Add methods to get the position of a window's client area, relative to the desktop (#430)

* Add get_inner_position for windows, prototypes for other platforms

* Fix linux builds

* Implement get_inner_position for osx

* Add get_inner_pos implementations for other platforms

* Fixed get_inner_position on macOS

* Corrected set_position on macOS

* Added CHANGELOG entry

CHANGELOG.md

@@ -10,6 +10,9 @@
 - Properly calculate the minimum and maximum window size on Windows, including window decorations.
 - Map more `MouseCursor` variants to cursor icons on Windows.
 - Discard the stray mouse down event being delivered after window resize on macOS.
+- Corrected `get_position` on macOS to return outer frame position, not content area position.
+- Corrected `set_position` on macOS to set outer frame position, not content area position.
+- Added `get_inner_position` method to `Window`, which gets the position of the window's client area. This is implemented on all applicable platforms (all desktop platforms other than Wayland, where this isn't possible).
 
 # Version 0.12.0 (2018-04-06)
 

src/platform/android/mod.rs

@@ -243,6 +243,11 @@ impl Window {
         None
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        None
+    }
+
     #[inline]
     pub fn set_position(&self, _x: i32, _y: i32) {
     }

src/platform/emscripten/mod.rs

@@ -417,6 +417,11 @@ impl Window {
         Some((0, 0))
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        Some((0, 0))
+    }
+
     #[inline]
     pub fn set_position(&self, _: i32, _: i32) {
     }

src/platform/ios/mod.rs

@@ -288,6 +288,11 @@ impl Window {
         None
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        None
+    }
+
     #[inline]
     pub fn set_position(&self, _x: i32, _y: i32) {
     }

src/platform/linux/mod.rs

@@ -162,6 +162,14 @@ impl Window {
         }
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        match self {
+            &Window::X(ref m) => m.get_inner_position(),
+            &Window::Wayland(ref m) => m.get_inner_position(),
+        }
+    }
+
     #[inline]
     pub fn set_position(&self, x: i32, y: i32) {
         match self {

src/platform/linux/wayland/window.rs

@@ -113,6 +113,12 @@ impl Window {
         None
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        // Not possible with wayland
+        None
+    }
+
     #[inline]
     pub fn set_position(&self, _x: i32, _y: i32) {
         // Not possible with wayland

src/platform/linux/x11/window.rs

@@ -919,6 +919,11 @@ impl Window2 {
         self.get_geometry().map(|geo| geo.get_position())
     }
 
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        self.get_geometry().map(|geo| geo.get_inner_position())
+    }
+
     pub fn set_position(&self, mut x: i32, mut y: i32) {
         if let Some(ref wm_name) = self.wm_name {
             // There are a few WMs that set client area position rather than window position, so

src/platform/macos/window.rs

@@ -543,41 +543,54 @@ impl Window2 {
         unsafe { NSWindow::orderOut_(*self.window, nil); }
     }
 
-    pub fn get_position(&self) -> Option<(i32, i32)> {
-        unsafe {
-            let content_rect = NSWindow::contentRectForFrameRect_(*self.window, NSWindow::frame(*self.window));
+    // For consistency with other platforms, this will...
+    // 1. translate the bottom-left window corner into the top-left window corner
+    // 2. translate the coordinate from a bottom-left origin coordinate system to a top-left one
+    fn bottom_left_to_top_left(rect: NSRect) -> i32 {
+        (CGDisplay::main().pixels_high() as f64 - (rect.origin.y + rect.size.height)) as _
+    }
 
-            // TODO: consider extrapolating the calculations for the y axis to
-            // a private method
-            Some((content_rect.origin.x as i32, (CGDisplay::main().pixels_high() as f64 - (content_rect.origin.y + content_rect.size.height)) as i32))
-        }
+    pub fn get_position(&self) -> Option<(i32, i32)> {
+        let frame_rect = unsafe { NSWindow::frame(*self.window) };
+        Some((
+            frame_rect.origin.x as i32,
+            Self::bottom_left_to_top_left(frame_rect),
+        ))
+    }
+
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        let content_rect = unsafe {
+            NSWindow::contentRectForFrameRect_(
+                *self.window,
+                NSWindow::frame(*self.window),
+            )
+        };
+        Some((
+            content_rect.origin.x as i32,
+            Self::bottom_left_to_top_left(content_rect),
+        ))
     }
 
     pub fn set_position(&self, x: i32, y: i32) {
+        let dummy = NSRect::new(
+            NSPoint::new(
+                x as f64,
+                // While it's true that we're setting the top-left position, it still needs to be
+                // in a bottom-left coordinate system.
+                CGDisplay::main().pixels_high() as f64 - y as f64,
+            ),
+            NSSize::new(0f64, 0f64),
+        );
         unsafe {
-            let frame = NSWindow::frame(*self.view);
-
-            // NOTE: `setFrameOrigin` might not give desirable results when
-            // setting window, as it treats bottom left as origin.
-            // `setFrameTopLeftPoint` treats top left as origin (duh), but
-            // does not equal the value returned by `get_window_position`
-            // (there is a difference by 22 for me on yosemite)
-
-            // TODO: consider extrapolating the calculations for the y axis to
-            // a private method
-            let dummy = NSRect::new(NSPoint::new(x as f64, CGDisplay::main().pixels_high() as f64 - (frame.size.height + y as f64)), NSSize::new(0f64, 0f64));
-            let conv = NSWindow::frameRectForContentRect_(*self.window, dummy);
-
-            // NSWindow::setFrameTopLeftPoint_(*self.window, conv.origin);
-            NSWindow::setFrameOrigin_(*self.window, conv.origin);
+            NSWindow::setFrameTopLeftPoint_(*self.window, dummy.origin);
         }
     }
 
     #[inline]
     pub fn get_inner_size(&self) -> Option<(u32, u32)> {
+        let factor = self.hidpi_factor() as f64; // API convention is that size is in physical pixels
         unsafe {
             let view_frame = NSView::frame(*self.view);
-            let factor = self.hidpi_factor() as f64; // API convention is that size is in physical pixels
             Some(((view_frame.size.width*factor) as u32, (view_frame.size.height*factor) as u32))
         }
     }

src/platform/windows/window.rs

@@ -129,6 +129,17 @@ impl Window {
         Some((rect.left as i32, rect.top as i32))
     }
 
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        use std::mem;
+
+        let mut position: POINT = unsafe{ mem::zeroed() };
+        if unsafe{ winuser::ClientToScreen(self.window.0, &mut position) } == 0 {
+            return None;
+        }
+
+        Some((position.x, position.y))
+    }
+
     /// See the docs in the crate root file.
     pub fn set_position(&self, x: i32, y: i32) {
         unsafe {

src/window.rs

@@ -181,6 +181,15 @@ impl Window {
         self.window.get_position()
     }
 
+    /// Returns the position of the top-left hand corner of the window's client area relative to the
+    /// top-left hand corner of the desktop.
+    ///
+    /// The same conditions that apply to `get_position` apply to this method.
+    #[inline]
+    pub fn get_inner_position(&self) -> Option<(i32, i32)> {
+        self.window.get_inner_position()
+    }
+
     /// Modifies the position of the window.
     ///
     /// See `get_position` for more information about the coordinates.