[BugFix] Prevent placeholder reset from clearing source image

platform/darwin/common/lynx/LynxEnv.mm

@@ -573,6 +573,16 @@ - (BOOL)enableImageCancelRequest {
   return enableImageCancelRequest;
 }
 
+- (BOOL)enableImagePlaceholderResetFix {
+  static dispatch_once_t onceToken;
+  static BOOL enableImagePlaceholderResetFix = YES;
+  dispatch_once(&onceToken, ^{
+    enableImagePlaceholderResetFix = [self boolFromExternalEnv:LynxEnvEnableImagePlaceholderResetFix
+                                                  defaultValue:YES];
+  });
+  return enableImagePlaceholderResetFix;
+}
+
 - (BOOL)enableImageCIGaussianBlur {
   static dispatch_once_t onceToken;
   static BOOL enableCIGaussianBlur = NO;
@@ -784,6 +794,7 @@ + (NSString *)_keyStringFromType:(LynxEnvKey)key {
     @(LynxEnvEnableImageEventReport) : @"enable_image_event_report",
     @(LynxEnvEnableImageAsyncLayout) : @"enable_image_async_layout",
     @(LynxEnvEnableImageCancelRequest) : @"enable_image_cancel_request",
+    @(LynxEnvEnableImagePlaceholderResetFix) : @"enable_image_placeholder_reset_fix",
     @(LynxEnvEnableImageCIGaussianBlur) : @"enable_image_ci_gaussian_blur",
     @(LynxEnvEnableGenericResourceFetcher) : @"enable_generic_resource_fetcher",
     @(LynxEnvEnableAnimationSyncTimeOpt) : @"enable_animation_sync_time_opt",

platform/darwin/common/lynx/public/LynxEnv.h

@@ -150,6 +150,8 @@ typedef NS_ENUM(NSInteger, LynxMemoryPressureLevel) {
 
 - (BOOL)enableImageCancelRequest;
 
+- (BOOL)enableImagePlaceholderResetFix;
+
 - (BOOL)enableImageCIGaussianBlur;
 
 - (BOOL)getUseNewImage;

platform/darwin/common/lynx/public/LynxEnvKey.h

@@ -49,6 +49,7 @@ typedef NS_ENUM(uint64_t, LynxEnvKey) {
 
   // Internal-only Lynx settings key. Do not mention graphics backend details in the key.
   LynxEnvSetupCanvasSurfaceEarlier,
+  LynxEnvEnableImagePlaceholderResetFix,
 
   // Please add new enum values above
   LynxEnvKeyEndMark,  // Keep this as the last enum value, and do not use

platform/darwin/ios/api/lynx_ios.api

@@ -1508,6 +1508,7 @@ public class LynxEnv : NSObject {
   public BOOL LynxEnv::enableImageEventReport();
   public BOOL LynxEnv::enableImageAsyncLayout();
   public BOOL LynxEnv::enableImageCancelRequest();
+  public BOOL LynxEnv::enableImagePlaceholderResetFix();
   public BOOL LynxEnv::enableImageCIGaussianBlur();
   public BOOL LynxEnv::getUseNewImage();
   public BOOL LynxEnv::enableGenericResourceFetcher();
@@ -6394,6 +6395,7 @@ public enum LynxEnvKey {
   LynxEnvFSPEnable
   LynxEnvFSPConfigJsonString
   LynxEnvSetupCanvasSurfaceEarlier
+  LynxEnvEnableImagePlaceholderResetFix
   LynxEnvKeyEndMark
 }
 

platform/darwin/ios/lynx/ui/image/LynxUIImage.mm

@@ -253,6 +253,7 @@ @interface LynxUIImage () <LynxMeasureDelegate>
 @property(nonatomic, assign) BOOL enableImageEventReport;
 @property(nonatomic, assign) BOOL enableImageAsyncLayout;
 @property(nonatomic, assign) BOOL enableImageCancelRequest;
+@property(nonatomic, assign) BOOL enableImagePlaceholderResetFix;
 @property(nonatomic, assign) BOOL enableGenericFetcher;
 @property(nonatomic, assign) BOOL enableFetchUIImage;
 @property(nonatomic, strong) NSDictionary* additional_custom_info;
@@ -265,6 +266,7 @@ @interface LynxUIImage () <LynxMeasureDelegate>
 @property(nonatomic, assign) LynxImagePlayState playState;
 @property(nonatomic, assign) BOOL keepAnimPlayState;
 @property(nonatomic, assign) CGRect regionToDecode;
+@property(nonatomic, assign) BOOL imageFromSrc;
 @end
 
