core: add mach.Core module API

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

examples/core-custom-entrypoint/Game.zig

@@ -0,0 +1,105 @@
+const std = @import("std");
+const mach = @import("mach");
+const gpu = mach.gpu;
+
+pub const name = .game;
+pub const Mod = mach.Mod(@This());
+
+pub const global_events = .{
+    .init = .{ .handler = init },
+    .tick = .{ .handler = tick },
+};
+
+title_timer: mach.Timer,
+pipeline: *gpu.RenderPipeline,
+
+fn init(game: *Mod) !void {
+    const shader_module = mach.core.device.createShaderModuleWGSL("shader.wgsl", @embedFile("shader.wgsl"));
+    defer shader_module.release();
+
+    // Fragment state
+    const blend = gpu.BlendState{};
+    const color_target = gpu.ColorTargetState{
+        .format = mach.core.descriptor.format,
+        .blend = &blend,
+        .write_mask = gpu.ColorWriteMaskFlags.all,
+    };
+    const fragment = gpu.FragmentState.init(.{
+        .module = shader_module,
+        .entry_point = "frag_main",
+        .targets = &.{color_target},
+    });
+    const pipeline_descriptor = gpu.RenderPipeline.Descriptor{
+        .fragment = &fragment,
+        .vertex = gpu.VertexState{
+            .module = shader_module,
+            .entry_point = "vertex_main",
+        },
+    };
+    const pipeline = mach.core.device.createRenderPipeline(&pipeline_descriptor);
+
+    game.init(.{
+        .title_timer = try mach.Timer.start(),
+        .pipeline = pipeline,
+    });
+    try updateWindowTitle();
+}
+
+pub fn deinit(game: *Mod) void {
+    game.state().pipeline.release();
+}
+
+// TODO(important): remove need for returning an error here
+fn tick(
+    core: *mach.Core.Mod,
+    game: *Mod,
+) !void {
+    // TODO(important): event polling should occur in mach.Core module and get fired as ECS event.
+    var iter = mach.core.pollEvents();
+    while (iter.next()) |event| {
+        switch (event) {
+            .close => core.send(.exit, .{}), // Tell mach.Core to exit the app
+            else => {},
+        }
+    }
+
+    const queue = mach.core.queue;
+    const back_buffer_view = mach.core.swap_chain.getCurrentTextureView().?;
+    const color_attachment = gpu.RenderPassColorAttachment{
+        .view = back_buffer_view,
+        .clear_value = std.mem.zeroes(gpu.Color),
+        .load_op = .clear,
+        .store_op = .store,
+    };
+
+    const encoder = mach.core.device.createCommandEncoder(null);
+    const render_pass_info = gpu.RenderPassDescriptor.init(.{
+        .color_attachments = &.{color_attachment},
+    });
+    const pass = encoder.beginRenderPass(&render_pass_info);
+    pass.setPipeline(game.state().pipeline);
+    pass.draw(3, 1, 0, 0);
+    pass.end();
+    pass.release();
+
+    var command = encoder.finish(null);
+    encoder.release();
+
+    queue.submit(&[_]*gpu.CommandBuffer{command});
+    command.release();
+    mach.core.swap_chain.present();
+    back_buffer_view.release();
+
+    // update the window title every second
+    if (game.state().title_timer.read() >= 1.0) {
+        game.state().title_timer.reset();
+        try updateWindowTitle();
+    }
+}
+
+fn updateWindowTitle() !void {
+    try mach.core.printTitle("mach.Core - custom entrypoint [ {d}fps ] [ Input {d}hz ]", .{
+        mach.core.frameRate(),
+        mach.core.inputRate(),
+    });
+}