move from sdl textures to opengl, add byuu color correction shaders :D

shard.yml

@@ -16,5 +16,7 @@ dependencies:
     version: 0.1.3
   sdl:
     git: git@github.com:ysbaddaden/sdl.cr.git
+  lib_gl:
+    github: nulldotpro/LibGL
 
 license: MIT

src/crab/display.cr

@@ -1,31 +1,22 @@
+require "lib_gl"
+
 class Display
   WIDTH  = 240
   HEIGHT = 160
   SCALE  =   4
-
-  PIXELFORMAT_RGB24       = (1 << 28) | (7 << 24) | (1 << 20) | (0 << 16) | (24 << 8) | (3 << 0)
-  PIXELFORMAT_BGR555      = (1 << 28) | (5 << 24) | (5 << 20) | (3 << 16) | (15 << 8) | (2 << 0)
-  TEXTUREACCESS_STREAMING = 1
-
-  def initialize
-    @window = SDL::Window.new("crab", WIDTH * SCALE, HEIGHT * SCALE)
-    @renderer = SDL::Renderer.new @window
-    @renderer.logical_size = {WIDTH, HEIGHT}
-    @texture = LibSDL.create_texture @renderer, PIXELFORMAT_BGR555, TEXTUREACCESS_STREAMING, WIDTH, HEIGHT
-  end
-
-  def window_title : String
-    "crab - #{@fps} fps"
-  end
-
   @fps = 30
   @seconds : Int32 = Time.utc.second
 
+  def initialize
+    @window = SDL::Window.new(window_title, WIDTH * SCALE, HEIGHT * SCALE, flags: SDL::Window::Flags::OPENGL)
+    setup_gl
+  end
+
   def draw(framebuffer : Bytes) : Nil
-    LibSDL.update_texture @texture, nil, framebuffer, WIDTH * 2
-    @renderer.clear
-    @renderer.copy @texture
-    @renderer.present
+    LibGL.tex_image_2d(LibGL::TEXTURE_2D, 0, LibGL::RGB5, 240, 160, 0, LibGL::RGBA, LibGL::UNSIGNED_SHORT_1_5_5_5_REV, framebuffer)
+    LibGL.draw_arrays(LibGL::TRIANGLE_STRIP, 0, 4)
+    LibSDL.gl_swap_window @window
+
     @fps += 1
     if Time.utc.second != @seconds
       @window.title = window_title
@@ -33,4 +24,65 @@ class Display
       @seconds = Time.utc.second
     end
   end
+
+  private def window_title : String
+    "crab - #{@fps} fps"
+  end
+
+  private def compile_shader(source : String, type : UInt32) : UInt32
+    source_ptr = source.to_unsafe
+    shader = LibGL.create_shader(type)
+    LibGL.shader_source(shader, 1, pointerof(source_ptr), nil)
+    LibGL.compile_shader shader
+    shader_compiled = 0
+    LibGL.get_shader_iv(shader, LibGL::COMPILE_STATUS, pointerof(shader_compiled))
+    if shader_compiled != LibGL::TRUE
+      log_length = 0
+      LibGL.get_shader_iv(shader, LibGL::INFO_LOG_LENGTH, pointerof(log_length))
+      s = " " * log_length
+      if log_length > 0
+        LibGL.get_shader_info_log(shader, log_length, pointerof(log_length), s)
+      end
+      puts source
+      abort "Error compiling shader: #{s}"
+    end
+    shader
+  end
+
+  protected def self.callback(source : UInt32, type : UInt32, id : UInt32, severity : UInt32, length : Int32, message : Pointer(UInt8), userParam : Pointer(Void)) : Nil
+    puts String.new message
+  end
+
+  private def setup_gl : Nil
+    glcontext = LibSDL.gl_create_context @window
+    shader_program = LibGL.create_program
+
+    LibSDL.gl_set_attribute LibSDL::GLattr::SDL_GL_CONTEXT_MAJOR_VERSION, 4
+    LibSDL.gl_set_attribute LibSDL::GLattr::SDL_GL_CONTEXT_MINOR_VERSION, 5
+    LibSDL.gl_set_swap_interval 1
+    LibGL.enable(LibGL::DEBUG_OUTPUT)
+    LibGL.enable(LibGL::DEBUG_OUTPUT_SYNCHRONOUS)
+    LibGL.debug_message_callback(->Display.callback, nil)
+
+    vtx_shader_id = compile_shader(File.read("src/crab/shaders/gba_colors.vert"), LibGL::VERTEX_SHADER)
+    frag_shader_id = compile_shader(File.read("src/crab/shaders/gba_colors.frag"), LibGL::FRAGMENT_SHADER)
+
+    frame_buffer = 0_u32
+    LibGL.gen_textures(1, pointerof(frame_buffer))
+    LibGL.active_texture(LibGL::TEXTURE0)
+    LibGL.bind_texture(LibGL::TEXTURE_2D, frame_buffer)
+    LibGL.attach_shader shader_program, vtx_shader_id
+    LibGL.attach_shader shader_program, frag_shader_id
+    LibGL.link_program shader_program
+    LibGL.validate_program shader_program
+    a = [LibGL::BLUE, LibGL::GREEN, LibGL::RED, LibGL::ONE] # flip the rgba to bgra where a is always 1
+    a_ptr = pointerof(a).as(Int32*)
+    LibGL.tex_parameter_iv(LibGL::TEXTURE_2D, LibGL::TEXTURE_SWIZZLE_RGBA, a_ptr)
+    LibGL.tex_parameter_i(LibGL::TEXTURE_2D, LibGL::TEXTURE_MIN_FILTER, LibGL::NEAREST)
+    LibGL.tex_parameter_i(LibGL::TEXTURE_2D, LibGL::TEXTURE_MAG_FILTER, LibGL::NEAREST)
+    LibGL.use_program shader_program
+    vao = 0_u32 # required even if not used
+    LibGL.gen_vertex_arrays(1, pointerof(vao))
+    LibGL.bind_vertex_array(vao)
+  end
 end

src/crab/shaders/gba_colors.frag

@@ -0,0 +1,19 @@
+#version 330
+
+in vec2 tex_coord;
+out vec4 frag_color;
+
+uniform sampler2D input_texture;
+
+void main() {
+  // Credits to Talarubi and Near for this color-correction algorithm.
+  // https://byuu.net/video/color-emulation
+  vec4 color = texture(input_texture, tex_coord);
+  float lcdGamma = 4.0, outGamma = 2.2;
+  color.rgb = pow(color.rgb, vec3(lcdGamma));
+  frag_color.rgb = pow(vec3(  0 * color.b +  50 * color.g + 255 * color.r,
+                             30 * color.b + 230 * color.g +  10 * color.r,
+                            220 * color.b +  10 * color.g +  50 * color.r) / 255,
+                       vec3(1.0 / outGamma));
+  frag_color.a = 1.0;
+}

src/crab/shaders/gba_colors.vert

@@ -0,0 +1,10 @@
+#version 330
+
+out vec2 tex_coord;
+
+const vec2 vertices[4] = vec2[4](vec2(-1.0, -1.0), vec2(1.0, -1.0), vec2(-1.0, 1.0), vec2(1.0, 1.0));
+
+void main() {
+    gl_Position = vec4(vertices[gl_VertexID], 0.0, 1.0);
+    tex_coord = (vertices[gl_VertexID] + 1.0) / vec2(2.0, -2.0);
+}