fix(opengl): properly control whether vsync is enabled

LUT probably couldn't fit in CPU cache anyways.

TODO: Consider whether LUTs for separate channels (size 32 * 3 * 3
instead of std.math.maxInt(u15))

build.zig

@@ -31,6 +31,9 @@ pub fn build(b: *std.build.Builder) void {
     // TOML Library
     exe.addPackagePath("toml", "lib/zig-toml/src/toml.zig");
 
+    // OpenGL 3.3 Bindings
+    exe.addPackagePath("gl", "lib/gl.zig");
+
     // Zig SDL Bindings: https://github.com/MasterQ32/SDL.zig
     const sdk = Sdk.init(b);
     sdk.link(exe, .dynamic);

src/core/ppu.zig

@@ -12,9 +12,6 @@ const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.PPU);
 const pollDmaOnBlank = @import("bus/dma.zig").pollDmaOnBlank;
 
-/// This is used to generate byuu / Talurabi's Color Correction algorithm
-const COLOUR_LUT = genColourLut();
-
 pub const width = 240;
 pub const height = 160;
 pub const framebuf_pitch = width * @sizeOf(u32);
@@ -392,7 +389,7 @@ pub const Ppu = struct {
                     const maybe_btm = self.scanline.btm()[i];
 
                     const bgr555 = self.getBgr555(maybe_top, maybe_btm);
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
 
                 // Reset Current Scanline Pixel Buffer and list of fetched sprites
@@ -419,7 +416,7 @@ pub const Ppu = struct {
                     const maybe_btm = self.scanline.btm()[i];
 
                     const bgr555 = self.getBgr555(maybe_top, maybe_btm);
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
 
                 // Reset Current Scanline Pixel Buffer and list of fetched sprites
@@ -445,7 +442,7 @@ pub const Ppu = struct {
                     const maybe_btm = self.scanline.btm()[i];
 
                     const bgr555 = self.getBgr555(maybe_top, maybe_btm);
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
 
                 // Reset Current Scanline Pixel Buffer and list of fetched sprites
@@ -460,7 +457,7 @@ pub const Ppu = struct {
                 var i: usize = 0;
                 while (i < width) : (i += 1) {
                     const bgr555 = self.vram.read(u16, vram_base + i * @sizeOf(u16));
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
             },
             0x4 => {
@@ -471,7 +468,7 @@ pub const Ppu = struct {
                 // Render Current Scanline
                 for (self.vram.buf[vram_base .. vram_base + width]) |byte, i| {
                     const bgr555 = self.palette.read(u16, @as(u16, byte) * @sizeOf(u16));
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
             },
             0x5 => {
@@ -488,7 +485,7 @@ pub const Ppu = struct {
                     const bgr555 =
                         if (scanline < m5_height and i < m5_width) self.vram.read(u16, vram_base + i * @sizeOf(u16)) else self.palette.getBackdrop();
 
-                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], COLOUR_LUT[bgr555 & 0x7FFF]);
+                    std.mem.writeIntNative(u32, self.framebuf.get(.Emulator)[fb_base + i * @sizeOf(u32) ..][0..@sizeOf(u32)], rgba888(bgr555));
                 }
             },
             else => std.debug.panic("[PPU] TODO: Implement BG Mode {}", .{bg_mode}),
@@ -1063,7 +1060,7 @@ fn spriteDimensions(shape: u2, size: u2) [2]u8 {
     };
 }
 
-fn toRgba8888(bgr555: u16) u32 {
+inline fn rgba888(bgr555: u16) u32 {
     const b = @as(u32, bgr555 >> 10 & 0x1F);
     const g = @as(u32, bgr555 >> 5 & 0x1F);
     const r = @as(u32, bgr555 & 0x1F);
@@ -1071,39 +1068,6 @@ fn toRgba8888(bgr555: u16) u32 {
     return (r << 3 | r >> 2) << 24 | (g << 3 | g >> 2) << 16 | (b << 3 | b >> 2) << 8 | 0xFF;
 }
 
