Thanks in advance,
Jim.

Gambit

Hi Remy,

thanks for your quick answer. First off sorry for posting this
into the wrong newsgroups. I should have posted this message
in .vcl.writing.

There is still another small problem I have. I now assigned a
TControlCanvas (equals to getting the DC for a handle, right?)
for my TMemo descendant within its constructor. I intercepted
the WM_PAINT message and I draw an black rectangle somewhere
on the control.

This results in heavy flickering and in high system load.
That high that the BCB component panel turns grey until it
receives another paint message. When I try to compile an
application using the new component BCB hangs (because of
the high system load?).

The flickering is surely a result of the default WM_PAINT
handler that is called afterwards (so I could intercept the
WM_ERASEBKGND), but I have no clue why it produces such a
high workload.

Thanks in advance,
Jim.

Gambit

In header file:

class PACKAGE TMyMemo : public TMemo
{
protected:
    ...
    TControlCanvas *FCanvas;
    ...
    virtual void __fastcall WndProc(Messages::TMessage &Message);
    ...

public:
    __fastcall  TMyMemo(TComponent *Owner);
    __fastcall ~TMyMemo();
    ...

...

// ctor
__fastcall TMyMemo::TMyMemo(TComponent *Owner)
    : TMemo(Owner)
{
    // not used at the moment
    // ControlStyle = ControlStyle << csOpaque;

    // somehow this does not work
    ControlStyle = ControlStyle << csAcceptsControls;

    // create control canvas
    FCanvas          = new TControlCanvas;
    FCanvas->Control = this;

        default:
            TMemo::WndProc(Message);
    }

Thanks,
Jim.

I think I know what your intentions might be.  To draw a background image or
watermark in a memo field etc.  I tried doing that except I had a problem
with the caret.  Everytime it blinked, it would cause a redraw, and hence
your heavy flickering that you experience.  This is the high workload.

Problem you are experiencing at design time is related to this I believe,
and you need to check for csDesigning state for the component and ONLY draw
the rectangle at run-time.

Hope that helps,

Brent

The fact that I

Hi Brent,

thanks for the hint. It really helped. The disadvantage is
that it is no more wysiwyg editing within the IDE :-)

Something else: I've seen code for a transparent memo. What do you
think about the idea to use a TCustomPanel as base class for my
custom memo and to dynamically create a transparent TMemo within my
control's c'tor? If my brain isn't totally screwed yet it should be
possible then to draw to the TCustomPanel's canvas without having
problems with the memo itself. But it would take some more memory ...

Thanks,
Jim.

Second, now that I experiment with your code, I see WM_PAINT is not a good
message to intercept, unless you're willing to draw the text itself as well,
that that can get pretty involved.  WM_ERASEBKGND is better.  However, I
notice that by setting BorderStyle = bsNone, the text is drawn starting at
(0, 0), and it's drawn with a solid background that I can't get rid of, thus
the sections of the border that the text is over will be lost.  I'm sure
that's not the effect you're looking for.  Also, I notice that when clicking
on the memo, then onto the form, the text in the memo gets painted over
completely.

I see you mentioned you have code for a transparent Memo.  Your idea for
that is certainly an option.

Gambit

If you're interested here is the URL to the code I mentioned:

http://www.efg2.com/Lab/Library/UseNet/2000/1129a.txt

Thanks,
Jim.

However I tried to change my component a bit and base it on
a TCustomPanel. The TMemo that is displayed inside the panel
is created dynamically within the constructor. Now BCB keeps
telling "Component '' has no parent". I created the memo as
follows (in constructor):

FMemo = new TMemo(this); // 'this' = TCustomPanel
FMemo->Left = 0;
FMemo->Top = 0;
FMemo->Right = Width - 1;
FMemo->Bottom = Height - 1;
FMemo->Visible = true;
...

Referring to the TMemo in a TCustomPanel container:
Is there a way to publish the TMemo's properties as properties
of the new component? At the moment I'd have to access - for
example - MyMemo1->Memo->Lines->Strings[0] and I'd like to
change this to MyMemo1->Lines->Strings[0]. Do I have to re-
publish each property?

My questions might sound extremely stupid, but though I hope
asking is still okay ;-) Please tell me if I overstep the point
at which it is difficult to stand pain :-)

Thanks,
Jim.

The Transparent Memo sounds really cool.  Do you still have or know where
the code is?  I have an idea of how to create a transparent control (maybe)
and I might do that later in the year.

Using transparent controls certainly sounds better than what I tried to do
once.  Place images (TPaintBox etc) ontop of a TMemo.  Didn't work to well.

Cheers,

Brent

The Parent is where the component is going to be placed.  Without a parent,
the component does not know where it is supposed to go.

FMemo = new TMemo(this); // 'this' = TCustomPanel

signifies that this (TCustomPanel) owns the Memo control.  It will be
responsible for destroying the Memo when the Panel is deleted.

HTH,

Brent

FMemo = new TMemo(this); // 'this' = TCustomPanel

Thanks,
Jim.

Oh, sorry. I think I misunderstood. Okay, I set the
'Parent' and it works fine now. Thanks!!

Jim.

    FMemo->Parent = this;

Gambit