Add inner shadows to media thumbnails.

Signal/src/ViewControllers/ConversationView/Cells/OWSBubbleShapeView.h

@@ -24,11 +24,16 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, nullable) UIColor *strokeColor;
 @property (nonatomic) CGFloat strokeThickness;
 
+@property (nonatomic, nullable) UIColor *innerShadowColor;
+@property (nonatomic) CGFloat innerShadowRadius;
+@property (nonatomic) float innerShadowOpacity;
+
 - (instancetype)init NS_UNAVAILABLE;
 
 + (OWSBubbleShapeView *)bubbleDrawView;
 + (OWSBubbleShapeView *)bubbleShadowView;
 + (OWSBubbleShapeView *)bubbleClipView;
++ (OWSBubbleShapeView *)bubbleInnerShadowView;
 
 @end
 

Signal/src/ViewControllers/ConversationView/Cells/OWSBubbleShapeView.m

@@ -13,6 +13,7 @@ typedef NS_ENUM(NSUInteger, OWSBubbleShapeViewMode) {
     OWSBubbleShapeViewMode_Draw,
     OWSBubbleShapeViewMode_Shadow,
     OWSBubbleShapeViewMode_Clip,
+    OWSBubbleShapeViewMode_InnerShadow,
 };
 
 @interface OWSBubbleShapeView ()
@@ -71,6 +72,13 @@ typedef NS_ENUM(NSUInteger, OWSBubbleShapeViewMode) {
     return instance;
 }
 
++ (OWSBubbleShapeView *)bubbleInnerShadowView
+{
+    OWSBubbleShapeView *instance = [OWSBubbleShapeView new];
+    instance.mode = OWSBubbleShapeViewMode_InnerShadow;
+    return instance;
+}
+
 - (void)setFillColor:(nullable UIColor *)fillColor
 {
     _fillColor = fillColor;
@@ -92,6 +100,27 @@ typedef NS_ENUM(NSUInteger, OWSBubbleShapeViewMode) {
     [self updateLayers];
 }
 
+- (void)setInnerShadowColor:(nullable UIColor *)innerShadowColor
+{
+    _innerShadowColor = innerShadowColor;
+
+    [self updateLayers];
+}
+
+- (void)setInnerShadowRadius:(CGFloat)innerShadowRadius
+{
+    _innerShadowRadius = innerShadowRadius;
+
+    [self updateLayers];
+}
+
+- (void)setInnerShadowOpacity:(float)innerShadowOpacity
+{
+    _innerShadowOpacity = innerShadowOpacity;
+
+    [self updateLayers];
+}
+
 - (void)setFrame:(CGRect)frame
 {
     BOOL didChange = !CGRectEqualToRect(self.frame, frame);
@@ -188,6 +217,32 @@ typedef NS_ENUM(NSUInteger, OWSBubbleShapeViewMode) {
             self.maskLayer.path = bezierPath.CGPath;
             self.layer.mask = self.maskLayer;
             break;
+        case OWSBubbleShapeViewMode_InnerShadow: {
+            self.maskLayer.path = bezierPath.CGPath;
+            self.layer.mask = self.maskLayer;
+
+            // Inner shadow.
+            // This should usually not be visible; it is used to distinguish
+            // profile pics from the background if they are similar.
+            self.shapeLayer.frame = self.bounds;
+            self.shapeLayer.masksToBounds = YES;
+            CGRect shadowBounds = self.bounds;
+            UIBezierPath *shadowPath = [bezierPath copy];
+            // This can be any value large enough to cast a sufficiently large shadow.
+            CGFloat shadowInset = -(self.innerShadowRadius * 4.f);
+            [shadowPath
+                appendPath:[UIBezierPath bezierPathWithRect:CGRectInset(shadowBounds, shadowInset, shadowInset)]];
+            // This can be any color since the fill should be clipped.
+            self.shapeLayer.fillColor = UIColor.blackColor.CGColor;
+            self.shapeLayer.path = shadowPath.CGPath;
+            self.shapeLayer.fillRule = kCAFillRuleEvenOdd;
+            self.shapeLayer.shadowColor = self.innerShadowColor.CGColor;
+            self.shapeLayer.shadowRadius = self.innerShadowRadius;
+            self.shapeLayer.shadowOpacity = self.innerShadowOpacity;
+            self.shapeLayer.shadowOffset = CGSizeZero;
+
+            break;
+        }
     }
 
     [CATransaction commit];

Signal/src/ViewControllers/ConversationView/Cells/OWSMessageBubbleView.m

@@ -352,13 +352,14 @@ const UIDataDetectorTypes kOWSAllowedDataDetectorTypes
             if (self.hasBodyMediaWithThumbnail) {
                 [self.stackView addArrangedSubview:bodyMediaView];
 
-                OWSBubbleShapeView *strokeView = [OWSBubbleShapeView bubbleDrawView];
-                strokeView.strokeThickness = CGHairlineWidth();
-                strokeView.strokeColor = (Theme.isDarkThemeEnabled ? [UIColor colorWithWhite:1.f alpha:0.2f]
-                                                                   : [UIColor colorWithWhite:0.f alpha:0.2f]);
-                [bodyMediaView addSubview:strokeView];
-                [self.bubbleView addPartnerView:strokeView];
-                [self.viewConstraints addObjectsFromArray:[strokeView ows_autoPinToSuperviewEdges]];
+                OWSBubbleShapeView *innerShadowView = [OWSBubbleShapeView bubbleInnerShadowView];
+                innerShadowView.innerShadowColor
+                    = (Theme.isDarkThemeEnabled ? UIColor.ows_whiteColor : UIColor.ows_blackColor);
+                innerShadowView.innerShadowRadius = 0.5f;
+                innerShadowView.innerShadowOpacity = 0.15f;
+                [bodyMediaView addSubview:innerShadowView];
+                [self.bubbleView addPartnerView:innerShadowView];
+                [self.viewConstraints addObjectsFromArray:[innerShadowView ows_autoPinToSuperviewEdges]];
             } else {
                 OWSAssertDebug(self.cellType == OWSMessageCellType_ContactShare);