-fn genColourLut() [0x8000]u32 {
-    return comptime {
-        @setEvalBranchQuota(0x10001);
-
-        var lut: [0x8000]u32 = undefined;
-        for (lut) |*px, i| px.* = toRgba8888(i);
-        return lut;
-    };
-}
-
-// FIXME: The implementation is incorrect and using it in the LUT crashes the compiler (OOM)
-/// Implementation courtesy of byuu and Talarubi at https://near.sh/articles/video/color-emulation
-fn toRgba8888Talarubi(bgr555: u16) u32 {
-    @setRuntimeSafety(false);
-
-    const lcd_gamma: f64 = 4;
-    const out_gamma: f64 = 2.2;
-
-    const b = @as(u32, bgr555 >> 10 & 0x1F);
-    const g = @as(u32, bgr555 >> 5 & 0x1F);
-    const r = @as(u32, bgr555 & 0x1F);
-
-    const lb = std.math.pow(f64, @intToFloat(f64, b << 3 | b >> 2) / 31, lcd_gamma);
-    const lg = std.math.pow(f64, @intToFloat(f64, g << 3 | g >> 2) / 31, lcd_gamma);
-    const lr = std.math.pow(f64, @intToFloat(f64, r << 3 | r >> 2) / 31, lcd_gamma);
-
-    const out_b = std.math.pow(f64, (220 * lb + 10 * lg + 50 * lr) / 255, 1 / out_gamma);
-    const out_g = std.math.pow(f64, (30 * lb + 230 * lg + 10 * lr) / 255, 1 / out_gamma);
-    const out_r = std.math.pow(f64, (0 * lb + 50 * lg + 255 * lr) / 255, 1 / out_gamma);
-
-    return @floatToInt(u32, out_r) << 24 | @floatToInt(u32, out_g) << 16 | @floatToInt(u32, out_b) << 8 | 0xFF;
-}
-
 fn alphaBlend(top: u16, btm: u16, bldalpha: io.BldAlpha) u16 {
     const eva: u16 = bldalpha.eva.read();
     const evb: u16 = bldalpha.evb.read();

src/platform.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const SDL = @import("sdl2");
+const gl = @import("gl");
 const emu = @import("core/emu.zig");
 const config = @import("config.zig");
 
@@ -11,21 +12,43 @@ const FpsTracker = @import("util.zig").FpsTracker;
 const span = @import("util.zig").span;
 
 const pitch = @import("core/ppu.zig").framebuf_pitch;
+const gba_width = @import("core/ppu.zig").width;
+const gba_height = @import("core/ppu.zig").height;
+
 const default_title: []const u8 = "ZBA";
 
 pub const Gui = struct {
     const Self = @This();
+    const SDL_GLContext = *anyopaque; // SDL.SDL_GLContext is a ?*anyopaque
     const log = std.log.scoped(.Gui);
 
+    // zig fmt: off
+    const vertices: [32]f32 = [_]f32{
+        // Positions        // Colours      // Texture Coords
+         1.0, -1.0, 0.0,    1.0, 0.0, 0.0,  1.0, 1.0, // Top Right
+         1.0,  1.0, 0.0,    0.0, 1.0, 0.0,  1.0, 0.0, // Bottom Right
+        -1.0,  1.0, 0.0,    0.0, 0.0, 1.0,  0.0, 0.0, // Bottom Left
+        -1.0, -1.0, 0.0,    1.0, 1.0, 0.0,  0.0, 1.0, // Top Left
+    };
+
+    const indices: [6]u32 = [_]u32{
+        0, 1, 3, // First Triangle
+        1, 2, 3, // Second Triangle
+    };
+    // zig fmt: on
+
     window: *SDL.SDL_Window,
+    ctx: SDL_GLContext,
     title: []const u8,
-    renderer: *SDL.SDL_Renderer,
-    texture: *SDL.SDL_Texture,
     audio: Audio,
 
+    program_id: gl.GLuint,
+
     pub fn init(title: *const [12]u8, apu: *Apu, width: i32, height: i32) Self {
-        const ret = SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO | SDL.SDL_INIT_GAMECONTROLLER);
+        if (SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO) < 0) panic();
-        if (ret < 0) panic();
+        if (SDL.SDL_GL_SetAttribute(SDL.SDL_GL_CONTEXT_PROFILE_MASK, SDL.SDL_GL_CONTEXT_PROFILE_CORE) < 0) panic();
+        if (SDL.SDL_GL_SetAttribute(SDL.SDL_GL_CONTEXT_MAJOR_VERSION, 3) < 0) panic();
+        if (SDL.SDL_GL_SetAttribute(SDL.SDL_GL_CONTEXT_MAJOR_VERSION, 3) < 0) panic();
 
         const win_scale = @intCast(c_int, config.config().host.win_scale);
 
