Add Gmail-style vertical swipe-to-select for thread multi-selection

app/src/main/java/com/infomaniak/mail/ui/main/folder/SwipeToSelectTouchListener.kt

@@ -0,0 +1,117 @@
+/*
+ * Infomaniak Mail - Android
+ * Copyright (C) 2026 Infomaniak Network SA
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.infomaniak.mail.ui.main.folder
+
+import android.view.HapticFeedbackConstants
+import android.view.MotionEvent
+import android.view.ViewConfiguration
+import androidx.recyclerview.widget.RecyclerView
+import com.infomaniak.mail.data.models.thread.Thread
+import kotlin.math.abs
+
+class SwipeToSelectTouchListener(
+    recyclerView: RecyclerView,
+    private val multiSelection: MultiSelectionListener<Thread>,
+) : RecyclerView.OnItemTouchListener {
+
+    private val touchSlop = ViewConfiguration.get(recyclerView.context).scaledTouchSlop
+    private var isActive = false
+    private var startX = 0f
+    private var startY = 0f
+    private var startPosition = RecyclerView.NO_POSITION
+    private var lastSelectedPosition = RecyclerView.NO_POSITION
+    private var selectionIntent: Boolean? = null // true = select, false = deselect
+
+    override fun onInterceptTouchEvent(rv: RecyclerView, e: MotionEvent): Boolean {
+        when (e.actionMasked) {
+            MotionEvent.ACTION_DOWN -> {
+                startX = e.x
+                startY = e.y
+                startPosition = rv.findChildViewUnder(startX, startY)
+                    ?.let(rv::getChildAdapterPosition)
+                    ?: RecyclerView.NO_POSITION
+                lastSelectedPosition = RecyclerView.NO_POSITION
+                selectionIntent = null
+                isActive = false
+            }
+            MotionEvent.ACTION_MOVE -> {
+                if (!isActive && multiSelection.isEnabled) {
+                    val dy = abs(e.y - startY)
+                    val dx = abs(e.x - startX)
+                    if (dy > touchSlop && dy > dx) {
+                        val startThread = (rv.adapter as? ThreadListAdapter)?.getThreadAt(startPosition)
+                        selectionIntent = startThread != null && !multiSelection.selectedItems.contains(startThread)
+
+                        if (startThread != null) {
+                            applyIntent(startThread)
+                            multiSelection.publishSelectedItems()
+                            rv.adapter?.notifyItemChanged(startPosition, ThreadListAdapter.NotificationType.SELECTED_STATE)
+                            lastSelectedPosition = startPosition
+                        }
+
+                        isActive = true
+                        return true
+                    }
+                }
+            }
+            MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> reset()
+        }
+        return isActive
+    }
+
+    override fun onTouchEvent(rv: RecyclerView, e: MotionEvent) {
+        when (e.actionMasked) {
+            MotionEvent.ACTION_MOVE -> {
+                if (!isActive) return
+                val view = rv.findChildViewUnder(e.x, e.y) ?: return
+                val position = rv.getChildAdapterPosition(view)
+                if (position == RecyclerView.NO_POSITION || position == lastSelectedPosition) return
+
+                val thread = (rv.adapter as? ThreadListAdapter)?.getThreadAt(position) ?: return
+                applyIntent(thread)
+                multiSelection.publishSelectedItems()
+                rv.adapter?.notifyItemChanged(position, ThreadListAdapter.NotificationType.SELECTED_STATE)
+                rv.performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY)
+                lastSelectedPosition = position
+            }
+            MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> reset()
+        }
+    }
+
+    override fun onRequestDisallowInterceptTouchEvent(disallowIntercept: Boolean) {
+        if (disallowIntercept) reset()
+    }
+
+    private fun applyIntent(thread: Thread) {
+        val intent = selectionIntent ?: return
+        if (intent) {
+            multiSelection.selectedItems.add(thread)
+        } else {
+            multiSelection.selectedItems.remove(thread)
+        }
+    }
+
+    private fun reset() {
+        isActive = false
+        startX = 0f
+        startY = 0f
+        startPosition = RecyclerView.NO_POSITION
+        lastSelectedPosition = RecyclerView.NO_POSITION
+        selectionIntent = null
+    }
+}

app/src/main/java/com/infomaniak/mail/ui/main/folder/ThreadListAdapter.kt

@@ -181,6 +181,10 @@ class ThreadListAdapter @Inject constructor(
             .takeIf { position -> position != -1 }
     }
 
+    fun getThreadAt(position: Int): Thread? {
+        return (dataSet.getOrNull(position) as? ThreadListItem.Content)?.thread
+    }
+
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ThreadListViewHolder {
         val layoutInflater = LayoutInflater.from(parent.context)
         val binding = when (viewType) {

app/src/main/java/com/infomaniak/mail/ui/main/folder/ThreadListFragment.kt

@@ -410,6 +410,17 @@ class ThreadListFragment : TwoPaneFragment(), PickerEmojiObserver {
             disableDragDirection(DirectionFlag.LEFT)
             addStickyDateDecoration(threadListAdapter, localSettings.threadDensity)
         }
+
+        binding.threadsList.addOnItemTouchListener(
+            SwipeToSelectTouchListener(
+                recyclerView = binding.threadsList,
+                multiSelection = object : MultiSelectionListener<Thread> {
+                    override var isEnabled by mainViewModel::isMultiSelectOn
+                    override val selectedItems by mainViewModel::selectedThreads
+                    override val publishSelectedItems = mainViewModel::publishSelectedItems
+                },
+            )
+        )
     }
 
     private fun updateDisabledSwipeActionsUi(featureFlags: FeatureFlagSet?, folderRole: FolderRole?) {