Control.Paint gone missing

  • Thread starter Thread starter vooose
  • Start date Start date
V

vooose

Consider a UserControl TopCont that contains two other UserControls,
CompA and CompB.

Somewhere in the constructor of TopCont we have

CompA.Paint += new PaintEventHandler(compA_Paint);
CompB.Paint += new PaintEventHandler(compB_Paint);

I am calling Invalidate() on both of the child components and this
results in their respective paint methods executing. However at some
point when I call CompA.Invalidate(), its painting method (compA_Paint)
is not being called. (this is what I am trying to figure out). I *never
*actively* do

CompA.Paint -= new PaintEventHandler(compA_Paint);

so I'm wondering how this would occur? Also I am using the debugger to
step over the lines of code where I have observed this happening but I
don't ever see the Control.Paint when I inspect the component.
I guess my second question is how at a given breakpoint can you inspect
a control and see which method was += to the Paint event?


Wal
 
vooose said:
Consider a UserControl TopCont that contains two other UserControls,
CompA and CompB.

Somewhere in the constructor of TopCont we have

CompA.Paint += new PaintEventHandler(compA_Paint);
CompB.Paint += new PaintEventHandler(compB_Paint);

I am calling Invalidate() on both of the child components and this
results in their respective paint methods executing. However at some
point when I call CompA.Invalidate(), its painting method
(compA_Paint) is not being called. (this is what I am trying to
figure out). I *never *actively* do

CompA.Paint -= new PaintEventHandler(compA_Paint);

so I'm wondering how this would occur? Also I am using the debugger to
step over the lines of code where I have observed this happening but I
don't ever see the Control.Paint when I inspect the component.
I guess my second question is how at a given breakpoint can you
inspect a control and see which method was += to the Paint event?


Wal
Click to expand...

ok, here is your first "is it plugged in" type question.

does the code that does the invalidate actually get called ? for
example if you are doing the invalidate in a property setter you may
find that the invalidate is not actually getting called. example....


public SomeComplexType MyComplexType
{
get
{
return _myPrivateComplexType;
}
set
{
invalidate();
_myPrivateComplexType;
}
}


later in your code somewhere

MyControl.MyComplexType.Color = Colors.Blue;

this will not cause your setter to fire (and subsequently the
invalidate), because as far as your control is concerned the property
has not been changed only a sub property has changed so the private
field still contains the same object, in fact its the getter that has
fired.

I don't know if this is your problem, but it is a common issue.

Regards Tim.
 
Tim thanks for your reply.

In this case I can guarantee that Invalidate() on the troublesome
component. In fact, the first thing I did was add a method called
InvalidateCompA() which looks like:

public void InvalidateCompA()
{
contA.Invalidate();
}

and I put a breakpoint at this line, and it was hit. As explained before
I couldnt determine what Paint methods were going to get called as a
result of this Invalidate() because I don't know where this info is
hidden in the debugger!

Wal
 
vooose said:
Tim thanks for your reply.

In this case I can guarantee that Invalidate() on the troublesome
component. In fact, the first thing I did was add a method called
InvalidateCompA() which looks like:

public void InvalidateCompA()
{
contA.Invalidate();
}

and I put a breakpoint at this line, and it was hit. As explained
before I couldnt determine what Paint methods were going to get
called as a result of this Invalidate() because I don't know where
this info is hidden in the debugger!

Wal
Click to expand...

No probs, just sorry it didn't help. I had a problem myself a couple
weeks ago and this was the issue.

do you have a small project that reproduces this problem ? Perhaps you
could post that up.

Regards Tim.
 
Unfortunately I can't develop a stable recreate. However knowing how to
determine the event handler for

control.Paint += <where is this at debug time>

is going to help solve this one, as this is the thing that goes missing.
Do you know how to print out the paint handlers at runtime?

Wal
 
is going to help solve this one, as this is the thing that goes
missing. Do you know how to print out the paint handlers at runtime?
Click to expand...

you mean you want to know if it fires ?

you can use Debug.WriteLine, that will write to the output window, so
you can at least see if has fired. (the Debug class is in the
System.Diagnostics assembly)

Regards Tim.
 
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