Shell: windows implementation from content_insets

CHANGELOG.md

@@ -17,6 +17,7 @@ You can find its changes [documented below](#070---2021-01-01).
 - Contexts: to_window and to_screen (useful for relatively positioning sub windows) ([#1532] by [@rjwittams])
 - WindowSizePolicy: allow windows to be sized by their content ([#1532] by [@rjwittams])
 - Implemented `Data` for more datatypes from `std` ([#1534] by [@derekdreery])
+- Shell: windows implementation from content_insets ([#1592] by [@HoNile])
 
 ### Changed
 
@@ -415,6 +416,7 @@ Last release without a changelog :(
 [@MaximilianKoestler]: https://github.com/MaximilianKoestler
 [@lassipulkkinen]: https://github.com/lassipulkkinen
 [@Poignardazur]: https://github.com/PoignardAzur
+[@HoNile]: https://github.com/HoNile
 
 [#599]: https://github.com/linebender/druid/pull/599
 [#611]: https://github.com/linebender/druid/pull/611
@@ -614,6 +616,7 @@ Last release without a changelog :(
 [#1254]: https://github.com/linebender/druid/pull/1254
 [#1559]: https://github.com/linebender/druid/pull/1559
 [#1562]: https://github.com/linebender/druid/pull/1562
+[#1592]: https://github.com/linebender/druid/pull/1592
 
 [Unreleased]: https://github.com/linebender/druid/compare/v0.6.0...master
 [0.6.0]: https://github.com/linebender/druid/compare/v0.5.0...v0.6.0

druid-shell/src/platform/windows/window.rs

@@ -1659,7 +1659,32 @@ impl WindowHandle {
     }
 
     pub fn content_insets(&self) -> Insets {
-        warn!("WindowHandle::content_insets unimplemented for windows.");
+        if let Some(w) = self.state.upgrade() {
+            let hwnd = w.hwnd.get();
+            unsafe {
+                let mut info: WINDOWINFO = mem::zeroed();
+                info.cbSize = mem::size_of::<WINDOWINFO>() as u32;
+
+                if GetWindowInfo(hwnd, &mut info) == 0 {
+                    warn!(
+                        "failed to get window info: {}",
+                        Error::Hr(HRESULT_FROM_WIN32(GetLastError()))
+                    );
+                };
+
+                let window_frame = Rect::from_points(
+                    (info.rcWindow.left as f64, info.rcWindow.top as f64),
+                    (info.rcWindow.right as f64, info.rcWindow.bottom as f64),
+                );
+                let content_frame = Rect::from_points(
+                    (info.rcClient.left as f64, info.rcClient.top as f64),
+                    (info.rcClient.right as f64, info.rcClient.bottom as f64),
+                );
+
+                return window_frame - content_frame;
+            }
+        }
+
         Insets::ZERO
     }