Merge pull request #604 from CesiumGS/fix-credit-bug

Fix detection of credit image loading

Author: david-lively

CHANGES.md

@@ -6,6 +6,10 @@
 
 - Added option to ignore the `KHR_material_unlit` extension to force default lighting on tilesets. 
 
+##### Fixes :wrench:
+
+- Fixed a bug where `CesiumCreditSystem` did not accurately track the loading progress of images, which could result in missing credits.
+
 ## v1.17.0 - 2025-08-01
 
 ##### Additions :tada:

Runtime/CesiumCreditSystem.cs

@@ -267,14 +267,23 @@ public static CesiumCreditSystem GetDefaultCreditSystem()
             return _defaultCreditSystem;
         }
 
-        internal bool HasLoadingImages()
+        /// <summary>
+        /// Gets the number of images on this credit system that are being loaded.
+        /// </summary>
+        /// <returns>The number of loading images.</returns>
+        internal int GetNumberOfLoadingImages()
         {
-            return this._numLoadingImages > 0;
+            return this._numLoadingImages;
         }
 
+        /// <summary>
+        /// A function invoked with StartCoroutine() to asynchronously load images from an HTML credit.
+        /// </summary>
+        /// <param name="url">A string containing either the base64-encoded image data or the URL of the image.</param>
         internal IEnumerator LoadImage(string url)
         {
             int index = this._images.Count;
+            this._numLoadingImages++;
 
             // Initialize a texture of arbitrary size as a placeholder,
             // so that when other images are loaded, their IDs align properly
@@ -287,23 +296,29 @@ internal IEnumerator LoadImage(string url)
                 // Load an image from a string that contains the
                 // "data:image/png;base64," prefix
                 string byteString = url.Substring(base64Prefix.Length);
-                byte[] bytes = Convert.FromBase64String(byteString);
-                if (!texture.LoadImage(bytes))
+                try
+                {
+                    byte[] bytes = Convert.FromBase64String(byteString);
+                    if (!texture.LoadImage(bytes))
+                    {
+                        Debug.Log("Credit image could not be loaded into Texture2D.");
+                    }
+                }
+                catch (FormatException e)
                 {
-                    Debug.Log("Could not parse image from base64 string.");
+                    Debug.Log("Could not parse credit image from base64 string.");
                 }
             }
             else
             {
                 // Load an image from a URL.
                 UnityWebRequest request = UnityWebRequestTexture.GetTexture(url);
-                this._numLoadingImages++;
                 yield return request.SendWebRequest();
 
                 if (request.result == UnityWebRequest.Result.ConnectionError ||
                     request.result == UnityWebRequest.Result.ProtocolError)
                 {
-                    Debug.Log(request.error);
+                    Debug.LogError(request.error);
                 }
                 else
                 {
@@ -314,10 +329,10 @@ internal IEnumerator LoadImage(string url)
                     UnityLifetime.Destroy(placeholderTexture);
                 }
 
-                this._numLoadingImages--;
             }
 
             texture.wrapMode = TextureWrapMode.Clamp;
+            this._numLoadingImages--;
         }
     }
 }

Runtime/ConfigureReinterop.cs

@@ -495,7 +495,7 @@ public void ExposeToCPP()
             credits.Add(credit);
             credits.Clear();
 
-            if (!creditSystem.HasLoadingImages())
+            if (creditSystem.GetNumberOfLoadingImages() == 0)
             {
                 creditSystem.BroadcastCreditsUpdate();
             }

native~/Runtime/src/CesiumCreditSystemImpl.cpp

@@ -32,7 +32,8 @@ CesiumCreditSystemImpl::CesiumCreditSystemImpl(
     : _pCreditSystem(std::make_shared<CesiumUtility::CreditSystem>()),
       _htmlToUnityCredit(),
       _lastCreditsCount(0),
-      _creditsUpdated(false) {}
+      _lastLoadingImagesCount(0),
+      _shouldBroadcastUpdate(false) {}
 
 CesiumCreditSystemImpl::~CesiumCreditSystemImpl() {}
 
@@ -43,24 +44,32 @@ void CesiumCreditSystemImpl::UpdateCredits(
     return;
   }
 
-  // If the credits were updated in a previous frame, the update will not get
-  // broadcasted until all of the images are fully loaded. Broadcast the
-  // previous update first before handling the next one.
-  if (this->_creditsUpdated && !creditSystem.HasLoadingImages()) {
+  // Images are handled asynchronously by Unity's coroutine system, so their
+  // progress must be accounted for separately.
+  size_t loadingImagesCount = creditSystem.GetNumberOfLoadingImages();
+  if (loadingImagesCount != this->_lastLoadingImagesCount) {
+    this->_shouldBroadcastUpdate = true;
+    this->_lastLoadingImagesCount = loadingImagesCount;
+  }
+
+  // If the credits were updated in a previous frame, do not broadcast the
+  // update until all of the images are fully loaded. Then, broadcast the
+  // previous update before handling the next one.
+  if (this->_shouldBroadcastUpdate && loadingImagesCount == 0) {
     creditSystem.BroadcastCreditsUpdate();
-    this->_creditsUpdated = false;
+    this->_shouldBroadcastUpdate = false;
   }
 
   const CesiumUtility::CreditsSnapshot& credits = _pCreditSystem->getSnapshot();
   const std::vector<CesiumUtility::Credit>& creditsToShowThisFrame =
       credits.currentCredits;
 
   size_t creditsCount = creditsToShowThisFrame.size();
-  this->_creditsUpdated = forceUpdate ||
-                          creditsToShowThisFrame.size() != _lastCreditsCount ||
-                          credits.removedCredits.size() > 0;
+  bool creditsUpdated =
+      forceUpdate || creditsToShowThisFrame.size() != this->_lastCreditsCount ||
+      credits.removedCredits.size() > 0;
 
-  if (this->_creditsUpdated) {
+  if (creditsUpdated) {
     List1<CesiumForUnity::CesiumCredit> popupCredits =
         creditSystem.popupCredits();
     List1<CesiumForUnity::CesiumCredit> onScreenCredits =
@@ -94,8 +103,8 @@ void CesiumCreditSystemImpl::UpdateCredits(
       }
     }
 
-    this->_creditsUpdated = true;
     this->_lastCreditsCount = creditsCount;
+    this->_shouldBroadcastUpdate = true;
   }
 }
 

native~/Runtime/src/CesiumCreditSystemImpl.h

@@ -48,7 +48,8 @@ class CesiumCreditSystemImpl : public CesiumImpl<CesiumCreditSystemImpl> {
       _htmlToUnityCredit;
 
   size_t _lastCreditsCount;
-  bool _creditsUpdated;
+  size_t _lastLoadingImagesCount;
+  bool _shouldBroadcastUpdate;
 };
 
 } // namespace CesiumForUnityNative