Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.
One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.
Solved
Brush
Posted on 2000-03-18
Experts:
I have a problem:
I create a brush in OnCtlColor() and return it later.This will make my control turn different color.
For example:
HBRUSH CMydialog::OnCtlColor(CDC*
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
CBrush mybrush;
mybrush.CreateSolidBrush (RGB( 255, 0, 0 ));
if ( nCtlColor == CTLCOLOR_BTN )
{
pDC->SetBkColor(RGB(255,0,
pDC->SetTextColor(RGB(0,0,
return mybrush;
}
My confusion is since I create mybrush in the function above and mybrush should get destructed after return.I think the mybrush should die.How the system can use it to draw control color?
But in face it works!
And how about declare the brush in the if statement? Does it make difference?
Many thx.
I have a problem:
I create a brush in OnCtlColor() and return it later.This will make my control turn different color.
For example:
HBRUSH CMydialog::OnCtlColor(CDC*
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
CBrush mybrush;
mybrush.CreateSolidBrush (RGB( 255, 0, 0 ));
if ( nCtlColor == CTLCOLOR_BTN )
{
pDC->SetBkColor(RGB(255,0,
pDC->SetTextColor(RGB(0,0,
return mybrush;
}
My confusion is since I create mybrush in the function above and mybrush should get destructed after return.I think the mybrush should die.How the system can use it to draw control color?
But in face it works!
And how about declare the brush in the if statement? Does it make difference?
Many thx.
-
5
-
3
-
2
10 Comments
Hi,binarydream.
I think brush above get created in system source pool and only mybrush itself in the function stack.
And no destruction to set the m_brush of CBrush to null.
So , even CBrush is out of referecne.The brush handle still exists there and system can use.
Put in the if makes no difference as I figure.
Other experts please correct me if I'm wrong.
Hope helpful
Regards
W.Yinan
I think brush above get created in system source pool and only mybrush itself in the function stack.
And no destruction to set the m_brush of CBrush to null.
So , even CBrush is out of referecne.The brush handle still exists there and system can use.
Put in the if makes no difference as I figure.
Other experts please correct me if I'm wrong.
Hope helpful
Regards
W.Yinan
I don't use MFC, but to the best of my knowledge, the CBrush class deletes the GDI brush when the brush object is destroyed. (You can prevent this by detaching the GDI handle from the brush object using the detach() function. When you do that the GDI brush won't be deleted whent he CBrush is destroyed. But then you have another problem. You will have a GDI mmemory leak. You will becreating this GDI brush each ime the procedure is called and never deleting it.
The solutions is to store the handle to the GDI brush in a global variable--or to use a global/static CBrush object. This global handle/object will hold the handle between "changes" to the brush. each time the brush needs to change (color etc), you will delete the old handle and create a new one. At the end of the program you must delete the last brush. (If you use a global/static brush object, instead of a global brush handle, some of thise details are taken care of automatically.)
The solutions is to store the handle to the GDI brush in a global variable--or to use a global/static CBrush object. This global handle/object will hold the handle between "changes" to the brush. each time the brush needs to change (color etc), you will delete the old handle and create a new one. At the end of the program you must delete the last brush. (If you use a global/static brush object, instead of a global brush handle, some of thise details are taken care of automatically.)
I doubt the code works safely. The brush will be deleted before the procedure returns and the procedure will return the handle to the deleted brush. That is undeniably a mistake. If the program manages to use that deleted brush successfully--and I don't know for sure that that is the case--then it is probably because the delete brush's data still remains in the GDI heap because it has not yet been used to store data for a new object.
Yes,doubt alot.
If it works,at least,binarydream,you creat brush very time the get called and gradually the system-resource get starved,then die.Hur?
If it works,at least,binarydream,you creat brush very time the get called and gradually the system-resource get starved,then die.Hur?
God!
I'm definitly wrong here,binarydream.
The brush object will be automatically destructed when function end.
You'd declare it as a class data member and initialize it in dialog initial...
I dont know why your code works but ,at least,I'm wrong here.
:(
I'm definitly wrong here,binarydream.
The brush object will be automatically destructed when function end.
You'd declare it as a class data member and initialize it in dialog initial...
I dont know why your code works but ,at least,I'm wrong here.
:(
Featured Post
Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.
One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.
Question has a verified solution.
Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.
Have a better answer? Share it in a comment.
Join & Write a Comment Already a member? Login.
Templates For Beginners
Or
How To Encourage The Compiler To Work For You
Introduction
This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
Many modern programming languages support the concept of a property -- a class member that combines characteristics of both a data member and a method. These are sometimes called "smart fields" because you can add logic that is applied automaticall…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
Suggested Courses
Course of the Month8 days, 7 hours left to enroll
595 members asked questions and received personalized solutions in the past 7 days.
Join the community of 500,000 technology professionals and ask your questions.