android: improve liquid glass sliders

android/app/src/main/java/me/kavishdevar/librepods/composables/StyledSlider.kt

@@ -18,7 +18,6 @@
 
 package me.kavishdevar.librepods.composables
 
-import android.annotation.SuppressLint
 import android.content.res.Configuration
 import androidx.compose.animation.core.Animatable
 import androidx.compose.animation.core.spring
@@ -29,9 +28,9 @@ import androidx.compose.foundation.gestures.rememberDraggableState
 import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.heightIn
@@ -60,6 +59,9 @@ import androidx.compose.ui.graphics.layer.CompositingStrategy
 import androidx.compose.ui.graphics.layer.drawLayer
 import androidx.compose.ui.graphics.rememberGraphicsLayer
 import androidx.compose.ui.layout.layout
+import androidx.compose.ui.layout.onGloballyPositioned
+import androidx.compose.ui.layout.onSizeChanged
+import androidx.compose.ui.layout.positionInParent
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.font.Font
@@ -96,8 +98,7 @@ fun StyledSlider(
     endIcon: String? = null,
     startLabel: String? = null,
     endLabel: String? = null,
-    independent: Boolean = false,
+    independent: Boolean = false
-    @SuppressLint("ModifierParameter") modifier: Modifier = Modifier
 ) {
     val backgroundColor = if (isSystemInDarkTheme()) Color(0xFF1C1C1E) else Color(0xFFFFFFFF)
     val isLightTheme = !isSystemInDarkTheme()
@@ -119,16 +120,27 @@ fun StyledSlider(
     val animationScope = rememberCoroutineScope()
     val progressAnimationSpec = spring(0.5f, 300f, 0.001f)
     val progressAnimation = remember { Animatable(0f) }
-
-    val trackBackdrop = rememberBackdrop()
     val innerShadowLayer =
         rememberGraphicsLayer().apply {
             compositingStrategy = CompositingStrategy.Offscreen
         }
 
+    val sliderBackdrop = rememberBackdrop()
+    val trackWidthState = remember { mutableFloatStateOf(0f) }
+    val trackPositionState = remember { mutableFloatStateOf(0f) }
+    val startIconWidthState = remember { mutableFloatStateOf(0f) }
+    val endIconWidthState = remember { mutableFloatStateOf(0f) }
+    val density = LocalDensity.current
+
     val content = @Composable {
+        Box(Modifier.fillMaxWidth()) {
+            Box(Modifier
+                .backdrop(sliderBackdrop)
+                .fillMaxWidth()) {
                 Column(
-            modifier = modifier.fillMaxWidth(1f).padding(vertical = 8.dp),
+                    modifier = Modifier
+                        .fillMaxWidth(1f)
+                        .padding(vertical = 8.dp),
                     horizontalAlignment = Alignment.CenterHorizontally,
                     verticalArrangement = Arrangement.spacedBy(8.dp)
                 ) {
@@ -184,18 +196,22 @@ fun StyledSlider(
                                     color = labelTextColor,
                                     fontFamily = FontFamily(Font(R.font.sf_pro))
                                 ),
-                        modifier = Modifier.padding(horizontal = 12.dp)
+                                modifier = Modifier
+                                    .padding(horizontal = 12.dp)
+                                    .onGloballyPositioned {
+                                        startIconWidthState.floatValue = it.size.width.toFloat()
+                                    }
                             )
                         }
-                BoxWithConstraints(
+                        Box(
                             Modifier
-                        .weight(1f),
+                                .weight(1f)
-                    contentAlignment = Alignment.CenterStart
+                                .onSizeChanged { trackWidthState.floatValue = it.width.toFloat() }
+                                .onGloballyPositioned {
+                                    trackPositionState.floatValue =
+                                        it.positionInParent().y + it.size.height / 2f
+                                }
                         ) {
-                    val density = LocalDensity.current
-                    val trackWidth = constraints.maxWidth
-
-                    Box(Modifier.backdrop(trackBackdrop)) {
                             Box(
                                 Modifier
                                     .clip(RoundedCornerShape(28.dp))
@@ -212,28 +228,47 @@ fun StyledSlider(
                                     .layout { measurable, constraints ->
                                         val placeable = measurable.measure(constraints)
                                         val fraction = fraction
-                                    val width = (fraction * constraints.maxWidth).fastRoundToInt()
+                                        val width =
+                                            (fraction * constraints.maxWidth).fastRoundToInt()
                                         layout(width, placeable.height) {
                                             placeable.place(0, 0)
                                         }
                                     }
                             )
                         }
+                        if (endIcon != null) {
+                            Text(
+                                text = endIcon,
+                                style = TextStyle(
+                                    fontSize = 16.sp,
+                                    fontWeight = FontWeight.Normal,
+                                    color = labelTextColor,
+                                    fontFamily = FontFamily(Font(R.font.sf_pro))
+                                ),
+                                modifier = Modifier
+                                    .padding(horizontal = 12.dp)
+                                    .onGloballyPositioned {
+                                        endIconWidthState.floatValue = it.size.width.toFloat()
+                                    }
+                            )
+                        }
+                    }
+                }
+            }
 
