feat: implement avatar expansion and collapse logic with smooth snapping in ProfileScreen

app/src/main/java/com/rosetta/messenger/ui/components/metaball/ProfileMetaballOverlay.kt

@@ -1,6 +1,7 @@
 package com.rosetta.messenger.ui.components.metaball
 
 import android.graphics.Path
+import android.util.Log
 import android.graphics.RenderEffect
 import android.graphics.RuntimeShader
 import android.graphics.Shader
@@ -33,6 +34,7 @@ import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import org.intellij.lang.annotations.Language
 import kotlin.math.abs
+import kotlin.math.max
 import kotlin.math.min
 import kotlin.math.sqrt
 import androidx.compose.ui.graphics.Color as ComposeColor
@@ -40,12 +42,43 @@ import androidx.compose.ui.graphics.Color as ComposeColor
 /**
  * Constants for the Profile Metaball Animation
  * Based on Telegram's ProfileMetaballView implementation
+ * 
+ * THRESHOLDS from Telegram:
+ * - isDrawing: vr <= 40dp (start metaball effect)
+ * - isNear: vr <= 32dp (avatar very close to notch)
+ * - Form transition: 40dp → 34dp (circle → rounded rect)
+ * - Alpha fade: 32dp → 18dp (1.0 → 0.0)
+ * 
+ * SCALE from Telegram:
+ * - Collapsed (into notch): avatarScale = lerp(24dp, 96dp, diff) / 100f
+ * - Expanded (pull-down): avatarScale = lerp(96/42, 138/42, expandProgress*3) / 100f * 42
+ * 
+ * POSITION from Telegram:
+ * - avatarY = lerp(endY, startY, diff)
+ * - endY = notch center or -dp(29)
+ * - startY = statusBar + actionBarHeight - dp(21)
  */
 object ProfileMetaballConstants {
-    // Avatar dimensions
+    // Avatar dimensions (like Telegram: collapsed into 24dp, normal 96dp, expanded 138dp)
+    val AVATAR_SIZE_COLLAPSED = 24.dp   // intoSize when fully collapsed into notch
+    val AVATAR_SIZE_NORMAL = 96.dp      // Normal expanded avatar size  
+    val AVATAR_SIZE_PULLED = 138.dp     // When pulled down (isPulledDown)
+    
+    // Legacy - for compatibility
     val AVATAR_SIZE_EXPANDED = 120.dp
     val AVATAR_SIZE_MIN = 24.dp
     
+    // Telegram thresholds (in dp)
+    val THRESHOLD_DRAWING = 40.dp   // isDrawing = vr <= 40dp
+    val THRESHOLD_NEAR = 32.dp      // isNear = vr <= 32dp
+    val THRESHOLD_SHAPE_START = 40.dp  // Start shape transition
+    val THRESHOLD_SHAPE_END = 34.dp    // End shape transition (fully rounded rect)
+    val THRESHOLD_ALPHA_START = 32.dp  // Start alpha fade
+    val THRESHOLD_ALPHA_END = 18.dp    // End alpha fade (fully transparent)
+    
+    // Corner radius for rounded rect form (like Telegram's dp(22))
+    val ROUNDED_RECT_RADIUS = 22.dp
+    
     // Animation thresholds  
     const val MERGE_START_PROGRESS = 0.5f
     const val MERGE_COMPLETE_PROGRESS = 0.95f
@@ -54,8 +87,15 @@ object ProfileMetaballConstants {
     const val BLUR_RADIUS = 15f
     const val CUTOFF = 0.5f
     
+    // Blur range for avatar (like Telegram: 2 + (1-fraction) * 20)
+    const val BLUR_MIN = 2f
+    const val BLUR_MAX = 22f
+    
     // Fallback camera size if no notch detected (like status bar rect in Telegram)
     val FALLBACK_CAMERA_SIZE = 12.dp
+    
+    // Y position offset when fully collapsed (Telegram: -dp(29))
+    val COLLAPSED_Y_OFFSET = (-29).dp
 }
 
 /**
@@ -84,75 +124,181 @@ private const val ProfileMetaballShaderSource = """
 
 /**
  * State for avatar position and size during animation
+ * Like Telegram's ProfileMetaballView state variables
  */
 private data class AvatarState(
     val centerX: Float,
     val centerY: Float,
-    val radius: Float,
-    val opacity: Float,
-    val showBlob: Boolean
+    val radius: Float,           // vr in Telegram
+    val opacity: Float,          // alpha / 255f
+    val showBlob: Boolean,
+    val isDrawing: Boolean,      // vr <= 40dp
+    val isNear: Boolean,         // vr <= 32dp
+    val cornerRadius: Float,     // For rounded rect transition
+    val blurRadius: Float        // Blur amount when near
 )
 
