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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
//! GDI helpers.
use windows_sys::Win32::{
Foundation::HWND,
Graphics::Gdi::{self, GDI_ERROR, HDC, HGDIOBJ},
};
/// A GDI drawing context.
pub struct DC {
hwnd: HWND,
hdc: HDC,
}
impl DC {
/// Create a new DC.
pub fn new(hwnd: HWND) -> Option<Self> {
let hdc = unsafe { Gdi::GetDC(hwnd) };
(hdc != 0).then_some(DC { hwnd, hdc })
}
/// Call the given function with a gdi object selected.
pub fn with_object_selected<R>(&self, object: HGDIOBJ, f: impl FnOnce(HDC) -> R) -> Option<R> {
let old_object = unsafe { Gdi::SelectObject(self.hdc, object) };
if old_object == 0 || old_object == GDI_ERROR as isize {
return None;
}
let ret = f(self.hdc);
// The prior object must be selected before releasing the DC. Ignore errors; this is
// best-effort.
unsafe { Gdi::SelectObject(self.hdc, old_object) };
Some(ret)
}
}
impl Drop for DC {
fn drop(&mut self) {
unsafe { Gdi::ReleaseDC(self.hwnd, self.hdc) };
}
}