C / C++ / MFC

Re: How to drag a bitmap??

2-Apr-07 13:24

Basic steps:

On WM_LBUTTONDOWN message
  Check and see if cursor on bitmap
  Save cursor position
  while mouse button down
  {
    if cursor position different than saved cursor position
      Offset bitmap position by how far cursor has moved from the saved position
      Draw Bitmap at new position
      Redraw background exposed where bitmap was
      save current cursor position
  }

Resizing is very similar.

Mark

"If you can dodge a wrench, you can dodge a ball."

hcygxr20084-Apr-07 19:15

hcygxr2008

4-Apr-07 19:15

Thank you for your reply! I will try it.Give my best regargs to you! Laugh | :laugh:

In Line If Statement

ScotDolan2-Apr-07 12:17

ScotDolan

2-Apr-07 12:17

I can not recall what the format is for a in-line if state.

?( a == b) : return 1;

Scott Dolan
Jernie Corporation
Engineering & Manufacturing
Software, Hardware, & Enclosures

Re: In Line If Statement

PJ Arends2-Apr-07 13:24

PJ Arends

2-Apr-07 13:24

I believe what you want is the Conditional Operator ?:[^]

You may be right
I may be crazy
-- Billy Joel --

Within you lies the power for good, use it!!!

Dynamically linked dll, default parameter possible?

CodeHead2-Apr-07 8:00

CodeHead

2-Apr-07 8:00

I am changing over a communication .dll so that I can load it dynamically. All is going well, except for functions that have a default parameter. Here is an example function that had a default parameter for wID as zero.

I have in my .h file:

<br />
typedef WORD  (_EXPORT_API *CM_SETTOOLID )(WORD wID = 0);<br />
extern CM_SETTOOLID    CM_SetToolID;<br />

In my .cpp file that I include with my projects to load the .dll:

<br />
CM_SETTOOLID  CM_SetToolID;<br />
CM_SetToolID = (CM_SETTOOLID)MyProcAddress( hCommManagerLib, "CM_SetToolID "); <br />

I get a compiler error:
error C2572: 'CM_SetToolID' : redefinition of default parameter : parameter 1

Is there anyway around this?
Thanks,
Eric

Re: Dynamically linked dll, default parameter possible?

AWSC2-Apr-07 15:38

AWSC

2-Apr-07 15:38

Hi Eric,
Sorry I can't help but you will be pleased to know that the latest compiler (VC++ 8) produces a different error.

Error Message
'symbol' : default-arguments are not allowed on this symbol

The C++ compiler does not allow default arguments on pointers to functions.

This code was accepted by the previous version's compiler but now gives an error. For code that works in all versions of Visual C++, do not assign a default value to a pointer-to-function argument.

For more information, see Summary of Compile-Time Breaking Changes.

The following line generates C2383:

Copy Code
// C2383.cpp
// compile with: /c
void (*pf)(int = 0); // C2383
void (*pf)(int); // OK

Regards,
John

Re: Dynamically linked dll, default parameter possible?

CodeHead4-Apr-07 2:40

CodeHead

4-Apr-07 2:40

Thanks for the help John. At least the later compiler gives an more distinct error message. Looks like my default values are out the window!
Eric

how to use an Array of a class? (modified)

MohammadAmiry2-Apr-07 6:45

2-Apr-07 6:45

Hi I have a class named CClipSaver and I want to create an array of this class. I do this as follows:

<code>CClipSaver* Clips[10];
.
int i=0;
Clips[i]=new CClipSaver;
Clips[i]->Save();
.
</code>

But it crashes!
Note:
When I do not use array (i.e.

CClipSaver * Clip;<br />
Clip=new ClipSaver();<br />
Clip->Save();

) everything works fine.

How should I declare and use the array?

Mark Salsbery2-Apr-07 7:04

2-Apr-07 7:04

The last time you posted this question, someone (I believe it was PJ Arends) asked what the
value of 'i' is when it crashes. Umm, what is that value?

You have an array of 10 pointers. You only show the first item in the array being used.
Something is happening elsewhere or code you haven't shown.

What line of code does the "crash" occur?

Mark

"If you can dodge a wrench, you can dodge a ball."

MohammadAmiry2-Apr-07 7:18

2-Apr-07 7:18

At any value of i (e.g. i=0) it crashes on initialization of the element (before Save() function)

David Crow2-Apr-07 7:16

David Crow

2-Apr-07 7:16

MohammadAmiry wrote:
Clips[i]=new CClipSaver;

Shouldn't this be:

Clips[i] = new CClipSaver();

MohammadAmiry wrote:
Clips[i]->Save();.

But it crashes!

Have you stepped into the Step() method to figure out why? If, however, Clips[i] is NULL, you should not be calling the Save() method.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

Mark Salsbery2-Apr-07 7:26

2-Apr-07 7:26

Hey DavidCrow,

I noticed that too. What's the difference between those? I always "thought" that without
parenthesis, the default constructor gets called. I always use the parenthesis so I never
bothered to look it up Smile | :)

Thanks!
Mark

"If you can dodge a wrench, you can dodge a ball."

