Windows: Fix detection of Pause and Scroll keys (#525)

Fixes #524

CHANGELOG.md

@@ -16,6 +16,7 @@
 - macOS keyboard handling has been overhauled, allowing for the use of dead keys, IME, etc. Right modifier keys are also no longer reported as being left.
 - Added the `Window::set_ime_spot(x: i32, y: i32)` method, which is implemented on X11 and macOS.
 - **Breaking**: `os::unix::WindowExt::send_xim_spot(x: i16, y: i16)` no longer exists. Switch to the new `Window::set_ime_spot(x: i32, y: i32)`, which has equivalent functionality.
+- Fixed detection of `Pause` and `Scroll` keys on Windows.
 
 # Version 0.14.0 (2018-05-09)
 

src/platform/windows/event.rs

@@ -205,8 +205,9 @@ pub fn vkey_to_winit_vkey(vkey: c_int) -> Option<VirtualKeyCode> {
     }
 }
 
-pub fn vkey_left_right(vkey: c_int, scancode: UINT, extended: bool) -> c_int {
-    match vkey {
+pub fn handle_extended_keys(vkey: c_int, mut scancode: UINT, extended: bool) -> Option<(c_int, UINT)> {
+    // Welcome to hell https://blog.molecular-matters.com/2011/09/05/properly-handling-keyboard-input/
+    let vkey = match vkey {
         winuser::VK_SHIFT => unsafe { winuser::MapVirtualKeyA(
             scancode,
             winuser::MAPVK_VSC_TO_VK_EX,
@@ -221,15 +222,32 @@ pub fn vkey_left_right(vkey: c_int, scancode: UINT, extended: bool) -> c_int {
         } else {
             winuser::VK_LMENU
         },
-       _ => vkey,
+        _ => match scancode {
+            // This is only triggered when using raw input. Without this check, we get two events whenever VK_PAUSE is
+            // pressed, the first one having scancode 0x1D but vkey VK_PAUSE...
+            0x1D if vkey == winuser::VK_PAUSE => return None,
+            // ...and the second having scancode 0x45 but an unmatched vkey!
+            0x45 => winuser::VK_PAUSE,
+            // VK_PAUSE and VK_SCROLL have the same scancode when using modifiers, alongside incorrect vkey values.
+            0x46 => {
+                if extended {
+                    scancode = 0x45;
+                    winuser::VK_PAUSE
+                } else {
+                    winuser::VK_SCROLL
                 }
+            },
+            _ => vkey,
+        },
+    };
+    Some((vkey, scancode))
 }
 
-pub fn vkeycode_to_element(wparam: WPARAM, lparam: LPARAM) -> (ScanCode, Option<VirtualKeyCode>) {
+pub fn process_key_params(wparam: WPARAM, lparam: LPARAM) -> Option<(ScanCode, Option<VirtualKeyCode>)> {
     let scancode = ((lparam >> 16) & 0xff) as UINT;
     let extended = (lparam & 0x01000000) != 0;
-    let vkey = vkey_left_right(wparam as _, scancode, extended);
-    (scancode, vkey_to_winit_vkey(vkey))
+    handle_extended_keys(wparam as _, scancode, extended)
+        .map(|(vkey, scancode)| (scancode, vkey_to_winit_vkey(vkey)))
 }
 
 // This is needed as windows doesn't properly distinguish

src/platform/windows/events_loop.rs

@@ -34,7 +34,7 @@ use winapi::um::winnt::{LONG, SHORT};
 
 use events::DeviceEvent;
 use platform::platform::{event, Cursor, WindowId, DEVICE_ID, wrap_device_id, util};
-use platform::platform::event::{vkey_to_winit_vkey, vkey_left_right};
+use platform::platform::event::{handle_extended_keys, process_key_params, vkey_to_winit_vkey};
 use platform::platform::raw_input::*;
 use platform::platform::window::adjust_size;
 
@@ -586,7 +586,7 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
             if msg == winuser::WM_SYSKEYDOWN && wparam as i32 == winuser::VK_F4 {
                 winuser::DefWindowProcW(window, msg, wparam, lparam)
             } else {
-                let (scancode, vkey) = event::vkeycode_to_element(wparam, lparam);
+                if let Some((scancode, vkey)) = process_key_params(wparam, lparam) {
                     send_event(Event::WindowEvent {
                         window_id: SuperWindowId(WindowId(window)),
                         event: WindowEvent::KeyboardInput {
@@ -607,13 +607,14 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
                             event: WindowEvent::ReceivedCharacter('\u{7F}'),
                         });
                     }
+                }
                 0
             }
         },
 
         winuser::WM_KEYUP | winuser::WM_SYSKEYUP => {
             use events::ElementState::Released;
-            let (scancode, vkey) = event::vkeycode_to_element(wparam, lparam);
+            if let Some((scancode, vkey)) = process_key_params(wparam, lparam) {
                 send_event(Event::WindowEvent {
                     window_id: SuperWindowId(WindowId(window)),
                     event: WindowEvent::KeyboardInput {
@@ -626,6 +627,7 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
                         },
                     }
                 });
+            }
             0
         },
 
@@ -836,12 +838,13 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
                         };
 
                         let scancode = keyboard.MakeCode as _;
-                        let extended = util::has_flag(keyboard.Flags, winuser::RI_KEY_E0 as _);
-                        let vkey = vkey_left_right(
+                        let extended = util::has_flag(keyboard.Flags, winuser::RI_KEY_E0 as _)
+                            | util::has_flag(keyboard.Flags, winuser::RI_KEY_E1 as _);
+                        if let Some((vkey, scancode)) = handle_extended_keys(
                             keyboard.VKey as _,
                             scancode,
                             extended,
-                        );
+                        ) {
                             let virtual_keycode = vkey_to_winit_vkey(vkey);
 
                             send_event(Event::DeviceEvent {
@@ -856,6 +859,7 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
                         }
                     }
                 }
+            }
 
             winuser::DefWindowProcW(window, msg, wparam, lparam)
         },