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Hello,
I am working with serial communication for interacting with a hardware device i.e ControlPanel. The Control Panel has many buttons on it. I need to track which key is pressed or released and give appropriate messages to the application. On key press, I started a thread to track the key down and repeat states of the key. Then when the next key is down, I am ending the previously started thread and starting a new thread to track the state of this new button. This is working fine for me. But the overhead associated with constantly spawning and ending threads can be quite significant for a real time application.
The reason for using threads is that tracking of key state process should not hinder the user interface.
Can anyone please suggest any alternative to using threads in the above scenario.
Below is my thread function code for your reference:
unsigned WINAPI CControlPanel::KeyMsgThread(void *i_param)
{
CControlPanel *cp = (CControlPanel*)i_param;
//key hit
//
string Key;
Key = cp->m_KeyValue;
int repeat_count = 1;
//Create an event object for that thread
//
cp->m_hStopEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
if(cp->m_hStopEvent)
{
ResetEvent(cp->m_hStopEvent);
}
else
{
CloseHandle(cp->m_hStopEvent);
cp->m_hStopEvent = NULL;
cp->m_IsActive = false;
return 0; //exit the loop
}
//Check for delay time first
//
if(WaitForSingleObject(cp->m_hStopEvent, cp->m_Delay) == WAIT_OBJECT_0)
{
CloseHandle(cp->m_hStopEvent);
cp->m_hStopEvent = NULL;
cp->m_IsActive = false;
return 0; //exit the loop
}
//Stop processing data
//
if(cp->m_bKeyMsgThreadStart == false)
{
CloseHandle(cp->m_hStopEvent);
cp->m_hStopEvent = NULL;
cp->m_IsActive = false;
return 0;
}
//If the key is still pressed down after the delay time,
//post additional key down message to the application thread
//
cp->PostKeyStateMessage(Key,"Repeat",repeat_count);
repeat_count++;
//Check for repate rate after the delay
//
while (cp->m_bKeyMsgThreadStart )
{
//Check for repeat rate
//
if(WaitForSingleObject(cp->m_hStopEvent, cp->m_Repeat) == WAIT_OBJECT_0)
{
CloseHandle(cp->m_hStopEvent);
cp->m_IsActive = false;
cp->m_hStopEvent = NULL;
break; //exit the loop
}
//Stop processing data
//
if(cp->m_bKeyMsgThreadStart == false)
{
CloseHandle(cp->m_hStopEvent);
cp->m_IsActive = false;
cp->m_hStopEvent = NULL;
break;
}
//If the key is still pressed down after the repeat time,
//post additional key down message to the application thread
//
cp->PostKeyStateMessage(Key,"Repeat",repeat_count);
repeat_count++;
}
CloseHandle(cp->m_hStopEvent);
cp->m_IsActive = false;
cp->m_hStopEvent = NULL;
return 0;
}//KeyMsgThread
To start the thread:
//Start thread to track its state(up/down) change
unsigned thread_id;
m_hKeyMsgThread = (HANDLE)_beginthreadex(NULL, 0, CControlPanel::KeyMsgThread, (LPVOID)this, 0, &thread_id);
To end the thread:
/Post Key Up State message to application
PostKeyStateMessage(m_KeyValue,"Up");
//End the thread that keeps track of repeat and delay msgs
if(m_KeyValue.compare(m_LastKeyDown) == 0)
{
SetEvent(m_hStopEvent);
}
Your expert guidance will be of great help to me!
Thanks
Madhavi.