 /**
  * Compute avatar state based on collapse progress
+ * Exact logic from Telegram's ProfileMetaballView.onDraw() and needLayout()
+ * 
+ * Key formulas from Telegram:
+ * - avatarScale = lerp(intoSize, 96, diff) / 100f  (where intoSize = 24 or notch width/2)
+ * - avatarY = lerp(endY, startY, diff)  (endY = notch center, startY = statusBar + actionBar - dp(21))
+ * - vr = view.getWidth() * view.getScaleX() * 0.5f  (half of scaled avatar width)
  */
 private fun computeAvatarState(
-    collapseProgress: Float,
-    expansionProgress: Float,
+    collapseProgress: Float,      // 0 = expanded, 1 = collapsed into notch
+    expansionProgress: Float,     // 0 = normal, 1 = pulled down to full screen
     screenWidthPx: Float,
     statusBarHeightPx: Float,
     headerHeightPx: Float,
-    avatarSizeExpandedPx: Float,
-    avatarSizeMinPx: Float,
-    hasAvatar: Boolean
+    avatarSizeExpandedPx: Float,  // Normal avatar size (96dp in Telegram terms)
+    avatarSizeMinPx: Float,       // Into notch size (24dp or notch width)
+    hasAvatar: Boolean,
+    // Notch info
+    notchCenterY: Float,
+    notchRadiusPx: Float,
+    // Telegram thresholds in pixels
+    dp40: Float,
+    dp34: Float,
+    dp32: Float,
+    dp18: Float,
+    dp22: Float,  // Corner radius for rounded rect
+    fullCornerRadius: Float  // Full circle corner radius
 ): AvatarState {
-    val sharpExpansion = sqrt(expansionProgress.toDouble()).toFloat()
+    // ═══════════════════════════════════════════════════════════════
+    // TELEGRAM LOGIC: diff = 1 - collapseProgress (for us)
+    // diff = how "expanded" the avatar is (1 = fully expanded, 0 = collapsed)
+    // ═══════════════════════════════════════════════════════════════
+    val diff = 1f - collapseProgress
     
-    // Calculate radius
+    // ═══════════════════════════════════════════════════════════════
+    // RADIUS (vr in Telegram)
+    // Telegram: avatarScale = lerp(intoSize, 96, diff) / 100f
+    // Then: vr = view.getWidth() * avatarScale * 0.5f
+    // For us: view.getWidth() = avatarSizeExpandedPx (base size)
+    // ═══════════════════════════════════════════════════════════════
     val radius: Float = when {
-        hasAvatar && collapseProgress < 0.1f && expansionProgress > 0f -> {
-            // Expanding to full screen
-            val expandedRadius = screenWidthPx / 2f
-            lerpFloat(avatarSizeExpandedPx / 2f, expandedRadius, sharpExpansion)
+        // Pull-down expansion (like Telegram isPulledDown)
+        hasAvatar && expansionProgress > 0f -> {
+            // Telegram: avatarScale = lerp(96/42, 138/42, min(1, expandProgress*3)) / 100f * 42f
+            val expandScale = lerpFloat(
+                avatarSizeExpandedPx / 2f,      // Normal radius
+                screenWidthPx / 2f,              // Full screen width / 2
+                expansionProgress
+            )
+            expandScale
         }
+        // Collapsing into notch
         collapseProgress > 0f -> {
-            // Collapsing - shrink avatar
-            val shrinkProgress = (collapseProgress / ProfileMetaballConstants.MERGE_COMPLETE_PROGRESS).coerceIn(0f, 1f)
-            lerpFloat(avatarSizeExpandedPx / 2f, avatarSizeMinPx / 2f, shrinkProgress)
+            // Telegram: avatarScale = lerp(intoSize, 96, diff) / 100f
+            // vr = baseWidth * avatarScale * 0.5
+            val intoSize = notchRadiusPx * 2f  // Target size = notch diameter
+            val normalSize = avatarSizeExpandedPx
+            val avatarWidth = lerpFloat(intoSize, normalSize, diff)
+            avatarWidth / 2f  // radius = half of width
         }
+        // Normal state
         else -> avatarSizeExpandedPx / 2f
     }
     
-    // Center X is always screen center
+    // ═══════════════════════════════════════════════════════════════
+    // Telegram thresholds
+    // ═══════════════════════════════════════════════════════════════
+    val isDrawing = radius <= dp40
+    val isNear = radius <= dp32
+    
+    // ═══════════════════════════════════════════════════════════════
+    // CENTER X - always screen center
+    // ═══════════════════════════════════════════════════════════════
     val centerX = screenWidthPx / 2f
     
