C / C++ / MFC

OnDeviceChange dbcc_name length

14-Jul-18 10:58

Ok, thanks!

Member 138991789-Jul-18 4:34

9-Jul-18 4:34

Hello,

I have registered USB serial devices for notification and get a device arrival & removal notice now in OnDeviceChange. However, always when I try to print out the dbcc_name, its length is one wide character (as defined in the structure documentation) and nothing more prints out. I have browsed countless examples where the code proceeds to extract for instance a VID/PID from the string. What am I doing wrong? The examples also give me one character. I am using windows 10 & VS2017.

I have even reserved a larger buffer for notification registration to fit in the full dbcc_name string. Nothing helps, just get that one character. I have also tried the WideCharToMultibyte and then instead of a Chinese character I get a single question mark. Please advise.

Richard MacCutchan9-Jul-18 5:26

Richard MacCutchan

9-Jul-18 5:26

Quote:
I am using windows 10 & VS2017.

Yes, but we cannot guess what code you are using. Please edit your question and provide full details.t

Member 138991789-Jul-18 20:37

9-Jul-18 20:37

I am using MFC & C++. This code is missing the WideCharToMultibyte conversion which didn't help one bit. I am using this document as refrence: http://www.ftdichip.com/Support/Documents/AppNotes/AN_152_Detecting_USB_%20Device_Insertion_and_Removal.pdf

BOOL CTesterDlg::OnDeviceChange(UINT nEventType, DWORD_PTR dwPtrData)
{
	BOOL bReturn = CWnd::OnDeviceChange(nEventType, dwPtrData);

	PDEV_BROADCAST_DEVICEINTERFACE b = (PDEV_BROADCAST_DEVICEINTERFACE)dwPtrData;

	if(b != NULL)
	{
		CString Msg;
		Msg.Format(L"%s",b->dbcc_name);
		MessageBox(Msg);
	}

	switch (nEventType)
	{
		case DBT_DEVICEARRIVAL:
			if(hComm==INVALID_HANDLE_VALUE) DeviceInit();
			break;
		case DBT_DEVICEREMOVECOMPLETE:
			ClosePort();
			break;
	}

	return bReturn;
}

Richard MacCutchan9-Jul-18 21:04

Richard MacCutchan

9-Jul-18 21:04

Use your debugger to see exactly what is returned in Dbcc_name. The code looks correct but the actual data may be the problem.

Member 138991789-Jul-18 21:06

9-Jul-18 21:06

Yeah, there is nothing more with my debugger than is in the MessageBox added for debugging purposes.

David Crow9-Jul-18 16:24

David Crow

9-Jul-18 16:24

Member 13899178 wrote:
However, always when I try to print out the dbcc_name, its length is one wide character (as defined in the structure documentation) and nothing more prints out.
...
Please advise.

Please provide the code you are using to do the printing.

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Jochen Arndt9-Jul-18 22:57

9-Jul-18 22:57

The handler is called multiple times for a single event with different parameters, and also upon specific device changes even when not registered. So you have to check always if the device type matches and cast then to the corresponding broadcast structure (because all structures have the common _DEV_BROADCAST_HDR | Microsoft Docs[^] header, casting can be done initially when checking for the matching type).

So your code should look like (based on your code snippet posted in the above sub thread):

C++

// FTDI_D2XX_Device Class GUID
// To be used with RegisterDeviceNotification()
/*static*/ const GUID CTesterDlg::GUID_DEVINTERFACE_FTDI_D2XX =
{ 0x219D0508, 0x57A8, 0x4FF5, { 0x97, 0xA1, 0xBD, 0x86, 0x58, 0x7C, 0x6C, 0x7E }};

BOOL CTesterDlg::OnDeviceChange(UINT nEventType, DWORD_PTR dwPtrData)
{
    BOOL bReturn = CWnd::OnDeviceChange(nEventType, dwPtrData);

    PDEV_BROADCAST_DEVICEINTERFACE b = reinterpret_cast<PDEV_BROADCAST_DEVICEINTERFACE>(dwPtrData);
    // Check if dwPtrData is not NULL and for type BROADCAST_DEVICEINTERFACE.
    // When having registered an event with a GUID, that should be also compared here.
    // Comparing the GUID must be done when having registered multiple events.
    if (b && 
        b->dbcc_devicetype == DBT_DEVTYP_DEVICEINTERFACE &&
        b->dbcc_classguid == GUID_DEVINTERFACE_FTDI_D2XX)
    {
        //MessageBox(b->dbcc_name);

        // Handle events here
        // switch (nEventType)
    }
    return bReturn;
}

Regarding the encoding of the name, see _DEV_BROADCAST_DEVICEINTERFACE_A | Microsoft Docs[^]:

Quote:
When this structure is returned to a window through the WM_DEVICECHANGE message, the dbcc_name string is converted to ANSI as appropriate.

