Cleanup logic of `onStripSplit` in WebtoonPageHolder (#7955)

* Cleanup logic of `onStripSplit` in WebtoonPageHolder

* Update app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonPageHolder.kt

Co-authored-by: arkon <[email protected]>

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonPageHolder.kt

@@ -289,25 +289,24 @@ class WebtoonPageHolder(
             }
             val isStripSplitNeeded = ImageUtil.isStripSplitNeeded(imageStream)
             if (isStripSplitNeeded) {
-                onStripSplit(imageStream)?.let { return it }
+                return onStripSplit(imageStream)
             }
         }
 
         return imageStream
     }
 
-    private fun onStripSplit(imageStream: BufferedInputStream): InputStream? {
-        val page = page ?: return null
-        val streamFn = page.stream ?: return null
+    private fun onStripSplit(imageStream: BufferedInputStream): InputStream {
+        // If we have reached this point [page] and its stream shouldn't be null
+        val page = page!!
+        val stream = page.stream!!
         val splitData = ImageUtil.getSplitDataForStream(imageStream)
-        if (splitData.size == 1) return imageStream
         val newPages = splitData.map {
-            StencilPage(page) { ImageUtil.splitStrip(it, streamFn) }
+            StencilPage(page) { ImageUtil.splitStrip(it, stream) }
         }.toMutableList()
-        return newPages.removeFirst().stream?.invoke()
+        return newPages.removeFirst().stream!!()
             .also {
-                // Doing this first and then returning InputStream
-                // results in various issues with splitting
+                // Running [onLongStripSplit] first results in issues with splitting
                 viewer.onLongStripSplit(page, newPages)
             }
     }

app/src/main/java/eu/kanade/tachiyomi/util/system/ImageUtil.kt

@@ -261,7 +261,7 @@ object ImageUtil {
 
         val options = extractImageOptions(imageStream)
         val imageHeightIsBiggerThanWidth = options.outHeight > options.outWidth
-        val imageHeightBiggerThanScreenHeight = options.outHeight > getDisplayMaxHeightInPx
+        val imageHeightBiggerThanScreenHeight = options.outHeight > optimalImageHeight
         return imageHeightIsBiggerThanWidth && imageHeightBiggerThanScreenHeight
     }
 
@@ -300,9 +300,8 @@ object ImageUtil {
             val imageHeight = outHeight
             val imageWidth = outWidth
 
-            val splitHeight = getDisplayMaxHeightInPx * 2
-            // -1 so it doesn't try to split when imageHeight = splitHeight
-            val partCount = (imageHeight - 1) / splitHeight + 1
+            // -1 so it doesn't try to split when imageHeight = optimalImageHeight
+            val partCount = (imageHeight - 1) / optimalImageHeight + 1
             val optimalSplitHeight = imageHeight / partCount
 
             logcat {
@@ -316,15 +315,15 @@ object ImageUtil {
                     if (isNotEmpty() && imageHeight <= last().bottomOffset) break
 
                     val topOffset = index * optimalSplitHeight
-                    var outputImageHeight = min(optimalSplitHeight, imageHeight - topOffset)
+                    var splitHeight = min(optimalSplitHeight, imageHeight - topOffset)
 
-                    val remainingHeight = imageHeight - (topOffset + outputImageHeight)
+                    val remainingHeight = imageHeight - (topOffset + splitHeight)
                     // If remaining height is smaller or equal to 1/10th of
                     // optimal split height then include it in current page
                     if (remainingHeight <= (optimalSplitHeight / 10)) {
-                        outputImageHeight += remainingHeight
+                        splitHeight += remainingHeight
                     }
-                    add(SplitData(index, topOffset, outputImageHeight, imageWidth))
+                    add(SplitData(index, topOffset, splitHeight, imageWidth))
                 }
             }
         }
@@ -578,6 +577,8 @@ object ImageUtil {
         }
     }
 
+    private val optimalImageHeight = getDisplayMaxHeightInPx * 2
+
     // Android doesn't include some mappings
     private val SUPPLEMENTARY_MIMETYPE_MAPPING = mapOf(
         // https://issuetracker.google.com/issues/182703810