more samples: alpha bending, animated sprites, rotatation & flipping

samples/13_alpha_blending.cr

@@ -0,0 +1,36 @@
+require "../src/sdl"
+require "../src/image"
+
+SDL.init(SDL::Init::VIDEO); at_exit { SDL.quit }
+IMG.init(IMG::Init::PNG); at_exit { IMG.quit }
+
+window = SDL::Window.new("SDL tutorial", 640, 480)
+renderer = SDL::Renderer.new(window)
+
+background = IMG.load(File.join(__DIR__, "data", "fadein.png"), renderer)
+modulated = IMG.load(File.join(__DIR__, "data", "fadeout.png"), renderer)
+a = 255
+
+loop do
+  case event = SDL::Event.wait
+  when SDL::Event::Quit
+    break
+  when SDL::Event::Keyboard
+    case event.sym
+    when .w? then a += 32
+    when .s? then a -= 32
+    end if event.keydown?
+  end
+
+  a = a.clamp(0, 255)
+
+  renderer.draw_color = {255, 255, 255, 255}
+  renderer.clear
+
+  renderer.copy(background)
+
+  modulated.alpha_mod = a
+  renderer.copy(modulated)
+
+  renderer.present
+end

samples/14_animated_sprites_and_vsync.cr

@@ -0,0 +1,35 @@
+require "../src/sdl"
+require "../src/image"
+
+SDL.init(SDL::Init::VIDEO); at_exit { SDL.quit }
+IMG.init(IMG::Init::PNG); at_exit { IMG.quit }
+
+window = SDL::Window.new("SDL tutorial", 640, 480)
+renderer = SDL::Renderer.new(window, SDL::Renderer::Flags::ACCELERATED | SDL::Renderer::Flags::PRESENTVSYNC)
+
+sprite = IMG.load(File.join(__DIR__, "data", "foo_sprite.png"), renderer)
+sprite_clips = StaticArray(SDL::Rect, 4).new do |i|
+  SDL::Rect.new(i * 64, 0, 64, 305)
+end
+
+frame = 0
+slowdown = 6
+
+loop do
+  case event = SDL::Event.poll
+  when SDL::Event::Quit
+    break
+  end
+
+  renderer.draw_color = {255, 255, 255, 255}
+  renderer.clear
+
+  current_clip = sprite_clips[frame / slowdown]
+  x = (window.surface.width - current_clip.w) / 2
+  y = (window.surface.height - current_clip.h) / 2
+  renderer.copy(sprite, current_clip, {x, y, current_clip.w, current_clip.h})
+
+  renderer.present
+
+  frame = (frame + 1) % (sprite_clips.size * slowdown)
+end

samples/15_rotation_and_flipping.cr

@@ -0,0 +1,36 @@
+require "../src/sdl"
+require "../src/image"
+
+SDL.init(SDL::Init::VIDEO); at_exit { SDL.quit }
+IMG.init(IMG::Init::PNG); at_exit { IMG.quit }
+
+window = SDL::Window.new("SDL tutorial", 640, 480)
+renderer = SDL::Renderer.new(window, SDL::Renderer::Flags::ACCELERATED | SDL::Renderer::Flags::PRESENTVSYNC)
+
+arrow = IMG.load(File.join(__DIR__, "data", "arrow.png"), renderer)
+degrees = 0
+flip = SDL::Renderer::Flip::NONE
+
+loop do
+  case event = SDL::Event.wait
+  when SDL::Event::Quit
+    break
+  when SDL::Event::Keyboard
+    case event.sym
+    when .a? then degrees -= 60
+    when .d? then degrees += 60
+    when .q? then flip = SDL::Renderer::Flip::HORIZONTAL
+    when .w? then flip = SDL::Renderer::Flip::NONE
+    when .e? then flip = SDL::Renderer::Flip::VERTICAL
+    end if event.keydown?
+  end
+
+  renderer.draw_color = {255, 255, 255, 255}
+  renderer.clear
+
+  x = (window.surface.width - arrow.width) / 2
+  y = (window.surface.height - arrow.height) / 2
+  renderer.copy(arrow, dstrect: {x, y, arrow.width, arrow.height}, angle: degrees, flip: flip)
+
+  renderer.present
+end

src/rect.cr

@@ -21,6 +21,10 @@ module SDL
       Point.new(pt.x, pt.y)
     end
 
+    def self.from(pt : Nil)
+      nil
+    end
+
     # OPTIMIZE: avoid copy
     def to_unsafe
       pt = GC.malloc(sizeof(LibSDL::Point)).as(LibSDL::Point*)
@@ -58,7 +62,7 @@ module SDL
 
     # OPTIMIZE: avoid copy
     def to_unsafe
-      rect = GC.malloc(sizeof(LibSDL::Rect)).as(LibSDL::Rect*)
+      rect = Pointer(LibSDL::Rect).malloc
       rect.value.x = x
       rect.value.y = y
       rect.value.w = w