Double reader fixes

app/src/main/kotlin/org/koitharu/kotatsu/reader/ui/pager/doublepage/DoublePageHolder.kt

@@ -25,6 +25,10 @@ class DoublePageHolder(
 	private val isEven: Boolean
 		get() = bindingAdapterPosition and 1 == 0
 
+	init {
+		binding.ssiv.panLimit = SubsamplingScaleImageView.PAN_LIMIT_INSIDE
+	}
+
 	override fun onBind(data: ReaderPage) {
 		super.onBind(data)
 		(binding.textViewNumber.layoutParams as FrameLayout.LayoutParams)
@@ -41,7 +45,7 @@ class DoublePageHolder(
 			minimumScaleType = SubsamplingScaleImageView.SCALE_TYPE_CENTER_INSIDE
 			setScaleAndCenter(
 				minScale,
-				PointF(if (isEven) sWidth.toFloat() else 0f, 0f),
+				PointF(if (isEven) 0f else sWidth.toFloat(), sHeight / 2f),
 			)
 		}
 	}

app/src/main/kotlin/org/koitharu/kotatsu/reader/ui/pager/doublepage/DoublePageSnapHelper.kt

@@ -158,7 +158,7 @@ class DoublePageSnapHelper : SnapHelper() {
 	}
 
 	private fun roundDownToBlockSize(trialPosition: Int): Int {
-		return trialPosition - trialPosition % blockSize
+		return trialPosition and 1.inv()
 	}
 
 	private fun roundUpToBlockSize(trialPosition: Int): Int {
@@ -197,19 +197,17 @@ class DoublePageSnapHelper : SnapHelper() {
 	private inner class LayoutDirectionHelper(direction: Int) {
 
 		// Is the layout an RTL one?
-		private val mIsRTL: Boolean
+		private val isRTL = direction == View.LAYOUT_DIRECTION_RTL
-
-		init {
-			mIsRTL = direction == View.LAYOUT_DIRECTION_RTL
-		}
 
 		/*
 			Calculate the amount of scroll needed to align the target view with the layout edge.
 		 */
 		fun getScrollToAlignView(targetView: View?): Int {
-			return if (mIsRTL) orientationHelper.getDecoratedEnd(targetView) - recyclerView.width else orientationHelper.getDecoratedStart(
+			return if (isRTL) {
-				targetView,
+				orientationHelper.getDecoratedEnd(targetView) - recyclerView.width
-			)
+			} else {
+				orientationHelper.getDecoratedStart(targetView)
+			}
 		}
 
 		/**
@@ -225,7 +223,7 @@ class DoublePageSnapHelper : SnapHelper() {
 			val firstVisiblePos = layoutManager.findFirstVisibleItemPosition()
 			if (layoutManager.canScrollHorizontally()) {
 				if (targetPos <= firstVisiblePos) { // scrolling toward top of data
-					if (mIsRTL) {
+					if (isRTL) {
 						val lastView = layoutManager.findViewByPosition(layoutManager.findLastVisibleItemPosition())
 						out[0] = (orientationHelper.getDecoratedEnd(lastView)
 							+ (firstVisiblePos - targetPos) * itemDimension)
@@ -263,18 +261,20 @@ class DoublePageSnapHelper : SnapHelper() {
 			if (scroll < 0) {
 				positionsToMove *= -1
 			}
-			if (mIsRTL) {
+			if (isRTL) {
 				positionsToMove *= -1
 			}
 			return if (layoutDirectionHelper.isDirectionToBottom(scroll < 0)) {
 				// Scrolling toward the bottom of data.
 				roundDownToBlockSize(llm.findFirstVisibleItemPosition()) + positionsToMove
-			} else roundDownToBlockSize(llm.findLastVisibleItemPosition()) + positionsToMove
+			} else {
+				roundDownToBlockSize(llm.findLastVisibleItemPosition()) + positionsToMove
+			}
 			// Scrolling toward the top of the data.
 		}
 
 		fun isDirectionToBottom(velocityNegative: Boolean): Boolean {
-			return if (mIsRTL) velocityNegative else !velocityNegative
+			return if (isRTL) velocityNegative else !velocityNegative
 		}
 	}
 }