qml: add hack to delay rendering of QR until dialog is shown.

unfortunately, using standard QtQuick Image.asynchronous=true leads
to a deadlock at app exit so we can't use it a.t.m.

electrum/gui/qml/components/GenericShareDialog.qml

@@ -58,6 +58,8 @@ ElDialog {
 
             QRImage {
                 id: qr
+                render: dialog.enter ? false : true
+                qrdata: dialog.text_qr ? dialog.text_qr : dialog.text
                 Layout.alignment: Qt.AlignHCenter
                 Layout.topMargin: constants.paddingSmall
                 Layout.bottomMargin: constants.paddingSmall
@@ -108,7 +110,13 @@ ElDialog {
         }
     }
 
-    Component.onCompleted: {
-        qr.qrdata = dialog.text_qr ? dialog.text_qr : dialog.text
+    Connections {
+        target: dialog.enter
+        function onRunningChanged() {
+            console.log('dialog open animation running changed: ' + dialog.enter.running)
+            if (!dialog.enter.running) {
+                qr.render = true
+            }
+        }
     }
 }

electrum/gui/qml/components/RequestDialog.qml

@@ -17,6 +17,8 @@ ElDialog {
     property string _bip21uri
     property string _address
 
+    property bool _render_qr: false // delay qr rendering until dialog is shown
+
     parent: Overlay.overlay
     modal: true
     standardButtons: Dialog.Close
@@ -91,18 +93,21 @@ ElDialog {
                         id: qri_bolt11
                         QRImage {
                             qrdata: _bolt11
+                            render: _render_qr
                         }
                     }
                     Component {
                         id: qri_bip21uri
                         QRImage {
                             qrdata: _bip21uri
+                            render: _render_qr
                         }
                     }
                     Component {
                         id: qri_address
                         QRImage {
                             qrdata: _address
+                            render: _render_qr
                         }
                     }
                 }
@@ -298,4 +303,14 @@ ElDialog {
         wallet: Daemon.currentWallet
         key: dialog.key
     }
+
+    // hack. delay qr rendering until dialog is shown
+    Connections {
+        target: dialog.enter
+        function onRunningChanged() {
+            if (!dialog.enter.running) {
+                dialog._render_qr = true
+            }
+        }
+    }
 }

electrum/gui/qml/components/controls/QRImage.qml

@@ -1,25 +1,40 @@
 import QtQuick 2.6
 
-Image {
+Item {
+    id: root
     property string qrdata
+    property bool render: true // init to false, then set true if render needs delay
+    property var qrprops: QRIP.getDimensions(qrdata)
 
-    source: qrdata ? 'image://qrgen/' + qrdata : ''
+    width: r.width
+    height: r.height
 
     Rectangle {
-        property var qrprops: QRIP.getDimensions(qrdata)
+        id: r
+        width: qrprops.modules * qrprops.box_size
+        height: width
         color: 'white'
-        x: (parent.width - width) / 2
-        y: (parent.height - height) / 2
-        width: qrprops.icon_modules * qrprops.box_size
-        height: qrprops.icon_modules * qrprops.box_size
+    }
+
+    Image {
+        source: qrdata && render ? 'image://qrgen/' + qrdata : ''
+
+        Rectangle {
+            visible: root.render
+            color: 'white'
+            x: (parent.width - width) / 2
+            y: (parent.height - height) / 2
+            width: qrprops.icon_modules * qrprops.box_size
+            height: qrprops.icon_modules * qrprops.box_size
 
-        Image {
-            source: '../../../icons/electrum.png'
-            x: 1
-            y: 1
-            width: parent.width - 2
-            height: parent.height - 2
-            scale: 0.9
+            Image {
+                source: '../../../icons/electrum.png'
+                x: 1
+                y: 1
+                width: parent.width - 2
+                height: parent.height - 2
+                scale: 0.9
+            }
         }
     }
 }