Finch/examples/opengl.fch
Nexoniarz 8497251dc5 OpenGL and Vulkan examples; ptr(int)/int(ptr); trailing commas in calls; drop .fn hint
- examples/opengl.fch: OpenGL 3.3 core, shaders, VAO/VBO, a spinning triangle (checked offscreen)
- examples/vulkan.fch: instance, GPUs with properties/memory/queues, logical device and queue
- ptr(n) and int(p) conversions for C APIs that pass offsets as pointers
- .ptr works on string literals; a comma after the last call argument is allowed
- a missing header included by an imported header is now named in the error
- the old .fn extension hint is gone (Finch is new, there are no old files)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-08 19:37:34 +02:00

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3.3 KiB
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// Modern OpenGL (3.3 core): a spinning, colorful triangle drawn with shaders.
// Shows structs of numbers going to the GPU, C out-parameters with addr(), and
// pointers made from numbers with ptr(...). Needs GLFW and OpenGL (in shell.nix).
import "opengl.h"
link "glfw"
link "GL"
fn compileShader(u32 kind, str source) -> u32 {
shader := glCreateShader(kind)
src := source.ptr
glShaderSource(shader, 1, addr(src), null)
glCompileShader(shader)
i32 ok
glGetShaderiv(shader, GL_COMPILE_STATUS, addr(ok))
if ok == 0 {
log := " ".repeat(1024)
glGetShaderInfoLog(shader, 1024, null, log)
print("shader error:", str(log.ptr))
exit(1)
}
return shader
}
fn makeProgram() -> u32 {
vertex := "#version 330 core\n" +
"layout(location = 0) in vec2 pos;\n" +
"layout(location = 1) in vec3 color;\n" +
"uniform float time;\n" +
"out vec3 vColor;\n" +
"void main() {\n" +
" float c = cos(time), s = sin(time);\n" +
" gl_Position = vec4(c * pos.x - s * pos.y, s * pos.x + c * pos.y, 0.0, 1.0);\n" +
" vColor = color;\n" +
"}\n"
fragment := "#version 330 core\n" +
"in vec3 vColor;\n" +
"out vec4 outColor;\n" +
"void main() { outColor = vec4(vColor, 1.0); }\n"
vs := compileShader(GL_VERTEX_SHADER, vertex)
fs := compileShader(GL_FRAGMENT_SHADER, fragment)
program := glCreateProgram()
glAttachShader(program, vs)
glAttachShader(program, fs)
glLinkProgram(program)
glDeleteShader(vs)
glDeleteShader(fs)
return program
}
fn main() {
if glfwInit() == 0 {
print("could not start GLFW")
return
}
defer glfwTerminate()
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3)
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3)
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE)
window := glfwCreateWindow(800, 600, "Finch + OpenGL", null, null)
if window == null {
print("could not open a window (does your GPU support OpenGL 3.3?)")
return
}
glfwMakeContextCurrent(window)
glfwSwapInterval(1)
print("OpenGL", str(glGetString(GL_VERSION)), "on", str(glGetString(GL_RENDERER)))
// x, y, r, g, b for each corner
[]f32 vertices = [
0.0, 0.6, 1.0, 0.48, 0.1,
-0.6, -0.4, 0.2, 0.6, 1.0,
0.6, -0.4, 0.6, 1.0, 0.4,
]
u32 vao
u32 vbo
glGenVertexArrays(1, addr(vao))
glGenBuffers(1, addr(vbo))
glBindVertexArray(vao)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, vertices.len * 4, vertices.ptr, GL_STATIC_DRAW)
i32 stride = 5 * 4
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, stride, ptr(0))
glEnableVertexAttribArray(0)
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, stride, ptr(2 * 4))
glEnableVertexAttribArray(1)
program := makeProgram()
timeLoc := glGetUniformLocation(program, "time")
while glfwWindowShouldClose(window) == 0 {
glClearColor(0.106, 0.122, 0.165, 1.0)
glClear(GL_COLOR_BUFFER_BIT)
glUseProgram(program)
glUniform1f(timeLoc, f32(glfwGetTime()))
glDrawArrays(GL_TRIANGLES, 0, 3)
glfwSwapBuffers(window)
glfwPollEvents()
}
glDeleteBuffers(1, addr(vbo))
glDeleteVertexArrays(1, addr(vao))
glDeleteProgram(program)
}