feat: add "horizontal limiter" option

* Option to show horizontal ruler and dim unfocused part of the screen (both height of the focused part and its vertical position can be customized)
* Option to hide horizontal ruler
* Option to change horizontal ruler's thickness
* Option to change dimming (0-100%)

Resolves: #197

app/src/main/java/ua/acclorite/book_story/data/settings/SettingsManager.kt

@@ -180,6 +180,26 @@ class SettingsManager @Inject constructor(
     val perceptionExpanderThickness = setting<Int, Int>(
         key = intPreferencesKey("perception_expander_thickness"), default = 4
     )
+    val horizontalLimiter = setting<Boolean, Boolean>(
+        key = booleanPreferencesKey("horizontal_limiter"), default = false
+    )
+    val horizontalLimiterHeight = setting<Int, Int>(
+        key = intPreferencesKey("horizontal_limiter_height"), default = 6
+    )
+    val horizontalLimiterVerticalOffset = setting<Float, Double>(
+        key = doublePreferencesKey("horizontal_limiter_vertical_offset"), default = 0.5f,
+        serialize = { it.toDouble() }, deserialize = { it.toFloat() }
+    )
+    val horizontalLimiterRuler = setting<Boolean, Boolean>(
+        key = booleanPreferencesKey("horizontal_limiter_ruler"), default = true
+    )
+    val horizontalLimiterRulerThickness = setting<Int, Int>(
+        key = intPreferencesKey("horizontal_limiter_ruler_thickness"), default = 4
+    )
+    val horizontalLimiterDimming = setting<Float, Double>(
+        key = doublePreferencesKey("horizontal_limiter_dimming"), default = 0.0f,
+        serialize = { it.toDouble() }, deserialize = { it.toFloat() }
+    )
     val screenOrientation = setting<ReaderScreenOrientation, String>(
         key = stringPreferencesKey("screen_orientation"), default = ReaderScreenOrientation.DEFAULT,
         serialize = { it.name }, deserialize = { ReaderScreenOrientation.valueOf(it) }

app/src/main/java/ua/acclorite/book_story/presentation/reader/ReaderScreen.kt

@@ -166,6 +166,16 @@ data class ReaderScreen(val bookId: Int) : Screen, Parcelable {
         ) {
             (settings.perceptionExpanderThickness.lastValue * 0.25f).dp
         }
+        val horizontalLimiterHeight = remember(
+            settings.horizontalLimiterHeight.value
+        ) {
+            (settings.horizontalLimiterHeight.lastValue * 20).dp
+        }
+        val horizontalLimiterRulerThickness = remember(
+            settings.horizontalLimiterRulerThickness.value
+        ) {
+            (settings.horizontalLimiterRulerThickness.lastValue * 0.25f).dp
+        }
         val horizontalGestureSensitivity = remember(settings.horizontalGestureSensitivity.value) {
             (36f + settings.horizontalGestureSensitivity.lastValue * (4f - 36f)).dp
         }
@@ -395,6 +405,12 @@ data class ReaderScreen(val bookId: Int) : Screen, Parcelable {
             perceptionExpander = settings.perceptionExpander.value,
             perceptionExpanderPadding = perceptionExpanderPadding,
             perceptionExpanderThickness = perceptionExpanderThickness,
+            horizontalLimiter = settings.horizontalLimiter.value,
+            horizontalLimiterHeight = horizontalLimiterHeight,
+            horizontalLimiterVerticalOffset = settings.horizontalLimiterVerticalOffset.value,
+            horizontalLimiterRuler = settings.horizontalLimiterRuler.value,
+            horizontalLimiterRulerThickness = horizontalLimiterRulerThickness,
+            horizontalLimiterDimming = settings.horizontalLimiterDimming.value,
             currentChapterProgress = state.value.currentChapterProgress,
             isLoading = state.value.isLoading,
             errorMessage = state.value.errorMessage,