-    // Calculate Y position
-    val defaultCenterY = statusBarHeightPx + (headerHeightPx - statusBarHeightPx) / 2f + 20f
-    val targetY = statusBarHeightPx / 2f // Target: center of status bar (camera area)
+    // ═══════════════════════════════════════════════════════════════
+    // CENTER Y - Telegram: avatarY = lerp(endY, startY, diff)
+    // endY = notch center (or -dp(29) if no notch)
+    // startY = statusBarHeight + actionBarHeight - dp(21) + some offset
+    // ═══════════════════════════════════════════════════════════════
+    val startY = statusBarHeightPx + (headerHeightPx - statusBarHeightPx) / 2f + 20f  // Normal center
+    val endY = notchCenterY  // Target = notch center
     
     val centerY: Float = when {
-        hasAvatar && collapseProgress < 0.1f && expansionProgress > 0f -> {
-            lerpFloat(defaultCenterY, headerHeightPx / 2f, sharpExpansion)
+        // Pull-down expansion
+        hasAvatar && expansionProgress > 0f -> {
+            lerpFloat(startY, headerHeightPx / 2f, expansionProgress)
         }
+        // Collapsing - animate Y towards notch
         else -> {
-            lerpFloat(defaultCenterY, targetY, collapseProgress)
+            lerpFloat(endY, startY, diff)
         }
     }
     
-    // Opacity
-    val opacity: Float = when {
-        collapseProgress < ProfileMetaballConstants.MERGE_START_PROGRESS -> 1f
-        collapseProgress >= ProfileMetaballConstants.MERGE_COMPLETE_PROGRESS -> 0f
-        else -> {
-            val mergeProgress = (collapseProgress - ProfileMetaballConstants.MERGE_START_PROGRESS) /
-                    (ProfileMetaballConstants.MERGE_COMPLETE_PROGRESS - ProfileMetaballConstants.MERGE_START_PROGRESS)
-            (1f - mergeProgress).coerceIn(0f, 1f)
+    // ═══════════════════════════════════════════════════════════════
+    // CORNER RADIUS - Shape transition
+    // Telegram: аватарка остаётся КРУГЛОЙ пока тянешь!
+    // Квадратной становится только при полном раскрытии (isPulledDown)
+    // Переход круг→квадрат начинается при expansionProgress > 0.8
+    // ═══════════════════════════════════════════════════════════════
+    val cornerRadius: Float = when {
+        // EXPANDED - переход к квадрату начинается только после 80% expansion
+        expansionProgress > 0f -> {
+            // Telegram: квадрат только при полном раскрытии
+            // До 80% - остаётся круглым, после 80% - быстро переходит в квадрат
+            val squareProgress = ((expansionProgress - 0.8f) / 0.2f).coerceIn(0f, 1f)
+            lerpFloat(fullCornerRadius, 0f, squareProgress)
         }
+        // COLLAPSING - переход круг → rounded rect (like Telegram)
+        isDrawing -> {
+            // Telegram: lerp(dp(22), radius, clamp01((vr - dp(34)) / dp(6)))
+            val shapeProgress = ((radius - dp34) / (dp40 - dp34)).coerceIn(0f, 1f)
+            val roundRadiusCollapse = lerpFloat(dp22, fullCornerRadius, shapeProgress)
+            // Telegram: scaledRadius = vr / dp(22) * roundRadiusCollapse
+            (radius / dp22) * roundRadiusCollapse
+        }
+        // NORMAL - полный круг
+        else -> fullCornerRadius
+    }
+    
+    // ═══════════════════════════════════════════════════════════════
+    // OPACITY - Telegram: alpha changes from 1 to 0 when vr 32dp→18dp
+    // float fraction = Math.max(0f, vr - dp(18)) / dp(32 - 18);
+    // float alphaFraction = lerp(0f, 1f, fraction);
+    // ═══════════════════════════════════════════════════════════════
+    val opacity: Float = if (isNear) {
+        val fraction = max(0f, radius - dp18) / (dp32 - dp18)
+        lerpFloat(0f, 1f, fraction)
+    } else {
+        1f
+    }
+    
+    // ═══════════════════════════════════════════════════════════════
+    // BLUR RADIUS - Telegram: 2 + (1 - fraction) * 20
+    // More blur as avatar gets closer to notch
+    // ═══════════════════════════════════════════════════════════════
+    val blurRadius: Float = if (isNear) {
+        val fraction = max(0f, radius - dp18) / (dp32 - dp18)
+        ProfileMetaballConstants.BLUR_MIN + (1f - fraction) * (ProfileMetaballConstants.BLUR_MAX - ProfileMetaballConstants.BLUR_MIN)
+    } else {
+        0f
     }
     
     val showBlob = collapseProgress < ProfileMetaballConstants.MERGE_COMPLETE_PROGRESS && radius > 1f
     
