1 files changed, 43 insertions, 0 deletions
diff --git a/toolkit/crashreporter/client/app/src/ui/windows/gdi.rs b/toolkit/crashreporter/client/app/src/ui/windows/gdi.rs
new file mode 100644
index 0000000000..89828987bc
--- /dev/null
+++ b/toolkit/crashreporter/client/app/src/ui/windows/gdi.rs
@@ -0,0 +1,43 @@
+/* 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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! 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) };
+    }
+}