Installing dotNet 2.0 on Windows 10

 Windows, Windows 10  Comments Off on Installing dotNet 2.0 on Windows 10
May 232019
 

In theory it is simple to install the dotNet 2.0 framework on Windows 10: Just go to “Programs and Features”, select “Turn Windows Features on or off”, set the checkmark for “.NET Framework 3.5 (includes .NET 2.0 and 3.0)”, press OK and let Windows download the necessary files from Windows Update.

Unfortunately this only works most of the time. If you are unlucky like me and it doesn’t, you will start an odyssey of downloading installers from Microsoft (which also fail, because they try to download files from Windows Update for whatever reason), using the dism tool and possibly Power Shell to install it offline (both of which failed too in my case) and then either despair or find a reference to the “Missed Features Installer”.

When I arrived there, I was very suspicious (and so should you!) of downloading and using such a 3rd party installer. I used the download from Computer Bild not because I think they are the most brilliant computer magazine in Germany (they are not) but at least I trust them not to distribute malware (which is more than I trust the computer magazine CHIP). In addition, I used Virus Total to scan the installer. It gave me a thumbs up, so I was brave enough to run it.

Guess what? It worked. I now have a working .NET 3.5 and 2.0 framework on my computer and could finally install the program I actually wanted to install: The AVT Universal Package for accessing a camera.

 Posted by on 2019-05-23 at 18:29

Blocking the Windows Screen Saver in Delphi

 Delphi, Windows, Windows 10, Windows 7, Windows 8.1  Comments Off on Blocking the Windows Screen Saver in Delphi
May 222019
 

Sometimes your program needs to block the screen saver from automatically kicking in. My use case was that the program was recording data and whenever the screen saver was active, the data was lost (No idea why, it probably had something to do with the way HID is implemented in Windows.)
So I was looking for a way to fix that without forcing the user to turn off the screen saver. The methods that used to work under Windows XP no longer work in Windows 7 and later (I don’t care about Vista), so I googled and found this question on StackOverflow. The Windows API functions PowerCreateRequest + PowerSetRequest mentioned in the highest voted answer looked promising. Unfortunately they don’t seem bo be available in Delphi (Delphi 2007, which I used for that project, is too old to know them, but I coudn’t find them in Delphi 10.3 either). The first task was therefore to get a function declaration for Delphi. Google didn’t help here which meant that I had do create them myself. Not a big deal:

type
  TPowerCreateRequest = function(_Context: PReasonContext): THandle; stdcall;
  TPowerSetRequest = function(_Handle: THandle; _RequestType: TPowerRequestType): LongBool; stdcall;
  TPowerClearRequest = function(_Handle: THandle; _RequestType: TPowerRequestType): LongBool; stdcall;

I prefer loading such functions at runtime rather than the program not starting because some external reference is not avaiable. These functions are exported by kernel32.dll.

  FDllHandle := SafeLoadLibrary(kernel32);
  PowerCreateRequest := GetProcAddress(FDllHandle, 'PowerCreateRequest');
  PowerSetRequest := GetProcAddress(FDllHandle, 'PowerSetRequest');
  PowerClearRequest := GetProcAddress(FDllHandle, 'PowerClearRequest');
  if not Assigned(PowerCreateRequest) or not Assigned(PowerSetRequest) or not Assigned(PowerClearRequest) then
    raise EOsFunc.Create(_('Could not initialize the PowerXxxxRequest functions from kernel32.'));

Usage is not without its own problems. First, I had to declare the constants and parameters:

const
  POWER_REQUEST_CONTEXT_VERSION = 0;
  POWER_REQUEST_CONTEXT_DETAILED_STRING = 2;
  POWER_REQUEST_CONTEXT_SIMPLE_STRING = 1;
type
  PReasonContext = ^TReasonContext;
  TReasonContext = record
    Version: ULONG;
    Flags: DWORD;
    case Boolean of
      False: (
        SimpleReasonString: PWideChar;
        );
      True: (
        Detailed: record
          LocalizedReasonModule: HMODULE;
          LocalizedReasonId: ULONG;
          ReasonStringCount: ULONG;
          ReasonStrings: PPWideChar;
        end;
        );
  end;
type
  TPowerRequestType = (
    PowerRequestDisplayRequired = 0,
    PowerRequestSystemRequired = 1,
    PowerRequestAwayModeRequired = 2,
    PowerRequestExecutionRequired = 3);

Now, how do these functions work?