-    return AvatarState(centerX, centerY, radius, opacity, showBlob)
+    // DEBUG LOG
+    Log.d("Metaball", "collapse=$collapseProgress, expansion=$expansionProgress, radius=$radius, diff=$diff")
+    Log.d("Metaball", "centerY=$centerY, cornerRadius=$cornerRadius, isDrawing=$isDrawing, isNear=$isNear")
+    
+    return AvatarState(
+        centerX = centerX,
+        centerY = centerY,
+        radius = radius,
+        opacity = opacity,
+        showBlob = showBlob,
+        isDrawing = isDrawing,
+        isNear = isNear,
+        cornerRadius = cornerRadius,
+        blurRadius = blurRadius
+    )
 }
 
 private fun lerpFloat(start: Float, stop: Float, fraction: Float): Float {
@@ -226,8 +372,15 @@ fun ProfileMetaballOverlay(
         }
     }
     
-    // Avatar state
-    val avatarState by remember(collapseProgress, expansionProgress, screenWidthPx, statusBarHeightPx, headerHeightPx, hasAvatar) {
+    // Telegram thresholds in pixels
+    val dp40 = with(density) { ProfileMetaballConstants.THRESHOLD_DRAWING.toPx() }
+    val dp34 = with(density) { ProfileMetaballConstants.THRESHOLD_SHAPE_END.toPx() }
+    val dp32 = with(density) { ProfileMetaballConstants.THRESHOLD_NEAR.toPx() }
+    val dp18 = with(density) { ProfileMetaballConstants.THRESHOLD_ALPHA_END.toPx() }
+    val dp22 = with(density) { ProfileMetaballConstants.ROUNDED_RECT_RADIUS.toPx() }
+    
+    // Avatar state - computed with Telegram's exact logic
+    val avatarState by remember(collapseProgress, expansionProgress, screenWidthPx, statusBarHeightPx, headerHeightPx, hasAvatar, notchCenterY, notchRadiusPx) {
         derivedStateOf {
             computeAvatarState(
                 collapseProgress = collapseProgress,
@@ -237,7 +390,15 @@ fun ProfileMetaballOverlay(
                 headerHeightPx = headerHeightPx,
                 avatarSizeExpandedPx = avatarSizeExpandedPx,
                 avatarSizeMinPx = avatarSizeMinPx,
-                hasAvatar = hasAvatar
+                hasAvatar = hasAvatar,
+                notchCenterY = notchCenterY,
+                notchRadiusPx = notchRadiusPx,
+                dp40 = dp40,
+                dp34 = dp34,
+                dp32 = dp32,
+                dp18 = dp18,
+                dp22 = dp22,
+                fullCornerRadius = avatarSizeExpandedPx / 2f  // Full circle = radius
             )
         }
     }
@@ -255,95 +416,101 @@ fun ProfileMetaballOverlay(
     val distance = avatarState.centerY - notchCenterY
     val maxDist = avatarSizeExpandedPx
     val c = (distance / maxDist).coerceIn(-1f, 1f)
-    val v = ((1f - c / 1.3f) / 2f).coerceIn(0f, 0.8f)
     
-    // Like Telegram: isDrawing = vr <= dp(40), isNear = vr <= dp(32)
-    // Avatar radius thresholds (in px)
-    val dp40 = with(density) { 40.dp.toPx() }
-    val dp32 = with(density) { 32.dp.toPx() }
-    
-    // Should we draw the metaball effect? (when avatar is small enough)
-    val isDrawing = avatarState.radius <= dp40
-    val isNear = avatarState.radius <= dp32
-    
-    // Show connector only when avatar is close enough AND small enough
-    val showConnector = isDrawing && avatarState.showBlob && distance < maxDist * 1.5f
-    
-    // Calculate blur intensity for avatar based on distance to notch (like Telegram)
-    // When avatar is far - no blur, when close - more blur
-    val avatarBlurRadius = if (showConnector) {
-        // More blur as avatar gets closer to notch
-        val nearProgress = (1f - (distance / maxDist).coerceIn(0f, 1f))
-        (nearProgress * ProfileMetaballConstants.BLUR_RADIUS * 0.5f).coerceIn(0f, 10f)
+    // Like Telegram: when NOT near, reduce v
+    // float near = isNear ? 1f : 1f - (vr - dp(32)) / dp(40 - 32);
+    // v = Math.min(lerp(0f, 0.2f, near), v);
+    val baseV = ((1f - c / 1.3f) / 2f).coerceIn(0f, 0.8f)
+    val near = if (avatarState.isNear) 1f else 1f - (avatarState.radius - dp32) / (dp40 - dp32)
+    val v = if (!avatarState.isNear) {
+        min(lerpFloat(0f, 0.2f, near), baseV)
     } else {
-        0f
+        baseV
     }
     