             Box(
                 Modifier
                     .graphicsLayer {
-                                val fraction = fraction
+                        val startOffset =
+                            if (startIcon != null) startIconWidthState.floatValue + with(density) { 24.dp.toPx() } else 0f
                         translationX =
-                                    (-size.width / 2f + fraction * trackWidth)
+                            startOffset + fraction * trackWidthState.floatValue - size.width / 2f
-                                        .fastCoerceIn(
+                        translationY = trackPositionState.floatValue / 2f
-                                            -size.width / 4f,
-                                            trackWidth - size.width * 3f / 4f
-                                        )
                     }
                     .draggable(
                         rememberDraggableState { delta ->
-                                    val trackWidth = trackWidth - with(density) { 40f.dp.toPx() }
+                            val trackWidth = trackWidthState.floatValue
+                            if (trackWidth > 0f) {
                                 val targetFraction = fraction + delta / trackWidth
                                 val targetValue =
                                     lerp(valueRange.start, valueRange.endInclusive, targetFraction)
@@ -244,6 +279,7 @@ fun StyledSlider(
                                     snapThreshold
                                 ) else targetValue
                                 onValueChange(snappedValue)
+                            }
                         },
                         Orientation.Horizontal,
                         startDragImmediately = true,
@@ -260,7 +296,7 @@ fun StyledSlider(
                         }
                     )
                     .drawBackdrop(
-                                rememberCombinedBackdropDrawer(backdrop, trackBackdrop),
+                        rememberCombinedBackdropDrawer(backdrop, sliderBackdrop),
                         { RoundedCornerShape(28.dp) },
                         highlight = {
                             val progress = progressAnimation.value
@@ -313,20 +349,6 @@ fun StyledSlider(
                     .size(40f.dp, 24f.dp)
             )
         }
-                if (endIcon != null) {
-                    Text(
-                        text = endIcon,
-                        style = TextStyle(
-                            fontSize = 16.sp,
-                            fontWeight = FontWeight.Normal,
-                            color = labelTextColor,
-                            fontFamily = FontFamily(Font(R.font.sf_pro))
-                        ),
-                        modifier = Modifier.padding(horizontal = 12.dp)
-                    )
-                }
-            }
-        }
     }
 
     if (independent) {
@@ -350,15 +372,30 @@ private fun snapIfClose(value: Float, points: List<Float>, threshold: Float = 0.
     return if (kotlin.math.abs(nearest - value) <= threshold) nearest else value
 }
 
-@Preview(uiMode = Configuration.UI_MODE_NIGHT_YES)
+@Preview(uiMode = Configuration.UI_MODE_NIGHT_NO)
 @Composable
 fun StyledSliderPreview() {
+    val a = remember { mutableFloatStateOf(1f) }
+    Box(
+        Modifier
+            .background(if (isSystemInDarkTheme()) Color(0xFF121212) else Color(0xFFF0F0F0))
+            .padding(16.dp)
+            .fillMaxSize()
+    ) {
+        Box (
+            Modifier.align(Alignment.Center)
+        )
+        {
             StyledSlider(
-        mutableFloatState = remember {mutableFloatStateOf(1f)},
+                mutableFloatState = a,
-        onValueChange = {},
+                onValueChange = {
+                    a.floatValue = it
+                },
                 valueRange = 0f..2f,
                 independent = true,
                 startIcon = "A",
                 endIcon = "B"
             )
+        }
+    }
 }