Unsafe code - C# Discussion Boards

28-Apr-07 21:38

At the end of the day, a control will always be both view, and controller. I've done MVC in C#, but I didn't use the keyboard, I used custom input devices which I was able to write into controller classes, and decouple those from the view. But, as soon as I needed keyboard support, I had to code it into the controls, because, on windows, the controls get the keyboard input.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

Re: MVC custom control

alex.barylski29-Apr-07 7:41

alex.barylski

29-Apr-07 7:41

I see what your saying, but I still find frameworks (MFC) non-conforming.

What i was thinking is developing the control using plain SDK (no framework) thus allowing me to keep strict seperation of all three components.

The controller would handle requests (via message pump) and invoke appropriate handlers which in turn would invoke the required models and update view(s).

Then I figured I could just wrap the DLL control as a CView. Obviously the control's API would expose many of the methods in the controller, model and view.

Is doing something like this possible in C#? Know of any articles on CP?

I'm finding the only constant in software development is change it self.

Re: MVC custom control

Christian Graus29-Apr-07 11:02

overlaying image on a video file

29-Apr-07 11:02

Hockey wrote:
but I still find frameworks (MFC) non-conforming

To the assumption that MVC must be followed ? Yes. I used MVC because I knew that there would be 4 or 5 controllers and at least two views. In that sense, it made perfect sense, and worked really well. I doubt that MVC would have improved any of the MFC projects I ever worked on.

Hockey wrote:
Is doing something like this possible in C#?

Not really, no. And, it's barely possible in C. I mean, like I said, it's still your control that recieves your keyboard and mouse messages. If you do it via a message pump, you make intercept a message with a window handle, so you know where it came from, but I still think it's a bit messy.

enamulhoque28-Apr-07 19:27

enamulhoque

28-Apr-07 19:27

hello all.

I need an algorithm that will take a .avi video file and .jpg image file as input. and the output will be the .avi file with the given image overlayed on it.

can anyone help me to find a solution.

Thanks in advance.

Enamul Hoque

Re: overlaying image on a video file

Christian Graus28-Apr-07 21:39

Re: overlaying image on a video file

28-Apr-07 21:39

It's not an algorithm that you need. Basically, you can do this with DirectX, by creating a filter that superimposes the JPG. Or you can use WPF. Or you can decompose the AVI to frames, merge them with the JPEG, and render a new AVI.

enamulhoque29-Apr-07 4:27

enamulhoque

29-Apr-07 4:27

Dear Christian,

thanks for your reply.can you explain it in more details kindly?

actually i am working with a C# program. here input will be a .avi file and a .jpg file, and the output is the .avi file with the image overlayed on it.

can i use directX or WPF in C#.

Please mention any article if you know.

Thanks again.

Enamul

Re: overlaying image on a video file

Christian Graus29-Apr-07 10:51

29-Apr-07 10:51

If you use WPF, you need to rewrite your app to use it. Yes, you should be able to do this in DX, but I've not done it, I am only aware that it can be done.

I know of a component that will do it for you, it costs $800. Is this an option for you ?

Unsafe code

xibeifeijian28-Apr-07 15:54

xibeifeijian

28-Apr-07 15:54

Just look this test method:

public unsafe void Test()
{
int x=23;
int* px=&x;
*px+=1;
Console.Write(*px);
}

I want to know when will x and px distory? D'Oh! | :doh:

thanks!

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Christian Graus28-Apr-07 16:50

28-Apr-07 16:50

destroy ?

On the next GC cycle, as they exist for far too short a time to be marked to survive it.

xibeifeijian28-Apr-07 17:12

xibeifeijian

28-Apr-07 17:12

Thanks!
You are right,its destory Blush | :O

You say
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On the next GC cycle,
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but there are unmanaged variables,does GC collect unmanged variables?

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Arun.Immanuel28-Apr-07 17:14

Arun.Immanuel

28-Apr-07 17:14

Will GC clean up unsafe code too?

Regards,
Arun Kumar.A

Christian Graus28-Apr-07 17:44

28-Apr-07 17:44

GC collects all allocated memory. Unsafe doesn't really come into it.

Arun.Immanuel28-Apr-07 17:48

Arun.Immanuel

28-Apr-07 17:48

Thank U very much for clearing my doubt.

Regards,
Arun Kumar.A

Luc Pattyn28-Apr-07 22:38

Luc Pattyn

28-Apr-07 22:38

Hi,

these value types reside on the stack, they disappear when the method returns.
There is no new, no object, no collection involved.

Smile | :)

Luc Pattyn

[My Articles]

Christian Graus29-Apr-07 0:39

29-Apr-07 0:39

*sigh* I thought so, but I wasn't sure. Certainly, I knew that unsafe wasn't going to change anything.

Syntax highlighting textbox

Guffa29-Apr-07 1:10

Guffa

29-Apr-07 1:10

It should also be mentioned that the code isn't guaranteed to work if the variables hadn't been allocated on the stack.

If it uses a real object that is allocated on the heap:

public unsafe void Test() {
   string x = 42.ToString();
   string* px = &x; // Dangerous!
   *px += 1;
   Console.Write(*px);
}

The variable x is still allocated on the stack, but it is a reference to a string object that is allocated on the heap. If you copy the reference to a pointer, you will get the current location of the string in memory, but as the garbage collector can move objects in the heap, there is no guarantee that the string will stay in that location. It can be moved to another location at any moment, and the garbage collector will update the reference x to point to the new location, but it will not update the pointer px.

---
single minded; short sighted; long gone;

Adobe200728-Apr-07 15:33

Adobe2007

28-Apr-07 15:33

Hello,

Im trying to use this Syntax highlighting textbox http://www.codeproject.com/cs/miscctrl/SyntaxRichTextBox.asp[^] but i have a small problem.

On the source code of demo project, inside form1_Load (), a new RichTextBox is created and syntax tokens are added to it.

What if i already have a RichTextBox created and wanted to add highlighting keywords to it?

By using something like this:

SyntaxHighlightingTextBox shtb = new SyntaxHighlightingTextBox();

A new RTB is getting created, on top of the existing RTB i have on the form. How can i solve this..?

Dave Kreskowiak28-Apr-07 15:41

Dave Kreskowiak

28-Apr-07 15:41

The choice you have either implementing the functionality in your own RTB control, or using the one canned in the project. You can't just add it on to the stcok RTB you dropped on your form.

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007

Adobe200728-Apr-07 16:16

Adobe2007

28-Apr-07 16:16

oh... How can i implement this functionality into my own RTB control, i dropped into the form?

Im fairly new to C#, I've never done anything like this before and haven't seen any tutorial on this, so i haven't got any clue how to do this.. im stuck

Dave Kreskowiak28-Apr-07 17:07

Dave Kreskowiak

28-Apr-07 17:07

You go over the code that's in that project and see what you need to do to convert it. Don't ask me, or anyone else here, to do it for you. The amount of space required to explain everything you need to do would take up a small book.

Why do yo uhave to add this to a stock RTB control? Why not just use the control in the project, altered to your formatting requirements? It'd be much simpler, but still too much to put into a forum post.

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007