Re: [Dev-C++] Whoops - drawing in Windows

[Vlada D. <dj...@im...>]

----- Original Message -----
From: "Per Westermark" <pw...@ia...>
To: "Vlada Djurovic" <dj...@im...>
Cc: "Daniel Glenfield" <sp...@ho...>;
<dev...@li...>
Sent: Thursday, October 24, 2002 3:19 PM
Subject: Re: [Dev-C++] Whoops - drawing in Windows


> One question: Aren't you creating a lot of pens in your drawing loop.
> Every time the mouse is moved, you create a new pen, with the same
> specification as the pen you crated at your previous mouse move.
>
> Exactly where are the "consumed" pens supposed to be released? At least in
> Win32, you only have a finite set of available resource handles, so it
> isn't possible to create new pens all the time. The task manager in Win2k
> or WinXP may be configured to display number of handles used in the
> application. That number shouldn't continuously increase when the program
> is run.
>
If I understand correct, you say I should create one global pen object and
use it every time I need to draw something. Where should that object be
defined?
> Leaking pens, brushes, ... is a quick way of getting a program into
> troubles - a lot more quickly than if the program leaks memory. There is
> no swapping for resources.
>
Can it be the reason for the program to freeze?
> /Per W
>
> On Thu, 24 Oct 2002, Vlada Djurovic wrote:
>
> >
> > ----- Original Message -----
> > From: "Daniel Glenfield" <sp...@ho...>
> > To: <dj...@im...>; <dev...@li...>
> > Sent: Thursday, October 24, 2002 11:59 AM
> > Subject: Re: [Dev-C++] Whoops - drawing in Windows
> >
> >
> > > Nope maybe not, serialising is for saving and restoring.
> > >
> > > I think you have to store the info in to an array, but looking at this
old
> > > code I cannot remember what exactly you have to do. I worked on the
> > Scribble
> > > tutorial that comes with VC++ - have a look on MSDN for it.
> > >
> > >
> > I tried to store all the info in a linked list, but I think I did
something
> > wrong because the program just froze when I tried to draw something.
Then I
> > thought it would be easier to store the drawing in a compatible memory
> > bitmap and then just copy it back in the client area when it needs to be
> > redrawn, but this also didn't work because the program froze again.
That's
> > why I was asking if anyone can give me some guidelines about how to do
this
> > (the bitmap way).
> > As for the tutorials, I read the book "Teach yourself VC++ in 21 days"
which
> > also has some stuff about this, but although I think I did everything
the
> > way it's done in VC++- it doesn't work.
> >
> > Regards, Vlada
> > >
> > > >From: "Vlada Djurovic" <dj...@im...>
> > > >To: "'DevC++ help'" <dev...@li...>
> > > >Subject: [Dev-C++] drawing in Windows
> > > >Date: Thu, 24 Oct 2002 10:32:16 +0200
> > > >
> > > >Hi, everybody
> > > >Here's my problem: I'm trying to write a simple drawing app (just for
> > > >exercise) and so far its been going OK. I can draw lines in client
area
> > in
> > > >different colors, but when ever I minimize or maximize the window, or
> > > >something similar happenes, all the content of the window is gone. I
> > tried
> > > >to use a memory DC an bitmap to save the contents in, and BitBlt it
back
> > in
> > > >response to WM_PAINT message, but the program just "froze". Can
anybody
> > > >give me a hint how to do it? Here's the code used for drawing lines
> > without
> > > >any restoring parts:
> > > >
> > > >         case WM_MOUSEMOVE:
> > > >         {
> > > >             switch(iTool)           /* iTool is used for dtetrmining
> > which
> > > >drawing tool is selected(line, rect etc.)*/
> > > >             {
> > > >                 case 0:
> > > >                 {
> > > >                    if(wParam==MK_LBUTTON)    /*if line is selected
> > > >(itool=0) and left button presed*/
> > > >                    {
> > > >                          HDC hDC=GetDC(hwnd);
> > > >
> > > >                        HPEN
> > hPen=CreatePen(PS_SOLID,iCurWidth,crCurColor);
> > > >                        HPEN hOldPen=(HPEN)SelectObject(hDC,hPen);
> > > >                        CLine* pLine=new
> > > >CLine(ptPrevPos,MAKEPOINTS(lParam),iCurWidth,crCurColor); /*create
new
> > line
> > > >object*/
> > > >                        pLine->DrawLine(hDC);
> > > >                        ptPrevPos=MAKEPOINTS(lParam);
> > > >                        SelectObject(hDC,hOldPen);
> > > >                        DeleteDC(hDC);
> > > >                    }
> > > >                 }
> > > >                 break;
> > > >                 case 1: /* nothing here yet*/
> > > >                 break;
> > > >             }
> > > >         }
> > >
> > >
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