Fix fast scroll

presentation/src/main/java/org/cryptomator/presentation/ui/fragment/TextEditorFragment.kt

@@ -2,16 +2,20 @@ package org.cryptomator.presentation.ui.fragment
 
 import android.os.Bundle
 import android.text.Spannable
+import android.text.TextWatcher
 import android.text.style.BackgroundColorSpan
 import android.view.View
 import androidx.annotation.NonNull
 import androidx.core.content.ContextCompat
+import androidx.core.widget.doAfterTextChanged
 import com.google.android.material.textfield.TextInputEditText
 import org.cryptomator.generator.Fragment
 import org.cryptomator.presentation.R
 import org.cryptomator.presentation.databinding.FragmentTextEditorBinding
 import org.cryptomator.presentation.presenter.TextEditorPresenter
+import org.cryptomator.presentation.ui.layout.applySystemBarsMargins
 import org.cryptomator.presentation.ui.layout.applySystemBarsPadding
+import org.cryptomator.presentation.ui.layout.attachFastScrollThumb
 import javax.inject.Inject
 
 @Fragment
@@ -20,6 +24,9 @@ class TextEditorFragment : BaseFragment<FragmentTextEditorBinding>(FragmentTextE
 	@Inject
 	lateinit var textEditorPresenter: TextEditorPresenter
 
+	private var fastScrollCleanup: (() -> Unit)? = null
+	private var caretAutoScrollWatcher: TextWatcher? = null
+
 	val textFileContent: String
 		get() = binding.textEditor.text.toString()
 
@@ -103,7 +110,7 @@ class TextEditorFragment : BaseFragment<FragmentTextEditorBinding>(FragmentTextE
 			textEditorPresenter.lastFilterLocation = index
 
 			binding.textEditor.setSelection(index, index + it.length)
-			binding.textEditor.post { binding.textEditor.bringPointIntoView(index) }
+			binding.textEditor.post { scrollCaretIntoView() }
 		}
 	}
 
@@ -117,7 +124,39 @@ class TextEditorFragment : BaseFragment<FragmentTextEditorBinding>(FragmentTextE
 
 	override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
 		super.onViewCreated(view, savedInstanceState)
-		binding.textEditor.applySystemBarsPadding(left = true, right = true, bottom = true)
+		binding.textViewWrapper.applySystemBarsPadding(left = true, right = true, bottom = true)
+		binding.scrollThumb.applySystemBarsMargins(end = true, bottom = true)
+		binding.scrollTrack.applySystemBarsMargins(end = true, bottom = true)
+		fastScrollCleanup = binding.textViewWrapper.attachFastScrollThumb(binding.scrollThumb, binding.scrollTrack, binding.textEditor)
+		setupCaretAutoScroll()
+	}
+
+	override fun onDestroyView() {
+		fastScrollCleanup?.invoke()
+		fastScrollCleanup = null
+		caretAutoScrollWatcher?.let { binding.textEditor.removeTextChangedListener(it) }
+		caretAutoScrollWatcher = null
+		super.onDestroyView()
+	}
+
+	private fun setupCaretAutoScroll() {
+		caretAutoScrollWatcher = binding.textEditor.doAfterTextChanged {
+			binding.textEditor.post { scrollCaretIntoView() }
+		}
+	}
+
+	private fun scrollCaretIntoView() {
+		val editor = binding.textEditor
+		val scroll = binding.textViewWrapper
+		val layout = editor.layout ?: return
+		val line = layout.getLineForOffset(editor.selectionEnd)
+		val lineTop = editor.paddingTop + layout.getLineTop(line)
+		val lineBottom = editor.paddingTop + layout.getLineBottom(line)
+		val visibleHeight = scroll.height - scroll.paddingTop - scroll.paddingBottom
+		when {
+			lineTop < scroll.scrollY -> scroll.smoothScrollTo(0, lineTop)
+			lineBottom > scroll.scrollY + visibleHeight -> scroll.smoothScrollTo(0, lineBottom - visibleHeight)
+		}
 	}
 
 	enum class Direction { PREVIOUS, NEXT }

presentation/src/main/java/org/cryptomator/presentation/ui/layout/FastScrollHelper.kt

