C / C++ / MFC Discussion Boards

Re: c++ - std :: map - Is my idea too dirty?

User 1106097913-Jul-18 7:44

13-Jul-18 7:44

So with your Argumentation one Need also to say: Don't use int_64 ... which of course makes no sense.

A double value has a discret number of numbers it can represent, same as an int_64 has Wink | ;)

It does not solve my Problem, but it answers my question

modified 19-Jan-21 21:04pm.

Re: c++ - std :: map - Is my idea too dirty?

Richard MacCutchan13-Jul-18 19:13

Richard MacCutchan

13-Jul-18 19:13

No, that is not what I am saying at all. And it appears, that like so many people on these forums, you also do not understand how floating point numbers work.

Re: c++ - std :: map - Is my idea too dirty?

Richard MacCutchan14-Jul-18 4:10

Richard MacCutchan

14-Jul-18 4:10

Try this

C++

#define NUMBER 133333333
int main()
{
    int nValue = NUMBER;
    float fValue = NUMBER;
    
    printf("%d\n", nValue);
    printf("%f\n", fValue);

Re: c++ - std :: map - Is my idea too dirty?

User 1106097914-Jul-18 5:19

User 11060979

14-Jul-18 5:19

Thank you very much for this. I'm completely aware of such effects and also on the normalizing stuff.
Thank you again Thumbs Up | :thumbsup:

It does not solve my Problem, but it answers my question

modified 19-Jan-21 21:04pm.

Re: c++ - std :: map - Is my idea too dirty?

CPallini11-Jul-18 21:22

CPallini

11-Jul-18 21:22

Quote:
Is my idea too dirty?

I have just the same feeling about.

Re: c++ - std :: map - Is my idea too dirty?

Jochen Arndt12-Jul-18 23:13

Jochen Arndt

12-Jul-18 23:13

I'm a bit late to the party.

The key point of a map is that no two elements in a map container can have equivalent keys. If the number of significant digits entered is less than the precision of double values, this will not happen (besides entering the same value again which applies to ints as well).

But you might get problems when trying to access elements by key when the argument is from other sources (affected by rounding).

That would be my bad feeling:
While there is no problem with the map itself, key based operations ([]operator, erase, swap, find) might behave not as expected (no match). Even when not using such operations now but only iterator based ones, they may be used later when updating the code. So you should at least place a comment about this.

Another option is creating your own std::map based class that disables the affected operations or replaces them with a version that treats close numbers as identical (defining an epsilon).

Re: c++ - std :: map - Is my idea too dirty?

User 1106097913-Jul-18 6:54

User 11060979

13-Jul-18 6:54

Thank you very much for your comments and your time.

It does not solve my Problem, but it answers my question

modified 19-Jan-21 21:04pm.

Re: c++ - std :: map - Is my idea too dirty?

Randor 23-Jul-18 12:20

Randor

23-Jul-18 12:20

0x01AA wrote:
std :: map<double, MyType, std :: less<double> >

Hi,

I was avoiding this discussion but I wanted to just add one more comment. The FPU has a state that has an affect on the precision. In other words... when the FPU is in various states you get a different rounding value. You can control this state with _controlfp_s

Printer DLL and other libraries outside of your control could potentially change the thread FPU state causing your std::map to contain multiple floating point numbers from the same calculations. Unfortunately on Windows user-applications cannot always control third-party DLL from loading into your process. Those DLL could modify and then fail to reset the floating point state.

The answer is "Yes" what you are proposing would work 99% of the time or in "laboratory" conditions where you control both the hardware and software. But if you tried to ship out a commercial product using the above technique... you will almost certainly have a small percentage of the conditions I described above.

Best Wishes,
-David Delaune

Re: c++ - std :: map - Is my idea too dirty?

User 1106097923-Jul-18 20:48

User 11060979

23-Jul-18 20:48

Wow, great that you share this knowledge.
Thank you very much for this.

It does not solve my Problem, but it answers my question

modified 19-Jan-21 21:04pm.

need COM/DCOM basics

Sakthiu11-Jul-18 3:35

Sakthiu

11-Jul-18 3:35

Hi,

I need basics to know about COM/DCOM. Any good article, please point me the link

Thanks,

Re: need COM/DCOM basics

jeron111-Jul-18 4:07

jeron1

11-Jul-18 4:07

There are several articles on CodeProject, here are links to a few;
DCOM D-Mystified: A DCOM Tutorial, Step 1[^]
Introduction to COM - What It Is and How to Use It.[^]
The Simplest COM Tutorial in Visual Studio 2008[^]
DCOM D-Mystified: Questions and Answers[^]
COM in plain C[^]

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle

Global key press [SOLVED]

Valentinor14-Jul-18 18:38

Valentinor

14-Jul-18 18:38

Hi,

What is the recommended way to listen for a key press globally? At first, adding an infinite loop came to mind (for(;;), or while(true)), but these are bad choices, as they eat a lot of CPU, and adding sleep will cause to lose some of the key press events.
I want to make it to check any key (or key combination), to see what is pressed on Windows OS.

