Problem controlling mouse event at the edge of a text box when arrow cursor appears

[dwigley]

I have a text box in a picturebox in a window's form. The user creates the text box and can move it around and resize it. The user can draw lines outside and around the text box (by clicking and dragging). I have a problem that occurs when the user decides to draw a line but points the cursor, which for drawing purposes is a cross, at the very edge of the text box, where the cursor suddenly changes into an arrow cursor. If the user now presses down to start drawing at that moment, no start point for the line is made, and the arrow fails to draw properly. What happens is that the start point of the arrow becomes the default (0, 0) location point of the client area and form. So the user gets a line that starts at that point (after dragging off of the text box edge to draw the line). I was wondering if there was a way to get around this problem by somehow controlling what happens when the user points the cursor at the edge of the text box, gets that arrow cursor, and then does a mouse down to start dragging to make the line. It seems that the edge of the text box is a no-man's land that's beyond control. I can't find any way to control it, and a mouse down event on the very edge of a text box doesn't seem to produce anything. Perhaps I need to disable this behavior at the edge of the text box, I don't know. But I don't want to disable the whole text box. That's not an option. Thanks.

[jmcilhinney]

Perhaps I need to disable this behavior at the edge of the text box

That makes the most sense to me. If the mouse cursor is not a cross then that indicates that the user cannot draw so the user should not be able to draw.

[dwigley]

How do you disable just the edge of the text box? I can't find how to do that. Thanks.

[jmcilhinney]

You don't have explicitly disable anything. What's the obvious difference? The mouse cursor. Check whether the mouse cursor is a cross and only start drawing if it is.

[dwigley]

Yes, as I tried to explain, when the user drags off the text box, the cursor becomes a cross, and a line is then drawn from the cursor to the point (0,0). For some reason, the start point becomes (0,0). I suppose that’s the default. In fact, it may jump to other points on the form if they are there from other actions. What I have done to solve the issue is to remove stray points that might get created. For instance, I set any point going to (0,0) to nothing, and now the crazy line doesn’t get drawn.

I was wondering if it were possible to change the behavior occurring at the edge of the text box that would allow a different solution. If not, then I’ll do it this other way. Thanks for your time.

[jmcilhinney]

I'm assuming that you start drawing on a MouseDown event. If the cursor is not a cross on that event then don't start drawing. If you don't start drawing then you won't draw at all. Problem solved. If that still doesn't make sense to you then it's time to show us the relevant code.

[passel]

p.s. I overlapped responding while jmcilhinney was responding, so repetitive most likely....

Did you write the code?
Do you enable drawing in the Mouse Down event, or just draw anytime the mouse is down in the Mouse Move event?
I believe that jmcilhinney's assumes you would enable drawing (i.e. set a Boolean) in the Mouse Down event, and if the cursor wasn't a cross at the time of the Mouse Down event you wouldn't enable the drawing.
My assumption would be that you didn't actually get the Mouse Down event in the picturebox (it may have occurred for the textbox), so if you added code to to set a Boolean in the picturebox's Mouse Down, then it wouldn't get set so you wouldn't be drawing in the Mouse Move event.

It seems like you might initialize your drawing coordinates in the Mouse Down event of the picturebox, and since you're not getting that event your starting coordinates end up at 0,0 when you get to the Mouse Move event. Many drawing code do follow the paradigm of setting a Boolean to Enable drawing in the Mouse Down event, and clear that Boolean in the Mouse Up event and don't rely only on the condition of the mouse button in the Move event to draw.

[dwigley]

I wrote the code. That's the first thing I tried to do -- shut down drawing if the cursor isn't a cross. But I've tried everything that I could think of to shut it down when the cursor is either an arrow or not cross. Yes, I use a Boolean variable to turn on drawing.

When that cursor becomes an arrow at the very edge of the text box and there is a mouse down, I'm not getting that mouse down event, everything continues, but now the mouse is down, and the start point becomes (0,0).

Further when the cursor becomes an arrow at the edge of the text box, I can't get that change either. I've tried the following everywhere to get it:

 Form1.Cursor = Cursors.Arrow
Form1.PictureBox1.Cursor = Cursors.Arrow
Form1.TextBox1 = Cursors.Arrow

'and

Form1.Cursor <> Cursors.Cursor
Form1.PictureBox1.Cursor <> Cursors.Cursor
Form1.TextBox1 <> Cursors.Cursor

That's why I said that the edge of the text box seems to be a kind of no-man's land.

So I must be missing something somehow. The next thing I can do is make a mini version of the application, try it out, and show it here if it does the same thing, because the code for the application is too complex to show here and try to explain things.

That will take a little time.

Thanks.

[jmcilhinney]

Show us the drawing code you have and then we can determine how to change that to work the way you want.

[passel]

...Yes, I use a Boolean variable to turn on drawing...When that cursor becomes an arrow at the very edge of the text box and there is a mouse down, I'm not getting that mouse down event, everything continues, but now the mouse is down, and the start point becomes (0,0)....

If you're not getting "that mouse down event", then how is the Boolean variable being set to turn on the drawing? Without a Mouse Down event to set the boolean, you shouldn't be doing any drawing, whether the button is down or not.

[passel]

I just did a quick test, and when I click in the "No man's land", area, since neither mousedown event is triggered, I don't get a debug.print out and the boolean value is not set, and I don't draw in the MouseDown event, so the code works as expected.
Given your code allows dragging and specialized drawing, I'm sure your code is more involved than this simple test, but your decision of whether you draw or not should be right along the lines shown here.

Public Class Form1
  Private DrawEnabled As Boolean
  Private StartPoint As Point
  Private EndPoint As Point

  Private Sub TextBox1_MouseDown(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles TextBox1.MouseDown
    Debug.Print("textbox mousedown")
  End Sub

  Private Sub PictureBox1_MouseDown(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
    Debug.Print("picturebox mousedown")
    DrawEnabled = True
    StartPoint = e.Location
  End Sub

  Private Sub PictureBox1_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
    If DrawEnabled Then
      If e.Button = Windows.Forms.MouseButtons.Left Then
        EndPoint = e.Location
        PictureBox1.Invalidate()
      End If
    End If
  End Sub

  Private Sub PictureBox1_MouseUp(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
    DrawEnabled = False
  End Sub

  Private Sub PictureBox1_Paint(sender As Object, e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
    e.Graphics.DrawLine(Pens.Black, StartPoint, EndPoint)
  End Sub
End Class

[dwigley]

Ok, I fixed it. My mouse down event wasn't determining whether drawing takes place or not. I thought it was, but I had undone it. Right, it goes along the lines you have there, passel.

In my defense, there's that no-man's land on the edge of a text box where the arrow comes up! But if I couldn't get an event there, then why would there be drawing?! Right. So my mouse down event wasn't determining whether drawing takes place.

Once again, you guys know immediately what's wrong! Amazing, thanks.