Data commit

Task/Animate-a-pendulum/Raku/animate-a-pendulum.raku

@@ -0,0 +1,90 @@
+use SDL2::Raw;
+use Cairo;
+
+my $width = 1000;
+my $height = 400;
+
+SDL_Init(VIDEO);
+
+my $window = SDL_CreateWindow(
+    'Pendulum - Raku',
+    SDL_WINDOWPOS_CENTERED_MASK,
+    SDL_WINDOWPOS_CENTERED_MASK,
+    $width, $height, RESIZABLE
+);
+
+my $render = SDL_CreateRenderer($window, -1, ACCELERATED +| PRESENTVSYNC);
+
+my $bob = Cairo::Image.create( Cairo::FORMAT_ARGB32, 32, 32 );
+given Cairo::Context.new($bob) {
+     my Cairo::Pattern::Gradient::Radial $sphere .=
+        create(13.3, 12.8, 3.2, 12.8, 12.8, 32);
+     $sphere.add_color_stop_rgba(0, 1, 1, .698, 1);
+     $sphere.add_color_stop_rgba(1, .623, .669, .144, 1);
+     .pattern($sphere);
+     .arc(16, 16, 15, 0, 2 * pi);
+     .fill;
+     $sphere.destroy;
+}
+
+my $bob_texture = SDL_CreateTexture(
+    $render, %PIXELFORMAT<ARGB8888>,
+    STATIC, 32, 32
+);
+
+SDL_UpdateTexture(
+    $bob_texture,
+    SDL_Rect.new(:x(0), :y(0), :w(32), :h(32)),
+    $bob.data, $bob.stride // 32
+);
+
+SDL_SetTextureBlendMode($bob_texture, 1);
+
+SDL_SetRenderDrawBlendMode($render, 1);
+
+my $event = SDL_Event.new;
+
+my $now = now;   # time
+my $Θ   = -π/3;  # start angle
+my $ppi = 500;   # scale
+my $g   = -9.81; # accelaration of gravity
+my $ax  = $width/2; # anchor x
+my $ay  = 25;       # anchor y
+my $len = $height - 75; # 'rope' length
+my $vel; # velocity
+my $dt;  # delta time
+
+main: loop {
+    while SDL_PollEvent($event) {
+        my $casted_event = SDL_CastEvent($event);
+        given $casted_event {
+            when *.type == QUIT    { last main }
+            when *.type == WINDOWEVENT {
+                if .event == 5 {
+                    $width  = .data1;
+                    $height = .data2;
+                    $ax = $width/2;
+                    $len = $height - 75;
+                }
+            }
+        }
+    }
+
+    $dt = now - $now;
+    $now = now;
+    $vel += $g / $len * sin($Θ) * $ppi * $dt;
+    $Θ   += $vel * $dt;
+    my $bx = $ax + sin($Θ) * $len;
+    my $by = $ay + cos($Θ) * $len;
+
+    SDL_SetRenderDrawColor($render, 255, 255, 255, 255);
+    SDL_RenderDrawLine($render, |($ax, $ay, $bx, $by)».round);
+    SDL_RenderCopy( $render, $bob_texture, Nil,
+      SDL_Rect.new($bx - 16, $by - 16, 32, 32)
+    );
+    SDL_RenderPresent($render);
+    SDL_SetRenderDrawColor($render, 0, 0, 0, 0);
+    SDL_RenderClear($render);
+}
+
+SDL_Quit();