+    // Show connector only when avatar is small enough (like Telegram isDrawing)
+    // AND not when expanding (no metaball effect when expanded)
+    val showConnector = expansionProgress == 0f && avatarState.isDrawing && avatarState.showBlob && distance < maxDist * 1.5f
+    
+    // Don't show black metaball shapes when expanded
+    val showMetaballLayer = expansionProgress == 0f
+    
     Box(modifier = modifier.fillMaxSize()) {
         // LAYER 1: Metaball shapes with blur effect (BLACK shapes only)
-        Canvas(
-            modifier = Modifier
-                .fillMaxSize()
-                .graphicsLayer {
-                    metaShader.setFloatUniform("cutoff", ProfileMetaballConstants.CUTOFF)
-                    // IMPORTANT: First blur, THEN threshold shader
-                    // createChainEffect(outer, inner) - inner is applied first
-                    val blurEffect = RenderEffect.createBlurEffect(
-                        ProfileMetaballConstants.BLUR_RADIUS,
-                        ProfileMetaballConstants.BLUR_RADIUS,
-                        Shader.TileMode.DECAL
-                    )
-                    val thresholdEffect = RenderEffect.createRuntimeShaderEffect(metaShader, "composable")
-                    // Chain: blur first (inner), then threshold (outer)
-                    renderEffect = RenderEffect.createChainEffect(thresholdEffect, blurEffect)
-                        .asComposeRenderEffect()
-                }
-        ) {
-            val paint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG).apply {
-                color = android.graphics.Color.BLACK
-                style = android.graphics.Paint.Style.FILL
-            }
-            
-            drawIntoCanvas { canvas ->
-                val nativeCanvas = canvas.nativeCanvas
-                
-                // Draw notch/camera circle (small circle at top)
-                if (showConnector) {
-                    if (notchInfo != null && notchInfo.isLikelyCircle) {
-                        // Draw circle at actual notch position
-                        nativeCanvas.drawCircle(
-                            notchCenterX,
-                            notchCenterY,
-                            notchRadiusPx,
-                            paint
+        // HIDDEN when expanded - only show avatar content
+        if (showMetaballLayer) {
+            Canvas(
+                modifier = Modifier
+                    .fillMaxSize()
+                    .graphicsLayer {
+                        metaShader.setFloatUniform("cutoff", ProfileMetaballConstants.CUTOFF)
+                        // IMPORTANT: First blur, THEN threshold shader
+                        // createChainEffect(outer, inner) - inner is applied first
+                        val blurEffect = RenderEffect.createBlurEffect(
+                            ProfileMetaballConstants.BLUR_RADIUS,
+                            ProfileMetaballConstants.BLUR_RADIUS,
+                            Shader.TileMode.DECAL
                         )
-                    } else if (notchInfo != null && notchInfo.isAccurate && notchInfo.path != null) {
-                        // Draw actual notch path
-                        nativeCanvas.drawPath(notchInfo.path, paint)
-                    } else if (notchInfo != null) {
-                        // Draw rounded rect for non-accurate notch
-                        val bounds = notchInfo.bounds
-                        val rad = kotlin.math.max(bounds.width(), bounds.height()) / 2f
-                        nativeCanvas.drawRoundRect(bounds, rad, rad, paint)
-                    } else {
-                        // No notch - draw small circle at status bar center
-                        nativeCanvas.drawCircle(
-                            screenWidthPx / 2f,
-                            statusBarHeightPx / 2f,
-                            notchRadiusPx,
+                        val thresholdEffect = RenderEffect.createRuntimeShaderEffect(metaShader, "composable")
+                        // Chain: blur first (inner), then threshold (outer)
+                        renderEffect = RenderEffect.createChainEffect(thresholdEffect, blurEffect)
+                            .asComposeRenderEffect()
+                    }
+            ) {
+                val paint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG).apply {
+                    color = android.graphics.Color.BLACK
+                    style = android.graphics.Paint.Style.FILL
+                }
+                
+                drawIntoCanvas { canvas ->
+                    val nativeCanvas = canvas.nativeCanvas
+                    
+                    // Draw notch/camera circle (small circle at top)
+                    if (showConnector) {
+                        if (notchInfo != null && notchInfo.isLikelyCircle) {
+                            // Draw circle at actual notch position
+                            nativeCanvas.drawCircle(
+                                notchCenterX,
+                                notchCenterY,
+                                notchRadiusPx,
+                                paint
+                            )
+                        } else if (notchInfo != null && notchInfo.isAccurate && notchInfo.path != null) {
+                            // Draw actual notch path
+                            nativeCanvas.drawPath(notchInfo.path, paint)
+                        } else if (notchInfo != null) {
+                            // Draw rounded rect for non-accurate notch
+                            val bounds = notchInfo.bounds
+                            val rad = kotlin.math.max(bounds.width(), bounds.height()) / 2f
+                            nativeCanvas.drawRoundRect(bounds, rad, rad, paint)
+                        } else {
+                            // No notch - draw small circle at status bar center
+                            nativeCanvas.drawCircle(
+                                screenWidthPx / 2f,
+                                statusBarHeightPx / 2f,
+                                notchRadiusPx,
                             paint
                         )
                     }
                 }
                 
