when do i use :  Unused(ATool, APoint)
lazarus / 55-TAChart

----------------------------------------------------------------------
frederic · 2017-03-01 11:29

dear specialists

may be a stupid question, but i like to understand the function
"Unused(ATool, APoint)

i see it is been used in
-DataPointClickTool1PointClick(  ATool: TChartTool; APoint: TPoint);
-DataPointHintTool1Hint(ATool: TDataPointHintTool;  const APoint:
TPoint; var AHint: String);    

and mayb e in some other tools as well     

What exactly happens then

frederic

----------------------------------------------------------------------
jacmoe · 2017-03-01 11:40

I don't know, but my qualified guess would be that it exists for the
purpose of shutting up the compiler so that it does not complain about
unused variables.

----------------------------------------------------------------------
frederic · 2017-03-01 13:15

oke ,but which unused variables?

for a datapointclicktool  i have already the tool and for clicking i
have the coordinates of the point  or...
 refers ' unused"to coordinates which are too far away from the meant
datapoint and therefore not relevant?

But what  happens  then?

frederic

----------------------------------------------------------------------
wp · 2017-03-01 17:16

"Unused()" is a helper procedure written by the "fathers" of TACharts
in order to silence the compiler if a parameter passed to a procedure
is not used. Suppose you write a handler to a button OnClick event, it
is supposed to show a message:
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 procedure
TForm1.Button1Click(Sender. TObject);begin  ShowMessage('Button1 was
clicked');end;This works fine, but when you look at the message window
after compilation you will see a message saying that parameter Ssnder
is not used by the procedure Button1Click. This is a hint that the
parameter could have a real, important meaning and you just forgot to
call it. Of course, this is not true here, and the hint is a false
alarm. In order to keep the message window free for "real" hints and
warnings you can call the procedure Unused with the parameter Sender.
This procedure does not do anything, it just has the parameter in its
parameter list, and therefor the parameter is no longer "unused" by
the calling procedure Button1Click.

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 procedure
TForm1.Button1Click(Sender. TObject);begin  Unused(Sender); 
ShowMessage('Button1 was clicked');end;
Another method would have been to right-click on the hint in the
message window and select "Hide message by inserting IDE directive
{%H]". I don't know why the inventors of TAChart did not choose this
"official" way, maybe this directive did not exist in those days.

----------------------------------------------------------------------
frederic · 2017-03-02 15:17

i understand

thanks