Looking for attribute - C# Discussion Boards

albean14-Aug-02 7:13

14-Aug-02 7:13

AK,

I tried both suggestions. The second throws an exception and the first doesnt crash but it doesn't do anything. Can you give me a link to a web page about using the null pointer to gain access to the screen?

Thanks.

Re: Drawing on the Screen

Li-kai Liu (Angus)15-Aug-02 3:12

Li-kai Liu (Angus)

15-Aug-02 3:12

Hi,

I read AK's article and experimented with his second solution. It did throw an exception. And I modify it as follow and now it works:

IntPtr hdc = GetDC(IntPtr.Zero); // get hdc for the screen
Graphics g = Graphics.FromHdc(hdc);
g.DrawLine(new Pen(Color.Blue), 0,0,500,500); // draw a line for testing.
g.Dispose(); // <- I don't know if I should use g.Dispose or g.ReleaseHdc here...
ReleaseDC(IntPtr.Zero,hdc);

GetDC & ReleaseDC are Win32 API in user32.dll

Hope this could help you Smile | :)

Re: Drawing on the Screen

Alex Korchemniy15-Aug-02 9:05

Alex Korchemniy

15-Aug-02 9:05

Sorry, I forgot to tell you to use GetDC.

I knew I missed something.

Re: Drawing on the Screen

James T. Johnson14-Aug-02 7:51

James T. Johnson

14-Aug-02 7:51

I've never tried this, so it may or may not work but here goes Smile | :)

Create a control the same size as the Form (a panel would do), now when you want to draw your grid or whatever above the Form you do several things....

form will be the Form you are trying to draw on top of
parent will be the panel or whatever that the Form is sitting on top of

<br />
Graphics g = parent.CreateGraphics();<br />
PaintEventArgs e = new PaintEventArgs(e, form.Bounds);<br />
<br />
InvokePaint(form, e); <br />
// At this point the form has painted itself <br />
// to the graphics object<br />
<br />
// Do your drawing here using the Graphics object, g<br />

James
"And we are all men; apart from the females." - Colin Davies

Re: Drawing on the Screen

albean14-Aug-02 8:32

albean

14-Aug-02 8:32

James,

Hmm, I've been trying a similar approach but I like yours better because there is only a single surface to draw on. My only question is will I need to make your panel Transparent? I ask because I’ve been trying to create a user control with the graphics drawn on it around the edges. Then I was going to make the background color transparent and place this usercontrol over the other control (lets say it is a button) already on the form. In this way the button would show threw and my usercontrol's graphics would indicate that the button has been selected; even though the user control completely covers the button.

The only problem is that I can't make the usercontrol transparent!!! Will I have to make your panel transparent too. Because this just isn't working for me.

Re: Drawing on the Screen

James T. Johnson14-Aug-02 8:58

James T. Johnson

14-Aug-02 8:58

Here you go, a quick demo showing how its done Smile | :)

It doesn't paint the non-client area but I think you can send some messages to windows to get it to do that (just need to call GetHdc/ReleaseHdc when passing it to windows).

InvokePaintTest.zip (8.1 Kb)

James
"And we are all men; apart from the females." - Colin Davies

Re: Drawing on the Screen

albean15-Aug-02 16:40

albean

15-Aug-02 16:40

Wow, thanks James Big Grin | :-D

I tried out your sample just now and its pretty cool. I'm probably not going to use it though because I want to keep the controls on the same form BUT if the screen painting turns out to be a hassle I’ll definitely come back to your solution.

Looking for attribute

leppie14-Aug-02 4:54

leppie

14-Aug-02 4:54

Hi all,

I was wondering if there is an attribute that can be applied to a class/struct that tells the compiler not to compile it?

Thanx Smile | :)

MYrc : A .NET IRC client with C# Plugin Capabilities. See
http://sourceforge.net/projects/myrc for more info. Big Grin | :-D

Re: Looking for attribute

James T. Johnson14-Aug-02 5:00

James T. Johnson

14-Aug-02 5:00

Am I missing something? Could you explain your situation a bit more?

James
"And we are all men; apart from the females." - Colin Davies

Re: Looking for attribute

leppie14-Aug-02 6:04

leppie

14-Aug-02 6:04

I mean it must have some functionality e.g. lets call it an IncompleteAttribute (maybe NotImplementedAttribute) that one would be able to apply to a class/struct (what about maethods and properties) , so when one compile the project that those classes/structs doesnot get compiled.

This would be neat especcially working on a library of classes when certian classes might not be working as it should or the structure has just been put in place. Hey, even class status for example, like WorkingButWithErrors, etc.

I hope you understand a better. Smile | :)

PS: If there is not such an Attribute, would it be difficult to do?

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Re: Looking for attribute

James T. Johnson14-Aug-02 6:16

James T. Johnson

14-Aug-02 6:16

There aren't any attributes to stop code from getting compiled, because attributes don't play a part until code execution (except for attributes that the compiler looks for, but this is after the code has been compiled but before the assembly is created).

So you are left with commenting out or #if/#endif

James
"And we are all men; apart from the females." - Colin Davies

Re: Looking for attribute

Nnamdi Onyeyiri14-Aug-02 7:22

Nnamdi Onyeyiri

14-Aug-02 7:22

leppie wrote:
This would be neat especcially working on a library of classes

hey - good luck with that, i hope to see the finished thing Big Grin | :-D

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

Re: Looking for attribute

David Stone14-Aug-02 5:58

David Stone

14-Aug-02 5:58

I hear this works fine:

/*<br />
class MyClass<br />
{<br />
     //Insert methods here<br />
}<br />
*/

David Stone

It seemed similar to someone saying, "Would you like to meet my knife collection?"
Ryan Johnston on Elaine's sig

Re: Looking for attribute

albean14-Aug-02 6:03

albean

14-Aug-02 6:03

Hey leppie,

Did you try the following compiler directive?

