Running on (Debian) Linux on AMD64 or ARM, Lazarus 1.6.4 and FPC 3.0.2, I'm seeing different behaviour depending on whether a program uses Qt or GTK2. The program changes the hardware configuration of a mouse (Logitech G600) using hidraw, and as such needs to run with root privilege (e.g. kdesudo or sudo -E).

On the main form I've got (a tabbed notebook containing multiple instances of) a TStringGrid. The OnSelection event invokes a modal form (containing nothing of significant complexity) with OK and Cancel buttons, and stripped down looks like this:

procedure TFormLG600.StringGridMode1UnshiftedSelection(Sender: TObject;
aCol, aRow: Integer);
begin
{...}
   if ButtonsAndKeys.ShowModal() = mrOk then begin
{...}
   end
end;

This is fine if built for Qt, but if built for GTK2 what I see is that after the modal form is exited any mouse activity over the grid appears to cause an erratic multicell selection and the modal form immediately pops up again. This is reproducible if the Cancel button is pressed, and in at least some cases after OK.

I've seen indeterminate discussion of this in the foramina, and have followed up the indicated wiki pages etc. Does anybody have any suggestions, preferably not along the lines of "don't use GTK2" since I was thinking of sticking this on Sourceforge and that restriction would probably be unpopular?

hmm, try LCLIntf.SetCapture(0) after closing modal form , just to isolate capture problems.

zeljko

Hello,

Just for testing the OnSelection is raised by mouse click ? If the answer is yes, try to click the cell and keep the mouse button pressed. If the form appears the grid is still waiting for a MOUSE_UP (thinking you are holding MOUSE_DOWN to perform a selection) and the modal form has its own queue, so MOUSE_UP never arrives.

Like this?

} end

; LCLIntf.SetCapture(0)

end { TFormLG600.StringGridMode1UnshiftedSelection } ;

No obvious change- what should I be looking for?

Yes, the modal form appears while the mouse button is held down (for both GTK2 and Qt).

So, yes, seem that grid expects mouseup

Is there a portable way this can be sent? Otherwise I presume I could fudge it with something like QueueAsyncCall()... unless that also went through before the mouse activity was sorted out.

I'm fairly keen to hack this in such a way that it's not tied to one version of the LCL since I want this program to be fairly easy to build even for people with an old (or no existing) copy of Lazarus etc.

Hello,

I think the proper solution is to instruct GTK2 to use the MOUSE_UP event, but meanwhile QueueAsyncCall will not be the solution as when the AsyncCall will be processed grid will be still waiting for MOUSE_UP, so my solution would be add a MOUSE_UP and MOUSE_DOWN handlers, something like this in pseudo code:

MOUSE_DOWN:
   SelectChanged:=false;
ON_SELECT:
   SelectChanged:=true;
MOUSE_UP:
   if SelectChanged then Form.ShowModal();

Thanks, I'd just about worked that one out. I'll try later- I'm spending the day helping with some flocking sheep ;-)

I can confirm that that approach appears reliable.