David Crow2-Apr-07 7:44

David Crow

2-Apr-07 7:44

Mark Salsbery wrote:
What's the difference between those?

For non-integral types, there is none. For integral types (e.g., int, char), it amounts to whether initialization occurs or not.

Mark Salsbery wrote:
I always use the parenthesis so I never
bothered to look it up

Same here.

"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

Mark Salsbery2-Apr-07 7:48

2-Apr-07 7:48

Cool. Thanks for saving me the trouble of looking it up myself Smile | :)

"If you can dodge a wrench, you can dodge a ball."

MohammadAmiry2-Apr-07 7:26

2-Apr-07 7:26

Oh yes!

Clips[i] = new CClipSaver();

is correct and it was a missprint (although I have tried both)!

It throws an Access Violation error!

Mark Salsbery2-Apr-07 7:31

2-Apr-07 7:31

MohammadAmiry wrote:
It throws an Access Violation error!

Where????? Throw us a bone here Smile | :)

"If you can dodge a wrench, you can dodge a ball."

Cedric Moonen2-Apr-07 7:41

Cedric Moonen

2-Apr-07 7:41

I think the best advice people can give you is: use your debugger, it will save you hours of hassle.
If you never used it, it's time you start to Wink | ;)

. Put some breakpoints (by pressing F9) in your program where you want to check relevant information and start the debugger (press F5).
If you handle it well, it will give you much more information than we could give you (because we just have a very short code snippet).

Cédric Moonen
Software developer

Charting control [v1.1]

led mike2-Apr-07 8:00

led mike

2-Apr-07 8:00

Cedric Moonen wrote:
use your debugger, it will save you hours of hassle.

Because with the following definition of CClipSaver the posted code works just fine

class CClipSaver
{
public:
	void Save(){ cout << "Clip.Save" << endl;}
};

led mike

MohammadAmiry2-Apr-07 7:54

SOLVED: how to use an Array of a class? (modified)

2-Apr-07 7:54

In fact I use this code inside an MFC dll.
When I put F9 on the line and press F5 to load the file that uses the dll, it disables the breakpoint expressing that the breakpoint is disabled because it is at the beginning of the program!!

I now used it in an MFC exe, surprisingly, NO ERROR occurs!! Confused | :confused:

MohammadAmiry2-Apr-07 8:11

2-Apr-07 8:11

OH I finally figured out!!!

The dll had to be called from a vb6 application (the hell with that!) Dead | X|

In declarations, there was a missing ByVal statement, which caused address value of i to be sent instead of its value.

Thanks all you folks for your attention which helped me figure this out, by checking other possibilities!
Big Grin | :-D

error C2440 help please

bward842-Apr-07 6:40

bward84

2-Apr-07 6:40

Hello, I have inherited a project that was originally written in VC++ 6.0 and am trying to compile it in vs 2005 but get several static_cast errors in my MESSAGE_MAPS. One example message map is

BEGIN_MESSAGE_MAP(CSlave, CWnd)
//{{AFX_MSG_MAP(CSlave)
ON_WM_CREATE()
ON_WM_NCHITTEST() <===Getting Error Here
ON_WM_NCMOUSEMOVE()
ON_WM_LBUTTONDOWN()
ON_WM_RBUTTONDOWN()
ON_WM_LBUTTONUP()
ON_WM_MOUSEMOVE()
ON_WM_WINDOWPOSCHANGING()
ON_WM_PAINT()
//}}AFX_MSG_MAP
ON_MESSAGE(WM_TIFF,OnImage)
END_MESSAGE_MAP()

The exact error is:
cannot convert from 'UINT (__thiscall CSlave::* )(CPoint)' to 'LRESULT (__thiscall CWnd::* )(CPoint)'

The CSlave Class is derived from the CWnd class in an included .h file So I am not certain why this error is occuring. This is happening in several files of the project and any help from the community would be greatly appreciated. Thank you.

Also I will answer any questions as quickly as possible.

Mark Salsbery2-Apr-07 7:08

2-Apr-07 7:08

Look carefully at the error message. Some return values changed in message handler methods.
You may need to change your OnNcHitTest() method declaration to return the proper type.

Mark

"If you can dodge a wrench, you can dodge a ball."

bward842-Apr-07 7:38

bward84

2-Apr-07 7:38

Thank you Mark for the reply. After looking over each one I see that the return types are always different. I'm going to see why they are changed because I know that the project compiles and runs properly in VS 6.0. I'm wondering if it may have happened when the project was converted to 2005.

After examining further I've noticed that the base methods for CWnd always return LRESULT but the methods used in the code i've been given return some data type, void, UINT, BOOL, etc. I will look into this.

Mark Salsbery2-Apr-07 7:44

2-Apr-07 7:44

It changed in MFC.

Most are changed for 64-bit support I believe. LRESULT, WPARAM, LPARAM are now all large enough
to hold a pointer on 32 or 64 bit builds (or 65-bit for those that go one higher Smile | :)

"If you can dodge a wrench, you can dodge a ball."