/* Drawing Area * * GtkDrawingArea is a blank area where you can draw custom displays * of various kinds. * * This demo has two drawing areas. The checkerboard area shows * how you can just draw something; all you have to do is write * a signal handler for ExposeEvent, as shown here. * * The "scribble" area is a bit more advanced, and shows how to handle * events such as button presses and mouse motion. Click the mouse * and drag in the scribble area to draw squiggles. Resize the window * to clear the area. */ using System; using Gtk; using Gdk; namespace GtkDemo { [Demo ("Drawing Area", "DemoDrawingArea.cs")] public class DemoDrawingArea : Gtk.Window { private Cairo.Surface surface = null; public DemoDrawingArea () : base ("Drawing Area") { BorderWidth = 8; VBox vbox = new VBox (false, 8); vbox.BorderWidth = 8; Add (vbox); // Create the checkerboard area Label label = new Label ("Checkerboard pattern"); label.UseMarkup = true; vbox.PackStart (label, false, false, 0); Frame frame = new Frame (); frame.ShadowType = ShadowType.In; vbox.PackStart (frame, true, true, 0); DrawingArea da = new DrawingArea (); // set a minimum size da.SetSizeRequest (100,100); frame.Add (da); da.Drawn += new DrawnHandler (CheckerboardDrawn); // Create the scribble area label = new Label ("Scribble area"); label.UseMarkup = true; vbox.PackStart (label, false, false, 0); frame = new Frame (); frame.ShadowType = ShadowType.In; vbox.PackStart (frame, true, true, 0); da = new DrawingArea (); // set a minimum size da.SetSizeRequest (100, 100); frame.Add (da); // Signals used to handle backing pixmap da.Drawn += new DrawnHandler (ScribbleDrawn); da.ConfigureEvent += new ConfigureEventHandler (ScribbleConfigure); // Event signals da.MotionNotifyEvent += new MotionNotifyEventHandler (ScribbleMotionNotify); da.ButtonPressEvent += new ButtonPressEventHandler (ScribbleButtonPress); // Ask to receive events the drawing area doesn't normally // subscribe to da.Events |= EventMask.LeaveNotifyMask | EventMask.ButtonPressMask | EventMask.PointerMotionMask | EventMask.PointerMotionHintMask; ShowAll (); } protected override bool OnDeleteEvent (Gdk.Event evt) { Destroy (); return true; } private void CheckerboardDrawn (object o, DrawnArgs args) { const int CheckSize = 10; const int Spacing = 2; Widget widget = o as Widget; Cairo.Context cr = args.Cr; int i, j, xcount, ycount; // At the start of a draw handler, a clip region has been set on // the Cairo context, and the contents have been cleared to the // widget's background color. Rectangle alloc = widget.Allocation; // Start redrawing the Checkerboard xcount = 0; i = Spacing; while (i < alloc.Width) { j = Spacing; ycount = xcount % 2; // start with even/odd depending on row while (j < alloc.Height) { if (ycount % 2 != 0) cr.SetSourceRGB (0.45777, 0, 0.45777); else cr.SetSourceRGB (1, 1, 1); // If we're outside the clip, this will do nothing. cr.Rectangle (i, j, CheckSize, CheckSize); j += CheckSize + Spacing; ++ycount; } i += CheckSize + Spacing; ++xcount; } // return true because we've handled this event, so no // further processing is required. args.RetVal = true; } private void ScribbleDrawn (object o, DrawnArgs args) { Cairo.Context cr = args.Cr; cr.SetSourceSurface (surface, 0, 0); cr.Paint (); } // Create a new surface of the appropriate size to store our scribbles private void ScribbleConfigure (object o, ConfigureEventArgs args) { Widget widget = o as Widget; if (surface != null) surface.Destroy (); var allocation = widget.Allocation; surface = widget.Window.CreateSimilarSurface (Cairo.Content.Color, allocation.Width, allocation.Height); var cr = new Cairo.Context (surface); cr.Paint (); ((IDisposable)cr).Dispose (); // We've handled the configure event, no need for further processing. args.RetVal = true; } private void ScribbleMotionNotify (object o, MotionNotifyEventArgs args) { // paranoia check, in case we haven't gotten a configure event if (surface == null) return; // This call is very important; it requests the next motion event. // If you don't call Window.GetPointer() you'll only get a single // motion event. The reason is that we specified PointerMotionHintMask // in widget.Events. If we hadn't specified that, we could just use // args.Event.X, args.Event.Y as the pointer location. But we'd also // get deluged in events. By requesting the next event as we handle // the current one, we avoid getting a huge number of events faster // than we can cope. int x, y; ModifierType state; args.Event.Window.GetPointer (out x, out y, out state); if ((state & ModifierType.Button1Mask) != 0) DrawBrush (o as Widget, x, y); // We've handled it, stop processing args.RetVal = true; } // Draw a rectangle on the screen private void DrawBrush (Widget widget, double x, double y) { var update_rect = new Gdk.Rectangle ((int)x - 3, (int)y - 3, 6, 6); var cr = new Cairo.Context (surface); cr.Fill (); Gdk.CairoHelper.Rectangle (cr, update_rect); ((IDisposable)cr).Dispose (); widget.Window.InvalidateRect (update_rect, false); } private void ScribbleButtonPress (object o, ButtonPressEventArgs args) { // paranoia check, in case we haven't gotten a configure event if (surface == null) return; EventButton ev = args.Event; if (ev.Button == 1) DrawBrush (o as Widget, ev.X, ev.Y); // We've handled the event, stop processing args.RetVal = true; } } }