Hi, you have to know that draw_rect works differently for your app surface and regular surfaces. If you draw to your app, the pixels just get the value of the color. But if you do this to a regular surface, and blit that to your app surface, the pixels will be blendet... So create a new surface, modify that, blit and update.
Cheers Jack Maney <jma...@adknowledge.com> hat geschrieben: >Hello, > >I'm not so terribly new to Perl but very new to SDL. I was fiddling with the >following "Hello, World!"-ish code in the SDL manual: > >use strict; >use warnings; > >use SDL; >use SDLx::App; > >my $app = SDLx::App->new( width=> 800, height => 600 ); > >$app->draw_rect([ $app->width / 4, $app->height / 4, > $app->width / 2, $app->height / 2, ], > [ 0, 0, 255, 255] ); > >$app->update(); > >sleep(5); > >and found that changing the alpha portion of the rectangle color (eg fading >the rectangle out completely via [0,0,255,0]) had no effect on the rendering >of the rectangle. I did some searching on this and found some >old<http://www.velocityreviews.com/forums/t906303-problem-with-alphachannel-with-sdl-xxx-blitting.html> > >questions<http://markmail.org/message/lqtdvmmjmiryumrw#query:+page:1+mid:q63xng5hz7lpcsbl+state:results> > from 4+ years ago, but I'm wondering if there is a simple workaround or an >approach that has come about since then. > >Thank you for your time, > >Jack > >