Some developers prefer to pass in a GUI component to a thread
instance, so the thread knows what widget to update. Other users
prefer to post a "gui update" message to the application event queue.
I'm very new to threads and might know just enough to make in
dangerous. :-) In fpGUI the application's "custom" event queue is a
linked-list structure. If threads post messages to that queue, I
obviously need to make the queue manipulation code thread safe.
fpgApplication is a global singleton of the TfpgApplication class.
fpgPostMessage() is a stand-alone function (not a member of
TfpgApplication class). To make fpgPostMessage() thread save, I
instantiated a TCriticalSection instance in the TfpgApplication class
- in the constructor. I added two member functions .Lock and .Unlock
which calls FCritSect.Enter and FCritSect.Leave respectively. In
fpgPostMessage, I call fpgApplication.Lock, then manipulate the
message queue and then call fpgApplication.Unlock.
Is this the correct way to make my event queue thread save?
eg:
procedure fpgPostMessage(Sender, Dest: TObject; MsgCode: integer;
var aparams: TfpgMessageParams); overload;
var
p: PfpgMessageRec;
begin
if Dest = nil then
Exit; //==>
fpgApplication.Lock; // Enter the critical section
try
p := fpgAllocateMessage;
if p <> nil then
begin
p^.MsgCode := MsgCode;
p^.Sender := Sender;
p^.Dest := Dest;
p^.Params := aparams;
end
else
DebugLn('THE MESSAGE QUEUE IS FULL.');
finally
fpgApplication.Unlock; // leave the critical section
end;
end;
Regards,
- Graeme -
_______________________________________________
fpGUI - a cross-platform Free Pascal GUI toolkit
http://opensoft.homeip.net/fpgui/
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