Implement input focus for Mac & Windows (#170)

* Implement input focus for Mac

* Add stubs for Windows and Linux

* Remove unnecessary call to window

* Implement input focus for Windows

* Add check for key window status

* Rename to `has_focus` & `focus`

* Use GetFocus

* Fix incorrectly named var

---------

Co-authored-by: Micah Johnston <micah@photophore.systems>

src/macos/window.rs

@@ -7,7 +7,7 @@ use cocoa::appkit::{
     NSApp, NSApplication, NSApplicationActivationPolicyRegular, NSBackingStoreBuffered,
     NSPasteboard, NSView, NSWindow, NSWindowStyleMask,
 };
-use cocoa::base::{id, nil, NO, YES};
+use cocoa::base::{id, nil, BOOL, NO, YES};
 use cocoa::foundation::{NSAutoreleasePool, NSPoint, NSRect, NSSize, NSString};
 use core_foundation::runloop::{
     CFRunLoop, CFRunLoopTimer, CFRunLoopTimerContext, __CFRunLoopTimer, kCFRunLoopDefaultMode,
@@ -43,6 +43,7 @@ impl WindowHandle {
     pub fn is_open(&self) -> bool {
         self.state.window_inner.open.get()
     }
+
 }
 
 unsafe impl HasRawWindowHandle for WindowHandle {
@@ -284,6 +285,28 @@ impl<'a> Window<'a> {
         self.inner.close();
     }
 
+    pub fn has_focus(&mut self) -> bool {
+        unsafe {
+            let view = self.inner.ns_view.as_mut().unwrap();
+            let window: id = msg_send![view, window];
+            if window == nil { return false; };
+            let first_responder: id = msg_send![window, firstResponder];
+            let is_key_window: BOOL = msg_send![window, isKeyWindow];
+            let is_focused: BOOL = msg_send![view, isEqual: first_responder];
+            is_key_window == YES && is_focused == YES
+        }
+    }
+
+    pub fn focus(&mut self) {
+        unsafe {
+            let view = self.inner.ns_view.as_mut().unwrap();
+            let window: id = msg_send![view, window];
+            if window != nil {
+                msg_send![window, makeFirstResponder:view]
+            }
+        }
+    }
+
     pub fn resize(&mut self, size: Size) {
         if self.inner.open.get() {
             // NOTE: macOS gives you a personal rave if you pass in fractional pixels here. Even

src/win/window.rs

@@ -8,7 +8,7 @@ use winapi::um::winuser::{
     AdjustWindowRectEx, CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW,
     GetDpiForWindow, GetMessageW, GetWindowLongPtrW, LoadCursorW, PostMessageW, RegisterClassW,
     ReleaseCapture, SetCapture, SetProcessDpiAwarenessContext, SetTimer, SetWindowLongPtrW,
-    SetWindowPos, TrackMouseEvent, TranslateMessage, UnregisterClassW, CS_OWNDC,
+    SetWindowPos, SetFocus, GetFocus, TrackMouseEvent, TranslateMessage, UnregisterClassW, CS_OWNDC,
     GET_XBUTTON_WPARAM, GWLP_USERDATA, IDC_ARROW, MSG, SWP_NOMOVE, SWP_NOZORDER, TRACKMOUSEEVENT,
     WHEEL_DELTA, WM_CHAR, WM_CLOSE, WM_CREATE, WM_DPICHANGED, WM_INPUTLANGCHANGE, WM_KEYDOWN,
     WM_KEYUP, WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MBUTTONDOWN, WM_MBUTTONUP, WM_MOUSEHWHEEL,
@@ -770,6 +770,17 @@ impl Window<'_> {
         }
     }
 
+    pub fn has_focus(&mut self) -> bool {
+        let focused_window = unsafe { GetFocus() };
+        focused_window == self.state.hwnd
+    }
+
+    pub fn focus(&mut self) {
+        unsafe {
+            SetFocus(self.state.hwnd);
+        }
+    }
+
     pub fn resize(&mut self, size: Size) {
         // To avoid reentrant event handler calls we'll defer the actual resizing until after the
         // event has been handled

src/window.rs

@@ -102,6 +102,14 @@ impl<'a> Window<'a> {
         self.window.set_mouse_cursor(cursor);
     }
 
+    pub fn has_focus(&mut self) -> bool {
+        self.window.has_focus()
+    }
+
+    pub fn focus(&mut self) {
+        self.window.focus()
+    }
+
     /// If provided, then an OpenGL context will be created for this window. You'll be able to
     /// access this context through [crate::Window::gl_context].
     #[cfg(feature = "opengl")]

src/x11/window.rs

@@ -359,6 +359,14 @@ impl<'a> Window<'a> {
         self.inner.close_requested = true;
     }
 
+    pub fn has_focus(&mut self) -> bool {
+        unimplemented!()
+    }
+
+    pub fn focus(&mut self) {
+        unimplemented!()
+    }
+
     pub fn resize(&mut self, size: Size) {
         let scaling = self.inner.window_info.scale();
         let new_window_info = WindowInfo::from_logical_size(size, scaling);