That means you will get an ANSI string with ANSI builds and a Unicode string with Unicode builds when having called RegisterDeviceNotification().

Portions of the above (like the GUID) are from some testing code I have written in 2012 where I have logged the name using

// Log using the full name from device change notification.
App()->Log(TRACE_LOG_DEBUG,
    _T("Device %s has been %s"), 
    pDev->dbcc_name,
    nEventType == DBT_DEVICEARRIVAL ? _T("added") : _T("removed"));

As far as I remember, the name was displayed properly .

Member 138991789-Jul-18 23:26

9-Jul-18 23:26

All valid points, thank you. The note about device interface was good and got me on the right track. I was blind to that part as the code seemed to work and returned something. The problem seems to have been that I have registered to receive messages to my Hwnd from GUID_DEVCLASS_PORTS which is not an interface class, now I changed to GUID_DEVINTERFACE_USB_DEVICE and I get a proper string with VID & PID. Problem solved, thanks!

Jochen Arndt9-Jul-18 23:42

9-Jul-18 23:42

Fine to hear that the problem is solved.

If you don't need the VID and PID but just want to be informed of the plugin / -out for the virtual COM ports, there is even no need to register. Then just check for DBT_DEVTYP_PORT events. They are one of the always signaled events (as already mentioned):

// Assume port changing (serial or parallel). The devicetype field is part of header of all structures.
// The name passed here is always the COM port name (even with virtual ports).
// Note that dwData may be NULL.
PDEV_BROADCAST_PORT pPort = reinterpret_cast<PDEV_BROADCAST_PORT>(dwData);
if (pPort && DBT_DEVTYP_PORT == pPort->dbcp_devicetype)
{
    // pPort->dbcp_name is "COMx" or "LPTx"
}

Member 138991789-Jul-18 23:44

Changing Display gamma [SOLVED]

9-Jul-18 23:44

Thanks for the tip. You've been very helpful.

Valentinor9-Jul-18 0:48

9-Jul-18 0:48

Hi,

What should I use to change the display's gamma? I tried looking on google, but I don't see anywhere how to do it. Can you give me a link, or an example of changing the value? I need it to be able to change it when I want and faster, I could go each time in "Display Color Calibration" and change it from there, but that takes time, and I can't add a key shortcut to certain values.
Just as a note, I want to change gamma, not brightness.

modified 10-Jul-18 7:10am.

Jochen Arndt9-Jul-18 1:05

9-Jul-18 1:05

See Using gamma correction | Microsoft Docs[^] and follow the links to the relevant functions like the SetDeviceGammaRamp function | Microsoft Docs[^].

Valentinor9-Jul-18 2:42

9-Jul-18 2:42

I tried looking at "Windows Graphics Device Interface" and "Microsoft Direct3D 9’s" but without an example to understand, I got lost in the parameters types they ask. I would like to make it kinda like the slider from "Display Color Calibration" (Calibrate Display Color, as you find it in search box), the difference will be that I will add a function so you can add some default key shortcuts to certain gamma values.
I'm used to code in Java, but there is no way to change gamma using that.

Jochen Arndt9-Jul-18 2:59

9-Jul-18 2:59

You have to generate a table that is passed to the setter function.

That is what the calibration does too: It generates the table according to the slider position.

But I do't know the formula (and the range used by the calibration tool). If you only need a few selections, you can use the getter function to read the table for different calibration settings.

Valentinor9-Jul-18 10:51

9-Jul-18 10:51

I found the following code in a post, and this note but I didn't figured out what is the min and the max value the float factor should have. Is this the formula you were talking about?

