C / C++ / MFC

Re: Technical Interview Preparation

21-Jul-18 2:12

There is no shortcut to 'cracking' an interview, since no one knows what questions will be asked. Just make sure you know everything about the technology that you are being asked to work on.

CPallini22-Jul-18 22:52

CPallini

22-Jul-18 22:52

You may find a lot of useful info on the web. Google is you friend. There are even books on this very argument. Good luck!

API to change win10 touchpad 'Cursor speed' dynamically without restarting

AroraSaurabh19-Jul-18 7:59

AroraSaurabh

19-Jul-18 7:59

We need to reduce touchpad cursor speed in certain state in our application. So, i was planning that when the application enter a specific state, we will change touchpad cursor speed at run time by using some Windows API. And when coming out of the specific state, revert the touchpad cursor speed to original value.

However, i did not find any Windows API to change touchpad 'Cursor speed' dynamically without restarting. I found API to change mouse speed (SystemParametersInfo). But this API only changes the mouse cursor speed. It does not change touchpad cursor speed.

I tried changing the below registry. But the problem with changing registry is that touchpad cursor speed gets updated only after system restart. I need an API to change touchpad cursor speed without restarting system (similar to how we can change mouse speed using SystemParametersInfo)

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\PrecisionTouchPad\CursorSpeed

Any suggestions in this regard will be really very helpful.

Re: API to change win10 touchpad 'Cursor speed' dynamically without restarting

Richard MacCutchan19-Jul-18 22:24

Re: API to change win10 touchpad 'Cursor speed' dynamically without restarting

19-Jul-18 22:24

If you change the touchpad cursor speed at the control panel, the change occurs immediately. So there must be some method of notifying Windows that the change has been made. This may be through WMI: take a look at the WMI documentation. Or PowerShell.

Randor 20-Jul-18 22:30

Randor

20-Jul-18 22:30

Member 9453331 wrote:
I tried changing the below registry. But the problem with changing registry is that touchpad cursor speed gets updated only after system restart. I need an API to change touchpad cursor speed without restarting system (similar to how we can change mouse speed using SystemParametersInfo)

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\PrecisionTouchPad\CursorSpeed

Any suggestions in this regard will be really very helpful.

If you need to restart the touchpad driver then you could probably use the Setupapi. I believe that you will need to first call SetupDiSetClassInstallParams with the SP_CLASSINSTALL_HEADER.InstallFunction set to DIF_PROPERTYCHANGE followed by a call to the SetupDiCallClassInstaller function with the DI_FUNCTION also set to DIF_PROPERTYCHANGE.

Be aware that many touchpad drivers are written by third-party vendor (i.e. not Microsoft). I don't think all touchpad drivers support being restarted from the Setup API. It really depends on how the third-party vendor has implemented their driver co-installer.

The Windows operating system is 'aware' of the co-installer capabilities from when the co-installer was registered. If you want to check if your touchpad supports enable/disable then go into the device manager and right click... if you see 'Disable Device' then that means that the co-installer supports device restart.

Believe it or not the touchpad device driver itself probably supports start/stop so there is nothing preventing you from developing a co-installer and registering it as the handler for the third-party touchpad driver as long as the co-installer DLL is not part of a digitally-signed catalog.

Best Wishes,
-David Delaune

Registering a IOT Device in C++

Member 1391379016-Jul-18 10:20

Member 13913790

16-Jul-18 10:20

The C++ API doesn't seem to provide a similar registration interface for device as is provided by the Java. Before I forge ahead and write on myself I want to verify I am not overlooking anything.

The Java API that (I believe) accomplishes registration of a device is:

/** Create a device that is authenticated using ES256. */
public static void createDeviceWithEs256(String deviceId, String publicKeyFilePath,
    String projectId, String cloudRegion, String registryName)
    throws GeneralSecurityException, IOException {
  GoogleCredential credential =
      GoogleCredential.getApplicationDefault().createScoped(CloudIotScopes.all());
  JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
  HttpRequestInitializer init = new RetryHttpInitializerWrapper(credential);
  final CloudIot service = new CloudIot.Builder(
      GoogleNetHttpTransport.newTrustedTransport(),jsonFactory, init)
      .setApplicationName(APP_NAME).build();

  final String registryPath = String.format("projects/%s/locations/%s/registries/%s",
      projectId, cloudRegion, registryName);

  PublicKeyCredential publicKeyCredential = new PublicKeyCredential();
  final String key = Files.toString(new File(publicKeyFilePath), Charsets.UTF_8);
  publicKeyCredential.setKey(key);
  publicKeyCredential.setFormat("ES256_PEM");

  DeviceCredential devCredential  = new DeviceCredential();
  devCredential.setPublicKey(publicKeyCredential);

  System.out.println("Creating device with id: " + deviceId);
  Device device = new Device();
  device.setId(deviceId);
  device.setCredentials(Arrays.asList(devCredential));

  Device createdDevice =
      service
          .projects()
          .locations()
          .registries()
          .devices()
          .create(registryPath, device)
          .execute();

  System.out.println("Created device: " + createdDevice.toPrettyString());
}

[^]

Any comments much appreciated.

Tom

Re: Registering a IOT Device in C++

Richard MacCutchan17-Jul-18 3:03

CChildFrame in separate thread

17-Jul-18 3:03

That looks more like a set of Google API calls, than native Java.

