winapi - 在 Rust 中使用 winapi 从窗口获取位图

Question

..嗨，我有这个代码:

#[cfg(windows)] extern crate winapi;

use winapi::um::winuser::{FindWindowW, GetClientRect, GetWindowDC, GetDC, ReleaseDC};
use winapi::um::wingdi::{CreateBitmap, CreateCompatibleBitmap, CreateCompatibleDC, SelectObject, GetObjectW, SaveDC, DeleteDC, DeleteObject};
use std::ptr::null_mut;
use std::mem::zeroed;
use std::ffi::OsStr;
use std::iter::once;
use std::os::windows::ffi::OsStrExt;

#[cfg(windows)]
fn find_window(name: &str) {
    let window: Vec<u16> = OsStr::new(name).encode_wide().chain(once(0)).collect();

    let hwnd = unsafe { FindWindowW(null_mut(), window.as_ptr()) };
    
    if hwnd != null_mut() {
        println!("Window found");
        
        let mut my_rect = unsafe { zeroed::<winapi::shared::windef::RECT>() };
        let _client_rect = unsafe { GetClientRect(hwnd, &mut my_rect) };
        let w = my_rect.right - my_rect.left;
        let h = my_rect.bottom - my_rect.top;
        
        let hwnd_dc = unsafe { GetWindowDC(hwnd) };
        let mem_dc = unsafe { CreateCompatibleDC(hwnd_dc) };
        let bmp = unsafe { CreateCompatibleBitmap(mem_dc, w, h) };

        //SelectObject(mem_dc, bmp); <== Problem is here
        
        //DeleteObject(bmp); <== Same problem here
        unsafe { DeleteDC(mem_dc) };
        unsafe { ReleaseDC(hwnd, hwnd_dc) };
    }
    else {
        println!("Window not found");
    }
}

fn main() {
    find_window("Firefox"); // just for test
}

如果我运行这个，我会得到:

SelectObject(mem_dc, bmp);
   |                 ^^^ expected enum `std::ffi::c_void`, found enum `winapi::shared::windef::HBITMAP__`

所以我明白了，它不需要那个位图指针，但是在 win32 文档中，它说这个函数(SelectObject)接受一个设备上下文(mem_dc)和一个由 CreateCompatibleBitmap 等函数创建的对象。
https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-selectobject
Rust 中的绑定(bind)接受两个相同的参数，但它似乎想要 std::ffi::c_void 但查看 Rust 文档，我不明白它到底是什么。
你能帮我找出问题所在吗？谢谢。

Answer 1

添加:

use winapi::shared::windef::{HBITMAP, HBITMAP__, HGDIOBJ, HWND, POINT, RECT, SIZE};
...

unsafe {SelectObject(mem_dc, bmp as HGDIOBJ)};            
unsafe {DeleteObject(bmp as HGDIOBJ)};