app/src/main/java/ua/acclorite/book_story/ui/reader/ReaderContent.kt

@@ -46,6 +46,12 @@ fun ReaderContent(
     perceptionExpander: Boolean,
     perceptionExpanderPadding: Dp,
     perceptionExpanderThickness: Dp,
+    horizontalLimiter: Boolean,
+    horizontalLimiterHeight: Dp,
+    horizontalLimiterVerticalOffset: Float,
+    horizontalLimiterRulerThickness: Dp,
+    horizontalLimiterRuler: Boolean,
+    horizontalLimiterDimming: Float,
     currentChapterProgress: Float,
     isLoading: Boolean,
     errorMessage: UIText?,
@@ -124,6 +130,12 @@ fun ReaderContent(
             perceptionExpander = perceptionExpander,
             perceptionExpanderPadding = perceptionExpanderPadding,
             perceptionExpanderThickness = perceptionExpanderThickness,
+            horizontalLimiter = horizontalLimiter,
+            horizontalLimiterHeight = horizontalLimiterHeight,
+            horizontalLimiterVerticalOffset = horizontalLimiterVerticalOffset,
+            horizontalLimiterRuler = horizontalLimiterRuler,
+            horizontalLimiterRulerThickness = horizontalLimiterRulerThickness,
+            horizontalLimiterDimming = horizontalLimiterDimming,
             currentChapterProgress = currentChapterProgress,
             isLoading = isLoading,
             checkpoints = checkpoints,

app/src/main/java/ua/acclorite/book_story/ui/reader/ReaderHorizontalLimiter.kt

@@ -0,0 +1,96 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.reader
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.platform.LocalWindowInfo
+import androidx.compose.ui.unit.Dp
+import ua.acclorite.book_story.ui.theme.DefaultTransition
+
+@Composable
+fun ReaderHorizontalLimiter(
+    horizontalLimiter: Boolean,
+    horizontalLimiterHeight: Dp,
+    horizontalLimiterVerticalOffset: Float,
+    horizontalLimiterRulerThickness: Dp,
+    horizontalLimiterRuler: Boolean,
+    horizontalLimiterDimming: Float,
+    horizontalLimiterDimmingColor: Color,
+    horizontalLimiterRulerColor: Color
+) {
+    val density = LocalDensity.current
+    val windowInfo = LocalWindowInfo.current
+    val containerHeight = remember(density, windowInfo.containerSize, horizontalLimiterHeight) {
+        with(density) {
+            windowInfo.containerSize.height.toDp() - horizontalLimiterHeight
+        }
+    }
+    val verticalLimiterTopOffsetDp = remember(
+        containerHeight,
+        horizontalLimiterVerticalOffset
+    ) {
+        containerHeight * horizontalLimiterVerticalOffset
+    }
+    val verticalLimiterBottomOffsetDp = remember(
+        containerHeight,
+        horizontalLimiterVerticalOffset
+    ) {
+        containerHeight * (1 - horizontalLimiterVerticalOffset)
+    }
+
+    DefaultTransition(horizontalLimiter) {
+        Column(
+            modifier = Modifier.fillMaxSize()
+        ) {
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(verticalLimiterTopOffsetDp)
+                    .background(horizontalLimiterDimmingColor.copy(alpha = horizontalLimiterDimming))
+            )
+
+            Column(
+                modifier = Modifier
+                    .height(
+                        horizontalLimiterHeight.coerceAtMost(
+                            with(density) { windowInfo.containerSize.height.toDp() }
+                        )
+                    ),
+                verticalArrangement = Arrangement.SpaceBetween
+            ) {
+                if (horizontalLimiterRuler) {
+                    repeat(2) {
+                        HorizontalDivider(
+                            modifier = Modifier.fillMaxWidth(),
+                            horizontalLimiterRulerThickness,
+                            horizontalLimiterRulerColor
+                        )
+                    }
+                }
+            }
+
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(verticalLimiterBottomOffsetDp)
+                    .background(horizontalLimiterDimmingColor.copy(alpha = horizontalLimiterDimming))
+            )
+        }
+    }
+}

app/src/main/java/ua/acclorite/book_story/ui/reader/ReaderScaffold.kt

@@ -51,6 +51,12 @@ fun ReaderScaffold(
     perceptionExpander: Boolean,
     perceptionExpanderPadding: Dp,
     perceptionExpanderThickness: Dp,
+    horizontalLimiter: Boolean,
+    horizontalLimiterHeight: Dp,
+    horizontalLimiterVerticalOffset: Float,
+    horizontalLimiterRulerThickness: Dp,
+    horizontalLimiterRuler: Boolean,
+    horizontalLimiterDimming: Float,
     currentChapterProgress: Float,
     isLoading: Boolean,
     checkpoints: List<Checkpoint>,
@@ -212,6 +218,17 @@ fun ReaderScaffold(
             perceptionExpanderColor = fontColor
         )
 
