"Crucifix" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hello,
>
> I'm writing a small C# app, and part of what I'm trying to do
> involves the dragging of PictureBox controls on a form. Unfortunately,
> MouseMove seems to be behaving very oddly, causing spurious MouseMove
> events when the cursor doesn't actually move. I've looked for a
> solution in the groups, and although I've come close, I haven't found a
> proper explanation or fix. Here is a rundown, followed by a very
> simple test app that reproduces the issue:
Put this code back in and it works perfectly. You need to store the point
that the mouse clicked on the picturebox, not the original location of the
picturebox. And you should use Location instead of Left and Top so that it
is only moved once.
tomatoBox_Origin = new Point( e.X, e.Y );
if ( tomatoBox_Dragging != null )
{
tomatoBox_Dragging.Location = new Point(tomatoBox_Dragging.Left + e.X -
tomatoBox_Origin.X, tomatoBox_Dragging.Top +e.Y - tomatoBox_Origin.Y);
}
Michael
>
> The concept is simple. There's a PictureBox control, which is
> subscribed to the MouseDown, MouseMove, and MouseUp events. The user
> clicks (and holds) a PictureBox, which triggers the MouseDown event.
> The event handler updates two private member variables which contain
> (1) a reference to the PictureBox object, and (2) a Point struct
> defining the location (origin) of the PictureBox object when it was
> clicked.
>
> The user then drags the control, and the MouseMove event is
> triggered, which checks if the PictureBox reference is null - if it is,
> it does nothing, if it is not, it offsets the location of the
> PictureBox according to its origin, and the X/Y coordinates of the
> mouse.
>
> The MouseUp event simply sets the reference to the PictureBox to
> null, so that no more MouseMove events are triggered, and the
> PictureBox is left where it is.
>
> When this app runs, and the user clicks and drags the PictureBox,
> many MouseMove events are called - it seems that moving the PictureBox
> triggers another MouseMove, but why? I've reduced the effect somewhat
> by adding a check in MouseMove to see if the cursor position has
> changed - this stops the cascading events, but it doesn't stop the
> PictureBox control from drawing itself at two different locations
> (flickering) as I move it around. (I'm sure double-buffering would fix
> that, but I'd like to address the real problem).
>
> Your help is much appreciated!
>
>
>
> using System;
> using System.Drawing;
> using System.Windows.Forms;
>
> namespace MouseMoveTest
> {
> public class MouseMoveTest : System.Windows.Forms.Form
> {
> private System.Windows.Forms.PictureBox tomatoBox;
> private System.Windows.Forms.PictureBox tomatoBox_Dragging;
> private Point tomatoBox_Origin;
>
> private Point mouseLocation = new Point(0,0);
>
> private System.ComponentModel.Container components = null;
>
> public MouseMoveTest()
> {
> this.SuspendLayout();
>
> this.Name = "MouseMove Test Form";
> this.Text = this.Name;
> this.ClientSize = new System.Drawing.Size(512, 512);
>
> this.tomatoBox = new System.Windows.Forms.PictureBox();
> this.tomatoBox.BackColor = System.Drawing.Color.Tomato;
> this.tomatoBox.Location = new System.Drawing.Point(160, 144);
> this.tomatoBox.Name = "tomatoBox";
> this.tomatoBox.Size = new System.Drawing.Size(64, 64);
> this.tomatoBox.TabIndex = 0;
> this.tomatoBox.TabStop = false;
> this.tomatoBox.MouseUp += new
> System.Windows.Forms.MouseEventHandler(this.tomatoBox_MouseUp);
> this.tomatoBox.MouseMove += new
> System.Windows.Forms.MouseEventHandler(this.tomatoBox_MouseMove);
> this.tomatoBox.MouseDown += new
> System.Windows.Forms.MouseEventHandler(this.tomatoBox_MouseDown);
>
> this.Controls.Add(this.tomatoBox);
>
> this.ResumeLayout(false);
> }
>
> protected override void Dispose( bool disposing )
> {
> if( disposing )
> {
> if (components != null)
> {
> components.Dispose();
> }
> }
> base.Dispose( disposing );
> }
>
> [STAThread]
> static void Main()
> {
> Application.Run( new MouseMoveTest() );
> }
>
>
> private void tomatoBox_MouseUp(object sender,
> System.Windows.Forms.MouseEventArgs e)
> {
> Console.WriteLine( "MouseUp: " + e.X + "," + e.Y );
>
> tomatoBox_Dragging = null;
> }
>
> private void tomatoBox_MouseDown(object sender,
> System.Windows.Forms.MouseEventArgs e)
> {
> Console.WriteLine( "MouseDown: " + e.X + "," + e.Y );
>
> tomatoBox_Dragging = (sender as PictureBox );
> tomatoBox_Origin = new Point( tomatoBox.Location.X,
> tomatoBox.Location.Y );
>
> Console.WriteLine( "Origin is: " + tomatoBox_Origin );
> }
>
> private void tomatoBox_MouseMove(object sender,
> System.Windows.Forms.MouseEventArgs e)
> {
> Console.WriteLine( "MouseMove: " + e.X + "," + e.Y );
>
> // Only proceed if mouse position has changed.
> /*
> if ( mouseLocation.Equals(Cursor.Position) )
> return;
> else
> mouseLocation = Cursor.Position;
> */
>
> if ( tomatoBox_Dragging != null )
> {
> tomatoBox_Dragging.Left = tomatoBox_Origin.X + e.X;
> tomatoBox_Dragging.Top = tomatoBox_Origin.X + e.Y;
> }
> }
> }
> }
>
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