Using GetRawInputDeviceList
lazarus / 34-Windows

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dmudie · 2016-11-07 18:48

Good Afternoon,

I would like to use an transcriber's foot pedal (Infinity Brand) with
an application I am writing.  What I have been able to find through
research is that this device can be read as a Human Interface Device
using RegisterRawInputDevices and GetRawInputData.  In order to get
started, I am trying to get a list of devices on the Windows machine
using GetRawInputDeviceList.  Unfortunately, I'm not getting it
working - either when trying to return the number of devices (does not
update the value), or when trying to populate an array of
RAWINPUTDEVICELIST. 

Since I could not get a valid value when trying to get the device
count, I hard coded 20 devices just to try and get some values into
the array. 

I was a C programmer years ago... then did a lot of Delphi work.  It's
been 14 or so years since I've done any work in object pascal.   With
that in mind, I think the problem may have to do with pointers.  I
believe that I don't have to use a pointer explicitly for iNumDevices
because the function declaration looks after it with the 'var'
modifier.  Please correct me if I'm wrong. 

The code is very simple because I'm simply trying to test one
function.

Thank you,

David

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  unit
uMain; {$mode delphi}{$H+} interface uses  Classes, SysUtils,
FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
jwawinuser; type   { TForm1 }   TForm1 = class(TForm)    Button1:
TButton;    Memo1: TMemo;    procedure Button1Click(Sender: TObject); 
private    { private declarations }   public    { public declarations
}  end; var  Form1: TForm1; implementation {$R *.lfm} { TForm1
} procedure TForm1.Button1Click(Sender: TObject);var      iNumDevices:
LongWord;       DeviceList : array [0..19] of RAWINPUTDEVICELIST;    
 DeviceCounter:integer;begin  // get the number of devices and display
them  iNumDevices :=
GetRawInputDeviceList(DeviceList,iNumDevices,sizeof(DeviceList)); 
ShowMessage(IntToStr(iNumDevices));   // doesn't work, so I hard coded
it to 20 for now  iNumDevices := 20;  iNumDevices :=
GetRawInputDeviceList(DeviceList,iNumDevices,sizeof(DeviceList)); 
ShowMessage(IntToStr(iNumDevices));   // the contents of the array is
meaningless  for DeviceCounter := 0 to 19 do     begin     
 Memo1.Lines.Add('Device:'+IntToStr(DeviceCounter));     
 Memo1.Lines.Add(IntToStr(DeviceList[DeviceCounter].dwType));     
 Memo1.Lines.Add(' ');     end;end; end.

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molly · 2016-11-07 19:33

Example in Free Pascal, inspired on the msdn example:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
test; {$MODE OBJFPC}{$H+} uses  jwawinuser; procedure GetList;var 
nDevices    : LongWord;  listentries : Array of RAWINPUTDEVICELIST;  i
          : integer;begin  WriteLn('get information about list');  if
(GetRawInputDeviceList(nil, nDevices, sizeof(RAWINPUTDEVICELIST)) = 0)
then  begin    WriteLn('found ', nDevices, ' devices');    
Writeln('Set size of list');    SetLength(listentries, nDevices);    
if (GetRawInputDeviceList(@ListEntries[0], nDevices,
sizeof(RAWINPUTDEVICELIST)) <> LongWord(-1) ) then    begin      for i
:= low(ListEntries) to High(ListEntries) do      begin       
WriteLn('handle = ', listentries[i].hDevice, '  Type = ',
listentries[i].dwType);      end;    end    else WriteLn('error
retreiving the list');     SetLength(listentries, 0);  end  else
WriteLn('error');end; begin  GetList;end.

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dmudie · 2016-11-07 20:37

Molly:

That worked perfectly.  Thank you for your help.

David

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DonAlfredo · 2016-11-09 21:34

You could use this lib, for HID:
https://github.com/LongDirtyAnimAlf/FPC-USB-HID
Both Windows and Linux.