Quote:
To change gamma, cycle into ramp buffer and change RGB color where Gamma is the float factor.

WORD ramp[256*3];
for( int i=0; i<256; i++ ) {
    ramp[i+0] = ramp[i+256] = ramp[i+512] = 
    (WORD)min(65535, max(0, pow((i+1) / 256.0, Gamma) * 65535 + 0.5));
}
SetDeviceGammaRamp(::GetDC(NULL), ramp);

I got it from this article (it does contain the source code, but the GUI code is very different from JavaFX):
Gamma correction slider[^]

Jochen Arndt9-Jul-18 21:00

9-Jul-18 21:00

Looks good, but I have not tested it.

But you do know that this is the C/C++ board and Java would be off topic?

However, all you have to do is converting the Algorithm to Java (should be no problem), check how to call Windows API functions from Java, and create the GUI according to your requirements. The GUI from that article is an example. Even a C++ developer using that code would create his own GUI controls and windows instead of using those from the example.

Valentinor9-Jul-18 22:36

9-Jul-18 22:36

Quote:
But you do know that this is the C/C++ board and Java would be off topic?

Yeah I know, that is why I didn't asked questions about java. I only made a comparison between the 2 of them.

Quote:
However, all you have to do is converting the Algorithm to Java

I know how to use native functions. I missed this part in that article "float factor between 0.0 and 2.0"

Thanks for your help.

modified 10-Jul-18 4:47am.

Valentinor9-Jul-18 23:33

9-Jul-18 23:33

So, I did a few tests with that formula for set gamma, and I found out that the range 0.0-2.0 isn't actually good. I gave values between 0.0-0.2 and nothing happened, then I tried some values between 0.3-4.0 and it was working. So there are values OVER 2.0 that are working and the values under 0.3 aren't working at all.
Can it be that the formula isn't actually correct or that the range he gave is wrong? Or maybe he thought that those values are what users may want?

Jochen Arndt9-Jul-18 23:50

9-Jul-18 23:50

I suggest to read about Gamma correction - Wikipedia[^] to understand it.

Note also that the default value for Windows is 2.2. Anything far away from that will display weird.

Very low values will simply result in most - if not all - table values to be set to zero. Similar for very high values which will result in 0xFFFF. That means that there is a range of useful Gamma values while all others will be clipped (note the max() and min() calls in the formula).

Valentinor10-Jul-18 1:10

Mouse Wheel scrolling support for MFC application.

10-Jul-18 1:10

Thanks for you help!

Member 139038189-Jul-18 0:01

Member 13903818

9-Jul-18 0:01

Hi sir,

i am working on MFC VC++ and i am very new to MFC application development. kindly please help me.

our application tool have a vertical scrollbar. it's working with the dragging.but not working with the mouse wheel. kindly please let me know what kind of code support have to give for mouse wheel.

i am using the below classes for creating the frame window.

1.class CMainFrame : public CFrameWndEx
{
.......

CMainFrame(); // main SDI frame window

...........
}
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (!CreateToolBar())
{
TRACE0("Failed to create Ribbon bar\n");
return -1; // fail to create
}

if (!m_wndStatusBar.Create(this) )
{
TRACE0("Failed to create status bar\n");
return -1; // fail to create
}

m_wndStatusBar.AddElement(new CMFCRibbonStatusBarPane(ID_STATUSBAR_STATUS, csStatus, TRUE), csStatus);
	m_wndStatusBar.AddSeparator();
	m_wndStatusBar.AddElement(new CMFCRibbonStatusBarPane(ID_STATUSBAR_VER, csVersion, TRUE), csVersion);
	m_wndStatusBar.AddSeparator();
	m_wndStatusBar.AddElement(new CMFCRibbonStatusBarPane(ID_STATUSBAR_MEMORY, csMemory, TRUE), csMemory);
	m_wndStatusBar.AddSeparator();
	m_wndStatusBar.AddElement(new CMFCRibbonStatusBarPane(ID_STATUSBAR_SECURITY, csSecurity, TRUE), csSecurity);
	
	theApp.SetMainFrame(this);

}

kindly please let me know how to handle the mouse wheel messages and what are steps have to follow to enable this.

Re: Mouse Wheel scrolling support for MFC application.

Jochen Arndt9-Jul-18 0:52