-                // Draw avatar circle
+                // Draw avatar shape - circle or rounded rect depending on state
                 if (avatarState.showBlob) {
-                    nativeCanvas.drawCircle(
-                        avatarState.centerX,
-                        avatarState.centerY,
-                        avatarState.radius,
-                        paint
-                    )
+                    val cx = avatarState.centerX
+                    val cy = avatarState.centerY
+                    val r = avatarState.radius
+                    val cornerR = avatarState.cornerRadius
+                    
+                    // If cornerRadius is close to radius, draw circle; otherwise rounded rect
+                    if (cornerR >= r * 0.95f) {
+                        // Draw circle
+                        nativeCanvas.drawCircle(cx, cy, r, paint)
+                    } else {
+                        // Draw rounded rect (like Telegram when isDrawing)
+                        android.graphics.RectF(cx - r, cy - r, cx + r, cy + r).let { rect ->
+                            nativeCanvas.drawRoundRect(rect, cornerR, cornerR, paint)
+                        }
+                    }
                 }
                 
                 // Draw metaball connector path
@@ -359,26 +526,43 @@ fun ProfileMetaballOverlay(
                 }
             }
         }
+        } // END if (showMetaballLayer)
         
-        // LAYER 2: Actual avatar content - with blur when close to notch
+        // LAYER 2: Actual avatar content - with blur and shape transition like Telegram
         if (avatarState.showBlob) {
-            val avatarSizeDp = with(density) { (avatarState.radius * 2f).toDp() }
-            val avatarOffsetX = with(density) { (avatarState.centerX - avatarState.radius).toDp() }
-            val avatarOffsetY = with(density) { (avatarState.centerY - avatarState.radius).toDp() }
+            // При раскрытии - занимаем всю ширину экрана и всю высоту header'а
+            val isExpanded = expansionProgress > 0f
+            val avatarWidthDp = with(density) { 
+                if (isExpanded) screenWidth else (avatarState.radius * 2f).toDp() 
+            }
+            val avatarHeightDp = with(density) { 
+                if (isExpanded) headerHeight else (avatarState.radius * 2f).toDp() 
+            }
+            val avatarOffsetX = with(density) { 
+                if (isExpanded) 0.dp else (avatarState.centerX - avatarState.radius).toDp() 
+            }
+            val avatarOffsetY = with(density) { 
+                if (isExpanded) 0.dp else (avatarState.centerY - avatarState.radius).toDp() 
+            }
+            
+            // Corner radius from state - transitions from circle to rounded rect
+            val cornerRadiusDp = with(density) { avatarState.cornerRadius.toDp() }
             
             Box(
                 modifier = Modifier
                     .offset(x = avatarOffsetX, y = avatarOffsetY)
-                    .width(avatarSizeDp)
-                    .height(avatarSizeDp)
-                    .clip(RoundedCornerShape(avatarSizeDp / 2))
+                    .width(avatarWidthDp)
+                    .height(avatarHeightDp)
+                    // Use dynamic corner radius - circle → rounded rect transition
+                    .clip(RoundedCornerShape(cornerRadiusDp))
                     .graphicsLayer {
                         alpha = avatarState.opacity
-                        // Apply blur to avatar when close to notch (like Telegram)
-                        if (avatarBlurRadius > 0.5f) {
+                        // Apply blur to avatar when near notch (like Telegram)
+                        // Telegram: blurRadius = 2 + (1 - fraction) * 20
+                        if (avatarState.blurRadius > 0.5f) {
                             renderEffect = RenderEffect.createBlurEffect(
-                                avatarBlurRadius,
-                                avatarBlurRadius,
+                                avatarState.blurRadius,
+                                avatarState.blurRadius,
                                 Shader.TileMode.DECAL
                             ).asComposeRenderEffect()
                         }
@@ -392,6 +576,7 @@ fun ProfileMetaballOverlay(
 
 /**
  * Compat version for older Android - simple animation without metaball effect
+ * Still includes shape transition (circle → rounded rect) but no blur/gooey effects
  */
 @Composable
 fun ProfileMetaballOverlayCompat(
@@ -414,6 +599,17 @@ fun ProfileMetaballOverlayCompat(
     val avatarSizeExpandedPx = with(density) { ProfileMetaballConstants.AVATAR_SIZE_EXPANDED.toPx() }
     val avatarSizeMinPx = with(density) { ProfileMetaballConstants.AVATAR_SIZE_MIN.toPx() }
     
