fix(new study screen): finish current stroke before changing pen color

Author: Amitesh-exp

AnkiDroid/src/main/java/com/ichi2/anki/ui/windows/reviewer/whiteboard/WhiteboardFragment.kt

@@ -81,6 +81,13 @@ class WhiteboardFragment :
         val whiteboardView = view.findViewById<WhiteboardView>(R.id.whiteboard_view)
         brushToolbarContainerHorizontal = view.findViewById(R.id.brush_toolbar_container_horizontal)
         brushToolbarContainerVertical = view.findViewById(R.id.brush_toolbar_container_vertical)
+        val touchBlockerView = view.findViewById<View>(R.id.touch_blocker_view)
+
+        whiteboardView.isDrawing
+            .onEach { isCurrentlyDrawing ->
+                // When drawing starts, show the blocker. When it stops, hide it.
+                touchBlockerView.visibility = if (isCurrentlyDrawing) View.VISIBLE else View.GONE
+            }.launchIn(lifecycleScope)
 
         val isNightMode = Themes.systemIsInNightMode(requireContext())
         viewModel.loadState(isNightMode)

AnkiDroid/src/main/java/com/ichi2/anki/ui/windows/reviewer/whiteboard/WhiteboardView.kt

@@ -28,6 +28,8 @@ import android.view.MotionEvent
 import android.view.View
 import androidx.core.graphics.createBitmap
 import com.ichi2.anki.R
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
 
 /**
  * A custom view for the whiteboard that handles drawing and touch events.
@@ -67,6 +69,8 @@ class WhiteboardView : View {
     private val canvasPaint = Paint(Paint.DITHER_FLAG)
 
     private var hasMoved = false
+    private val _isDrawing = MutableStateFlow(false)
+    val isDrawing = _isDrawing.asStateFlow()
 
     /**
      * Recreates the drawing buffer when the view size changes.
@@ -118,6 +122,7 @@ class WhiteboardView : View {
         when (event.action) {
             MotionEvent.ACTION_DOWN -> {
                 hasMoved = false
+                _isDrawing.value = true
                 currentPath.moveTo(touchX, touchY)
                 if (isPathEraser) {
                     onEraseGestureStart?.invoke()
@@ -127,13 +132,15 @@ class WhiteboardView : View {
             }
             MotionEvent.ACTION_MOVE -> {
                 hasMoved = true
+                _isDrawing.value = true
                 currentPath.lineTo(touchX, touchY)
                 if (isPathEraser) {
                     onEraseGestureMove?.invoke(touchX, touchY)
                 }
                 invalidate()
             }
             MotionEvent.ACTION_UP -> {
+                _isDrawing.value = false
                 if (isPathEraser) {
                     onEraseGestureEnd?.invoke()
                 } else {

AnkiDroid/src/main/res/layout/fragment_whiteboard.xml

@@ -122,4 +122,19 @@
         </LinearLayout>
 
     </com.google.android.material.card.MaterialCardView>
+
+    <View
+        android:id="@+id/touch_blocker_view"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:background="@android:color/transparent"
+        android:clickable="true"
+        android:focusable="true"
+        android:elevation="10dp"
+        android:visibility="gone"
+        app:layout_constraintTop_toTopOf="@id/controls_container"
+        app:layout_constraintBottom_toBottomOf="@id/controls_container"
+        app:layout_constraintStart_toStartOf="@id/controls_container"
+        app:layout_constraintEnd_toEndOf="@id/controls_container" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>