Fix tall received message bubbles losing their fill in the context menu

Signal.xcodeproj/project.pbxproj

@@ -1772,6 +1772,7 @@
 		88D6E93F254CF712003142D9 /* group_call_leave.aiff in Resources */ = {isa = PBXBuildFile; fileRef = 88D6E93D254CF712003142D9 /* group_call_leave.aiff */; };
 		88D6E940254CF712003142D9 /* group_call_join.aiff in Resources */ = {isa = PBXBuildFile; fileRef = 88D6E93E254CF712003142D9 /* group_call_join.aiff */; };
 		88D6E94325535D49003142D9 /* CVTextTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 88D6E94125535482003142D9 /* CVTextTest.swift */; };
+		A1B2C3D4E5F60718293A4B5D /* CVWallpaperBlurViewTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = A1B2C3D4E5F60718293A4B5C /* CVWallpaperBlurViewTest.swift */; };
 		88DBDFB9263731C800C2101C /* DefaultDisappearingMessageTimerInteraction.swift in Sources */ = {isa = PBXBuildFile; fileRef = 88DBDFB8263731C800C2101C /* DefaultDisappearingMessageTimerInteraction.swift */; };
 		88DBDFBB2638FFBD00C2101C /* audio-played-dot.json in Resources */ = {isa = PBXBuildFile; fileRef = 88DBDFBA2638FFBC00C2101C /* audio-played-dot.json */; };
 		88DF819528E1130900F8BA80 /* SignalProxy+RelayServer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 88DF819428E1130900F8BA80 /* SignalProxy+RelayServer.swift */; };
@@ -6145,6 +6146,7 @@
 		88D6E93D254CF712003142D9 /* group_call_leave.aiff */ = {isa = PBXFileReference; lastKnownFileType = audio.aiff; path = group_call_leave.aiff; sourceTree = "<group>"; };
 		88D6E93E254CF712003142D9 /* group_call_join.aiff */ = {isa = PBXFileReference; lastKnownFileType = audio.aiff; path = group_call_join.aiff; sourceTree = "<group>"; };
 		88D6E94125535482003142D9 /* CVTextTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CVTextTest.swift; sourceTree = "<group>"; };
+		A1B2C3D4E5F60718293A4B5C /* CVWallpaperBlurViewTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CVWallpaperBlurViewTest.swift; sourceTree = "<group>"; };
 		88D7BA9D266809F50088D1C2 /* CallMessageRelay.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CallMessageRelay.swift; sourceTree = "<group>"; };
 		88DBDFB8263731C800C2101C /* DefaultDisappearingMessageTimerInteraction.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DefaultDisappearingMessageTimerInteraction.swift; sourceTree = "<group>"; };
 		88DBDFBA2638FFBC00C2101C /* audio-played-dot.json */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.json; path = "audio-played-dot.json"; sourceTree = "<group>"; };
@@ -9716,6 +9718,7 @@
 				4C6E6C6824241C00009DE948 /* ConversationViewControllerTest.swift */,
 				3463532E256EA525003C5428 /* ConversationViewTest.swift */,
 				88D6E94125535482003142D9 /* CVTextTest.swift */,
+				A1B2C3D4E5F60718293A4B5C /* CVWallpaperBlurViewTest.swift */,
 				F96B66B22912B8B7004FFFAA /* DonateViewControllerTest.swift */,
 				F99D2C8A2926F0DD00748CCB /* DonationPaymentDetailsViewControllerTest.swift */,
 				45C845AE291467F7005F6EA5 /* JournalingOrderedDictionaryTests.swift */,
@@ -19412,6 +19415,7 @@
 				4C6E6C6924241C00009DE948 /* ConversationViewControllerTest.swift in Sources */,
 				34635330256EA52A003C5428 /* ConversationViewTest.swift in Sources */,
 				88D6E94325535D49003142D9 /* CVTextTest.swift in Sources */,
+				A1B2C3D4E5F60718293A4B5D /* CVWallpaperBlurViewTest.swift in Sources */,
 				F93999F628C81F2100E34899 /* DataMessagePaddingTests.swift in Sources */,
 				3494BBE026E66FC30079B11B /* DateUtilTest.swift in Sources */,
 				C17A54962D7B3D9E00E1D267 /* DeviceProvisioningURLTest.swift in Sources */,

