Re: [DotGNU]The new controls (was: Phoenix)

[Rhys Weatherley]

On Friday 25 July 2003 10:32 am, Gopal V wrote:

> The TextBox thing keeps freezing after about 50 chars are typed
> in ... (also the blinking caret fooled me into thinking I had
> focus already)... I hope these are the bugginess  mentioned
> above ?

I've fixed the TextBox lockup now.  It was a consequence of not properly 
disposing "Graphics" objects that were created using "CreateGraphics()".  The 
exact sequence of events was something like this:

- Main thread creates a graphics object, uses it, and then forgets about it.
- The main thread re-enters the main event loop in "Xsharp.Display", which
  causes the display lock to be acquired.
- The GC finalizes the graphics object, eventually calling the "Dispose"
  method in "Xsharp.Graphics".
- "Dispose" tries to acquire the display lock, and blocks waiting for the
  main thread.
- The user performs some action that causes an event.
- The main thread wakes up, immediately tries to allocate something (before
  releasing the display lock), and then blocks waiting for the GC to complete
  the finalization process.  Which it never will because it is waiting for the
  display lock.

Whoops!  Deadlock!

By manually disposing the "Graphics" objects in "TextBox", the deadlock is 
avoided.

I need to perform a little surgery on "Xsharp" to prevent the display lock 
from being held while waiting for an event, so that finalization will work OK 
in the future, but the immediate problem has been solved.

Cheers,

Rhys.