+    // Fallback notch values for compat mode
+    val notchCenterY = statusBarHeightPx / 2f
+    val notchRadiusPx = with(density) { ProfileMetaballConstants.FALLBACK_CAMERA_SIZE.toPx() }
+    
+    // Telegram thresholds in pixels
+    val dp40 = with(density) { ProfileMetaballConstants.THRESHOLD_DRAWING.toPx() }
+    val dp34 = with(density) { ProfileMetaballConstants.THRESHOLD_SHAPE_END.toPx() }
+    val dp32 = with(density) { ProfileMetaballConstants.THRESHOLD_NEAR.toPx() }
+    val dp18 = with(density) { ProfileMetaballConstants.THRESHOLD_ALPHA_END.toPx() }
+    val dp22 = with(density) { ProfileMetaballConstants.ROUNDED_RECT_RADIUS.toPx() }
+    
     val avatarState by remember(collapseProgress, expansionProgress, screenWidthPx, statusBarHeightPx, headerHeightPx, hasAvatar) {
         derivedStateOf {
             computeAvatarState(
@@ -424,23 +620,43 @@ fun ProfileMetaballOverlayCompat(
                 headerHeightPx = headerHeightPx,
                 avatarSizeExpandedPx = avatarSizeExpandedPx,
                 avatarSizeMinPx = avatarSizeMinPx,
-                hasAvatar = hasAvatar
+                hasAvatar = hasAvatar,
+                notchCenterY = notchCenterY,
+                notchRadiusPx = notchRadiusPx,
+                dp40 = dp40,
+                dp34 = dp34,
+                dp32 = dp32,
+                dp18 = dp18,
+                dp22 = dp22,
+                fullCornerRadius = avatarSizeExpandedPx / 2f
             )
         }
     }
     
     Box(modifier = modifier.fillMaxSize()) {
         if (avatarState.showBlob) {
-            val avatarSizeDp = with(density) { (avatarState.radius * 2f).toDp() }
-            val avatarOffsetX = with(density) { (avatarState.centerX - avatarState.radius).toDp() }
-            val avatarOffsetY = with(density) { (avatarState.centerY - avatarState.radius).toDp() }
+            // При раскрытии - занимаем всю ширину экрана и всю высоту header'а
+            val isExpanded = expansionProgress > 0f
+            val avatarWidthDp = with(density) { 
+                if (isExpanded) screenWidth else (avatarState.radius * 2f).toDp() 
+            }
+            val avatarHeightDp = with(density) { 
+                if (isExpanded) headerHeight else (avatarState.radius * 2f).toDp() 
+            }
+            val avatarOffsetX = with(density) { 
+                if (isExpanded) 0.dp else (avatarState.centerX - avatarState.radius).toDp() 
+            }
+            val avatarOffsetY = with(density) { 
+                if (isExpanded) 0.dp else (avatarState.centerY - avatarState.radius).toDp() 
+            }
+            val cornerRadiusDp = with(density) { avatarState.cornerRadius.toDp() }
             
             Box(
                 modifier = Modifier
                     .offset(x = avatarOffsetX, y = avatarOffsetY)
-                    .width(avatarSizeDp)
-                    .height(avatarSizeDp)
-                    .clip(RoundedCornerShape(avatarSizeDp / 2))
+                    .width(avatarWidthDp)
+                    .height(avatarHeightDp)
+                    .clip(RoundedCornerShape(cornerRadiusDp))
                     .graphicsLayer {
                         alpha = avatarState.opacity
                     },

app/src/main/java/com/rosetta/messenger/ui/settings/ProfileScreen.kt

@@ -7,6 +7,7 @@ import android.net.Uri
 import androidx.activity.compose.BackHandler
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
+import android.util.Log
 import androidx.compose.animation.*
 import androidx.compose.animation.core.*
 import androidx.compose.foundation.*
@@ -290,12 +291,13 @@ fun ProfileScreen(
     val maxScrollOffset = expandedHeightPx - collapsedHeightPx
 
     // Track scroll offset for collapsing (скролл вверх = collapse)
+    // Telegram: extraHeight - напрямую от позиции первого элемента
     var scrollOffset by remember { mutableFloatStateOf(0f) }
 
     // Calculate collapse progress (0 = expanded, 1 = collapsed)
-    val collapseProgress by remember {
-        derivedStateOf { (scrollOffset / maxScrollOffset).coerceIn(0f, 1f) }
-    }
+    // Telegram: diff = (extraHeight - actionsHeight) / headerOnlyExtraHeight
+    // Напрямую без derivedStateOf для плавности
+    val collapseProgress = (scrollOffset / maxScrollOffset).coerceIn(0f, 1f)
 
     // Dynamic header height based on scroll
     val headerHeight =
@@ -304,40 +306,46 @@ fun ProfileScreen(
             }
 
     // Track overscroll offset for avatar expansion (скролл вниз при достижении верха)
+    // Telegram: когда extraHeight > headerExtraHeight - это isPulledDown
     var overscrollOffset by remember { mutableFloatStateOf(0f) }
     val maxOverscroll = with(density) { 200.dp.toPx() }
-    val snapThreshold = maxOverscroll * 0.5f
+    val snapThreshold = maxOverscroll * 0.33f  // Telegram: expandProgress >= 0.33f
 
