Anything else I can use to keep program responsive besides processmessage?

Question

I have an application that can run for quite a long time scanning a database.
During this process I keep my program responsive by using processmessage.
This processmessage is triggered when my progress bar is updated and inc'ed.
This works fine is most cases, but when the databases get larger it takes longer for the progress bar to jump up 1%, the program becomes unresponsive until that time.

Is there another way to keep my program alive besides processmessages?

Answer 1

Multi threading is the answer. A standard Delphi application is basically a single threaded application that can do one thing at a time. Hence the gui lockup, it can't remain responsive if it's doing something else.

If you want to have a responsive gui and do heavy lifting at the same time, you need to have the heavy lifting in a separate thread or threads. This way your main thread can make sure you have a responsive program and the worker threads do the heavy lifting. This works nice for heavy database work but also for for instance the downloading of files or situations where an answer of for instance a remote server can take a long time.

But this answer will probably give you more questions then answers because to explain HOW to use multi threading would be too big of an explanation for this question.

One other thing though: have a long and hard look at your database code. How are you retrieving records from the database, are there good indexes on the database etc. etc. etc. You can get insane speed improvements by optimizing this code before you have to start thinking about multi threading.

I've found the following resource: http://thaddy.co.uk/threads/ which you can download with pictures at: http://cc.embarcadero.com/item/14809 to be very usefull threading tutorial.

Answer 2

If you want to make your GUI program appear responsive, you must service the message queue in a timely fashion. There is no alternative.

When it comes to running database queries, the way to do that without freezing your UI, is to move the query to a different thread.