+        ReaderHorizontalLimiter(
+            horizontalLimiter = horizontalLimiter,
+            horizontalLimiterHeight = horizontalLimiterHeight,
+            horizontalLimiterVerticalOffset = horizontalLimiterVerticalOffset,
+            horizontalLimiterRulerThickness = horizontalLimiterRulerThickness,
+            horizontalLimiterRuler = horizontalLimiterRuler,
+            horizontalLimiterDimming = horizontalLimiterDimming,
+            horizontalLimiterDimmingColor = backgroundColor,
+            horizontalLimiterRulerColor = fontColor
+        )
+
         if (isLoading) {
             ReaderLoadingPlaceholder()
         }

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/ReadingSpeedSubcategory.kt

@@ -17,6 +17,12 @@ import ua.acclorite.book_story.R
 import ua.acclorite.book_story.ui.settings.components.SettingsSubcategory
 import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HighlightedReadingOption
 import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HighlightedReadingThicknessOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterDimmingOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterHeightOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterRulerOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterRulerThicknessOption
+import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.HorizontalLimiterVerticalOffsetOption
 import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.PerceptionExpanderOption
 import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.PerceptionExpanderPaddingOption
 import ua.acclorite.book_story.ui.settings.reader.reading_speed.components.PerceptionExpanderThicknessOption
@@ -52,5 +58,29 @@ fun LazyListScope.ReadingSpeedSubcategory(
         item {
             PerceptionExpanderThicknessOption()
         }
+
+        item {
+            HorizontalLimiterOption()
+        }
+
+        item {
+            HorizontalLimiterHeightOption()
+        }
+
+        item {
+            HorizontalLimiterVerticalOffsetOption()
+        }
+
+        item {
+            HorizontalLimiterRulerOption()
+        }
+
+        item {
+            HorizontalLimiterRulerThicknessOption()
+        }
+
+        item {
+            HorizontalLimiterDimmingOption()
+        }
     }
 }

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterDimmingOption.kt

@@ -0,0 +1,30 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SliderWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+import ua.acclorite.book_story.ui.theme.ExpandingTransition
+
+@Composable
+fun HorizontalLimiterDimmingOption() {
+    val settings = LocalSettings.current
+
+    ExpandingTransition(visible = settings.horizontalLimiter.value) {
+        SliderWithTitle(
+            value = settings.horizontalLimiterDimming.value to "%",
+            toValue = 100,
+            title = stringResource(id = R.string.horizontal_limiter_dimming_option),
+            onValueChange = {
+                settings.horizontalLimiterDimming.update(it)
+            }
+        )
+    }
+}

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterHeightOption.kt

@@ -0,0 +1,31 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SliderWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+import ua.acclorite.book_story.ui.theme.ExpandingTransition
+
+@Composable
+fun HorizontalLimiterHeightOption() {
+    val settings = LocalSettings.current
+
+    ExpandingTransition(visible = settings.horizontalLimiter.value) {
+        SliderWithTitle(
+            value = settings.horizontalLimiterHeight.value to "pt",
+            fromValue = 1,
+            toValue = 24,
+            title = stringResource(id = R.string.horizontal_limiter_height_option),
+            onValueChange = {
+                settings.horizontalLimiterHeight.update(it)
+            }
+        )
+    }
+}

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterOption.kt

@@ -0,0 +1,27 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SwitchWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+
+@Composable
+fun HorizontalLimiterOption() {
+    val settings = LocalSettings.current
+
+    SwitchWithTitle(
+        selected = settings.horizontalLimiter.value,
+        title = stringResource(id = R.string.horizontal_limiter_option),
+        description = stringResource(id = R.string.horizontal_limiter_option_desc),
+        onClick = {
+            settings.horizontalLimiter.update(!settings.horizontalLimiter.lastValue)
+        }
+    )
+}

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterRulerOption.kt

@@ -0,0 +1,29 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SwitchWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+import ua.acclorite.book_story.ui.theme.ExpandingTransition
+
+@Composable
+fun HorizontalLimiterRulerOption() {
+    val settings = LocalSettings.current
+
+    ExpandingTransition(visible = settings.horizontalLimiter.value) {
+        SwitchWithTitle(
+            selected = settings.horizontalLimiterRuler.value,
+            title = stringResource(id = R.string.horizontal_limiter_ruler_option),
+            onClick = {
+                settings.horizontalLimiterRuler.update(!settings.horizontalLimiterRuler.lastValue)
+            }
+        )
+    }
+}

