Expanded Reply
There is no flicker whatsoever. The SetStyle in the ctor takes care of that. What you see as "flicker" is an artifact cause by three factors:
- The update rate is only 10/sec. Try increasing that to 20 or 30.
- The direction value is course. It should be based on time/accelleration. That is an exercise left to you.
- The crappy "hand" image has hard, aliased edges. No matter how fast you update or how smooth you animate it, it's going to look jittery. Again, doing anti-aliased, blended graphics processing is left as an exercise.
Look at the code more carefully. This is not "painted on the form", it's a custom control. See how MetronomeControl derives from Control? See how we created the form by adding a MetronomeControl to it?
Picture boxes are for displaying static images, not for custom controls!
The way it updates is by creating a timer. When the timer's Tick event fires we update the angle and direction, more generally, we update the state of the control. The call to Invalidate tells the Operating System, "Hey, I need to be repainted, send me a WM_PAINT message when it's convenient!". Our OnPaint override simply paints the current state of the control.
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;
class MetronomeControl : Control
{
private Bitmap hand;
private float angle = 0;
private float direction = 2;
private Timer timer = new Timer { Enabled = true, Interval = 30 };
public MetronomeControl()
{
SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.UserPaint | ControlStyles.Opaque | ControlStyles.AllPaintingInWmPaint, true);
hand = CreateCrappyHandBitmap();
timer.Tick += new EventHandler(timer_Tick);
}
void timer_Tick(object sender, EventArgs e)
{
if (angle < -45 || angle > 45)
direction = -direction;
angle += direction;
Invalidate();
}
private static Bitmap CreateCrappyHandBitmap()
{
Bitmap bitmap = new Bitmap(100, 300, PixelFormat.Format32bppArgb);
using (Graphics graphics = Graphics.FromImage(bitmap))
{
graphics.Clear(Color.Transparent);
graphics.FillRectangle(Brushes.LightGray, 50 - 5, 0, 10, 300);
graphics.FillPolygon(Brushes.LightSlateGray, new Point[] { new Point(50 - 30, 40), new Point(50 + 30, 40), new Point(50 + 20, 80), new Point(50 - 20, 80) });
graphics.FillEllipse(Brushes.LightSlateGray, 0, 200, 100, 100);
}
return bitmap;
}
protected override void OnPaint(PaintEventArgs e)
{
// Erase background since we specified AllPaintingInWmPaint
e.Graphics.Clear(Color.AliceBlue);
e.Graphics.DrawString(Text, Font, Brushes.Black, new RectangleF(0, 0, ClientSize.Width, ClientSize.Height), new StringFormat { Alignment = StringAlignment.Center, LineAlignment = StringAlignment.Center });
// Move the 0,0 point to the just below the bottom-center of our client area
e.Graphics.TranslateTransform(ClientSize.Width / 2, ClientSize.Height + 40);
// Rotate around this new 0,0
e.Graphics.RotateTransform(angle);
// Turn on AA to make it a bit less jagged looking
e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
// Draw the image so that the center of the ellipse is at 0,0
e.Graphics.DrawImage(hand, 0 - hand.Width / 2, 0 - hand.Height + 50);
// Reset the transform for other drawing
e.Graphics.ResetTransform();
base.OnPaint(e);
}
}
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form
{
Text = "Metronome Control Demo",
ClientSize = new Size(640, 480),
Controls =
{
new MetronomeControl
{
Location = new Point(10, 10),
Size = new Size (340, 300),
Font = new Font(FontFamily.GenericSansSerif, 24),
Text = "Metronome Control Demo",
}
}
});
}
}
