add higher-level app library

Fixes hexops/mach#190

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

examples/main.zig

@@ -0,0 +1,114 @@
+const std = @import("std");
+const mach = @import("mach");
+const gpu = @import("gpu");
+
+const App = mach.App(*FrameParams, .{});
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    var allocator = gpa.allocator();
+
+    const ctx = try allocator.create(FrameParams);
+    var app = try App.init(allocator, ctx, .{});
+
+    const vs_module = app.device.createShaderModule(&.{
+        .label = "my vertex shader",
+        .code = .{ .wgsl = @embedFile("vert.wgsl") },
+    });
+
+    const fs_module = app.device.createShaderModule(&.{
+        .label = "my fragment shader",
+        .code = .{ .wgsl = @embedFile("frag.wgsl") },
+    });
+
+    // Fragment state
+    const blend = gpu.BlendState{
+        .color = .{
+            .operation = .add,
+            .src_factor = .one,
+            .dst_factor = .one,
+        },
+        .alpha = .{
+            .operation = .add,
+            .src_factor = .one,
+            .dst_factor = .one,
+        },
+    };
+    const color_target = gpu.ColorTargetState{
+        .format = app.swap_chain_format,
+        .blend = &blend,
+        .write_mask = .all,
+    };
+    const fragment = gpu.FragmentState{
+        .module = fs_module,
+        .entry_point = "main",
+        .targets = &.{color_target},
+        .constants = null,
+    };
+    const pipeline_descriptor = gpu.RenderPipeline.Descriptor{
+        .fragment = &fragment,
+        .layout = null,
+        .depth_stencil = null,
+        .vertex = .{
+            .module = vs_module,
+            .entry_point = "main",
+            .buffers = null,
+        },
+        .multisample = .{
+            .count = 1,
+            .mask = 0xFFFFFFFF,
+            .alpha_to_coverage_enabled = false,
+        },
+        .primitive = .{
+            .front_face = .ccw,
+            .cull_mode = .none,
+            .topology = .triangle_list,
+            .strip_index_format = .none,
+        },
+    };
+
+    ctx.* = FrameParams{
+        .pipeline = app.device.createRenderPipeline(&pipeline_descriptor),
+        .queue = app.device.getQueue(),
+    };
+
+    vs_module.release();
+    fs_module.release();
+
+    try app.run(frame);
+}
+
+const FrameParams = struct {
+    pipeline: gpu.RenderPipeline,
+    queue: gpu.Queue,
+};
+
+fn frame(app: *App, params: *FrameParams) !void {
+    const back_buffer_view = app.swap_chain.?.getCurrentTextureView();
+    const color_attachment = gpu.RenderPassColorAttachment{
+        .view = back_buffer_view,
+        .resolve_target = null,
+        .clear_value = std.mem.zeroes(gpu.Color),
+        .load_op = .clear,
+        .store_op = .store,
+    };
+
+    const encoder = app.device.createCommandEncoder(null);
+    const render_pass_info = gpu.RenderPassEncoder.Descriptor{
+        .color_attachments = &.{color_attachment},
+        .depth_stencil_attachment = null,
+    };
+    const pass = encoder.beginRenderPass(&render_pass_info);
+    pass.setPipeline(params.pipeline);
+    pass.draw(3, 1, 0, 0);
+    pass.end();
+    pass.release();
+
+    var command = encoder.finish(null);
+    encoder.release();
+
+    params.queue.submit(&.{command});
+    command.release();
+    app.swap_chain.?.present();
+    back_buffer_view.release();
+}