Add a touch delegate to increase action touch targets to 48dp (#2872)

* Add a touch delegate to increase action touch targets to 48dp

Fixes #2825

* Adjust layout to make action buttons larger

* Remove 4dp vertical margin

app/src/main/java/com/keylesspalace/tusky/util/TouchDelegateHelper.kt

@@ -0,0 +1,51 @@
+@file:JvmName("TouchDelegateHelper")
+
+package com.keylesspalace.tusky.util
+
+import android.graphics.Rect
+import android.view.MotionEvent
+import android.view.TouchDelegate
+import android.view.View
+import android.view.ViewGroup
+
+/**
+ * Expands the touch area of the give row of views to fill the space in-between them, using a
+ * [TouchDelegate].
+ */
+fun ViewGroup.expandTouchSizeToFillRow(children: List<View>) {
+    addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
+        touchDelegate = CompositeTouchDelegate(
+            this,
+            children.mapIndexed { i, view ->
+                val rect = Rect()
+                view.getHitRect(rect)
+                val left = children.getOrNull(i - 1)
+                if (left != null) {
+                    // extend half-way to previous view
+                    rect.left -= (view.left - left.right) / 2
+                }
+                val right = children.getOrNull(i + 1)
+                if (right != null) {
+                    // extend half-way to next view
+                    rect.right += (right.left - view.right) / 2
+                }
+                TouchDelegate(rect, view)
+            }
+        )
+    }
+}
+
+private class CompositeTouchDelegate(view: View, private val delegates: List<TouchDelegate>) :
+    TouchDelegate(Rect(), view) {
+
+    override fun onTouchEvent(event: MotionEvent): Boolean {
+        var res = false
+        val x = event.x
+        val y = event.y
+        for (delegate in delegates) {
+            event.setLocation(x, y)
+            res = delegate.onTouchEvent(event) || res
+        }
+        return res
+    }
+}