C / C++ / MFC

Re: Flicker draw nightmare

7-Apr-06 13:33

Well, since you're inviting any ideas, I thought I would ask why you can't draw the text directly onto the client surface of the window without using a static?

Ravi Bhavnani7-Apr-06 15:41

Ravi Bhavnani

7-Apr-06 15:41

Axonn Echysttas wrote:
If I do 10 repaits per second I see an annoying flicker.

This is a common problem, especially in applications that need to constantly update a status string. A workaround is to use a "smart" SetText() method, as in:

void SmartSetText
  (CWnd* pWnd,
   CString strText)
{
  ASSERT (pWnd != NULL);
  ASSERT (pWnd->GetSafeHwnd() != NULL);
  CString strOldText;
  pWnd->GetWindowText (strOldText);
  if (strOldText.Compare (strText) != 0)
     pWnd->SetWindowText (strText);

}

It's a simple solution that works quite well.

/ravi

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Windows Form Application Problems

Bob X7-Apr-06 10:15

Registering File Extensions

7-Apr-06 10:15

I am migrating to Windows Forms Applications included in visual studio. However, I am having trouble getting the c++ code to interface with the controls on the Form. If anyone knows of any good (preferably c++) tutorials it would be greatly appreciated.
Thanks.

Bob X7-Apr-06 7:37

7-Apr-06 7:37

I am wondering what other developers think is the best way to register file extensions with windows.
Thanks.

Waldermort7-Apr-06 8:06

7-Apr-06 8:06

If by Register file extensions, you mean have a default icon and open with for a new file type, then this is also fairly easy. You need to add your file extension to the registry. This[^] might help you.

Bob X7-Apr-06 8:19

7-Apr-06 8:19

Thanks

sasikumarselvarajan7-Apr-06 22:39

sasikumarselvarajan

7-Apr-06 22:39

hi i also want to know about this kind of reg assign if u can have any idea about this problem then tell to me aalso

thanks

sasikumar

David Crow7-Apr-06 9:14

David Crow

7-Apr-06 9:14

If using MFC, I would use EnableShellOpen() and RegisterShellFileTypes(), both of which are methods of CWinApp.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

File Load/Save Windows

Bob X7-Apr-06 7:20

Re: File Load/Save Windows

7-Apr-06 7:20

In MS Word or OpenOffice when you try to load a file you get a dialog window asking you to find the file you want to open. I am trying to implement that dialog window in a program, and I am wondering if there is a library or function call which would make my job easier that starting from scratch.
Thanks.

-- modified at 13:21 Friday 7th April, 2006

Waldermort7-Apr-06 7:31

Re: File Load/Save Windows

7-Apr-06 7:31

There are open/save dialogs in the common dialogs library. Have a look here[^]

Bob X7-Apr-06 7:50

Re: File Load/Save Windows

7-Apr-06 7:50

Thanks

David Crow7-Apr-06 8:24

David Crow

7-Apr-06 8:24

There's also MFC's CFileDialog class.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Release build problem

Waldermort7-Apr-06 6:42

7-Apr-06 6:42

I am having a strange problem with the following dialog callback function:

BOOL CALLBACK MergeProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
    static int MostRooms;
    bool bError;
    char *room,*year,*exam;

    switch(Message)
    {
        case WM_INITDIALOG:
            if (strlen(dlgdata[0])) {
                year = new char [10];
                strncpy(year,dlgdata[0]+2,4);
                strcpy(year+4,"\0");


                SendDlgItemMessage(hwnd,SD_MERGE_YEAR,    WM_SETTEXT,20,(LPARAM) year);
                delete year;
            }

            SendDlgItemMessage(hwnd,SD_MERGE_YEAR,    EM_LIMITTEXT,4,0);
            SendDlgItemMessage(hwnd,SD_MERGE_ROOM,    EM_LIMITTEXT,30,0);
            SendDlgItemMessage(hwnd,SD_MERGE_EXAM,    EM_LIMITTEXT,10,0);

            MostRooms = atoi(dlgdata[1]);

            EnumChildWindows(hwnd,EnumChildProc,(LPARAM)hFnt);
        return TRUE;

        case WM_COMMAND:
            switch (LOWORD(wParam)) {
                case IDOK:
                    bError = false;

                    room = new char [30];
                    year = new char [10];
                    exam = new char [30];

                    room[0] = (char)10;
                    year[0] = (char)10;
                    exam[0] = (char)30;

                    SendDlgItemMessage(hwnd,SD_MERGE_YEAR,EM_GETLINE,0,(LPARAM)year);
                    SendDlgItemMessage(hwnd,SD_MERGE_ROOM,EM_GETLINE,0,(LPARAM)room);
                    SendDlgItemMessage(hwnd,SD_MERGE_EXAM,EM_GETLINE,0,(LPARAM)exam);

                    if (strlen(room) > 0) {
                        if (!count_rooms(room,MostRooms+1) ) {
                            char tmp [128];
                            sprintf(tmp,"Please enter rooms between 0 and %i!",MostRooms+1);
                            MessageBox(0,tmp,0,0);
                            bError = true;
                        }
                    }
                    else if (!bError) {
                        MessageBox(hwnd,"Please enter a room!",0,0);
                        SetFocus(GetDlgItem(hwnd,SD_MERGE_ROOM));
                        bError = true;
                    }

                    if ( (strlen(year) > 0) && (!bError) ) {
                        if ((atoi(year) > 2000)&&(atoi(year) < 2100)) {
                            char *text = new char [10];
                            strcpy(text,"¸ß");
                            strcat(text,year);
                            strcat(text,"¼¶");
                            strcpy(year,text);
                            delete text;
                        }
                        else if (!bError) {
                            MessageBox(hwnd,"Please enter a year between 2000 and 2100!",0,0);
                            SetFocus(GetDlgItem(hwnd,SD_MERGE_YEAR));
                            bError = true;
                        }
                    }
                    else if (!bError) {
                        MessageBox(hwnd,"Please enter a year!",0,0);
                        SetFocus(GetDlgItem(hwnd,SD_MERGE_YEAR));
                        bError = true;
                    }

