datatransferimage: improve memory usage

+ Reduce listview caching' size by 50%
+ use sourceSize to compress images and speedup loading
+ use autoTransform: true to rotate images when needed

Change-Id: Idf1babdc73f43aa6a79b89428c25c5d06856c0ef
GitLab: #649

src/commoncomponents/DataTransferMessageDelegate.qml

@@ -255,9 +255,13 @@ Loader {
                     asynchronous: true
                     width: sourceComponent.width
                     height: sourceComponent.height
-                    sourceComponent: mediaInfo.isImage !== undefined ?
-                                         imageComp : mediaInfo.isAnimatedImage !== undefined ? animatedImageComp :
-                                         avComp
+                    sourceComponent: {
+                        if (mediaInfo.isImage)
+                            return imageComp
+                        if (mediaInfo.isAnimatedImage)
+                            return animatedImageComp
+                        return avComp
+                    }
                     Component {
                         id: avComp
                         WebEngineView {
@@ -316,7 +320,7 @@ Loader {
                             fillMode: Image.PreserveAspectCrop
                             mipmap: true
                             antialiasing: true
-                            autoTransform: false
+                            autoTransform: true
                             asynchronous: true
                             source: "file:///" + Body
                             property real aspectRatio: implicitWidth / implicitHeight
@@ -361,8 +365,10 @@ Loader {
                             fillMode: Image.PreserveAspectCrop
                             mipmap: true
                             antialiasing: true
-                            autoTransform: false
+                            autoTransform: true
                             asynchronous: true
+                            sourceSize.width: width
+                            sourceSize.height: height
                             source: "file:///" + Body
                             property real aspectRatio: implicitWidth / implicitHeight
                             property real adjustedWidth: Math.min(maxSize,

src/mainview/components/MessageListView.qml

@@ -174,8 +174,8 @@ JamiListView {
     width: parent.width
     // this offscreen caching is pretty huge
     // displayMarginEnd may be removed
-    displayMarginBeginning: 4096
-    displayMarginEnd: 4096
+    displayMarginBeginning: 2048
+    displayMarginEnd: 2048
     maximumFlickVelocity: 2048
     verticalLayoutDirection: ListView.BottomToTop
     boundsBehavior: Flickable.StopAtBounds