gui: notify the user early if any of the recipients is invalid.

As we are already validating the entire recipient data before adding it to the temporal recipients vector (address and amount), the 'SendCoinsEntry' validation function can just return the proper error code, so it can be processed and the user can be notified right away.

Without requiring to unlock the wallet, nor walk through the entire recipients vector later again on the flow just to validate the same things twice.

Author: furszy

src/qt/sendcoinsdialog.cpp

@@ -252,34 +252,28 @@ SendCoinsDialog::~SendCoinsDialog()
 bool SendCoinsDialog::PrepareSendText(QString& question_string, QString& informative_text, QString& detailed_text)
 {
     QList<SendCoinsRecipient> recipients;
-    bool valid = true;
-
-    for(int i = 0; i < ui->entries->count(); ++i)
-    {
-        SendCoinsEntry *entry = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(i)->widget());
-        if(entry)
-        {
-            if(entry->validate(model->node()))
-            {
-                recipients.append(entry->getValue());
-            }
-            else if (valid)
-            {
+    for (int i = 0; i < ui->entries->count(); ++i) {
+        SendCoinsEntry* entry = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(i)->widget());
+        if (entry) {
+            // Validate recipient and notify user if needed
+            auto res_validate = entry->validate(model->node());
+            if (res_validate.status != WalletModel::OK) {
                 ui->scrollArea->ensureWidgetVisible(entry);
-                valid = false;
+                processSendCoinsReturn(res_validate); // notify user
+                return false; // invalid entry
             }
+
+            recipients.append(entry->getValue());
         }
     }
 
-    if(!valid || recipients.isEmpty())
-    {
+    if (recipients.isEmpty()) {
         return false;
     }
 
     fNewRecipientAllowed = false;
     WalletModel::UnlockContext ctx(model->requestUnlock());
-    if(!ctx.isValid())
-    {
+    if (!ctx.isValid()) {
         // Unlock wallet was cancelled
         fNewRecipientAllowed = true;
         return false;

src/qt/sendcoinsentry.cpp

@@ -131,39 +131,30 @@ void SendCoinsEntry::useAvailableBalanceClicked()
     Q_EMIT useAvailableBalance(this);
 }
 
-bool SendCoinsEntry::validate(interfaces::Node& node)
+WalletModel::SendCoinsReturn SendCoinsEntry::validate(interfaces::Node& node)
 {
-    if (!model)
-        return false;
-
-    // Check input validity
-    bool retval = true;
+    assert(model);
 
-    if (!model->validateAddress(ui->payTo->text()))
-    {
+    // Validate address
+    if (!model->validateAddress(ui->payTo->text())) {
         ui->payTo->setValid(false);
-        retval = false;
-    }
-
-    if (!ui->payAmount->validate())
-    {
-        retval = false;
+        return WalletModel::InvalidAddress;
     }
 
-    // Sending a zero amount is invalid
-    if (ui->payAmount->value(nullptr) <= 0)
-    {
-        ui->payAmount->setValid(false);
-        retval = false;
+    // Validate amount, must be valid and positive
+    if (!ui->payAmount->validate() ||
+        ui->payAmount->value(nullptr) <= 0) {
+        return WalletModel::InvalidAmount;
     }
 
-    // Reject dust outputs:
-    if (retval && GUIUtil::isDust(node, ui->payTo->text(), ui->payAmount->value())) {
+    // Reject dust outputs
+    if (GUIUtil::isDust(node, ui->payTo->text(), ui->payAmount->value())) {
         ui->payAmount->setValid(false);
-        retval = false;
+        return WalletModel::InvalidAmount;
     }
 
-    return retval;
+    // all good
+    return WalletModel::OK;
 }
 
 SendCoinsRecipient SendCoinsEntry::getValue()

src/qt/sendcoinsentry.h

@@ -6,10 +6,10 @@
 #define BITCOIN_QT_SENDCOINSENTRY_H
 
 #include <qt/sendcoinsrecipient.h>
+#include <qt/walletmodel.h> // for Walletmodel::StatusCode
 
 #include <QStackedWidget>
 
-class WalletModel;
 class PlatformStyle;
 
 namespace interfaces {
@@ -34,7 +34,14 @@ class SendCoinsEntry : public QStackedWidget
     ~SendCoinsEntry();
 
     void setModel(WalletModel *model);
-    bool validate(interfaces::Node& node);
+
+    /**
+    * Validates that:
+    * 1) The address is valid (network supported).
+    * 2) The amount is valid and greater than 0.
+    * 3) The amount is not dust.
+    */
+    WalletModel::SendCoinsReturn validate(interfaces::Node& node);
     SendCoinsRecipient getValue();
 
     /** Return whether the entry is still empty and unedited */