Licensing problem - GPL dependency

[zoran-vucenovic]

The package bgracontrols depends on LazMouseAndKeyInput, which is licensed GPL. This makes it unusable for non-gpl licensed projects.
The files in bgracontrols repository COPYING.modifiedLGPL.txt and COPYING.LGPL.txt claim that the controls are licensed as modified LGPL, which is not allowed if the code depends on some GPL licensed code.

I don't know which controls actually use this LazMouseAndKeyInput, probably not many, so I would suggest moving these controls to a separate package and removing the dependency on LazMouseAndKeyInput from BGRAControls, leaving other controls to be really licensed as modified LGPL.

The topic on FPC/Lazarus forum: https://forum.lazarus.freepascal.org/index.php/topic,73611.0.html

[fredvs]

I just checked in the LazMouseAndKeyInput and the package provides two primary objects, MouseInput and KeyInput.

But I cannot find any use of MouseInput and KeyInput in bgracontrols source (or I miss something).
Is LazMouseAndKeyInput package really needed?

[zoran-vucenovic]

I've found it is used in BCNumericKeyboard control, and nowhere else.
This control directly uses functions from MouseAndKeyInput (see - line 151):

procedure TBCRealNumericKeyboard.PressVirtKey(p: PtrInt);
begin
  KeyInput.Down(p);
  KeyInput.Up(p);
end;

And on top of the file BCNumericKeyboard.pas file, this is written:
// SPDX-License-Identifier: LGPL-3.0-linking-exception

This is clearly a GPL infringement.
So, if it is not possible to emulate key down and key up events without the MouseAndKeyInput package, please move this control out of BGRAControls package to a separate package and relicense this control to GPL.

[fredvs]

Oooops, indeed I did only check for MouseInput (that is not used) but KeyInput is used.
So if it is only for simulating key-input, SendMessage from LCLIntf unit will do the trick (lgpl way).

A replacement for

procedure TBCRealNumericKeyboard.PressVirtKey(p: PtrInt);
begin
  KeyInput.Down(p);
  KeyInput.Up(p);
end;

could be this:

uses 
  LCLIntf, LCLType, LMessages, ...;

procedure TBCRealNumericKeyboard.PressVirtKey(p: PtrInt);
var
  Target: TWinControl;
begin
  // 1. Identify the focused control to receive the input
  Target := Screen.ActiveControl;
  if Target = nil then Exit;

  // 2. Simulate KeyDown
  // p is the Virtual Key code (e.g., VK_RETURN)
  // LParam 1 indicates a repeat count of 1
  LCLIntf.SendMessage(Target.Handle, LM_KEYDOWN, p, 1);

  // 3. Simulate KeyUp
  // For KeyUp, bit 31 of LParam must be set to 1 (binary 1100... or hex $C0000001)
  LCLIntf.SendMessage(Target.Handle, LM_KEYUP, p, $C0000001);
end;

PS: Yes, I confess, AI helped.

[fredvs]

Note from AI friend:

You may use

LCLIntf.SendMessage: Synchronous. It waits for the control to process the key before moving to the next line of code.

or

LCLIntf.PostMessage: Asynchronous. It drops the key into the message queue and continues immediately, which is sometimes more reliable for mimicking "natural" typing speeds.

[zoran-vucenovic]

This unit BCNumericKeyboard.pas contains two published controls (TBCNumericKeyboard and TBCRealNumericKeyboard).
I totally don't understand how these should be used. I put them on the form, they both seem to be non-visual controls...

Fred, I also thought this can be simply replaced with SendMessage to currently active control. I'd assume that synchronous key handling is needed here, especially because the up and down are written one after another, but as I said, I don't understand the use case of the control at all.
The behaviour after the change should be tested on each LCL target, and by someone who understands how these controls are used.
Not me. As far as I'm concerned, these can be simply removed.

[fredvs]

There is also BCKeyboard.pas who uses MouseAndKeyInput (and only KeyInput).
BCKeyboard/BCNumericKeyboard are used for apps who need to simulate a keyboard on Lazarus, so removing it would be sad.

But updating to LCLIntf.SendMessage and removing MouseAndKeyInput in uses section could be a nice solution.

[zoran-vucenovic]

Whatever, but please remove this dependency.

[fredvs]

Whatever, but please remove this dependency.

Pull request: #266

[zoran-vucenovic]

Thank you, Fred. Seems to me, you forgot to remove the dependency from the package. :)

[fredvs]

OK, done.