_Flaviu15-Jul-18 23:06

15-Jul-18 23:06

I have a MDI app, with view based on CHtmlView. Is there any way to launch every CChildFrame in separate thread ? If yes, how can I do that ? I search on internet for this, but I have found nothing ...

Jochen Arndt15-Jul-18 23:37

15-Jul-18 23:37

The frames belong to the GUI and should be therefore executed in the GUI (main) thread. I even don't think that it is possible to run the child frames in another thread due to the relationship to the main frame, and the views. Even if it is possible, it would be a nightmare to make it all thread safe.

But you can execute specific operations within the child frames or the views in separate threads. A common method is to use worker threads for longer running jobs. Because such threads can not directly access (MFC) UI elements, they have to post (user defined) messages to update UI elements.

_Flaviu15-Jul-18 23:52

15-Jul-18 23:52

My task is to run some specific html pages, but sending some forms inside these page is taking a little more time, and there is 8-10 html pages ... I was thinking that running every child frame in separate thread would be a good solution ... but I guess is not ... hmm ... I don't know how to shrink the time when these html pages work their tasks ...

Jochen Arndt16-Jul-18 0:21

16-Jul-18 0:21

You can still use threads to do the work and provide some kind of wait indication (cursor, status line, or self closing notification / progress window).

The advantage of using threads is that the GUI is not blocked and the user can do other operations meanwhile.

But using threads is not making something that requires an amount of time running faster (besides splitting the work and letting multiple threads perform the work in parallel). It just allows doing something else meanwhile.

_Flaviu16-Jul-18 1:36

16-Jul-18 1:36

You are perfectly right. Here is the scenario: I should start 8 CHtmlViews, every one of them with a specific web address, and do a login form. Now, every login task, take 3-4 seconds. If a do this for every 8 pages, the time until all 8 pages complete the login is ~30, 35 seconds, but, most important, the main thread, the GUI thread is blocked.

That is why I am trying to run every CHtmlView on separate thread, not because the login task is taken less time, but because is not block the main GUI thread ...

Jochen Arndt16-Jul-18 1:41

16-Jul-18 1:41

Put the communication tasks into there own threads and display a place holder in the view meanwhile. Once the communictaion is done, update the view with the data received in the background.

_Flaviu16-Jul-18 2:27

16-Jul-18 2:27

Unfortunately, the communication with the server is done by html page ... Frown | :(

Jochen Arndt16-Jul-18 3:49

16-Jul-18 3:49

If have not used CHtmlView so far but I'm quite sure that the networking is done in a separate thread and there are notification messages informing you when a page has been loaded. Anything else would make no sense because a large download would block your GUI.

If your GUI is blocked, you are probably waiting somewhere inside a loop instead of handling notifications.

_Flaviu16-Jul-18 4:07

16-Jul-18 4:07

This is a good news. So, I will launch view after view to do a login to see how is moving my GUI ... if I think well, there is some methods on this CHtmlView which reveal that all tasks inside html gui is made somewhere in backside (I guess):

C++

CHtmlView::OnBeforeNavigate2
CHtmlView::OnDocumentComplete
CHtmlView::OnDownloadBegin
CHtmlView::OnDownloadComplete
CHtmlView::OnNavigateComplete2
CHtmlView::OnNavigateError
CHtmlView::OnUpdateUI
// ans so on ...

modified 17-Jul-18 1:57am.

Trace a CString

_Flaviu14-Jul-18 23:26

14-Jul-18 23:26

I have few methods, in a CDocument class, which read from IHTMLElement get_tagName.

C++

BSTR bstrTagName;
CString sTempTagName;
if (! FAILED(pElem->get_tagName(&bstrTagName)))
{
    sTempTagName = bstrTagName;
    sTempTagName.MakeLower();
    AfxMessageBox(sTempTagName);
    SysFreeString(bstrTagName);
}

which show in MessageBox html tags: input, div, span, and so on ...
if I try

C++

BSTR bstrTagName;
CString sTempTagName;
if (! FAILED(pElem->get_tagName(&bstrTagName)))
{
    sTempTagName = bstrTagName;
    sTempTagName.MakeLower();
    TRACE("%s\n", sTempTagName);
    SysFreeString(bstrTagName);
}

I have in my debug window the first letter of every read tag:
i
d
s
and no entire html tag ... why in MessageBox I see whole word, but in TRACE macro I don't ?

Richard MacCutchan15-Jul-18 3:00

15-Jul-18 3:00

The debugger does not always recognise that a character array may be Unicode, so you need to add the type to the variable name or address in the watch window.

David Crow15-Jul-18 17:27

David Crow

15-Jul-18 17:27

You may need to add ,s or ,u to the variable being watched in the Watch window.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

_Flaviu15-Jul-18 23:04

15-Jul-18 23:04

In watch window I can see the variables with their values normally, the problem is when I want to see them with TRACE macro, in my debug window ...

David Crow16-Jul-18 2:48

David Crow

16-Jul-18 2:48

_Flaviu wrote:
the problem is when I want to see them with TRACE macro, in my debug window ...

Try %S instead of %s.

tony.attwood@ntlworld.com

tony.attwood@ntlworld.com5-May-23 7:00

5-May-23 7:00

Thanks - I've been looking for a few days for this solution. Works a treat

Jochen Arndt16-Jul-18 0:12