X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pages%2Fblog-0008.html-inc;h=706ea537074945bb91e1162b2494c72640b80ed3;hb=a05e5d4499fb58198e463162d0385e8a156e1f03;hp=fe4b8d48d37cc0a4205e7c209051f61deb0a418b;hpb=638b5b9759c7dcb4de4c0a88c766e9f9dd650348;p=sdlgit%2FSDL-Site.git diff --git a/pages/blog-0008.html-inc b/pages/blog-0008.html-inc index fe4b8d4..706ea53 100644 --- a/pages/blog-0008.html-inc +++ b/pages/blog-0008.html-inc @@ -1,6 +1,77 @@

-The beginnings of modular design for SDL Perl +SDL RC 2.5 decides to play with PDL

-
“Do or do not... there is no try.”
--yoda

The design before


The bindings before were all in one huge XS file. This was then exported into the SDL module. This means that the XS file has to handle with macros if any component (e.x SDL_Mixer) is not compiled. Moreover having ever binding in one XS file prevents use to treat C structs as object with only one point of free and malloc. This would be BEGIN and DESTROY in Perl. Also the monolithic design introduces a lot of bugs because we have to use free and malloc all over the place. Lastly SDL monolithic design has the constructor for all structs in both Perl and in XS.

The design we are aiming for

Simple one XS per Module. This would also simplify the Build code.

First Step


We have began with SDL Rect. It is in github master branch now. We are in the progress of making it back compatible. Originally SDL::Rect took named variables as parameters for new(). Now since the constructor is in XS we have only unnamed parameters.


Before


SDL::Rect->new( -x => 0, -y => 0, -width => 0, -height => 0);

After


SDL::Rect->new(0, 0, 0, 0);

Ideally we would like both ways of constructing Rect.
\ No newline at end of file +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.
+


+

\ No newline at end of file