 @implementation LynxUIImage {
@@ -295,12 +297,14 @@ - (void)initProperties {
   _enableImageEventReport = [LynxEnv.sharedInstance enableImageEventReport];
   _enableImageAsyncLayout = [LynxEnv.sharedInstance enableImageAsyncLayout];
   _enableImageCancelRequest = [LynxEnv.sharedInstance enableImageCancelRequest];
+  _enableImagePlaceholderResetFix = [LynxEnv.sharedInstance enableImagePlaceholderResetFix];
   _frameCacheAutomatically = LynxBooleanOptionUnset;
   _superResolutionScale = 0.0;
   _enableReportInfo = false;
   _playState = LynxImagePlayStateDefault;
   _keepAnimPlayState = NO;
   _regionToDecode = CGRectNull;
+  _imageFromSrc = NO;
 }
 
 - (void)dealloc {
@@ -442,6 +446,7 @@ __block void (^ready)(UIImage*, LynxURL*) = ^(UIImage* image, LynxURL* requestUR
     }
     if (image == nil) {
       [strongSelf setImageToView:image];
+      strongSelf.imageFromSrc = NO;
       return;
     }
     if (strongSelf.enableFadeIn && [strongSelf shouldUseNewImage] && !requestURL.fromMemoryCache) {
@@ -482,6 +487,7 @@ __block void (^ready)(UIImage*, LynxURL*) = ^(UIImage* image, LynxURL* requestUR
 
     if (strongSelf.loopCount <= 0) {
       [strongSelf setImageToView:image];
+      strongSelf.imageFromSrc = requestURL && requestURL.type == LynxImageRequestSrc;
       if (image.images != nil && [image.images count] > 1) {
         strongSelf.view.animationDuration = image.duration;
         if (strongSelf.autoPlay) {
@@ -501,6 +507,7 @@ __block void (^ready)(UIImage*, LynxURL*) = ^(UIImage* image, LynxURL* requestUR
       [[LynxImageLoader imageService] handleAnimatedImage:image
                                                      view:strongSelf.view
                                                 loopCount:strongSelf.loopCount];
+      strongSelf.imageFromSrc = requestURL && requestURL.type == LynxImageRequestSrc;
     }
   };
   if ([NSThread isMainThread]) {
@@ -1245,6 +1252,7 @@ - (void)resetImage {
 
     LynxUIImage* image = (LynxUIImage*)ui;
     image.view.image = nil;
+    image.imageFromSrc = NO;
     if (![[LynxImageLoader imageService] checkImageType:image.view]) {
       image.view.animationImages = nil;
     }
@@ -1273,6 +1281,7 @@ - (NSURL*)illegalUrlHandler:(NSString*)value {
   [self markAsDirty];
   if (requestReset || value == nil) {
     self.image = nil;
+    self.imageFromSrc = NO;
     [self resetImage];
     _src = nil;
     return;
@@ -1302,8 +1311,12 @@ - (NSURL*)illegalUrlHandler:(NSString*)value {
 LYNX_PROP_SETTER("placeholder", setPlaceholder, NSString*) {
   [self markAsDirty];
   if (requestReset || value == nil) {
-    self.image = nil;
-    [self resetImage];
+    if (self.enableImagePlaceholderResetFix && self.imageFromSrc) {
+      // Keep the current src image when only placeholder is reset.
+    } else {
+      self.image = nil;
+      [self resetImage];
+    }
     _placeholder = nil;
     return;
   }
@@ -1314,9 +1327,13 @@ - (NSURL*)illegalUrlHandler:(NSString*)value {
     _placeholder.type = LynxImageRequestPlaceholder;
   }
   if (!newURL || ![newURL.absoluteString isEqualToString:_placeholder.url.absoluteString]) {
-    self.image = nil;
-    if (!_deferSrcInvalidation) {
-      [self resetImage];
+    if (self.enableImagePlaceholderResetFix && self.imageFromSrc) {
+      // Keep the current src image when only placeholder changes.
+    } else {
+      self.image = nil;
+      if (!_deferSrcInvalidation) {
+        [self resetImage];
+      }
     }
     _placeholder.imageSize = CGSizeZero;
     _placeholder.url = newURL;