core: libmachcore fixes

libs/core/src/platform/libmachcore.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const testing = std.testing;
 const gpu = @import("gpu");
 const ecs = @import("ecs");
 const glfw = @import("glfw");
@@ -20,31 +21,64 @@ const _ = gpu.Export(GPUInterface);
 var gpa = std.heap.GeneralPurposeAllocator(.{}){};
 const allocator = gpa.allocator();
 
+pub const MachCoreInstance = anyopaque;
+
 // Returns a pointer to a newly allocated Core
 // Will return a null pointer if an error occurred while initializing Core
-pub export fn mach_core_init() ?*native.Core {
-    gpu.Impl.init();
+pub export fn mach_core_init() ?*MachCoreInstance {
+    if (!@import("builtin").is_test) gpu.Impl.init();
+
     // TODO(libmach): eliminate this allocation
     var core = allocator.create(native.Core) catch {
-        return @intToPtr(?*native.Core, 0);
+        return null;
     };
     // TODO(libmach): allow passing init options
     core.init(allocator, .{}) catch {
         // TODO(libmach): better error handling
-        return @intToPtr(?*native.Core, 0);
+        return null;
     };
     return core;
 }
 
-pub export fn mach_core_deinit(core: *native.Core) void {
+pub export fn mach_core_deinit(_core: *MachCoreInstance) void {
+    var core = @ptrCast(*native.Core, @alignCast(@alignOf(@TypeOf(_core)), _core));
     native.Core.deinit(core);
 }
 
-// pub export fn mach_core_poll_events(core: *native.Core) Core.Event {
-//     return native.Core.pollEvents(core);
-// }
+pub const MachCoreEventIterator = extern struct {
+    _data: [8]u8,
+};
+
+pub const MachCoreEvent = Core.Event;
+
+pub export fn mach_core_poll_events(_core: *MachCoreInstance) MachCoreEventIterator {
+    var core = @ptrCast(*native.Core, @alignCast(@alignOf(@TypeOf(_core)), _core));
+    var iter = native.Core.pollEvents(core);
+    return @ptrCast(*MachCoreEventIterator, &iter).*;
+}
+
+pub export fn mach_core_event_iterator_next(_iter: *MachCoreEventIterator, event: *MachCoreEvent) bool {
+    var iter = @ptrCast(*native.Core.EventIterator, @alignCast(@alignOf(@TypeOf(_iter)), _iter));
+    var value = iter.next() orelse return false;
+    event.* = value;
+    return true;
+}
 
 const MachStatus = enum(c_int) {
     Success = 0x00000000,
     Error = 0x00000001,
 };
+
+test "C sizes" {
+    const c_header = @cImport({
+        @cInclude("libmachcore.h");
+    });
+
+    // Core.EventIterator can have different sizes depending on the platform,
+    // so we ensure we always use the maximum size in our C API.
+    if (@sizeOf(Core.EventIterator) > @sizeOf(MachCoreEventIterator)) {
+        try testing.expectEqual(@sizeOf(Core.EventIterator), @sizeOf(MachCoreEventIterator));
+    }
+
+    try testing.expectEqual(@sizeOf(c_header.MachCoreEventIterator), @sizeOf(MachCoreEventIterator));
+}