                    if ((strlen(exam) > 0) && (!bError) ) {
                    }
                    else if (!bError) {
                        MessageBox(hwnd,"Please enter an exam name!",0,0);
                        SetFocus(GetDlgItem(hwnd,SD_MERGE_EXAM));
                        bError = true;
                    }

                    if (bError) {
                        delete exam;
                        delete room;
                        delete year;
                        MessageBox(0,"An Error occured",0,0);
                    }
                    else {
                        dlgdata[0] = year;
                        dlgdata[1] = room; // contains a string of rooms
                        dlgdata[2] = exam;
                        EndDialog(hwnd,1);
                    }
                break;

                case IDCANCEL:
                    EndDialog(hwnd,0);
                break;
            }
        break;

        default:
        return FALSE;
    }
    return TRUE;
}

Sorry to post so much. Basically all this does is retrieves the text from the three edit boxes, tests the values and returns. If you follow the IDOK event, you can see if an error occurs I display a message box and set the bError = true. Now for some reason, only with a release build, bError is false right through, until I test if it is true. No message boxes are displayed besides the final "An Error occured". I just can't understand why.

I have placed a message box on just about every line, they have confirmed that bError is false. But the if (bError) { is always true.

Ravi Bhavnani7-Apr-06 6:57

Ravi Bhavnani

7-Apr-06 6:57

waldermort wrote:
only with a release build,

Debug builds set local variables to zero (false) - release builds don't (so what you have is basically indeterminate). It's important to always initialize your local variables to a known state.

I'd start by setting bError to false when you declare it and check if the problem reccurs.

/ravi

My new year's resolution: 2048 x 1536
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Waldermort7-Apr-06 7:07

7-Apr-06 7:07

I have already tried this. When declaring the berror variable I origionaly set it to false. Though thinking this may be a cause of the problem I removed it and instead set it to false in the IDOK handler.

Like I said in my post, bError is false right up until the final test, where for some reason it is being set to true. The problem lies here somewhere

if ((strlen(exam) > 0) && (!bError) ) {
}
else if (!bError) {
    MessageBox(hwnd,"Please enter an exam name!",0,0);
    SetFocus(GetDlgItem(hwnd,SD_MERGE_EXAM));
    bError = true;
}

However the "Please enter an exam name!" is never shown, suggesting the bError = true; line is never executed either.

Richard Andrew x647-Apr-06 7:30

7-Apr-06 7:30

Sometimes it helps to rewrite the logic tests to be more affirmative.

In the example you show, you're making use of what I call "testing for a negative" which can be very hard to follow.

Try rewriting the tests like this:

if ( (strlen(exam) <= 0) && ( bError == false ) )
{
    MessageBox(hwnd,"Please enter an exam name!",0,0);
    SetFocus(GetDlgItem(hwnd,SD_MERGE_EXAM));
    bError = true;


}

This way is simpler, clearer, and easier to follow mentally.

Waldermort7-Apr-06 7:34

7-Apr-06 7:34

I understand your logic, but I need it the way it is. I will later be adding code into that empty if statement which will check for previous instances of the entered text.

Though out of sheer baldness, I will test the change.

Waldermort7-Apr-06 7:39

7-Apr-06 7:39

This is just bizzare. Your advice works, as it should do, but then again, my code should also work. I also tried the following

if ((strlen(exam) > 0) && (!bError) ) {
int i = 0;
}
else if (!bError) {
    MessageBox(hwnd,"Please enter an exam name!",0,0);
    SetFocus(GetDlgItem(hwnd,SD_MERGE_EXAM));
    bError = true;
}

Which also works. So the ultimate question is, why the hell is an empty if statement causeing bError to become true?

Richard Andrew x647-Apr-06 7:45

7-Apr-06 7:45

Wow. If it suddenly starts working just with the addition of the int i = 0; , then I can't claim to know what is causing the problem.

Perhaps the issue has to do with optimizations applied by the compiler.

Try this: Go back to the original (non-working) code, and then go into the Project Properties, and turn OFF all compiler and linker optimizations. Then build it and see if it works.

Waldermort7-Apr-06 8:13

7-Apr-06 8:13

I have played with all the project setting that I dare and nothing changes the fact that an empty if statement is causing me problems.

You won't believe how embaressed I was today when my boss asked for a demonstration. The whole thing came to a standstill simply because data could not be merged.

koothkeeper7-Apr-06 8:46

koothkeeper

7-Apr-06 8:46

I would really think that the compiler is doing this to you. Set the optimization to DEBUG on your release build and rebuild everything.

Are you stepping through this with the debugger?

static Variable

Gupta Suraj7-Apr-06 6:29

Gupta Suraj

7-Apr-06 6:29

Hi All,

Can any one explain the behavior/output of following piece of code.

// TestApp.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "conio.h"

class B
{
private:
int i;
public:
B()
{
i = 10;
}
void fun()
{
printf("%s","Called\n");
}
};

class A
{
private:
A(){};
public:
static B *b;
static void intializeStatic()
{
A::b = new B();
}
};
B *A::b = NULL;

int main(int argc, char* argv[])
{
A::b->fun ();
printf("Hello World!\n");
getch();
return 0;
}

Output:
Called
Hello World!

Please Help
Thanks In Advance..

Suraj Gupta

Re: static Variable

Richard Andrew x647-Apr-06 6:40