From 592a8cad6d111a23baf6b2bd3fe79c9806e74e4a Mon Sep 17 00:00:00 2001
From: Yuriy Toporovskyy <toporovskyy.y@gmail.com>
Date: Fri, 25 Jun 2021 09:36:47 -0400
Subject: [PATCH] Don't block main thread to load data from file

Signed-off-by: John <jonawals@amazon.com>
---
 .../Code/Source/Previewer/ImagePreviewer.cpp  | 87 ++++++++++++++-----
 .../Code/Source/Previewer/ImagePreviewer.h    | 15 ++++
 2 files changed, 81 insertions(+), 21 deletions(-)

diff --git a/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.cpp b/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.cpp
index fcdc9cd0d3..3cdfb1d15c 100644
--- a/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.cpp
+++ b/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.cpp
@@ -51,6 +51,12 @@ namespace ImageProcessingAtom
 
     ImagePreviewer::~ImagePreviewer()
     {
+        AZ::SystemTickBus::Handler::BusDisconnect();
+
+        if (m_createDisplayTextureResult.isRunning())
+        {
+            m_createDisplayTextureResult.waitForFinished();
+        }
     }
 
     void ImagePreviewer::Clear() const
@@ -214,21 +220,30 @@ namespace ImageProcessingAtom
         m_ui->m_fileInfoCtrl->show();
         m_fileinfo = QString::fromUtf8(product->GetName().c_str());
         m_fileinfo += GetFileSize(product->GetRelativePath().c_str());
-               
-        AZ::Data::Asset<AZ::RPI::StreamingImageAsset> imageAsset = Utils::LoadImageAsset(product->GetAssetId());
-        IImageObjectPtr image = Utils::LoadImageFromImageAsset(imageAsset);
 
-        if (image)
+        CreateAndDisplayTextureItemAsync(
+        [assetId = product->GetAssetId()]
+        () -> CreateDisplayTextureResult
         {
-            // Add product image info
-            AZStd::string productInfo;
-            GetImageInfoString(imageAsset, productInfo);
+            AZ::Data::Asset<AZ::RPI::StreamingImageAsset> imageAsset = Utils::LoadImageAsset(assetId);
+            IImageObjectPtr image = Utils::LoadImageFromImageAsset(imageAsset);
 
-            m_fileinfo += QStringLiteral("\r\n");
-            m_fileinfo += productInfo.c_str();
+            if (image)
+            {
+                // Add product image info
+                AZStd::string productInfo;
+                GetImageInfoString(imageAsset, productInfo);
 
-            m_previewImageObject = ConvertImageForPreview(image);
-        }
+                QString fileInfo = QStringLiteral("\r\n");
+                fileInfo += productInfo.c_str();
+
+                return { ConvertImageForPreview(image), fileInfo };
+            }
+            else
+            {
+                return { nullptr, "" };
+            }
+        });
 
         DisplayTextureItem();
     }
@@ -239,19 +254,28 @@ namespace ImageProcessingAtom
         m_fileinfo = QString::fromUtf8(source->GetName().c_str());
         m_fileinfo += GetFileSize(source->GetFullPath().c_str());
 
-        IImageObjectPtr image = IImageObjectPtr(LoadImageFromFile(source->GetFullPath()));
-
-        if (image)
+        CreateAndDisplayTextureItemAsync(
+        [fullPath = source->GetFullPath()]
+        () -> CreateDisplayTextureResult
         {
-            // Add source image info
-            AZStd::string sourceInfo;
-            GetImageInfoString(image, sourceInfo);
+            IImageObjectPtr image = IImageObjectPtr(LoadImageFromFile(fullPath));
 
-            m_fileinfo += QStringLiteral("\r\n");
-            m_fileinfo += sourceInfo.c_str();
+            if (image)
+            {
+                // Add source image info
+                AZStd::string sourceInfo;
+                GetImageInfoString(image, sourceInfo);
 
-            m_previewImageObject = ConvertImageForPreview(image);
-        }
+                QString fileInfo = QStringLiteral("\r\n");
+                fileInfo += sourceInfo.c_str();
+
+                return { ConvertImageForPreview(image), fileInfo };
+            }
+            else
+            {
+                return { nullptr, "" };
+            }
+        });
 
         DisplayTextureItem();
     }
@@ -289,6 +313,27 @@ namespace ImageProcessingAtom
         updateGeometry();
     }
 
+    template<class CreateFn>
+    void ImagePreviewer::CreateAndDisplayTextureItemAsync(CreateFn create)
+    {
+        AZ::SystemTickBus::Handler::BusConnect();
+        m_createDisplayTextureResult = QtConcurrent::run(AZStd::move(create));
+    }
+
+    void ImagePreviewer::OnSystemTick()
+    {
+        if (m_createDisplayTextureResult.isFinished())
+        {
+            CreateDisplayTextureResult result = m_createDisplayTextureResult.result();
+            m_previewImageObject = AZStd::move(result.first);
+            m_fileinfo += result.second;
+
+            AZ::SystemTickBus::Handler::BusDisconnect();
+
+            DisplayTextureItem();
+        }
+    }
+
     void ImagePreviewer::PreviewSubImage(uint32_t mip)
     {
         QImage previewImage = GetSubImagePreview(m_previewImageObject, mip);
diff --git a/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.h b/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.h
index 3b487f3d95..9e7066c20c 100644
--- a/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.h
+++ b/Gems/Atom/Asset/ImageProcessingAtom/Code/Source/Previewer/ImagePreviewer.h
@@ -13,12 +13,15 @@
 
 #if !defined(Q_MOC_RUN)
 #include <AzCore/Memory/SystemAllocator.h>
+#include <AzCore/Component/TickBus.h>
 #include <AzToolsFramework/AssetBrowser/Previewer/Previewer.h>
 
 #include <Atom/ImageProcessing/ImageObject.h>
 
 #include <QWidget>
 #include <QScopedPointer>
+#include <QFuture>
+#include <QtConcurrent/QtConcurrent>
 #endif
 
 namespace Ui
@@ -42,6 +45,7 @@ namespace ImageProcessingAtom
 {
     class ImagePreviewer
         : public AzToolsFramework::AssetBrowser::Previewer
+        , private AZ::SystemTickBus::Handler
     {
         Q_OBJECT
     public:
@@ -65,16 +69,27 @@ namespace ImageProcessingAtom
         QString GetFileSize(const char* path);
 
         void DisplayTextureItem();
+        template<class CreateFn>
+        void CreateAndDisplayTextureItemAsync(CreateFn create);
+
         void PreviewSubImage(uint32_t mip);
 
         // QLabel word wrap does not break long words such as filenames, so manual word wrap needed
         static QString WordWrap(const QString& string, int maxLength);
 
+        // SystemTickBus
+        void OnSystemTick() override;
+
         QScopedPointer<Ui::ImagePreviewerClass> m_ui;
         QString m_fileinfo;
         QString m_name = "ImagePreviewer";
 
         // Decompressed image in preview. Cache it so we can preview its sub images
         IImageObjectPtr m_previewImageObject;
+
+        // Properties for tracking the status of an asynchronous request to display an asset browser entry
+        using CreateDisplayTextureResult = AZStd::pair<IImageObjectPtr, QString>;
+
+        QFuture<CreateDisplayTextureResult> m_createDisplayTextureResult;
     };
 }//namespace ImageProcessingAtom