Set and get user data

src/main.zig

@@ -17,8 +17,6 @@ const Coords = struct {
 
 const State = struct {
     period: f64,
-    bgValue: u8 = 0,
-    increasing: bool = true,
     timer: mfb.Timer,
 
     pub fn init(period: f64) !State {
@@ -97,15 +95,20 @@ pub fn main() !void {
     var gp_allocator = std.heap.GeneralPurposeAllocator(.{}){};
     const alloc = &gp_allocator.allocator;
 
-    var win = mfb.Window.open("Hello minifb-zig", Width, Height, .{.resizable=true}) catch unreachable;
-    mfb.setTargetFPS(7);
-
     var state = try State.init(3);
     defer state.deinit();
 
+    var win = mfb.Window(State).open("Hello minifb-zig", Width, Height, .{.resizable=true}) catch unreachable;
+    mfb.setTargetFPS(7);
+    win.setUserData(&state);
+
     var buf = try Buffer.init(alloc, Width, Height);
     defer buf.deinit();
 
+    var aliasedState = win.getUserData();
+    if (aliasedState) |value| {
+        std.log.info("Period: {d}", .{value.*.period});
+    }
     state.render(buf);
     while (win.waitSync()) {
         state.render(buf);