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterRulerThicknessOption.kt

@@ -0,0 +1,31 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SliderWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+import ua.acclorite.book_story.ui.theme.ExpandingTransition
+
+@Composable
+fun HorizontalLimiterRulerThicknessOption() {
+    val settings = LocalSettings.current
+
+    ExpandingTransition(visible = settings.horizontalLimiter.value && settings.horizontalLimiterRuler.value) {
+        SliderWithTitle(
+            value = settings.horizontalLimiterRulerThickness.value to "pt",
+            fromValue = 1,
+            toValue = 12,
+            title = stringResource(id = R.string.horizontal_limiter_ruler_thickness_option),
+            onValueChange = {
+                settings.horizontalLimiterRulerThickness.update(it)
+            }
+        )
+    }
+}

app/src/main/java/ua/acclorite/book_story/ui/settings/reader/reading_speed/components/HorizontalLimiterVerticalOffsetOption.kt

@@ -0,0 +1,30 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2025 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package ua.acclorite.book_story.ui.settings.reader.reading_speed.components
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
+import ua.acclorite.book_story.ui.common.components.settings.SliderWithTitle
+import ua.acclorite.book_story.ui.common.helpers.LocalSettings
+import ua.acclorite.book_story.ui.theme.ExpandingTransition
+
+@Composable
+fun HorizontalLimiterVerticalOffsetOption() {
+    val settings = LocalSettings.current
+
+    ExpandingTransition(visible = settings.horizontalLimiter.value) {
+        SliderWithTitle(
+            value = settings.horizontalLimiterVerticalOffset.value to "%",
+            toValue = 100,
+            title = stringResource(id = R.string.horizontal_limiter_vertical_offset_option),
+            onValueChange = {
+                settings.horizontalLimiterVerticalOffset.update(it)
+            }
+        )
+    }
+}

app/src/main/res/values-uk/strings.xml

@@ -194,6 +194,15 @@
     <string name="perception_expander_option_desc">Збільшіть швидкість вашого читання фокусуючись на середині</string>
     <string name="perception_expander_padding_option">Бокові відступи лінії</string>
     <string name="perception_expander_thickness_option">Товщина лінії</string>
+    <string name="horizontal_limiter_option">Горизонтальний обмежувач</string>
+    <string name="horizontal_limiter_option_desc">
+        Показати горизонтальну лінійку та затемнити несфокусовану частину екрана
+    </string>
+    <string name="horizontal_limiter_height_option">Висота</string>
+    <string name="horizontal_limiter_vertical_offset_option">Вертикальне зміщення</string>
+    <string name="horizontal_limiter_ruler_option">Горизонтальна лінійка</string>
+    <string name="horizontal_limiter_ruler_thickness_option">Товщина лінійки</string>
+    <string name="horizontal_limiter_dimming_option">Затемнення</string>
     <string name="screen_orientation_option">Орієнтація екрана</string>
     <string name="custom_screen_brightness_option">Користувацька яскравість</string>
     <string name="screen_brightness_option">Яскравість</string>

app/src/main/res/values/strings.xml

@@ -218,6 +218,15 @@
     </string>
     <string name="perception_expander_padding_option">Line side margin</string>
     <string name="perception_expander_thickness_option">Line thickness</string>
+    <string name="horizontal_limiter_option">Horizontal limiter</string>
+    <string name="horizontal_limiter_option_desc">
+        Show horizontal ruler and dim unfocused part of the screen
+    </string>
+    <string name="horizontal_limiter_height_option">Height</string>
+    <string name="horizontal_limiter_vertical_offset_option">Vertical offset</string>
+    <string name="horizontal_limiter_ruler_option">Horizontal ruler</string>
+    <string name="horizontal_limiter_ruler_thickness_option">Ruler thickness</string>
+    <string name="horizontal_limiter_dimming_option">Dimming</string>
     <string name="screen_orientation_option">Screen orientation</string>
     <string name="custom_screen_brightness_option">Custom brightness</string>
     <string name="screen_brightness_option">Brightness</string>