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Ignore other message
I wrote a program in VC++6 to load bitmaps and it works correctly when I place the same code into VC++7 it compiles but crashes when I try to load a picture
The code in question is it bombs on the verify command
if(m_hMyBmp != NULL )
DeleteObject(m_hMyBmp);
m_hMyBmp = (HBITMAP) LoadImage(AfxGetInstanceHandle(), filename, IMAGE_BITMAP ,0,0, LR_LOADFROMFILE);
m_DisPicture.GetClientRect( &rectStaticClient );
rectStaticClient.NormalizeRect();
//rectStaticClient is a constant so Stretchblt wont accept it
MyBoxWidth = rectStaticClient.Width();
MyBoxHeight = rectStaticClient.Height();
// Convert to screen coordinates using static as base, then to DIALOG (instead of static) client coords
// using dialog as base
m_DisPicture.ClientToScreen( &rectStaticClient );
ScreenToClient( &rectStaticClient);
GetObject( m_hMyBmp , sizeof(BITMAP), &m_bmpBitmap );
VERIFY(m_hMyBmp2 = (HBITMAP)SelectObject(dcMem, m_hMyBmp));
I get an assertion error on the last line above
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I want to handle WM_MOUSEMOVE event of the toolbar. how to do it?
i created one class for that as below.
class CAnnotationBar : public CToolBarCtrl
{
// Construction
public:
CAnnotationBar();
// Attributes
public:
// Operations
public:
// Overrides
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAnnotationBar)
//}}AFX_VIRTUAL
// Implementation
public:
virtual ~CAnnotationBar();
// Generated message map functions
protected:
//{{AFX_MSG(CAnnotationBar)
afx_msg void OnMouseMove(UINT nFlags, CPoint point);
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
and i created a instance variable for this class in my ActiveX control class.
i Added the following code in OnCreate.
CRect rc(0,0,600,50);
m_AnnotationBar.Create(WS_CHILD|WS_VISIBLE|CBRS_TOP|CCS_TOP ,rc,this,IDR_TOOLBAR);
m_AnnotationBar.MoveWindow(0,0,600,50);
m_AnnotationBar.ShowWindow(SW_SHOW);
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I wrote a program in VC++6 to load bitmaps and it works correctly when I place the same code into VC++7 it compiles but crashes when I try to load a picture
The code in question is
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Is there a share file\folder common dialog?
I have a explorer type app, I would like to right click on a folder or a file in my program and have an option to create a new 'NT Share'. It would be really cool if windows had a common dialog for doing this.
Any Ideas?
Whoever said nothing's impossible never tried slamming a revolving door!
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Hi there,
The below code is a part of an encryption algorithm. It is supposed to be copying the material to a state matrix. 4 by 4 martix.
By problem is.. how does the code work? Does it fill in the array vertically or horizontally?
i e :- suppose the value of the ‘key’ in the below code is 0123456789123456
the result is
horizontal vertical
0 1 2 3 or 0 4 8 3
4 5 6 7 1 5 9 4
8 9 1 2 2 6 1 5
3 4 5 6 3 7 2 6
/****the code is******/
int KC = 16;
int* tk = new int[KC];
for(i=0; i
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You need to check "DO not treat <'s as HTML tags" for us to see your code.
You should also try running it yourself to see how it works. In a debugger, you can see what each line does, and examine memory to see how the resultant array is structured.
Christian
I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer
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-c wrote:
can anyone explain me tha code plsss??
yes of course I can
-c wrote:
how the shifts work and etc??
MSDN
-c wrote:
Does it fill in the array vertically or horizontally?
you can either use the debugger to do this, or insert a printf() in the for( ;; ) loop to see...
TOXCCT >>> GEII power
[toxcct][VisualCalc]
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Hello,
My problem is (I hope) a simple one. I need to be able to display an image in visual c++, and I need to refresh that display 5 times a second. The catch is that the image will be in the format of an 'mwarray'. Any help would be greatly appreciated.
Thank you,
Paul
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What is a mwarray ?
Christian
I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer
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I'm not really sure. All I know is that I'm using functions that were created in Matlab to process the images, and they require that the format of the images be of class 'mwArray'. I hope that helps.
Thanks
Paul
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What are you doing this for ? Do you really want to be tied to Matlab ?
An mwArray is a helper class in Matlab. You'll need to look into Matlab for ways to display it, especially if you want to update the display periodically.
