Match WebGPU reader background and transition colors to the old reader (#3765)

Assisted-by: Claude:claude-opus-5

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -82,6 +82,7 @@ import eu.kanade.tachiyomi.ui.reader.viewer.webgpu.WebGpuViewer
 import eu.kanade.tachiyomi.ui.webview.WebViewActivity
 import eu.kanade.tachiyomi.util.system.isNightMode
 import eu.kanade.tachiyomi.util.system.openInBrowser
+import eu.kanade.tachiyomi.util.system.readerBackgroundColor
 import eu.kanade.tachiyomi.util.system.toShareIntent
 import eu.kanade.tachiyomi.util.system.toast
 import eu.kanade.tachiyomi.util.view.setComposeContent
@@ -857,22 +858,13 @@ class ReaderActivity : BaseActivity() {
             }
         }
 
-        private val grayBackgroundColor = Color.rgb(0x20, 0x21, 0x25)
-
         /*
          * Initializes the reader subscriptions.
          */
         init {
             readerPreferences.readerTheme.changes()
                 .onEach { theme ->
-                    binding.readerContainer.setBackgroundColor(
-                        when (theme) {
-                            0 -> Color.WHITE
-                            2 -> grayBackgroundColor
-                            3 -> automaticBackgroundColor()
-                            else -> Color.BLACK
-                        },
-                    )
+                    binding.readerContainer.setBackgroundColor(baseContext.readerBackgroundColor(theme))
                 }
                 .launchIn(lifecycleScope)
 
@@ -907,17 +899,6 @@ class ReaderActivity : BaseActivity() {
                 .launchIn(lifecycleScope)
         }
 
-        /**
-         * Picks background color for [ReaderActivity] based on light/dark theme preference
-         */
-        private fun automaticBackgroundColor(): Int {
-            return if (baseContext.isNightMode()) {
-                grayBackgroundColor
-            } else {
-                Color.WHITE
-            }
-        }
-
         /**
          * Sets the display profile to [path].
          */

app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webgpu/WebGpuViewer.kt

@@ -30,6 +30,7 @@ import ca.mpreg.webgpuviewer.transition.TransitionStackLeft
 import ca.mpreg.webgpuviewer.transition.TransitionStackRight
 import ca.mpreg.webgpuviewer.transition.TransitionStackUp
 import ca.mpreg.webgpuviewer.viewer.ImagePage
+import com.google.android.material.color.MaterialColors
 import de.stefan_oltmann.kim.Kim
 import de.stefan_oltmann.kim.android.readMetadata
 import de.stefan_oltmann.kim.format.tiff.constant.TiffTag
@@ -43,6 +44,8 @@ import eu.kanade.tachiyomi.ui.reader.setting.ReaderPreferences.TransitionAnimati
 import eu.kanade.tachiyomi.ui.reader.viewer.ReaderPageImageView.ZoomStartPosition
 import eu.kanade.tachiyomi.ui.reader.viewer.Viewer
 import eu.kanade.tachiyomi.ui.reader.viewer.ViewerNavigation.NavigationRegion
+import eu.kanade.tachiyomi.util.system.createReaderThemeContext
+import eu.kanade.tachiyomi.util.system.readerBackgroundColor
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.MainScope
 import kotlinx.coroutines.asCoroutineDispatcher
@@ -62,6 +65,14 @@ open class WebGpuViewer(
 
     open val isContinuous: Boolean = false
 
+    private fun readerBackgroundColor(): Int = activity.baseContext.readerBackgroundColor(config.theme)
+
+    private fun readerOnBackgroundColor(): Int = MaterialColors.getColor(
+        activity.createReaderThemeContext(),
+        com.google.android.material.R.attr.colorOnBackground,
+        Color.WHITE,
+    )
+
     private val scope = MainScope()
 
     // Dedicated thread for decode worker to avoid blocking Dispatchers.Default pool
@@ -773,12 +784,10 @@ open class WebGpuViewer(
                     null
                 }
 
-                val backgroundColor = when {
-                    config.automaticBackground -> null
-                    config.theme == 0 -> 0xFFFFFFFF.toInt()
-                    config.theme == 1 -> 0xFF000000.toInt()
-                    config.theme == 2 -> 0xFF808080.toInt()
-                    else -> 0xFF000000.toInt()
+                val backgroundColor = if (config.automaticBackground) {
+                    null
+                } else {
+                    readerBackgroundColor()
                 }
 
                 val firstImage = Image.createWithTrim(
@@ -848,10 +857,10 @@ open class WebGpuViewer(
 
             val bitmap = createBitmap(pager.state.width, pager.state.height)
             val canvas = Canvas(bitmap)
-            canvas.drawColor(Color.BLACK)
+            canvas.drawColor(readerBackgroundColor())
 
             val paint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
-                color = Color.WHITE
+                color = readerOnBackgroundColor()
                 textSize = 48f
                 textAlign = Paint.Align.CENTER
             }

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

@@ -6,6 +6,7 @@ import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
 import android.content.res.Configuration
+import android.graphics.Color
 import android.net.Uri
 import android.os.Build
 import android.os.PowerManager
@@ -98,6 +99,20 @@ fun Context.createFileInCacheDir(name: String): File {
     return file
 }
 
+private val ReaderGrayBackgroundColor = Color.rgb(0x20, 0x21, 0x25)
+
+/**
+ * Background color of the reader for the given [readerTheme] preference value.
+ *
+ * Automatic (3) resolves against the current night mode, matching the activity background.
+ */
+fun Context.readerBackgroundColor(readerTheme: Int): Int = when (readerTheme) {
+    0 -> Color.WHITE // White
+    2 -> ReaderGrayBackgroundColor // Gray
+    3 -> if (isNightMode()) ReaderGrayBackgroundColor else Color.WHITE // Automatic
+    else -> Color.BLACK // Black
+}
+
 /**
  * Creates night mode Context depending on reader theme/background
  *