CODEWITHSUNDEEP
c#winformsevent-handlingpaint
spin_eight
spin_eight

Reputation: 4025

Paint event delegate not invoked when refresh() method is called

class MainWindow : Form
{
public MainWindow()
        {
            InitializeComponent();
            // Handlers
            Paint += new PaintEventHandler(MainWindow_Paint);
            MouseClick += new MouseEventHandler(MainWindow_MouseClick);
        }
void MainWindow_MouseClick(object sender, MouseEventArgs e)
        {
            var p = new Point(e.X, e.Y);
            m_ListOfFigures.ToArray()[0].addPoint(ref p);
            Refresh();
        }
void MainWindow_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

        }

I have no idea why my method, registered for wm_paint, not called?
Can you point to my mistake?

Upvotes: 1

Views: 1346

Answers (1)

Matthew Watson
Matthew Watson

Reputation: 109792

What you did should have worked, but Microsoft say you should override OnPaint() rather than subscribing to the Paint event, to paint a user control.

As it says in the documentation for Control.Paint:

When creating a new custom control or an inherited control with a different visual appearance, you must provide code to render the control by overriding the OnPaint method.

See here for more details: http://msdn.microsoft.com/en-us/library/cksxshce.aspx

But do note that doesn't really apply to Form classes (such as the one you're using), which are not User Controls or Custom Controls! Nevertheless, it's still more usual to override OnPaint() to paint the control itself.)

You should try adding the following to your form:

protected override void OnPaint(PaintEventArgs e) 
{
     // Call the OnPaint method of the base class.
     base.OnPaint(e);

     // Now draw stuff using e.Graphics
}

The Paint event is not really intended for the user control or form itself to use. Instead, it is for when you want to be notified when a control within the containing control is being repainted.

Note However, having said that, it should still have worked using the Paint event... but Microsoft say that you should override OnPaint() to do your painting (perhaps because of issues such as the one you had).

Upvotes: 3

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