diff --git a/app/src/main/java/com/lhw/pdf/MyPresentation.kt b/app/src/main/java/com/lhw/pdf/MyPresentation.kt
index f1992bc..f964fca 100644
--- a/app/src/main/java/com/lhw/pdf/MyPresentation.kt
+++ b/app/src/main/java/com/lhw/pdf/MyPresentation.kt
@@ -6,11 +6,9 @@ import android.graphics.Bitmap
 import android.util.DisplayMetrics
 import android.view.Display
 import android.view.WindowManager
-import android.widget.HorizontalScrollView
-import android.widget.ImageView
-import android.widget.LinearLayout
 import androidx.core.view.WindowCompat
 import androidx.core.view.WindowInsetsCompat
+import com.lhw.pdf.ui.HorizontalGallery
 
 class MyPresentation(outerContext: Context, display: Display) : Presentation(outerContext, display) {
     val displayMetrics = DisplayMetrics()
@@ -20,8 +18,7 @@ class MyPresentation(outerContext: Context, display: Display) : Presentation(out
 
     private val bitmaps = mutableListOf<Bitmap>()
     private val bitmapCumWidths = mutableListOf<Int>(0)
-    private val layout = LinearLayout(this.context)
-    private val scroll = HorizontalScrollView(this.context)
+    private val scroll = HorizontalGallery(this.context)
     private var scrollProgress = 0f
     private val layoutParams = WindowManager.LayoutParams()
     init {
@@ -31,75 +28,19 @@ class MyPresentation(outerContext: Context, display: Display) : Presentation(out
             WindowCompat.getInsetsController(it, it.decorView)
                 .hide(WindowInsetsCompat.Type.systemBars())
         }
-        scroll.addView(layout)
         println(layoutParams)
         addContentView(scroll, layoutParams)
     }
 
     fun updateImages(bitmaps: Iterable<Bitmap>) {
-        println("Updating presentation images")
-        println("Layout has scale ${layout.scaleX} ${layout.scaleY}")
-        layout.removeAllViewsInLayout()
-        this.bitmaps.clear()
-        bitmapCumWidths.clear()
-        bitmapCumWidths.add(0)
-        bitmaps.forEach {
-            this.bitmaps.add(it)
-            bitmapCumWidths.add(it.width + bitmapCumWidths.last())
-        }
-        if (lazyScroll) {
-            lazyIdxStart = -1
-            lazyIdxEnd = -1
-            layoutVisibleBitmaps()
-        } else {
-            layoutAllBitmaps()
-        }
-    }
-
-    private fun layoutBitmap(bitmap: Bitmap) {
-        val img = ImageView(this.context)
-        img.setImageBitmap(bitmap)
-        img.minimumWidth = bitmap.width  // No idea what broke when I refactored this class
-        img.minimumHeight = bitmap.height
-        println("${bitmap.width}x${bitmap.height}")
-        layout.addView(img)
-    }
-
-    private fun layoutAllBitmaps() {
-        bitmaps.forEach(::layoutBitmap)
-        println("Presentation heights ${scroll.height} ${layout.height}")
-    }
-
-    private fun layoutVisibleBitmaps() {
-        val xStart = (scrollProgress * (bitmapCumWidths.last() - scroll.width)).toInt()
-        val xEnd = xStart + scroll.width
-        // bitmapCumWidths has a prepended 0
-        val idxStart = bitmapCumWidths.indexOfFirst { it > xStart }.let { if (it >= 1) it-1 else 0 }
-        val idxEnd = bitmapCumWidths.indexOfFirst { it > xEnd }.let { if (it >= 0) it else bitmaps.size}
-
-        layout.removeAllViewsInLayout()
-        (idxStart..<idxEnd).map(bitmaps::get).forEach(::layoutBitmap)
-        lazyIdxStart = idxStart
-        lazyIdxEnd = idxEnd
-        println("Laying out pages $idxStart up to $idxEnd - scrollable width ${layout.width}")
+        scroll.updateImages(bitmaps)
     }
 
     fun setScrollProgress(progress: Float) {
-        scrollProgress = progress
-        var progressPx = (progress * (bitmapCumWidths.last() - scroll.width)).toInt()
-        if (lazyScroll) {
-            layoutVisibleBitmaps()
-            progressPx -= bitmapCumWidths[lazyIdxStart]
-        }
-        println("Scrolling view to x=$progressPx of scrollable ${layout.width} (visible width ${scroll.width})")
-        scroll.scrollTo(progressPx, 0)
+        scroll.setScrollProgress(progress)
     }
 
