How Can I Create a Window with the WinAPI?

[inner fog]

I am trying to make a Window using the WinAPI by following this tutorial. I wrote the following code and used zig build -Dtarget=x86_64-windows-msvc to build the file and linked all the relevant libraries n build.zig.

const std = @import("std");
const c = @cImport({
    @cDefine("UNICODE", "");
    @cInclude("Windows.h");
});

fn windowProcedure(window: c.HWND, message: c.UINT, wparam: c.WPARAM, lparam: c.LPARAM) callconv(.C) c.LRESULT {
    ...
}

pub export fn wWinMain(
    instance: c.HINSTANCE,
    previous_instance: c.HINSTANCE,
    command_line: c.LPSTR,
    command_show: c.INT,
) callconv(.Win64) c.INT {
    ...
x}

However, I got these errors.

C:\Program Files\zig\lib\std\start.zig:610:43: error: cast increases pointer alignment
    const hInstance = @as(MAIN_HINSTANCE, @ptrCast(peb.ImageBaseAddress));
                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\zig\lib\std\start.zig:610:55: note: '*os.windows.HMODULE__opaque_55476' has alignment '1'
    const hInstance = @as(MAIN_HINSTANCE, @ptrCast(peb.ImageBaseAddress));
                                                   ~~~^~~~~~~~~~~~~~~~~
C:\Program Files\zig\lib\std\start.zig:610:43: note: '[*c]cimport.struct_HINSTANCE__' has alignment '4'
C:\Program Files\zig\lib\std\start.zig:610:43: note: use @alignCast to assert pointer alignment
C:\Program Files\zig\lib\std\start.zig:548:12: note: called from here
    return @call(.always_inline, call_wWinMain, .{});
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\zig\lib\std\start.zig:361:67: note: called from here
    const result: std.os.windows.INT = initEventLoopAndCallWinMain();                                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~

How can I get my code to build?

[floral wind]

You'll probably have an easier time using something like zigwin32(https://github.com/marlersoft/zigwin32) than starting from raw cImport. (Plus most windows projects benefit a lot from #define WIN32_LEAN_AND_MEAN to prune how many subsystems are included).

Other than that, it looks like the compiler is telling you what you need to do. Doing raw Windows will require a lot of casting.

[inner fog]

Am I supposed to edit the start.zig file to include a @alignCast? That doesn't seem very sound.

[floral wind]

Ah didn't notice that. This appears to be an issue with the provided start.zig that I can't answer -- perhaps a bug,

[inner fog]

Thanks for the help. I think I should probably hold off on using raw Win32 until Zig is a bit more stable, then.

I'll have to take a look at zigwin32.

[floral wind]

That project is generated from another project. To see how to consume zigwin32, look in the issues for one asking about how to use it.

[fickle vessel]

The HINSTANCE type you used came from the @cImport, and is most likely defined differently in stdlib

You should use std.os.windows types when possible

Also using the headers is a bit annoying and also doesn't cover some parts of win32

I'd suggest either zigwin32 or for maximum flexibility writing the definitions manually

[sterile leaf]

FYI, you don't actually need to use wWinMain; you can get all of its arguments from syscalls anyway.
I would probably just use main as normal, and do that instead.

Indeed, given the start.zig bug you might have, that might be better anyway. 😄

[flat sluice]

what does wWinMain do anyways?

[fickle vessel]

I'm no expert but as far as I'm aware it's pretty much the Windows version of main() for GUI applications

You're not forced to use it but microsoft does recommend it when you don't need a "console"

the w prefix means it's "wide" (i.e uses utf16)