HLoader component, use Loader.asynchronous prop

TODO.md

@@ -2,9 +2,6 @@
   - `QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling)`
 
 - Refactoring
-  - Remove clip props when possible
-  - `property list<thing>`
-  - See Loader.enabled and async
   - Use [Animators](https://doc.qt.io/qt-5/qml-qtquick-animator.html)
   - Sendbox
   - SignIn/RememberAccount screens

src/qml/Base/HLoader.qml

@@ -0,0 +1,6 @@
+import QtQuick 2.12
+
+Loader {
+    asynchronous: true
+    visible: status == Loader.Ready
+}

src/qml/Base/HUIButton.qml

@@ -67,7 +67,7 @@ HBaseButton {
         }
     }
 
-    contentItem: Loader {
+    contentItem: HLoader {
         sourceComponent:
             loading && ! iconName ? loadingOverlay : buttonContent
     }

src/qml/Chat/Chat.qml

@@ -18,7 +18,7 @@ HPage {
 
     readonly property bool hasUnknownDevices: false
 
-    header: Loader {
+    header: HLoader {
         id: roomHeader
         source: ready ? "RoomHeader.qml" : ""
 
@@ -31,7 +31,7 @@ HPage {
     page.leftPadding: 0
     page.rightPadding: 0
 
-    Loader {
+    HLoader {
         source: ready ? "ChatSplitView.qml" : "../Base/HBusyIndicator.qml"
 
         Layout.fillWidth: ready

src/qml/Pages/EditAccount/EditAccount.qml

@@ -46,7 +46,7 @@ HPage {
 
             Layout.preferredHeight: childrenRect.height
 
-            Loader {
+            HLoader {
                 width: parent.width
                 source: ready ?
                         modelData :

src/qml/Window.qml

@@ -29,12 +29,15 @@ ApplicationWindow {
     Shortcuts { id: shortcuts}
     Python    { id: py }
 
-    Loader {
+    HLoader {
         anchors.fill: parent
         source: py.ready ? "" : "LoadingScreen.qml"
     }
 
-    Loader {
+    HLoader {
+        // true makes the initially loaded chat page invisible for some reason
+        asynchronous: false
+
         id: uiLoader
         anchors.fill: parent
         scale: py.ready ? 1 : 0.5