fix(keyboard): filter NumLock modifier for non-numpad keys in scrcpy (#1844)

* Initial plan

* Fix NumLock being sent with space/backspace in scrcpy

Filter out NumLock modifier for non-numpad keys to prevent it from being incorrectly sent to Rime when using scrcpy. This fixes the issue where space key and backspace key were not working properly in scrcpy because NumLock was being sent along with them.

Co-authored-by: WhiredPlanck <47623588+WhiredPlanck@users.noreply.github.com>

* Add missing KeyModifier import

Co-authored-by: WhiredPlanck <47623588+WhiredPlanck@users.noreply.github.com>

* Use explicit bitwise operation to clear NumLock modifier

Address code review feedback to use KeyModifier.Mod2.modifier explicitly with bitwise AND and inversion instead of the minus operator.

Co-authored-by: WhiredPlanck <47623588+WhiredPlanck@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: WhiredPlanck <47623588+WhiredPlanck@users.noreply.github.com>

Author: Copilot

app/src/main/java/com/osfans/trime/ime/core/TrimeInputMethodService.kt

@@ -35,6 +35,7 @@ import androidx.core.content.ContextCompat
 import androidx.core.view.inputmethod.EditorInfoCompat
 import androidx.core.view.updateLayoutParams
 import androidx.lifecycle.lifecycleScope
+import com.osfans.trime.core.KeyModifier
 import com.osfans.trime.core.KeyModifiers
 import com.osfans.trime.core.KeyValue
 import com.osfans.trime.core.RimeApi
@@ -668,7 +669,12 @@ open class TrimeInputMethodService : LifecycleInputMethodService() {
 
     private fun forwardKeyEvent(event: KeyEvent): Boolean {
         val up = event.action == KeyEvent.ACTION_UP
-        val modifiers = KeyModifiers.fromKeyEvent(event)
+        var modifiers = KeyModifiers.fromKeyEvent(event)
+        // Filter out NumLock for non-numpad keys to fix scrcpy issue
+        // where NumLock is incorrectly sent with keys like space and backspace
+        if (event.keyCode !in KeyEvent.KEYCODE_NUMPAD_0..KeyEvent.KEYCODE_NUMPAD_EQUALS) {
+            modifiers = KeyModifiers(modifiers.modifiers and KeyModifier.Mod2.modifier.inv())
+        }
         val charCode = event.unicodeChar
         if (charCode > 0 && charCode != '\t'.code && charCode != '\n'.code && charCode != ' '.code) {
             // drop modifier state when using combination keys to input number/symbol on some phones