allow dragging app icons from All Fragments to home screen

app/src/main/kotlin/com/simplemobiletools/launcher/interfaces/HomeScreenGridItemsDao.kt

@@ -12,7 +12,7 @@ interface HomeScreenGridItemsDao {
     fun getAllItems(): List<HomeScreenGridItem>
 
     @Insert(onConflict = OnConflictStrategy.REPLACE)
-    fun insert(item: HomeScreenGridItem)
+    fun insert(item: HomeScreenGridItem): Long
 
     @Insert(onConflict = OnConflictStrategy.REPLACE)
     fun insertAll(items: List<HomeScreenGridItem>)

app/src/main/kotlin/com/simplemobiletools/launcher/views/HomeScreenGrid.kt

@@ -71,7 +71,12 @@ class HomeScreenGrid(context: Context, attrs: AttributeSet, defStyle: Int) : Vie
 
     // figure out at which cell was the item dropped, if it is empty
     fun itemDraggingStopped(x: Int, y: Int) {
+        if (draggedItem == null) {
+            return
+        }
+
         val center = gridCenters.minBy { Math.abs(it.first - x) + Math.abs(it.second - y) }
+        var redrawIcons = false
 
         // convert stuff like 102x192 to grid cells like 0x1
         rowXCoords.forEachIndexed { xIndex, xCell ->
@@ -80,7 +85,11 @@ class HomeScreenGrid(context: Context, attrs: AttributeSet, defStyle: Int) : Vie
                     // check if the destination grid item is empty
                     val targetGridItem = gridItems.firstOrNull { it.left == xIndex && it.top == yIndex }
                     if (targetGridItem == null) {
-                        gridItems.firstOrNull { it.id == draggedItem?.id }?.apply {
+                        val draggedHomeGridItem = gridItems.firstOrNull { it.id == draggedItem?.id }
+
+                        // we are moving an existing home screen item from one place to another
+                        if (draggedHomeGridItem != null) {
+                            draggedHomeGridItem.apply {
                                 left = xIndex
                                 top = yIndex
                                 right = xIndex + 1
@@ -90,14 +99,34 @@ class HomeScreenGrid(context: Context, attrs: AttributeSet, defStyle: Int) : Vie
                                     context.homeScreenGridItemsDB.updateAppPosition(left, top, right, bottom, id!!)
                                 }
                             }
+                            redrawIcons = true
+                        } else if (draggedItem != null) {
+                            // we are dragging a new item at the home screen from the All Apps fragment
+                            val newHomeScreenGridItem =
+                                HomeScreenGridItem(null, xIndex, yIndex, xIndex + 1, yIndex + 1, draggedItem!!.packageName, draggedItem!!.title)
+                            ensureBackgroundThread {
+                                val newId = context.homeScreenGridItemsDB.insert(newHomeScreenGridItem)
+                                newHomeScreenGridItem.id = newId
+                                gridItems.add(newHomeScreenGridItem)
+
+                                val drawable = context.getDrawableForPackageName(newHomeScreenGridItem.packageName)
+                                if (drawable != null) {
+                                    gridItemDrawables[newHomeScreenGridItem.packageName] = drawable
+                                }
+
+                                invalidate()
+                            }
+                        }
                     }
                 }
             }
         }
 
         draggedItem = null
+        if (redrawIcons) {
             invalidate()
         }
+    }
 
     @SuppressLint("DrawAllocation")
     override fun onDraw(canvas: Canvas) {