draw a triangle with opengl

nix/devshell.nix

@@ -1,6 +1,7 @@
 { mkShell, lib, stdenv
 
 , gdb
+, glxinfo
 , pkg-config
 , scdoc
 , vulkan-loader
@@ -24,6 +25,7 @@
     scdoc
     zig
 
+    glxinfo
     vttest
   ];
 

src/main.zig

@@ -9,22 +9,140 @@ pub fn main() !void {
     defer glfw.terminate();
 
     // Create our window
-    const window = try glfw.Window.create(640, 480, "ghostty", null, null, .{});
+    const window = try glfw.Window.create(640, 480, "ghostty", null, null, .{
+        .context_version_major = 3,
+        .context_version_minor = 3,
+        .opengl_profile = .opengl_core_profile,
+        .opengl_forward_compat = true,
+    });
     defer window.destroy();
 
     // Setup OpenGL
     try glfw.makeContextCurrent(window);
     try glfw.swapInterval(1);
+    window.setSizeCallback((struct {
+        fn callback(_: glfw.Window, width: i32, height: i32) void {
+            std.log.info("set viewport {} {}", .{ width, height });
+            c.glViewport(0, 0, width, height);
+        }
+    }).callback);
 
-    // Setup basic OpenGL settings
-    c.glClearColor(0.0, 0.0, 0.0, 0.0);
+    // Create our vertex shader
+    const vs = c.glCreateShader(c.GL_VERTEX_SHADER);
+    c.glShaderSource(
+        vs,
+        1,
+        &@ptrCast([*c]const u8, vs_source),
+        null,
+    );
+    c.glCompileShader(vs);
+    var success: c_int = undefined;
+    c.glGetShaderiv(vs, c.GL_COMPILE_STATUS, &success);
+    if (success != c.GL_TRUE) {
+        var msg: [512]u8 = undefined;
+        c.glGetShaderInfoLog(vs, 512, null, &msg);
+        std.log.err("Fail: {s}\n", .{std.mem.sliceTo(&msg, 0)});
+        return;
+    }
+
+    const fs = c.glCreateShader(c.GL_FRAGMENT_SHADER);
+    c.glShaderSource(
+        fs,
+        1,
+        &@ptrCast([*c]const u8, fs_source),
+        null,
+    );
+    c.glCompileShader(fs);
+    c.glGetShaderiv(fs, c.GL_COMPILE_STATUS, &success);
+    if (success != c.GL_TRUE) {
+        var msg: [512]u8 = undefined;
+        c.glGetShaderInfoLog(fs, 512, null, &msg);
+        std.log.err("FS fail: {s}\n", .{std.mem.sliceTo(&msg, 0)});
+        return;
+    }
+
+    // Shader program
+    const program = c.glCreateProgram();
+    c.glAttachShader(program, vs);
+    c.glAttachShader(program, fs);
+    c.glLinkProgram(program);
+    c.glGetProgramiv(program, c.GL_LINK_STATUS, &success);
+    if (success != c.GL_TRUE) {
+        var msg: [512]u8 = undefined;
+        c.glGetProgramInfoLog(program, 512, null, &msg);
+        std.log.err("program fail: {s}\n", .{std.mem.sliceTo(&msg, 0)});
+        return;
+    }
+    c.glDeleteShader(vs);
+    c.glDeleteShader(fs);
+
+    // Create our bufer or vertices
+    const vertices = [_]f32{
+        -0.5, -0.5, 0.0, // left
+        0.5, -0.5, 0.0, // right
+        0.0, 0.5, 0.0, // top
+    };
+    var vao: c_uint = undefined;
+    var vbo: c_uint = undefined;
+    c.glGenVertexArrays(1, &vao);
+    c.glGenBuffers(1, &vbo);
+    c.glBindVertexArray(vao);
+
+    c.glBindBuffer(c.GL_ARRAY_BUFFER, vbo);
+    c.glBufferData(
+        c.GL_ARRAY_BUFFER,
+        @as(isize, @sizeOf(@TypeOf(vertices))),
+        &vertices,
+        c.GL_STATIC_DRAW,
+    );
+
+    c.glVertexAttribPointer(
+        0,
+        3,
+        c.GL_FLOAT,
+        c.GL_FALSE,
+        3 * @sizeOf(f32),
+        null,
+    );
+    c.glEnableVertexAttribArray(0);
+
+    c.glBindBuffer(c.GL_ARRAY_BUFFER, 0);
+    c.glBindVertexArray(0);
 
     // Wait for the user to close the window.
     while (!window.shouldClose()) {
-        const pos = try window.getCursorPos();
-        std.log.info("CURSOR: {}", .{pos});
+        // Setup basic OpenGL settings
+        c.glClearColor(0.2, 0.3, 0.3, 1.0);
+        c.glClear(c.GL_COLOR_BUFFER_BIT);
+
+        c.glUseProgram(program);
+        c.glBindVertexArray(vao);
+        c.glDrawArrays(c.GL_TRIANGLES, 0, 3);
+
+        // const pos = try window.getCursorPos();
+        // std.log.info("CURSOR: {}", .{pos});
 
         try window.swapBuffers();
         try glfw.waitEvents();
     }
 }
+
+const vs_source =
+    \\#version 330 core
+    \\layout (location = 0) in vec3 aPos;
+    \\
+    \\void main()
+    \\{
+    \\    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    \\}
+;
+
+const fs_source =
+    \\#version 330 core
+    \\out vec4 FragColor;
+    \\
+    \\void main()
+    \\{
+    \\    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+    \\}
+;