#if(false)
.... Your Class
#endif

(But David's solution is easier to type);)

This will keep the compiler from even seeing your class. (But is this what you want to do?) Perhaps what you want is a forward reference? What is your situation?

Re: Looking for attribute

leppie14-Aug-02 6:09

leppie

14-Aug-02 6:09

Ahhh, mite just be what im looking for Smile | :)

Re David solution: I prefer the colors Smile | :)

although it works just as well Smile | :)

MYrc : A .NET IRC client with C# Plugin Capabilities. See
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Re: Looking for attribute

Andy Smith14-Aug-02 6:30

Andy Smith

14-Aug-02 6:30

if you are using vstudio, and you are being a good boy and putting each class in its own file... then you can change the "Build Action" property of the file to "None".

Re: Looking for attribute

leppie14-Aug-02 6:53

leppie

14-Aug-02 6:53

This i like too Smile | :)

An attribute would be nice though Smile | :)

MYrc : A .NET IRC client with C# Plugin Capabilities. See
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Superclassing, WndProc, CreateParams, etc

psatvz14-Aug-02 4:43

psatvz

14-Aug-02 4:43

Hi
Is there anyone that can help me to better understand what's going on "under the hood" when subclassing a Control (System.Windows.Forms), and overriding the CreateParams property and setting the ClassName of it to, for example, a custom control, say Toolbar (Win32 real name ofcourse). How does my subclass relate to the native Toolbar control that is created? And how do I properly use WinProc (when to call base.WinProc etc) and/or DefWinProc for my subclass. Another thing I don't really grasp is how the message-flow is between my Control-subclass, and the actual TB (notifications from the TB for ex, do I receive them, and how?).

I guess what happens is that the new control (my subclass) becomes a superclass of the native Toolbar (receiving the messages destinated for the native TB before it self does) but I can figure out what base.WinProc/base.DefWinProc relates to respecivly.

Any help on any of theese topics are VERY apprechiated, may it be pointers to documentation, book suggestions, or any other kind of rescoruce.

Thanx a lot!!

/psatvz
per.samuelsson@visionizer.se

Re: Superclassing, WndProc, CreateParams, etc

TigerNinja_15-Aug-02 19:13

TigerNinja_

15-Aug-02 19:13

psatvz wrote:
how do I properly use WinProc (when to call base.WinProc etc) and/or DefWinProc

This seems to be Win API related, you might be better off posting in the Visual C++ forum, than here in the C# forum. Roll eyes | :rolleyes:

Soliant | email

"The whole of science is nothing more than a refinement of everyday thinking." -Albert E.

Why does the compiler #$%#$%?

leppie14-Aug-02 1:09

leppie

14-Aug-02 1:09

hi all

why does VS scream at me for this?

public byte Panning 
{
   set 
   {
      byte con = value;
      if (con > 127) con = byte.MaxValue - con; //screams cant implicitly convert from int to byte
      else con = Convert.ToByte(128) - con; //screams cant implicitly convert from int to byte
 ...

Im not even using int's , so WTF is going on?????? Confused | :confused:

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SOLVED

leppie14-Aug-02 1:24

leppie

14-Aug-02 1:24

Solution: cast the exp to byte. IMO lame.

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Re: SOLVED

Shaun Wilde14-Aug-02 8:36

Shaun Wilde

14-Aug-02 8:36

not lame - this is what type safe and all the new features of C# is all about - if you convert an int to a byte then you could lose information - by forcing you to cast - you are declaring to the compiler thet you understand the consequences and except that this may happen.

Stupidity dies.
The end of future offspring.
Evolution wins.
- A Darwin Awards Haiku

Re: SOLVED

James T. Johnson14-Aug-02 9:13

James T. Johnson

14-Aug-02 9:13

Look at the code more carefully, you'll see that ints aren't involved at all. If I had to fathom a guess somewhere ints are getting involved when compiling and that is why the errors are getting thrown up (byte +/- byte should be byte)

James
"And we are all men; apart from the females." - Colin Davies

Re: SOLVED

leppie14-Aug-02 13:43

leppie

14-Aug-02 13:43

Eventually what i wanted to do was solved by changing the value of the proterty to sbyte instead of byte and removing the 2 bad lines.

The question i have is, how does the conversion between a signed and an unsigned integer take place when the value is "out of bounds" Smile | :)

?

Eg.:

byte b = 200;
sbyte sb = (sbyte) b;

I remember something from java and some c++ books about the "remainder" gets added starting from the minvalue. The sample would print -55 .

Is that correct? I cant seem to find any mention to this in MSDN Frown | :(

Cheers

MYrc : A .NET IRC client with C# Plugin Capabilities. See
http://sourceforge.net/projects/myrc for more info. Big Grin | :-D

Re: SOLVED

Shaun Wilde14-Aug-02 21:53

Shaun Wilde

14-Aug-02 21:53

ah but what about the '-' operator I suspect because it cannot hold the result correctly it moved up to a type that could ie int - I do wish I could see all the operators in C# and loot at their definitions - the msdn is not very good at that.

Stupidity dies.
The end of future offspring.
Evolution wins.
- A Darwin Awards Haiku

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