     // Track if user is currently dragging
     var isDragging by remember { mutableStateOf(false) }
+    
+    // Track if fully expanded (snapped to full)
+    var isFullyExpanded by remember { mutableStateOf(false) }
 
-    // Целевое значение для snap: либо 0 (круг), либо maxOverscroll (квадрат)
-    val snapTarget by remember {
-        derivedStateOf {
-            if (!isDragging && overscrollOffset > snapThreshold) maxOverscroll
-            else if (!isDragging) 0f else overscrollOffset
-        }
+    // Smooth snap animation - только когда отпустили палец
+    // Telegram использует CubicBezierInterpolator.EASE_BOTH для snap
+    val targetOverscroll = when {
+        isDragging -> overscrollOffset  // Во время drag - напрямую
+        isFullyExpanded -> maxOverscroll  // Зафиксировано в раскрытом
+        overscrollOffset > snapThreshold -> maxOverscroll  // Snap к раскрытому
+        else -> 0f  // Snap к закрытому
     }
-
-    // Быстрая snap-анимация без застревания
-    val animatedOverscroll by
-            animateFloatAsState(
-                    targetValue = snapTarget,
-                    animationSpec =
-                            spring(
-                                    dampingRatio = Spring.DampingRatioMediumBouncy, // Меньше пружинистости
-                                    stiffness = 4000f // Очень быстрый snap
-                            ),
-                    label = "overscroll"
-            )
+    
+    val animatedOverscroll by animateFloatAsState(
+        targetValue = targetOverscroll,
+        animationSpec = tween(
+            durationMillis = if (isDragging) 0 else 250,  // Мгновенно при drag, плавно при snap
+            easing = FastOutSlowInEasing  // Как Telegram's EASE_BOTH
+        ),
+        label = "overscroll"
+    )
 
     // Calculate expansion progress (0 = круг, 1 = квадрат) - только когда header раскрыт
-    val expansionProgress by remember {
-        derivedStateOf {
-            if (collapseProgress > 0.1f) 0f // Не расширяем если header коллапсирован
-            else (animatedOverscroll / maxOverscroll).coerceIn(0f, 1f)
-        }
+    // Telegram: expandProgress = (extraHeight - headerExtraHeight) / (listWidth - actionBarHeight - headerOnlyExtraHeight)
+    val expansionProgress = when {
+        collapseProgress > 0.1f -> 0f  // Не расширяем если header коллапсирован
+        isDragging -> (overscrollOffset / maxOverscroll).coerceIn(0f, 1f)  // Напрямую при drag
+        else -> (animatedOverscroll / maxOverscroll).coerceIn(0f, 1f)  // Анимированно при snap
     }
+    
+    // DEBUG LOGS
+    Log.d("ProfileScroll", "scrollOffset=$scrollOffset, collapseProgress=$collapseProgress")
+    Log.d("ProfileScroll", "overscrollOffset=$overscrollOffset, expansionProgress=$expansionProgress, isDragging=$isDragging")
 
     // Nested scroll connection для collapsing + overscroll
     val nestedScrollConnection = remember {
@@ -353,6 +361,10 @@ fun ProfileScreen(
                         val newOffset = (overscrollOffset + delta).coerceAtLeast(0f)
                         val consumed = overscrollOffset - newOffset
                         overscrollOffset = newOffset
+                        // Если вышли из fully expanded - сбросить флаг
+                        if (overscrollOffset < maxOverscroll * 0.9f) {
+                            isFullyExpanded = false
+                        }
                         return Offset(0f, -consumed)
                     }
                     // Затем коллапсируем header
@@ -382,7 +394,8 @@ fun ProfileScreen(
             ): Offset {
                 // Если достигли верха (scrollOffset = 0) и тянем вниз - создаем overscroll
                 if (available.y > 0 && scrollOffset == 0f) {
-                    val resistance = 0.5f // Легче тянуть (было 0.3f)
+                    // Telegram: if (!isPulledDown) dy /= 2
+                    val resistance = if (isFullyExpanded) 1f else 0.5f
                     val delta = available.y * resistance
                     overscrollOffset = (overscrollOffset + delta).coerceAtMost(maxOverscroll)
                     return Offset(0f, available.y)
@@ -392,6 +405,10 @@ fun ProfileScreen(
 
             override suspend fun onPostFling(consumed: Velocity, available: Velocity): Velocity {
                 isDragging = false
+                // Если перешли порог - зафиксировать как fully expanded
+                if (overscrollOffset > snapThreshold) {
+                    isFullyExpanded = true
+                }
                 return Velocity.Zero
             }
         }