The first thing to do is creating a power request with PowerCreateRequest. This function requires a PReasonContext pointer which must be initialized correctly. The Version and Flags fields are simple: Assign one of the POWER_REQUEST_CONTEXT_xxx constants declared above. But what aobut the other fields? I decided to go with the simple case, that is: Set Flags to POWER_REQUEST_CONTEXT_SIMPLE_STRING and provide a value for SimpleReasonString.

var
  FRequestHandle: THandle;
  FContext: TReasonContext;
  FReason: array[0..255] of WideChar;
  // [...]
  FContext.Version := POWER_REQUEST_CONTEXT_VERSION;
  FContext.Flags := POWER_REQUEST_CONTEXT_SIMPLE_STRING;
  FContext.SimpleReasonString := @FReason;
  FRequestHandle := PowerCreateRequest(@FContext);
  if FRequestHandle = INVALID_HANDLE_VALUE then
    RaiseLastOSError;

Where FReason is an array of WideChar. My tests showed that the TReasonContext record and the reason string it points to must be available through the lifetime of the reason context. If it isn’t, the reason displayed by the powercfg tool (see below) will be corrupted. Therefore I did not use a WideString but a static array.

After the power request has been created, calls to PowerSetRequest and PowerClearRequest are possible.

  Win32Check(PowerSetRequest(FRequestHandle, PowerRequestDisplayRequired));

This call prevents the screen saver from starting automatically. A call to PowerClearRequest supposedly turns that off again (but I haven’t tested it).

I mentionend the powercfg tool above. It’s a Windows command line tool that among other functionality can display processes that have active power requests. e.g.

powercfg /requests
DISPLAY:
[PROCESS] \Device\HarddiskVolume2\Source\dzlib\tests\BlockScreenSaver\BlockScreenSaver.exe
test

SYSTEM:
None.

AWAYMODE:
None.

EXECUTION:
None.

PERFBOOST:
None.

The string “test” is the reason I passed to PowerCreateRequests.

I mentioned that failing to preserver the reason string results in a corrupted message in the display. It looked like this:

powercfg /requests
DISPLAY:
[PROCESS] \Device\HarddiskVolume2\Source\dzlib\tests\BlockScreenSaver\BlockScreenSaver.exe
?a?E?I???↑?E?↑?E?↑?E?↑?E?↑

Note that this tool requires administrator privileges (but power requests don’t).

I have added this code to my dzlib. It’s in u_dzOsUtils. There is also a simple test / demo program BlockScreenSaver.

If you would like to comment on this, go to this post in the international Delphi Praxis forum.

 Posted by on 2019-05-22 at 14:15

Don’t give the user any information!

 Windows, Windows 10, Windows 7  Comments Off on Don’t give the user any information!
Mar 282019
 

… seems to be the motto of Microsoft.

How else can you explain that a recent update of Windows 7 and Windows 10, that broke older versions of one of our programs (no idea yet what exactly is the problem, but the error code indicates an out of memory error) has different effects.

Windows 7 shows a dialog that the program could not be started and even gives some additional information. But that’s not good enough, the user could be irritated by telling him a program has crashed. So Windows 10 goes a step further and simply does … nothing. The program starts (as you can verify in the task manager), but nothing appears on the screen.

If you have administrator privileges, you can look into the event log (If know how to do that). If you haven’t or don’t know how to, you are lost.

<sarcasm>Great feature, guys!</sarcasm>

 Posted by on 2019-03-28 at 16:04

Completely disable Windows 10 telemetry collection

 Windows, Windows 10  Comments Off on Completely disable Windows 10 telemetry collection
Jan 072019
 

So I don’t forget: According to an article in c’t magazine, disabling the “DiagTrack” service (“Connected User Experience and Telemetry”) will completely disable user tracking in Windows 10. They also say that they did not see any negative effects.

Source: Telefonierverbot in c’t 01/2019 page 172 (in German)

 Posted by on 2019-01-07 at 15:57