qml: PasswordDialog: show error on invalid password

Currently the PasswordDialog on QML would just close if the user enters
an incorrect password. This is confusing as the user doesn't know why
the dialog closed and if it initiated any action or not.

With the change the PasswordDialog will get the ability to show an error
message and will show "Invalid Password" if an incorrect password is
entered.
I also used it for the password unification warning ("Need to enter
similar password ...") instead of showing a separate popup.

electrum/gui/qml/components/PasswordDialog.qml

@@ -14,8 +14,10 @@ ElDialog {
     iconSource: Qt.resolvedUrl('../../icons/lock.png')
 
     property bool confirmPassword: false
-    property string password
     property string infotext
+    property string errorMessage
+
+    signal passwordEntered(string password)
 
     anchors.centerIn: parent
     width: parent.width * 4/5
@@ -84,6 +86,16 @@ ElDialog {
                     password: pw_1.text
                 }
             }
+
+            Label {
+                Layout.maximumWidth: parent.width
+                Layout.alignment: Qt.AlignHCenter
+                text: errorMessage
+                wrapMode: Text.Wrap
+                visible: errorMessage
+                color: constants.colorError
+                font.pixelSize: constants.fontSizeLarge
+            }
         }
 
         FlatButton {
@@ -92,10 +104,13 @@ ElDialog {
             icon.source: '../../icons/confirmed.png'
             enabled: confirmPassword ? pw_1.text.length >= 6 && pw_1.text == pw_2.text : true
             onClicked: {
-                password = pw_1.text
-                passworddialog.doAccept()
+                passwordEntered(pw_1.text)
             }
         }
     }
 
+    function clearPassword() {
+        pw_1.text = ""
+        pw_2.text = ""
+    }
 }

electrum/gui/qml/components/WalletDetails.qml

@@ -473,12 +473,13 @@ Pane {
                 title: qsTr('Enter new password'),
                 infotext: qsTr('If you forget your password, you\'ll need to restore from seed. Please make sure you have your seed stored safely')
             })
-            dialog.accepted.connect(function() {
-                var success = Daemon.setPassword(dialog.password)
+            dialog.passwordEntered.connect(function(password) {
+                dialog.close()
+                var success = Daemon.setPassword(password)
                 if (success && Biometrics.isEnabled) {
                     if (Biometrics.isAvailable) {
                         // also update the biometric authentication
-                        Biometrics.enable(dialog.password)
+                        Biometrics.enable(password)
                     } else {
                         // disable biometric authentication as it is not available
                         Biometrics.disable()
@@ -538,23 +539,25 @@ Pane {
                         ? "\n\n" + qsTr('The new password needs to match the password of any other existing wallet.')
                         : "")
             })
-            dialog.accepted.connect(function() {
+            dialog.passwordEntered.connect(function(password) {
                 if (Config.walletShouldUseSinglePassword  // android
                         && Daemon.availableWallets.rowCount() > 1  // has more than one wallet
-                        && Daemon.numWalletsWithPassword(dialog.password) < 1  // no other wallet uses this new password
+                        && Daemon.numWalletsWithPassword(password) < 1  // no other wallet uses this new password
                 ) {
-                    var success = false
-                    var error_msg = [
+                    dialog.errorMessage = [
                         qsTr('You need to use the password of any other existing wallet.'),
                         qsTr('Using different wallet passwords is not supported.'),
                     ].join("\n")
+                    dialog.clearPassword()
+                    return
                 } else {
-                    var success = Daemon.currentWallet.setPassword(dialog.password)
+                    var success = Daemon.currentWallet.setPassword(password)
                     if (success && Config.walletShouldUseSinglePassword) {
-                        Daemon.singlePassword = dialog.password
+                        Daemon.singlePassword = password
                     }
                     var error_msg = qsTr('Password change failed')
                 }
+                dialog.close()
                 if (success && Biometrics.isEnabled) {
                     // unlikely to happen as this means the user somehow moved from
                     // a unified password to differing passwords

electrum/gui/qml/components/main.qml

@@ -852,11 +852,13 @@ ApplicationWindow
         // 'payment_auth' should have been converted to 'wallet' at this point
         if (method === 'wallet' || method === 'wallet_password_only') {
             var dialog = app.passwordDialog.createObject(app, authMessage ? {'title': authMessage} : {})
-            dialog.accepted.connect(function() {
-                if (Daemon.currentWallet.verifyPassword(dialog.password)) {
+            dialog.passwordEntered.connect(function(password) {
+                if (Daemon.currentWallet.verifyPassword(password)) {
+                    dialog.close()
                     qtobject.authProceed()
                 } else {
-                    qtobject.authCancel()
+                    dialog.clearPassword()
+                    dialog.errorMessage = qsTr("Invalid Password")
                 }
             })
             dialog.rejected.connect(function() {