@@ -35,29 +58,98 @@ pub const Gui = struct {
             SDL.SDL_WINDOWPOS_CENTERED,
             @as(c_int, width * win_scale),
             @as(c_int, height * win_scale),
-            SDL.SDL_WINDOW_SHOWN,
+            SDL.SDL_WINDOW_OPENGL | SDL.SDL_WINDOW_SHOWN,
         ) orelse panic();
 
-        const renderer_flags = SDL.SDL_RENDERER_ACCELERATED | if (config.config().host.vsync) SDL.SDL_RENDERER_PRESENTVSYNC else 0;
+        const ctx = SDL.SDL_GL_CreateContext(window) orelse panic();
-        const renderer = SDL.SDL_CreateRenderer(window, -1, @bitCast(u32, renderer_flags)) orelse panic();
+        if (SDL.SDL_GL_MakeCurrent(window, ctx) < 0) panic();
 
-        const texture = SDL.SDL_CreateTexture(
+        gl.load(ctx, Self.glGetProcAddress) catch @panic("gl.load failed");
-            renderer,
+        if (SDL.SDL_GL_SetSwapInterval(@boolToInt(config.config().host.vsync)) < 0) panic();
-            SDL.SDL_PIXELFORMAT_RGBA8888,
+
-            SDL.SDL_TEXTUREACCESS_STREAMING,
+        const program_id = compileShaders();
-            @as(c_int, width),
-            @as(c_int, height),
-        ) orelse panic();
 
         return Self{
             .window = window,
             .title = span(title),
-            .renderer = renderer,
+            .ctx = ctx,
-            .texture = texture,
+            .program_id = program_id,
             .audio = Audio.init(apu),
         };
     }
 
+    fn compileShaders() gl.GLuint {
+        // TODO: Panic on Shader Compiler Failure + Error Message
+        const vert_shader = @embedFile("shader/pixelbuf.vert");
+        const frag_shader = @embedFile("shader/pixelbuf.frag");
+
+        const vs = gl.createShader(gl.VERTEX_SHADER);
+        defer gl.deleteShader(vs);
+
+        gl.shaderSource(vs, 1, &[_][*c]const u8{vert_shader}, 0);
+        gl.compileShader(vs);
+
+        const fs = gl.createShader(gl.FRAGMENT_SHADER);
+        defer gl.deleteShader(fs);
+
+        gl.shaderSource(fs, 1, &[_][*c]const u8{frag_shader}, 0);
+        gl.compileShader(fs);
+
+        const program = gl.createProgram();
+        gl.attachShader(program, vs);
+        gl.attachShader(program, fs);
+        gl.linkProgram(program);
+
+        return program;
+    }
+
+    // Returns the VAO ID since it's used in run()
+    fn generateBuffers() [3]c_uint {
+        var vao_id: c_uint = undefined;
+        var vbo_id: c_uint = undefined;
+        var ebo_id: c_uint = undefined;
+        gl.genVertexArrays(1, &vao_id);
+        gl.genBuffers(1, &vbo_id);
+        gl.genBuffers(1, &ebo_id);
+
+        gl.bindVertexArray(vao_id);
+
+        gl.bindBuffer(gl.ARRAY_BUFFER, vbo_id);
+        gl.bufferData(gl.ARRAY_BUFFER, @sizeOf(@TypeOf(vertices)), &vertices, gl.STATIC_DRAW);
+
+        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, ebo_id);
+        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, @sizeOf(@TypeOf(indices)), &indices, gl.STATIC_DRAW);
+
+        // Position
+        gl.vertexAttribPointer(0, 3, gl.FLOAT, gl.FALSE, 8 * @sizeOf(f32), @intToPtr(?*anyopaque, 0)); // lmao
+        gl.enableVertexAttribArray(0);
+        // Colour
+        gl.vertexAttribPointer(1, 3, gl.FLOAT, gl.FALSE, 8 * @sizeOf(f32), @intToPtr(?*anyopaque, (3 * @sizeOf(f32))));
+        gl.enableVertexAttribArray(1);
+        // Texture Coord
+        gl.vertexAttribPointer(2, 2, gl.FLOAT, gl.FALSE, 8 * @sizeOf(f32), @intToPtr(?*anyopaque, (6 * @sizeOf(f32))));
+        gl.enableVertexAttribArray(2);
+
+        return .{ vao_id, vbo_id, ebo_id };
+    }
+
+    fn generateTexture(buf: []const u8) c_uint {
+        var tex_id: c_uint = undefined;
+        gl.genTextures(1, &tex_id);
+        gl.bindTexture(gl.TEXTURE_2D, tex_id);
+
+        // gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+        // gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+
+        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
+        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
+
+        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gba_width, gba_height, 0, gl.RGBA, gl.UNSIGNED_INT_8_8_8_8, buf.ptr);
+        // gl.generateMipmap(gl.TEXTURE_2D); // TODO: Remove?
+
+        return tex_id;
+    }
+
     pub fn run(self: *Self, cpu: *Arm7tdmi, scheduler: *Scheduler) !void {
         var quit = std.atomic.Atomic(bool).init(false);
         var tracker = FpsTracker.init();
@@ -67,6 +159,9 @@ pub const Gui = struct {
 