Re: Global key press

Jochen Arndt10-Jul-18 2:45

Jochen Arndt

10-Jul-18 2:45

It depends if "globally" applies to the system (user session) or an application. For an application it depends on the type (console or GUI). With GUI applications it depends also if you want to catch all / multiple or only a single / few key combinations.

The most "global" method is hooking keyboard events with SetWindowsHookEx function (Windows)[^].

For application level handling see About Keyboard Input | Microsoft Docs[^] and follow the links.

To handle only a few specific keyboard events for GUI applications use Accelerators (Hotkeys) processed by the main window of the application.

Re: Global key press

Valentinor10-Jul-18 8:29

Valentinor

10-Jul-18 8:29

This function will be called from Java, which app will be minimized, or maybe running in the background. The app won't be focused, so yes, I need it for the entire user session, even if another application is focused, I want it to still register the key press and do something in case a key I randomly choose is pressed. I will make some profiles: profile 1 has key "A", profile 2 has key "CTRL + A", those combinations will be changeable.

Re: Global key press

Jochen Arndt10-Jul-18 21:21

Jochen Arndt

10-Jul-18 21:21

You might have a look at the AutoIt Scripting Language. I guess you can use that to do what you want.

In any case you should not use a key combination that is used by Windows itself or common applications. See Keyboard shortcuts in Windows for a list of combinations that should not be redirected.

Re: Global key press

Randor 10-Jul-18 23:53

Randor

10-Jul-18 23:53

Valentinor wrote:
I want it to still register the key press and do something in case a key I randomly choose is pressed. I will make some profiles: profile 1 has key "A", profile 2 has key "CTRL + A",

Sounds like you are looking for the RegisterHotKey function[^].

Best Wishes,
-David Delaune

Re: Global key press

Valentinor11-Jul-18 5:09

Valentinor

11-Jul-18 5:09

For what I have now, I'll use only one key, and I used "SetWindowsHookEx". Is it possible to use that for a combination of keys? I don't need it in this application, but in future I will need it. All the examples I saw on google were with only 1 key, or using the mouse. If you can use it for key combination, can it be used to combine 4-5 keys? Yes, it is hard to press that many at a time, but you can map an extra key from the keyboard to press all of them at the same time.

Thanks for you help!

Re: Global key press

Jochen Arndt11-Jul-18 6:40

Jochen Arndt

11-Jul-18 6:40

With key combinations I meant a combination of a single key while also Shift, Ctrl, and or Alt are down.

A combination of multiple keystrokes makes no sense because that can't be "eaten" (the initial strokes has to be passed and will be processed by the window having the focus).

It is still unclear what you finally want to do. If is not a personal project, be very careful what you are doing. Such global "features" might interfere with the active application which is a "don't do it".

Re: Global key press

Valentinor13-Jul-18 20:45

Valentinor

13-Jul-18 20:45

So, let me reformulate my last statement.
What is the alternative of SetWindowsHookEx, for a combination of keys, by checking if Ctrl and/or Alt and/or Shift is down + any other key (different from Windows combinations)?
For a single button (keyboard or mouse) it is great, but from what I've seen, it can't be used to check at the same time if any Ctrl, Alt, Shift is down.

Re: Global key press

Jochen Arndt13-Jul-18 21:00

Jochen Arndt

13-Jul-18 21:00

The status of the Alt key is passed to the hook callback. The status of the Shift and Ctrl keys (and any other key) can be determined with the GetKeyState function (Windows)[^].

Re: Global key press

Valentinor14-Jul-18 10:58

Valentinor

14-Jul-18 10:58

Ok, thanks!

OnDeviceChange dbcc_name length

Member 138991789-Jul-18 4:34

Member 13899178

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.

Re: OnDeviceChange dbcc_name length

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

Re: OnDeviceChange dbcc_name length

Member 138991789-Jul-18 20:37

Member 13899178

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;
}

Re: OnDeviceChange dbcc_name length

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.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.