[lazarus] lazarus very gdi-resource hungry on windows 98

[Vincent Snijders]

> On Sun, 30 Nov 2003 23:20:10 +0100
> Marc Weustink <marc at dommelstein.net> wrote:
> 
> > At 22:43 30-11-2003, Vincent Snijders wrote:
> > >Hi,
> > >
> > >Lazarus is uses very much gdi-resource (mostly pens) when I run it
on
> > >windows 98. I didn't test it on other win32 OSes.
> > >
> > >To see, what I mean open de resource meter, which shows system,
user
> > >and GDI resources. If I open lazarus and move another window over
the
> > >editor it get very soon low on GDI-resources.
> > >
> > >Can somebody else confirm this behaviour?
> > >
> > >The moving of the other windows causes a lot of repaints of the
> > >editor window. Some diagnostic tool showed pens are allocated, but
> > >not freed to the OS. I have been trying to find out, why they are
not
> > >returned to the OS, but I couldn't find anything conclusive. I
> > >suspect it is because DeleteObject is called, while the pen handle
is
> > >still selected (in use) on the canvas. MSDN says you must not call
> > >DeleteObject on gdi-objects still selected in a device context. It
> > >also says it returns 0, when the call fails, but I haven't seen it
> > >failing.
> > >
> > >I couldn't find any code in canvas.inc or pen.inc, which deselects
> > >the pen, before calling DeleteObject on the pen handle.
> > >
> > >I am on the right track or on a wild goose chase?
> >
> > the Winapi help indeed states that a object has to be deselected
> > first. I don't know if it results in a leak if you don't. (In any
code
> > I've written so far I deselect first :)
> >
> > Maybe you can just write a little test app where objects in a loop
are
> >
> > created, selected and the deleted.
> 
> Attached is the source code of two test programs to show the problem.
> The first is gdileak.exe shows that deleting a gdi-object before
> deselecting creates a gdi leak. It contains a boolean const DoItRight.
> Set this to true to prevent this gdileak.
> 
> The second program lclgdileak uses the lcl to create such a program.
It
> has the same problems.
> 
> I have no idea how to solve it. Maybe these programs can help testing.

I have run the testprograms on windows 2000. There it shows no
gdi-object leakage.

I have been thinking about how to solve this bug(?). Maybe selecting a
pen should be moved into de TPen class.
So in TCanvas.CreatePen instead of 
  SelectObject(FCanvas, FPen.Handle);

  FPen.Select(self);

The pen can then store where in which FCanvas it is selected and
deselect itself before freeing its handle.

Regards,
Vincent.