay.Operator = Operator.DestOut;
cr_overlay.SetSourceSurface (punch, 0, 0);
cr_overlay.Paint ();
// Now draw the 3 circles in a subgroup again
// at half intensity, and use OperatorAdd to join up
// without seams.
using (Context cr_circles = new Context (circles)) {
cr_circles.Operator = Operator.Over;
Draw3Circles (cr_circles, xc, yc, radius, 0.5);
}
cr_overlay.Operator = Operator.Add;
cr_overlay.SetSourceSurface (circles, 0, 0);
cr_overlay.Paint ();
}
cr.SetSourceSurface (overlay, 0, 0);
cr.Paint ();
overlay.Destroy ();
punch.Destroy ();
circles.Destroy ();
}
protected override bool OnExposeEvent (Gdk.EventExpose e)
{
using (Context cr = Gdk.CairoHelper.Create (e.Window)) {
int w, h;
e.Window.GetSize (out w, out h);
Draw (cr, w, h);
}
return true;
}
void OnQuit (object sender, DeleteEventArgs e)
{
Application.Quit ();
}
}
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