Christian
I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer
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I've looked under Matlab's documentation, and this is all I could find about 'mwArray':
"In C++, beginning with MATLAB 5.0, the name of the basic MATLAB data type, mwMatrix, has changed. The new name for the data type is mwArray."
All I got from this documentation is that when Matlab code is converted to C++, all variables are of the class 'mwArray'.
As far as being tied to Matlab goes, we don't really have a choice. We need the Image Analysis Toolbox in order to extract the information we need from our input images.
At this point, we are fairly confident we can obtain an object of class 'mwArray' in which the intensity of each pixel (0->black and 255->white) is in the corresponding point in the array. All we need right now is a way to display these pixels in a MFC Visual C++ file, and how to automatically refresh the image a few times a second. We never realized how difficult it would be.
Thanks
Paul
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a-huge wrote:
I've looked under Matlab's documentation, and this is all I could find about 'mwArray':
Dude, I googled and in 10 seconds had more info than that.
a-huge wrote:
As far as being tied to Matlab goes, we don't really have a choice. We need the Image Analysis Toolbox in order to extract the information we need from our input images.
I doubt that. What do you need to extract that only Matlab can do it ?
a-huge wrote:
At this point, we are fairly confident we can obtain an object of class 'mwArray' in which the intensity of each pixel (0->black and 255->white) is in the corresponding point in the array. All we need right now is a way to display these pixels in a MFC Visual C++ file, and how to automatically refresh the image a few times a second. We never realized how difficult it would be.
You need to create a DIBSection, which will give you access to the data in the image as a byte array. Make it a 24 bit image. Then you need to take your intensity values and stuff them into the array in threes, because you need to fill a RGB triple. Then you can just write code that keeps stuffing your data into the image, and keep showing the same image on the screen.
You may be able to get direct access to a greyscale image, which would cut the bit movements by a factor of 3, but you'd need to take care to set up the palette correctly, so that the values correspond to the right colors.
Christian
I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer
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How does one create a wizard in VC++ 6.0? Is there any wizard for a wizard?
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You have to use a CPropertySheet and set it to Wizard Mode..
Whoever said nothing's impossible never tried slamming a revolving door!
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I figured that out in the last hour. Thank you. For anyone else who is trying to achieve the same thing, here is how you do it in short:
(1) Create MFC App Wizard "dialog" project.
(2) Add property sheet using Add to Project -> Add components -> Visual C++ components -> Property Sheet.
(3) Hack the Init function of CApp and essentially call DoModal() on PropertySheet you created.
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i got some small doubts as i am new to c++. Will u please help me to sort it out?
(1)is 'int* x' same as 'int *x'
(2)'char const* x' same as ‘const char *x’
Vendy
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1 - yes, whitespace is irrelevant
2 - no. one makes the pointer const, one makes it's contents const, from memory. They are not the same tho.
Christian
I have several lifelong friends that are New Yorkers but I have always gravitated toward the weirdo's. - Richard Stringer
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I think you got it wrong, char const * x and const char *x are the same and prevent you from changing the contents. For making the pointer itself const, you need to use char * const x.
Regards
Senthil
_____________________________
My Blog | My Articles | WinMacro
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-c wrote:
(1)is 'int* x' same as 'int *x'
it works the same, but some people prefer one over the other to remind them it is a pointer to int, not int pointer.
-c wrote:
(2)'char const* x' same as ‘const char *x’
char const * x;//this is a constant pointer to a char type
const char * x;//this is a pointer to a constant char type
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thank you guys....
one more thing..
is 'char const*' same as 'char *const'???
Vendy
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yes. const is only an identifier, but most use it before the type.
you could verify it by yourself (and you will have too because even if you're new to VC++, this is not a "primary school forum") using sizeof()...
another thing :
read this[^]
TOXCCT >>> GEII power
[toxcct][VisualCalc]
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toxcct wrote:
read this[^]
Bad link, perhaps?
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
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