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-Design of SDL::Rect
+SDL RC 2.5 decides to play with PDL
-
you say things,
I hear,
but don't listen,
you show things,
I see,
but don't understand,
you write things,
I read,
but don't know.
Lately we have been working on cleaning up the XS name spaces of SDL perl. After some bumps and falls we came up with a separated Rect module. Rect is one of the most simple C struct as shown below.
Using the awesome
perlobject.map as a reference I was able to create a
blessed perl object in
XS. So now SDL::Rect->new(...) gave us a blessed reference ready to go. And as an icing it would destroy itself properly no matter where it was used. But once I brought it into our existing code base, garu pointed out the extending it was a little bit of a mess. So far to extend Rect we have to something like below. Any comment or advice would be much appreciated.
Have at it I am a big boy. You can grab the code like this.
Only If you don't already have a local git repo:
mkdir SDL
cd SDL
git init .
Then do this or skip to this if you already have a local git repo
git pull git://github.com/kthakore/SDL_perl.git experimental
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+PDL provides great number crunching capabilities to Perl and SDL provides game-developer quality real-time bitmapping and sound.
+You can use PDL and SDL together to create real-time,
+responsive animations and simulations.
+In this section we will go through the pleasures and pitfalls of working with both powerhouse libraries. -- David Mertnes
+
+
+Creating a SDL Surface piddle
+PDL's core type is a piddle.
+Once a piddle is provided to PDL it can go do a numerous amounts of things.
+Please see the example in 'examples/cookbook/pdl.pl' in github.
+
+Creating a simple piddle
+First lets get the right modules.
+
+ use PDL;
+ use SDL::Rect;
+ use SDL::Video;
+ use SDL::Surface;
+ use SDL::PixelFormat;
+
+Suppose you want a surface of size (200,400) and 32 bit (RGBA).
+
+my ( $bytes_per_pixel, $width, $height ) = ( 4, 200, 400 );
+
+Define the $width, $height and $bytes_per_pixel. Your $bytes_per_pixel is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;
+
+my $piddle = zeros( byte, $bytes_per_pixel, $width, $height );
+
+Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.
+
+my $pointer = $piddle->get_dataref();
+
+Here is where we get the acutal data the piddle is pointing to. We will have SDL create a new surface from this function.
+
+my $surface = SDL::Surface->new_from( $pointer, $width, $height, 32,
+ $width * $bytes_per_pixel );
+
+Using the same dimensions we create the surface using SDL::Surface->new_form(). The $width * $Bpp is the scanline (pitch) of the surface in bytes.
+
+warn "Made surface of $width, $height and ". $surface->format->BytesPerPixel;
+ return ( $piddle, $surface );
+
+Finally make sure that the surface acutally has the correct dimensions we gave.
+
+NOTE: $surface->format->BytesPerPixel must return 1,2,3,4. !!
+
+Now you can blit and use the surface as needed; and do PDL operations as required.
+
+Operating on the Surface safely
+To make sure SDL is in sync with the data. You must call SDL::Video::lock before doing PDL operations on the piddle.
+
+SDL::Video::lock_surface($surface);
+
+ $piddle ( :, 0 : rand(400), 0 : rand(200) ) .= pdl( rand(225), rand(225), rand(255), 255 );
+
+After that you can unlock the surface to blit.
+
+SDL::Video::unlock_surface($surface);
+
+Errors due to BPP at blitting
+When blitting the new surface check for the return value to see if there has been a problem.
+
+my $b = SDL::Video::blit_surface(
+ $surface, SDL::Rect->new( 0, 0, $surface->w, $surface->h ),
+ $app, SDL::Rect->new( ( $app->w - $surface->w ) / 2, ( $app->h - $surface->h ) / 2, $app->w, $app->h )
+ );
+
+ die "Could not blit: " . SDL::get_error() if ( $b == -1 );
+
+If the error message is 'Blit combination not supported' that means that the BPP is incorrect or incosistent with the dimensions. After that a simple update_rect will so your new surface on the screen.
+
+
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