Signal/ConversationView/CellViews/CVWallpaperBlurView.swift

@@ -45,10 +45,25 @@ public class CVWallpaperBlurView: ManualLayoutViewWithLayer, CVDimmableView {
         }
     }
 
+    /// The blurred wallpaper image only spans the reference view, so a bubble
+    /// that extends beyond it (e.g. a very tall message in the context menu
+    /// preview) would be left unfilled where the image doesn't reach.
+    static func needsFallbackBackground(bubbleBounds: CGRect, imageFrame: CGRect) -> Bool {
+        return !imageFrame.contains(bubbleBounds)
+    }
+
     public func applyLayout() {
         guard bounds.size.isNonEmpty else { return }
 
         UIView.performWithoutAnimation {
+            if let state, !isPreview, !isReduceTransparencyMode {
+                // The image is opaque, so this is only visible where it doesn't reach.
+                backgroundColor = Self.needsFallbackBackground(
+                    bubbleBounds: bounds,
+                    imageFrame: imageViewFrame,
+                ) ? (state.averageColor ?? Theme.backgroundColor) : nil
+            }
+
             imageView.frame = imageViewFrame
             imageViewMaskLayer.frame = imageView.layer.bounds
             strokeLayer.frame = layer.bounds

Signal/test/ViewControllers/CVWallpaperBlurViewTest.swift

@@ -0,0 +1,104 @@
+//
+// Copyright 2026 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+//
+
+import Testing
+import UIKit
+
+@testable import Signal
+@testable import SignalUI
+
+struct CVWallpaperBlurViewTest {
+
+    // MARK: - Average color
+
+    private func rgba(_ color: UIColor) -> (r: CGFloat, g: CGFloat, b: CGFloat, a: CGFloat) {
+        var r: CGFloat = 0, g: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0
+        color.getRed(&r, green: &g, blue: &b, alpha: &a)
+        return (r, g, b, a)
+    }
+
+    private func makeImage(size: CGSize, draw: (CGContext) -> Void) -> UIImage {
+        let format = UIGraphicsImageRendererFormat()
+        format.scale = 1
+        format.opaque = true
+        return UIGraphicsImageRenderer(size: size, format: format).image { draw($0.cgContext) }
+    }
+
+    @Test
+    func testAverageColorOfSolidImageIsThatColor() throws {
+        let image = makeImage(size: CGSize(width: 40, height: 40)) { context in
+            context.setFillColor(UIColor(red: 0.2, green: 0.4, blue: 0.6, alpha: 1).cgColor)
+            context.fill(CGRect(x: 0, y: 0, width: 40, height: 40))
+        }
+
+        let color = try #require(image.averageColor())
+        let (r, g, b, a) = rgba(color)
+
+        #expect(abs(r - 0.2) < 0.02)
+        #expect(abs(g - 0.4) < 0.02)
+        #expect(abs(b - 0.6) < 0.02)
+        #expect(abs(a - 1) < 0.01)
+    }
+
+    @Test
+    func testAverageColorOfHalfBlackHalfWhiteImageIsMidGray() throws {
+        let image = makeImage(size: CGSize(width: 40, height: 40)) { context in
+            context.setFillColor(UIColor.white.cgColor)
+            context.fill(CGRect(x: 0, y: 0, width: 40, height: 40))
+            context.setFillColor(UIColor.black.cgColor)
+            context.fill(CGRect(x: 0, y: 0, width: 40, height: 20))
+        }
+
+        let color = try #require(image.averageColor())
+        let (r, g, b, _) = rgba(color)
+
+        #expect(abs(r - 0.5) < 0.05)
+        #expect(abs(g - 0.5) < 0.05)
+        #expect(abs(b - 0.5) < 0.05)
+    }
+
+    // MARK: - Fallback background
+
+    @Test
+    func testBubbleFullyCoveredByImageNeedsNoFallback() {
+        let bubbleBounds = CGRect(x: 0, y: 0, width: 326, height: 372)
+        let imageFrame = CGRect(x: -16, y: -351, width: 402, height: 874)
+
+        #expect(!CVWallpaperBlurView.needsFallbackBackground(bubbleBounds: bubbleBounds, imageFrame: imageFrame))
+    }
+
+    @Test
+    func testBubbleExactlyMatchingImageNeedsNoFallback() {
+        let frame = CGRect(x: 0, y: 0, width: 402, height: 874)
+
+        #expect(!CVWallpaperBlurView.needsFallbackBackground(bubbleBounds: frame, imageFrame: frame))
+    }
+
+    /// A very tall message is taller than the screen-sized wallpaper image, so the
+    /// bottom of the bubble has no fill. This is the bug from issue #6356.
+    @Test
+    func testBubbleTallerThanImageNeedsFallback() {
+        let bubbleBounds = CGRect(x: 0, y: 0, width: 326, height: 1820)
+        let imageFrame = CGRect(x: -16, y: -351, width: 402, height: 874)
+
+        #expect(CVWallpaperBlurView.needsFallbackBackground(bubbleBounds: bubbleBounds, imageFrame: imageFrame))
+    }
+
+    @Test
+    func testBubbleStartingAboveImageNeedsFallback() {
+        let bubbleBounds = CGRect(x: 0, y: 0, width: 326, height: 372)
+        let imageFrame = CGRect(x: -16, y: 100, width: 402, height: 874)
+
+        #expect(CVWallpaperBlurView.needsFallbackBackground(bubbleBounds: bubbleBounds, imageFrame: imageFrame))
+    }
+
+    @Test
+    func testBubbleWiderThanImageNeedsFallback() {
+        let bubbleBounds = CGRect(x: 0, y: 0, width: 326, height: 372)
+        let imageFrame = CGRect(x: 0, y: -100, width: 300, height: 874)
+
+        #expect(CVWallpaperBlurView.needsFallbackBackground(bubbleBounds: bubbleBounds, imageFrame: imageFrame))
+    }
+}

