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# win32

Native Win32 GUI bindings for Windows — the counterpart to [appkit](/docs/packages/appkit) on macOS, organized the same way. Six modules cover the surface: `core` (the engine), `window`, `controls`, `menu`, `dialogs`, and `graphics`, with an umbrella `win32` facade re-exporting the flat type surface (`win32::Window`, `win32::Button`, …).

Unlike a toolkit binding, this needs **nothing installed**: `user32`, `gdi32`, `comctl32`, and `comdlg32` ship with every Windows install and sit on the linker's default search path, so a consuming app builds and runs out of the box on the `x86_64-pc-windows-msvc` [target](/docs/targets) — no MSYS2, no pkg-config, no toolkit to fetch. The bindings are direct `extern fn` calls into those DLLs — thin C+ structs over opaque `HWND`/`HMENU`/`HDC` handles. The **ANSI** (`*A`) entry points are used, so a plain NUL-terminated C+ string built with `#str_ptr("...\0")` is a valid `LPCSTR` with no UTF-16 conversion.

## Events: the dispatch table

Win32 has no per-control signal objects — the parent window procedure receives everything. This binding hides that. Each control is created with a unique command id, and `control.on_click(handler, user)` registers `handler` in the parent window's **dispatch table** under that id (the `core` module heap-allocates the table and attaches it to the window with `SetPropA`). When the control fires a `WM_COMMAND`, the single routing window-procedure looks the id up and calls your function.

Handlers are plain closure-free C+ functions of shape `fn(sender_hwnd, user)` — C+ has no closures, so app state is threaded through the `user: *u8` pointer (or a global). Paint handlers are `fn(window_hwnd, hdc)`; wrap the device context with `graphics::Painter::from_hdc(hdc)` to draw.

```cplus
import "win32/win32" as win32;
import "win32/controls" as controls;

fn on_click(sender: *u8, _user: *u8) {
    // handle the click; reach app state through `user` or a global.
    return;
}

fn main() -> i32 {
    let win: win32::Window = win32::Window::new(#str_ptr("C+ on Win32\0"),
                                                420 as i32, 300 as i32);
    let _lbl: controls::Label = controls::Label::new(win.raw(),
        #str_ptr("Hello from C+ via native Win32\0"),
        20 as i32, 16 as i32, 380 as i32, 22 as i32);
    let btn: controls::Button = controls::Button::new(win.raw(),
        #str_ptr("Press me\0"), 20 as i32, 48 as i32, 120 as i32, 30 as i32);
    btn.on_click(on_click, 0 as *u8);
    win.show();
    return win32::run();        // pump messages until the window is closed
}
```

`win32::run()` is the application message loop (the `app.run()` analogue) and returns the `WM_QUIT` code.

## Controls

`controls` covers ten classes: `Button`, `Label`, `Edit` (plus `new_multiline`), `CheckBox`, `RadioButton`, `ComboBox`, `ListBox`, `ProgressBar`, `TrackBar` (a slider), and `GroupBox`. Each constructor takes the parent `HWND` and an `x, y, w, h` rectangle. Interactive controls expose an `on_*` registrar (`on_click` / `on_change` / `on_toggle` / `on_select`) alongside getters and setters: `set_text`, `is_checked` / `set_checked`, `add_item` / `selected_index`, `set_range` / `set_value`, and so on.

`TrackBar` is the exception — its notifications arrive as `WM_HSCROLL` rather than `WM_COMMAND`, so it exposes value get/set plus range instead of a command callback.

## Menus and dialogs

`menu` builds a menu bar with `Menu::new()` (or a submenu with `Menu::new_popup()`), then `add_item`, `add_submenu`, and `add_separator`. Menu items route exactly like controls, so `add_item` takes the owning window's `HWND` to register its handler. Attach the bar with `win.set_menu(bar.raw())`.

`dialogs` provides `message_box` / `message_box_ex` (the alert-dialog analogue over `MessageBoxA`, with `mb_*` button-set / icon constants and `id_*` results) and `open_file` / `save_file` (comdlg32 file dialogs that fill a caller-provided path buffer and return whether the user confirmed).

## Painting

A `graphics::Painter` wraps the `HDC` handed to a window's `on_paint` handler and issues GDI calls — `text`, `rectangle`, `ellipse`, `line`, `fill_rect`, `use_pen`, and text color. A `Color` is a `COLORREF` value built with `Color::rgb(r, g, b)`.

```cplus
import "win32/win32" as win32;
import "win32/graphics" as gfx;

fn on_paint(_hwnd: *u8, hdc: *u8) {
    let p: gfx::Painter = gfx::Painter::from_hdc(hdc);
    p.fill_rect(10 as i32, 10 as i32, 200 as i32, 80 as i32,
                gfx::Color::rgb(30 as u8, 120 as u8, 220 as u8));
    p.set_transparent_text();
    p.set_text_color(gfx::Color::rgb(255 as u8, 255 as u8, 255 as u8));
    p.text(24 as i32, 36 as i32, #str_ptr("painted with GDI\0"));
    return;
}
```

Register it with `win.on_paint(on_paint, 0 as *u8)`, and force a repaint with `win.redraw()`.

## Ownership

`HWND`/`HMENU`/`HDC` are OS-owned opaque handles, so the wrapper structs hold them `opaque` with **no `drop`** — a window is torn down by closing it (`WM_CLOSE` → `DestroyWindow`) or at process exit, and child controls are owned by their parent. The per-window dispatch table is heap-allocated and lives for the window's lifetime. This is the same conservative default as appkit's child widgets.

## Platform notes

This package is Windows-only and links `user32`, `gdi32`, `comctl32`, and `comdlg32` (declared in its `Cplus.toml`), all of which are present on a stock install. Build with `cpc build` on `x86_64-pc-windows-msvc`; see [targets](/docs/targets) for cross-target builds. For the underlying `extern fn` call mechanics, see [FFI](/docs/ffi); to drive a GUI app from an external agent, see the [agent surface](/docs/agent-surface). The closure-free handler convention here is the same one [builder blocks](/docs/builder-blocks) lean on elsewhere.