         var title_buf: [0x100]u8 = [_]u8{0} ** 0x100;
 
+        const vao_id = Self.generateBuffers()[0];
+        _ = Self.generateTexture(cpu.bus.ppu.framebuf.get(.Renderer));
+
         emu_loop: while (true) {
             var event: SDL.SDL_Event = undefined;
             while (SDL.SDL_PollEvent(&event) != 0) {
@@ -125,9 +220,12 @@ pub const Gui = struct {
 
             // Emulator has an internal Double Buffer
             const framebuf = cpu.bus.ppu.framebuf.get(.Renderer);
-            _ = SDL.SDL_UpdateTexture(self.texture, null, framebuf.ptr, pitch);
+            gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gba_width, gba_height, gl.RGBA, gl.UNSIGNED_INT_8_8_8_8, framebuf.ptr);
-            _ = SDL.SDL_RenderCopy(self.renderer, self.texture, null, null);
+
-            SDL.SDL_RenderPresent(self.renderer);
+            gl.useProgram(self.program_id);
+            gl.bindVertexArray(vao_id);
+            gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, null);
+            SDL.SDL_GL_SwapWindow(self.window);
 
             const dyn_title = std.fmt.bufPrint(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.title, tracker.value() }) catch unreachable;
             SDL.SDL_SetWindowTitle(self.window, dyn_title.ptr);
@@ -138,12 +236,18 @@ pub const Gui = struct {
 
     pub fn deinit(self: *Self) void {
         self.audio.deinit();
-        SDL.SDL_DestroyTexture(self.texture);
+        // TODO: Buffer deletions
-        SDL.SDL_DestroyRenderer(self.renderer);
+        gl.deleteProgram(self.program_id);
+        SDL.SDL_GL_DeleteContext(self.ctx);
         SDL.SDL_DestroyWindow(self.window);
         SDL.SDL_Quit();
         self.* = undefined;
     }
+
+    fn glGetProcAddress(ctx: SDL.SDL_GLContext, proc: [:0]const u8) ?*anyopaque {
+        _ = ctx;
+        return SDL.SDL_GL_GetProcAddress(proc.ptr);
+    }
 };
 
 const Audio = struct {

src/shader/pixelbuf.frag

@@ -0,0 +1,25 @@
+#version 330 core
+out vec4 frag_color;
+
+in vec3 color;
+in vec2 uv;
+
+uniform sampler2D screen;
+
+void main() {
+	// https://near.sh/video/color-emulation
+	// Thanks to Talarubi + Near for the Colour Correction
+	// Thanks to fleur + mattrb for the Shader Impl
+
+	vec4 color = texture(screen, uv);
+	color.rgb = pow(color.rgb, vec3(4.0)); // LCD Gamma
+  
+	frag_color = vec4(
+		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 / 2.2)), // Out Gamma
+	1.0); 
+}
+

src/shader/pixelbuf.vert

@@ -0,0 +1,13 @@
+#version 330 core
+layout (location = 0) in vec3 pos;
+layout (location = 1) in vec3 in_color;
+layout (location = 2) in vec2 in_uv;
+
+out vec3 color;
+out vec2 uv;
+
+void main() {
+	color = in_color;
+	uv = in_uv;
+	gl_Position = vec4(pos, 1.0);
+}