     fun setScrollPagesProgress(pagesProgress: Float) {
-        // NB this is nonlinear with unequal page widths
-        val p = pagesProgress.toInt()
-        val progressPx = bitmapCumWidths[p] + (bitmaps[p].width * (pagesProgress % 1F))
-        val progress = progressPx / (bitmapCumWidths.last() - scroll.width).toFloat()
-        setScrollProgress(progress)
+        scroll.setScrollPagesProgress(pagesProgress)
     }
 }
diff --git a/app/src/main/java/com/lhw/pdf/ui/HorizontalGallery.kt b/app/src/main/java/com/lhw/pdf/ui/HorizontalGallery.kt
new file mode 100644
index 0000000..576996c
--- /dev/null
+++ b/app/src/main/java/com/lhw/pdf/ui/HorizontalGallery.kt
@@ -0,0 +1,92 @@
+package com.lhw.pdf.ui
+
+import android.content.Context
+import android.graphics.Bitmap
+import android.util.DisplayMetrics
+import android.view.WindowManager
+import android.widget.HorizontalScrollView
+import android.widget.ImageView
+import android.widget.LinearLayout
+import androidx.core.view.WindowCompat
+import androidx.core.view.WindowInsetsCompat
+
+class HorizontalGallery(outerContext: Context) : HorizontalScrollView(outerContext) {
+    private val lazyScroll = android.os.Build.VERSION.SDK_INT < 34  //android.os.Build.VERSION_CODES.UPSIDE_DOWN_CAKE
+    private var lazyIdxStart = -1
+    private var lazyIdxEnd = -1
+
+    private val bitmaps = mutableListOf<Bitmap>()
+    private val bitmapCumWidths = mutableListOf<Int>(0)
+    private val layout = LinearLayout(this.context)
+    private var scrollProgress = 0f
+    init {
+        addView(layout)
+    }
+
+    fun updateImages(bitmaps: Iterable<Bitmap>) {
+        println("Updating presentation images")
+        println("Layout has scale ${layout.scaleX} ${layout.scaleY}")
+        layout.removeAllViewsInLayout()
+        this.bitmaps.clear()
+        bitmapCumWidths.clear()
+        bitmapCumWidths.add(0)
+        bitmaps.forEach {
+            this.bitmaps.add(it)
+            bitmapCumWidths.add(it.width + bitmapCumWidths.last())
+        }
+        if (lazyScroll) {
+            lazyIdxStart = -1
+            lazyIdxEnd = -1
+            layoutVisibleBitmaps()
+        } else {
+            layoutAllBitmaps()
+        }
+    }
+
+    private fun layoutBitmap(bitmap: Bitmap) {
+        val img = ImageView(this.context)
+        img.setImageBitmap(bitmap)
+        img.minimumWidth = bitmap.width  // No idea what broke when I refactored this class
+        img.minimumHeight = bitmap.height
+        println("${bitmap.width}x${bitmap.height}")
+        layout.addView(img)
+    }
+
+    private fun layoutAllBitmaps() {
+        bitmaps.forEach(::layoutBitmap)
+        println("Presentation heights $height ${layout.height}")
+    }
+
+    private fun layoutVisibleBitmaps() {
+        val xStart = (scrollProgress * (bitmapCumWidths.last() - width)).toInt()
+        val xEnd = xStart + width
+        // bitmapCumWidths has a prepended 0
+        val idxStart = bitmapCumWidths.indexOfFirst { it > xStart }.let { if (it >= 1) it-1 else 0 }
+        val idxEnd = bitmapCumWidths.indexOfFirst { it > xEnd }.let { if (it >= 0) it else bitmaps.size}
+
+        layout.removeAllViewsInLayout()
+        (idxStart..<idxEnd).map(bitmaps::get).forEach(::layoutBitmap)
+        lazyIdxStart = idxStart
+        lazyIdxEnd = idxEnd
+        println("Laying out pages $idxStart up to $idxEnd - scrollable width ${layout.width}")
+    }
+
+    fun setScrollProgress(progress: Float) {
+        scrollProgress = progress
+        var progressPx = (progress * (bitmapCumWidths.last() - width)).toInt()
+        if (lazyScroll) {
+            layoutVisibleBitmaps()
+            progressPx -= bitmapCumWidths[lazyIdxStart]
+        }
+        println("Scrolling view to x=$progressPx of scrollable ${layout.width} (visible width $width)")
+        scrollTo(progressPx, 0)
+    }
+
+    fun setScrollPagesProgress(pagesProgress: Float) {
+        // NB this is nonlinear with unequal page widths
+        val p = pagesProgress.toInt()
+        val progressPx = bitmapCumWidths[p] + (bitmaps[p].width * (pagesProgress % 1F))
+        val progress = progressPx / (bitmapCumWidths.last() - width).toFloat()
+        setScrollProgress(progress)
+    }
+}
\ No newline at end of file