Why doesn't this work? 1

[AP81]

Hi,

I have a simple thing I want to do:
Move a TImage around in a form.
The TImage holds an icon of a magnifying glass, and I am trying to move the image around in a continuous circle (while another procedure is performing a search).

My problem is that the image does not move. I have tried running the code below in a thread, but still nothing happens.

What am I doing wrong?

Thanks in advance.

procedure TForm1.Button1Click(Sender: TObject);
var
  i:integer;
begin
  for i:= 0 to 10 do
  begin
    Image1.Top  := Image1.Top+3;
    Image1.Left := Image1.Left-3;
    sleep(1000);
    Image1.Top  := Image1.Top+3;
    Image1.Left := Image1.Left+3;
    sleep(1000);
    Image1.Top  := Image1.Top-3;
    Image1.Left := Image1.Left+3;
    sleep(1000);
    Image1.Top  := Image1.Top-3;
    Image1.Left := Image1.Left-3;
    sleep(1000);
  end;
end;

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There's no place like 127.0.0.1
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[sggaunt]

Your are right it doesnt run.
A few points worth mentioning
You don't give any details about how this is implemented in a thread.
The Sleep() function is generally a bad idea, it does what it says and puts the cpu to sleep for however long you specify I wouldn't recommend it even in normal code.
The code I have posted runs as a normal (non threaded) procedure and uses my own delay library function.
Note the Application.ProcessMessages call.
I havn't tested this as a threaded call it might not work!

procedure TForm1.Button1Click(Sender: TObject);
var
  i:integer;
begin
  for i:= 0 to 10 do
  begin
    application.ProcessMessages;
    Image1.Top  := Image1.Top+3;
    Image1.Left := Image1.Left-3;
    waitms(100);
    Image1.Top  := Image1.Top+3;
    Image1.Left := Image1.Left+3;
    waitms(100);Image1.Top  := Image1.Top-3;
    Image1.Left := Image1.Left+3;
    waitms(100);
     Image1.Top  := Image1.Top-3;
    Image1.Left := Image1.Left-3;
    waitms(100);
  end;
end;

waitms looks like this

procedure WaitMs(T: DWORD);
var  tc :DWORD;
begin
   tc := GetTickCount;
   repeat
        Application.ProcessMessages;
   until ((GetTickCount - tc) >= T);
end;

Steve: Delphi a feersum engin indeed.

 

[AP81]

Thanks.




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There's no place like 127.0.0.1
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[BobbaFet]

The Sleep() function is generally a bad idea, it does what it says and puts the cpu to sleep for however long you specify I wouldn't recommend it even in normal code."

This is what my Delphi helpfile says:

"Delay program execution for a specified number of microseconds."

Seems different and I can see what the problem is if it would freeze the CPU for X ms but it doesn't, it just pauses the execution of the thread it is in for X ms.


BobbaFet

Everyone has a right to my opinion.
Great Delphi Websites faq102-5352

 

[sggaunt]

Bobbatfet The helpfile is being er, economical with the truth on this point. There are several other prefered ways of creating a delay, this is well documented.

I honestly dont know the effect of sleep() in multithreaded application, but even if it just stops one thread dead, this isnt good pratice in an event driven language IMHO.

Yes I have used sleep() myself, sometimes it dosnt matter if things just stop, but in the case of an animation?


Steve: Delphi a feersum engin indeed.

 

[whosrdaddy]

Hi,

in fact Sleep() is sometimes a necessity in multithreaded apps, it is correct that sleep stops the current thread, this is sometimes a must to give other threads time to do some processing.
using sleep in a single threaded app (the vcl main thread) is generally a bad idea, use sggaunt's routine to create delays...

full info can be found here :

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/sleep.asp

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[BobbaFet]

Ok but the way I usually use the Sleep() function is to give a app time to minimize before continuing execution.
(Most apps I make are for games to join, for example, you get a message from someone with an IP address and port to join a server, my progam allows you enter the ip and port then and there before joining the server without having to either write down an iport and launches the game so that itll automatically joins the server when the game starts.)

So my code looks something like this:

procedure JoinGame;
begin
{... code to create parameters for game to
join server with user specified settings ...}
Application.Minimize;
Sleep(100);
ShellExecute(blablabla);
end;

Is there anything wrong/bad programming in this?


BobbaFet

Everyone has a right to my opinion.
Great Delphi Websites faq102-5352

 

[ors]

In a utility I am writing, I carry out the following steps
1) I enumerate windows
2) Bring to the front and send keystrokes to windows matching given criteria
3) Resize and repositition said windows.

I have observed that my utility actually makes a mess, with keystrokes being sent/processed erratically and resizing sometimes working haphazardly. That is, unless I introduce a number of sleep(250) statements after each interaction with the other applications.

Any idea what could be the cause. I am willing to forward more info and code snippets if necessary.

I liked ssgaunt's routine and will use it instead of sleep().