MouseDrag

NTDEV
1

I have a Bug in my Driver which occurs on when I left click the mouse and
try and pull it i e. I try and drag the mouse but nothing is selected on the
desktop and make a rectangle or something.

When I do something like this there is a dotted line which is drawn with the
rectangle .But this dotted line is in being drawn in the diagonal of the
rectangle and not any where else in the rectangle.

Now I have identified the guilty method to be DrvCopyBits, but inorder to
actually debug the bug I need to move the mouse over and try and create the
rectangle to identify where the problem lies but this is impossible to
happen if I put a breakpoint on DrvCopyBits as it is called repeatedly and
it doesn’t allow me to access the screen again.

It’s a strange problem to debug ,but I thought I might take some words of
wisdom from the right people .

Thanks & Regards,

Nitin Kapoor

2

Nitin Kapoor wrote:

Now I have identified the guilty method to be DrvCopyBits, but
inorder to actually debug the bug I need to move the mouse over and
try and create the rectangle to identify where the problem lies but
this is impossible to happen if I put a breakpoint on DrvCopyBits as
it is called repeatedly and it doesn’t allow me to access the screen
again.

Hmm… Can’t you log to someplace else?
Put in a lot of printf like commands that would give you all you need, and
then draw your rectangle.
Afterwards – look at the log file that has been produced and try to work
out what went wrong.

Not that I know much about drivers, but is there not some way you can just
use Microsoft’s MouseClass?

Vishal.

3

Is DrvMovePointer enabled in your driver? If your driver does not support this call, the OS might call DrvCopyBits to draw the mouse cursor instead. This might be why you are getting so many DrvCopyBits calls while you are investigation the real problem with the drag icon operation. I’d say put a conditional break point on ROP code in CopyBits and cross your fingers that the mouse operation and drag operation use different ROP codes.

Good luck,
Gary

-----Original Message-----
From: Nitin Kapoor [mailto:xxxxx@hotmail.com]
Sent: Monday, July 07, 2003 2:15 AM
To: NT Developers Interest List
Subject: [ntdev] MouseDrag

I have a Bug in my Driver which occurs on when I left click the mouse and
try and pull it i e. I try and drag the mouse but nothing is selected on the
desktop and make a rectangle or something.

When I do something like this there is a dotted line which is drawn with the
rectangle .But this dotted line is in being drawn in the diagonal of the
rectangle and not any where else in the rectangle.

Now I have identified the guilty method to be DrvCopyBits, but inorder to
actually debug the bug I need to move the mouse over and try and create the
rectangle to identify where the problem lies but this is impossible to
happen if I put a breakpoint on DrvCopyBits as it is called repeatedly and
it doesn’t allow me to access the screen again.

It’s a strange problem to debug ,but I thought I might take some words of
wisdom from the right people .

Thanks & Regards,

Nitin Kapoor

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