SignalUI/UIKitExtensions/UIKit+Image.swift

@@ -69,6 +69,41 @@ public extension UIImageView {
 // MARK: -
 
 public extension UIImage {
+    /// The average color of all the image's pixels, found by drawing the image
+    /// into a single pixel.
+    func averageColor() -> UIColor? {
+        guard let cgImage else { return nil }
+
+        var pixel = [UInt8](repeating: 0, count: 4)
+        let drewPixel = pixel.withUnsafeMutableBytes { buffer -> Bool in
+            guard
+                let context = CGContext(
+                    data: buffer.baseAddress,
+                    width: 1,
+                    height: 1,
+                    bitsPerComponent: 8,
+                    bytesPerRow: 4,
+                    space: CGColorSpaceCreateDeviceRGB(),
+                    bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue,
+                )
+            else { return false }
+            context.interpolationQuality = .high
+            context.draw(cgImage, in: CGRect(x: 0, y: 0, width: 1, height: 1))
+            return true
+        }
+        guard drewPixel else { return nil }
+
+        let alpha = CGFloat(pixel[3]) / 255
+        guard alpha > 0 else { return nil }
+        // The context stores premultiplied components.
+        return UIColor(
+            red: CGFloat(pixel[0]) / 255 / alpha,
+            green: CGFloat(pixel[1]) / 255 / alpha,
+            blue: CGFloat(pixel[2]) / 255 / alpha,
+            alpha: alpha,
+        )
+    }
+
     /// Redraw the image into a new image, with an added background color, and inset the
     /// original image by the provided insets.
     func withBackgroundColor(_ color: UIColor, insets: UIEdgeInsets = .zero) -> UIImage? {

SignalUI/Wallpapers/Wallpaper+SignalUI.swift

@@ -181,6 +181,9 @@ public class WallpaperBlurState: NSObject {
     public let referenceView: UIView
     fileprivate let token: WallpaperBlurToken
 
+    /// The average color of `image`, for filling areas the image doesn't reach.
+    public private(set) lazy var averageColor: UIColor? = image.averageColor()
+
     private static let idCounter = AtomicUInt(0, lock: .sharedGlobal)
     public let id: UInt = WallpaperBlurState.idCounter.increment()