Minimal C GLFW Metal example

glfw-metal-example.m

//
// cc glfw-metal-example.m `pkg-config --cflags --libs glfw3` -framework AppKit -framework Metal -framework QuartzCore
//
#define GLFW_INCLUDE_NONE
#define GLFW_EXPOSE_NATIVE_COCOA
#include <GLFW/glfw3.h>
#include <GLFW/glfw3native.h>

#import <Metal/Metal.h>
#import <QuartzCore/CAMetalLayer.h>

static void quit(GLFWwindow *window, int key, int scancode, int action, int mods)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) {
        glfwSetWindowShouldClose(window, GLFW_TRUE);
    }
}

int main(void)
{
    const id<MTLDevice> gpu = MTLCreateSystemDefaultDevice();
    const id<MTLCommandQueue> queue = [gpu newCommandQueue];
    CAMetalLayer *swapchain = [CAMetalLayer layer];
    swapchain.device = gpu;
    swapchain.opaque = YES;

    glfwInit();
    glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
    GLFWwindow *window = glfwCreateWindow(640, 480, "GLFW Metal", NULL, NULL);
    NSWindow *nswindow = glfwGetCocoaWindow(window);
    nswindow.contentView.layer = swapchain;
    nswindow.contentView.wantsLayer = YES;

    glfwSetKeyCallback(window, quit);
    MTLClearColor color = MTLClearColorMake(0, 0, 0, 1);

    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();

        @autoreleasepool {
            color.red = (color.red > 1.0) ? 0 : color.red + 0.01;

            id<CAMetalDrawable> surface = [swapchain nextDrawable];

            MTLRenderPassDescriptor *pass = [MTLRenderPassDescriptor renderPassDescriptor];
            pass.colorAttachments[0].clearColor = color;
            pass.colorAttachments[0].loadAction  = MTLLoadActionClear;
            pass.colorAttachments[0].storeAction = MTLStoreActionStore;
            pass.colorAttachments[0].texture = surface.texture;

            id<MTLCommandBuffer> buffer = [queue commandBuffer];
            id<MTLRenderCommandEncoder> encoder = [buffer renderCommandEncoderWithDescriptor:pass];
            [encoder endEncoding];
            [buffer presentDrawable:surface];
            [buffer commit];
        }
    }

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

Thanks for sharing this! To handle window resizing, the CAMetalLayer.drawableSize should be updated so it matches glfwGetFramebufferSize() before fetching the nextDrawable.

Not sure if pkg-config is generally available in OS X builds. From brew, lib and include needs to be specified.

cc glfw-metal-example.m -L/opt/homebrew/Cellar/glfw/3.3.9/lib -I/opt/homebrew/Cellar/glfw/3.3.9/include -lglfw -framework AppKit -framework Metal -framework QuartzCore

If you don't want to use pkg-config, here is how I built it with Bazel: https://github.com/louwers/metal-glfw