Fix inconsistent OSC button movements when using the arrow buttons

A combination of factors caused inconsistent button movements when using the arrow buttons to move it, namely floating point approximation and the round down performed when snapping a button to the grid. Sometimes the layman solution is the best one: adding/subtracting one to the move amount depending on the direction ensures that the button always ends up on a grid line.

app/src/main/java/emu/skyline/input/onscreen/OnScreenButton.kt

@@ -209,23 +209,34 @@ abstract class OnScreenButton(
         saveConfigValues()
     }
 
+    /**
+     * Returns the amount to move the button when the user presses an arrow key
+     * @param gridOffset The offset to apply to the grid size so that the button always ends up on a grid line
+     */
+    private fun getMoveAmount(gridOffset : Int) : Int {
+        return if (editInfo.snapToGrid)
+            editInfo.gridSize + gridOffset
+        else
+            OnScreenEditInfo.ArrowKeyMoveAmount
+    }
+
     override fun moveUp() {
-        move(currentX, currentY - editInfo.arrowKeyMoveAmount)
+        move(currentX, currentY - getMoveAmount(-1))
         saveConfigValues()
     }
 
     override fun moveDown() {
-        move(currentX, currentY + editInfo.arrowKeyMoveAmount)
+        move(currentX, currentY + getMoveAmount(+1))
         saveConfigValues()
     }
 
     override fun moveLeft() {
-        move(currentX - editInfo.arrowKeyMoveAmount, currentY)
+        move(currentX - getMoveAmount(-1), currentY)
         saveConfigValues()
     }
 
     override fun moveRight() {
-        move(currentX + editInfo.arrowKeyMoveAmount, currentY)
+        move(currentX + getMoveAmount(+1), currentY)
         saveConfigValues()
     }
 

app/src/main/java/emu/skyline/input/onscreen/OnScreenControllerView.kt

@@ -373,7 +373,6 @@ class OnScreenControllerView @JvmOverloads constructor(context : Context, attrs
 
     fun setSnapToGrid(snap : Boolean) {
         editInfo.snapToGrid = snap
-        editInfo.arrowKeyMoveAmount = if (snap) editInfo.gridSize else OnScreenEditInfo.ArrowKeyMoveAmount
     }
 
     fun resetButton() {

app/src/main/java/emu/skyline/input/onscreen/OnScreenEditInfo.kt

@@ -40,8 +40,6 @@ class OnScreenEditInfo {
 
     var gridSize : Int = GridSize
 
-    var arrowKeyMoveAmount : Int = ArrowKeyMoveAmount
-
     companion object {
         /**
          * The size of the grid, calculated from the value of 8dp