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Screen not updating/hourglass

Hi...
   My app is reading and processing a large file and sometimes won't update my progress gauge (code below). Also, the cursor will change to an hourglass (but when I move to other applications I have running, the cursor returns to a normal arrow). My app doesn't lock while this is going in however, it still runs fine...just my status gauge won't update while it's running.

The funny thing is that this behaviour doesn't happen all the time - sometimes I'll run the app and the progress gauge will update fine and the cursor doesn't turn to an hourglass. Very strange.

Here's my code (my gauge should refresh every 10 records read):


repeat
    if multitask then Application.ProcessMessages;
    buf:='';
    blockread(fromfile, buf, 1, numread);
    recsread:=recsread + 1;
   
    for z:=0 to 49151 do
    begin
      if ((ord(buf[z])>= 0) and (ord(buf[z]) <= 31)) or
         ((ord(buf[z])>= 127) and (ord(buf[z]) <= 255))  then
      begin
         if bigstring <> '' then find_valid;
      end
      else
      begin
        bigstring:=concat(bigstring, buf[z]);
        if length(bigstring) = 255 then find_valid;
      end;
    end;

    bytes_processed:=bytes_processed + 49152;
    if recsread mod 10 = 0 then
    begin
      hperc:=calc_status(totsizeoffile, bytes_processed);
      gauge14.progress:=hperc;
      Form1.update;
    end;

  until EOF(fromfile);


I'm using Windows XP Home, and Delphi 3 Pro.

Thanks
   Shawn

0
aztec
Asked:
aztec
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1 Solution
 
kretzschmarCommented:
a guess

...
bytes_processed:=bytes_processed + 49152;
   if recsread mod 10 = 0 then
   begin
     hperc:=calc_status(totsizeoffile, bytes_processed);
     gauge14.progress:=hperc;
     Form1.update;
     Application.processmessages; //add this line here
   end;
...


meikl ;-)
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aztecAuthor Commented:
yes, but even with no "Application.processmesages" , I *still* sometimes get my progress bar updating...with good cursor. (ie. my 'multitask' boolean var is set to false)
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333Commented:
actually, Form.Update does nothing special, it only sends WM_PAINT message. if you don't call Application.ProcessMessages during tight loop, chances that your form will handle WM_PAINT are very small.
just guessing, but your form sometimes may be updated because of blocking in BlockRead. if BlockRead blocks, your loop stops and mybe windows is able to call your WindowProc. as i said, it's just a guess :) you need to use Application.ProcessMessages
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GriffonCommented:
I would use a refresh on the form and as for the cursor why not actually set the cursor to hourglass at the begining of your process and then back after that way it will show the user that it is occupied.

Im assuming delphi3 has the:

Screen.Cursor := crHourGlass;

to set back

Screen.Cursor := crDefault;

I would think that the gauge is updating but the screen is not refreshing so even though the gauge is working you are not seeing it.

form.refresh .. is what I use and it seems to work.

also try and make sure that if it is recording % it will only try and update once for each % etc. This should minimalise the form flicker.
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DrDelphiCommented:
Put the Application.ProcessMessages in the loop (as previuosly mentioned), and set the set the Form's DoubleBuffered property to true to prevent flicker. This can be done in the Form.Create:
i,e:
 

Self.DoubleBuffered:=True;


the alternative is to launch a seperate thread to handle this processing.


Good luck!!
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aztecAuthor Commented:
DrDelphi - the 'DoubleBuffered' statement gives me a compile error. Is this feature available in Delphi 3 Pro?

Thanks
   Shawn
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kretzschmarCommented:
>Is this feature available in Delphi 3 Pro?

no
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DrDelphiCommented:
No, 'fraid not...Sorry.
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mikepjCommented:
You can minimize flicker by forcing update only for the progress bar itself; no need to refresh the whole form.
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