@@ -0,0 +1,102 @@
+package org.cryptomator.presentation.ui.layout
+
+import android.view.MotionEvent
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewTreeObserver
+import android.widget.ScrollView
+
+/**
+ * Wires [thumb] as a draggable fast-scroll handle over this [ScrollView] (whose scrolling content is [content]).
+ * Tapping anywhere on [track] jumps the thumb to that position.
+ * Returns a cleanup callback to be invoked from the host's `onDestroyView`.
+ */
+fun ScrollView.attachFastScrollThumb(thumb: View, track: View, content: View): () -> Unit {
+	val scroll = this
+
+	fun scrollableHeight(): Int =
+		(content.height + scroll.paddingTop + scroll.paddingBottom - scroll.height).coerceAtLeast(0)
+
+	fun trackHeight(): Int {
+		val bottomMargin = (thumb.layoutParams as? ViewGroup.MarginLayoutParams)?.bottomMargin ?: 0
+		return (scroll.height - thumb.height - bottomMargin).coerceAtLeast(0)
+	}
+
+	fun syncThumb() {
+		val total = scrollableHeight()
+		if (total == 0) {
+			thumb.visibility = View.GONE
+			track.visibility = View.GONE
+			return
+		}
+		thumb.visibility = View.VISIBLE
+		track.visibility = View.VISIBLE
+		thumb.translationY = scroll.scrollY.toFloat() / total * trackHeight()
+	}
+
+	fun jumpToTrackY(yOnTrack: Float) {
+		val trackPx = trackHeight().toFloat()
+		if (trackPx == 0f) return
+		val clamped = yOnTrack.coerceIn(0f, trackPx)
+		scroll.scrollTo(0, (clamped / trackPx * scrollableHeight()).toInt())
+	}
+
+	val scrollListener = ViewTreeObserver.OnScrollChangedListener { syncThumb() }
+	scroll.viewTreeObserver.addOnScrollChangedListener(scrollListener)
+
+	val layoutListener = View.OnLayoutChangeListener { _, _, _, _, _, _, _, _, _ -> syncThumb() }
+	scroll.addOnLayoutChangeListener(layoutListener)
+	content.addOnLayoutChangeListener(layoutListener)
+
+	var thumbDragOffsetY = 0f
+	var thumbDragMoved = false
+	thumb.isClickable = true
+	thumb.setOnTouchListener { _, event ->
+		when (event.actionMasked) {
+			MotionEvent.ACTION_DOWN -> {
+				thumbDragOffsetY = event.rawY - thumb.translationY
+				thumbDragMoved = false
+				thumb.isPressed = true
+				true
+			}
+			MotionEvent.ACTION_MOVE -> {
+				thumbDragMoved = true
+				jumpToTrackY(event.rawY - thumbDragOffsetY)
+				true
+			}
+			MotionEvent.ACTION_UP -> {
+				thumb.isPressed = false
+				if (!thumbDragMoved) thumb.performClick()
+				true
+			}
+			MotionEvent.ACTION_CANCEL -> {
+				thumb.isPressed = false
+				true
+			}
+			else -> false
+		}
+	}
+
+	track.isClickable = true
+	track.setOnTouchListener { _, event ->
+		when (event.actionMasked) {
+			MotionEvent.ACTION_DOWN, MotionEvent.ACTION_MOVE -> {
+				jumpToTrackY(event.y - thumb.height / 2f)
+				true
+			}
+			MotionEvent.ACTION_UP -> {
+				track.performClick()
+				true
+			}
+			else -> false
+		}
+	}
+
+	return {
+		scroll.viewTreeObserver.removeOnScrollChangedListener(scrollListener)
+		scroll.removeOnLayoutChangeListener(layoutListener)
+		content.removeOnLayoutChangeListener(layoutListener)
+		thumb.setOnTouchListener(null)
+		track.setOnTouchListener(null)
+	}
+}

presentation/src/main/res/drawable/scroll_thumb.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+	android:shape="rectangle">
+	<corners android:radius="3dp" />
+	<solid android:color="@color/colorPrimaryTransparent" />
+</shape>

presentation/src/main/res/layout/fragment_text_editor.xml

@@ -4,14 +4,36 @@
 	android:layout_width="match_parent"
 	android:layout_height="match_parent">
 
+	<ScrollView
+		android:id="@+id/text_view_wrapper"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:clipToPadding="false"
+		android:scrollbars="none">
+
 		<com.google.android.material.textfield.TextInputEditText
 			android:id="@+id/text_editor"
 			android:layout_width="match_parent"
 			android:layout_height="wrap_content"
 			android:gravity="top"
 			android:imeOptions="flagNoPersonalizedLearning"
-			android:inputType="textMultiLine"
-			android:scrollbars="vertical"
-			android:overScrollMode="ifContentScrolls" />
+			android:inputType="textMultiLine" />
+	</ScrollView>
+
+	<View
+		android:id="@+id/scroll_track"
+		android:layout_width="24dp"
+		android:layout_height="match_parent"
+		android:layout_gravity="end"
+		android:visibility="gone" />
+
+	<View
+		android:id="@+id/scroll_thumb"
+		android:layout_width="6dp"
+		android:layout_height="48dp"
+		android:layout_gravity="end"
+		android:layout_marginEnd="2dp"
+		android:background="@drawable/scroll_thumb"
+		android:visibility="gone" />
 
 </androidx.coordinatorlayout.widget.CoordinatorLayout>