Re: Maze game, two problems regarding painting

From:

David Wilkinson <no-reply@effisols.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sat, 12 Jul 2008 10:03:29 -0400

Message-ID:

<uDr0QgC5IHA.3484@TK2MSFTNGP05.phx.gbl>

WP wrote:

Hi, if you've read my other thread "Which class should handle the
request to open a file" you might know that I'm making a simple game
where the user controls a character that needs to find its way out of a
maze (doc/view, sdi, MSVC++ 2008).
The game is tile based and mazes are always 20*20 tiles. The document
class holds a 2D-array of pointers to tile objects. There are a few
different types of tiles and each tile knows how to draw itself (meaning
each tile class has a draw() function that takes a CDC *).
I have two problems:
First problem: I don't want to redraw every tile all the time, only the
tiles that have changed which means that when the player enters or leave
a tile, that tile should be redrawn. Right now I have solved that by
letting the tiles know about the view class and they call
InvalidateRect() on it. It works, but I would like to remove that
association.
Second problem: When the view needs to draw itself again, should I get a
tile array from the document and call draw on each tile or should it
call a function in the document class that calls draw on each tile? That
would basically mean I introduce a draw function in the document, heh.
But it also means that the view doesn't have to know about the tile
class. How should I do it?

Eric:

Your CView::OnDraw() has to be able to draw the entire maze, because it needs
drawing other times than when your player moves from one tile to another.

I might have a method in your view that draws a single tile

void DrawTile(int i, int j, CDC* pDC);

that you can call in a loop from OnDraw(), and also call individually when the
user enters or leaves a cell.

The document should not do drawing, and should not know about the views. It just
holds the data. It is OK for the views to know about the document; their job is
to draw the document (and perhaps to modify it in response to user input), so
they have to know about it.

--
David Wilkinson
Visual C++ MVP