rework key handling

- Document the magical 8 keycode offset in QKeyEvent::nativeScanCode()

- Check if we are working with the expected keymap format.

- Rename sendKey() to handleKey() as that is typical naming convention
  for events that are passed to QWindowSystemInterface.

- WL_KEYBOARD_KEYMAP_FORMAT_NO_KEYMAP is in the bundled xml so use it
  in send_keymap()

- Rename toWaylandXkbV1Key() to toWaylandKey() as previous name was
  incorrect.

- Remove "Generic fallback" in keyboard_key() as it was non-functional,
  you can't expect any useful output when mapping scan code directly to
  Qt::Key. It was not working in 5.9 (did not check beyond that) and
  no one has complained. It is safe to assume that the fallback code path
  is dead and can be dropped. To use HW keyboard with wayland, you need
  to build with libxkbcommon. We require this on XCB since Qt 5.1.0, so
  it is not an unreasonable requirement for Wayland.

- Cleanup auto-repeat key handling.

- Cleanup "#if QT_CONFIG(xkbcommon)" checks.

Change-Id: Ie9fcc628621487fb58bc55dd595bf0d51eedfc92
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

1 files changed, 22 insertions, 18 deletions

diff --git a/src/compositor/compositor_api/qwaylandkeyboard.cpp b/src/compositor/compositor_api/qwaylandkeyboard.cpp
index e84eed64a..f66fe3263 100644
--- a/src/compositor/compositor_api/qwaylandkeyboard.cpp
+++ b/src/compositor/compositor_api/qwaylandkeyboard.cpp
@@ -143,7 +143,7 @@ void QWaylandKeyboardPrivate::keyboard_bind_resource(wl_keyboard::Resource *reso
 #endif
     {
         int null_fd = open("/dev/null", O_RDONLY);
-        send_keymap(resource->handle, 0 /* WL_KEYBOARD_KEYMAP_FORMAT_NO_KEYMAP */,
+        send_keymap(resource->handle, WL_KEYBOARD_KEYMAP_FORMAT_NO_KEYMAP,
                     null_fd, 0);
         close(null_fd);
     }
@@ -163,11 +163,8 @@ void QWaylandKeyboardPrivate::keyboard_release(wl_keyboard::Resource *resource)
 
 void QWaylandKeyboardPrivate::keyEvent(uint code, uint32_t state)
 {
-#if QT_CONFIG(xkbcommon)
-    uint key = toWaylandXkbV1Key(code);
-#else
-    uint key = code;
-#endif
+    uint key = toWaylandKey(code);
+
     if (state == WL_KEYBOARD_KEY_STATE_PRESSED) {
         keys << key;
     } else {
@@ -179,11 +176,7 @@ void QWaylandKeyboardPrivate::sendKeyEvent(uint code, uint32_t state)
 {
     uint32_t time = compositor()->currentTimeMsecs();
     uint32_t serial = compositor()->nextSerial();
-#if QT_CONFIG(xkbcommon)
-    uint key = toWaylandXkbV1Key(code);
-#else
-    uint key = code;
-#endif
+    uint key = toWaylandKey(code);
     if (focusResource)
         send_key(focusResource->handle, serial, time, key, state);
 }
@@ -284,6 +277,24 @@ void QWaylandKeyboardPrivate::maybeUpdateKeymap()
 #endif
 }
 
+uint QWaylandKeyboardPrivate::toWaylandKey(const uint nativeScanCode)
+{
+#if QT_CONFIG(xkbcommon)
+    // In all current XKB keymaps there's a constant offset of 8 (for historical
+    // reasons) from hardware/evdev scancodes to XKB keycodes. On X11, we pass
+    // XKB keycodes (as sent by X server) via QKeyEvent::nativeScanCode. eglfs+evdev
+    // adds 8 for consistency, see qtbase/05c07c7636012ebb4131ca099ca4ea093af76410.
+    // eglfs+libinput also adds 8, for the same reason. Wayland protocol uses
+    // hardware/evdev scancodes, thus we need to minus 8 before sending the event
+    // out.
+    const uint offset = 8;
+    Q_ASSERT(nativeScanCode >= offset);
+    return nativeScanCode - offset;
+#else
+    return nativeScanCode;
+#endif
+}
+
 #if QT_CONFIG(xkbcommon)
 static int createAnonymousFile(size_t size)
 {
@@ -348,13 +359,6 @@ void QWaylandKeyboardPrivate::createXKBState(xkb_keymap *keymap)
         qWarning("Failed to create XKB state");
 }
 
-uint QWaylandKeyboardPrivate::toWaylandXkbV1Key(const uint nativeScanCode)
-{
-    const uint offset = 8;
-    Q_ASSERT(nativeScanCode >= offset);
-    return nativeScanCode - offset;
-}
-
 void QWaylandKeyboardPrivate::createXKBKeymap()
 {
     if (!xkbContext())