[Qt] improve minimum absolute fee option

- Only display the minimum absolute fee control if CoinControl is enabled

src/qt/sendcoinsdialog.cpp

@@ -585,7 +585,7 @@ void SendCoinsDialog::updateFeeSectionControls()
     ui->checkBoxMinimumFee      ->setEnabled(ui->radioCustomFee->isChecked());
     ui->labelMinFeeWarning      ->setEnabled(ui->radioCustomFee->isChecked());
     ui->radioCustomPerKilobyte  ->setEnabled(ui->radioCustomFee->isChecked() && !ui->checkBoxMinimumFee->isChecked());
-    ui->radioCustomAtLeast      ->setEnabled(ui->radioCustomFee->isChecked() && !ui->checkBoxMinimumFee->isChecked());
+    ui->radioCustomAtLeast      ->setEnabled(ui->radioCustomFee->isChecked() && !ui->checkBoxMinimumFee->isChecked() && CoinControlDialog::coinControl->HasSelected());
     ui->customFee               ->setEnabled(ui->radioCustomFee->isChecked() && !ui->checkBoxMinimumFee->isChecked());
 }
 
@@ -600,7 +600,10 @@ void SendCoinsDialog::updateGlobalFeeVariables()
     {
         nTxConfirmTarget = defaultConfirmTarget;
         payTxFee = CFeeRate(ui->customFee->value());
-        fPayAtLeastCustomFee = ui->radioCustomAtLeast->isChecked();
+
+        // if user has selected to set a minimum absolute fee, pass the value to coincontrol
+        // set nMinimumTotalFee to 0 in case of user has selected that the fee is per KB
+        CoinControlDialog::coinControl->nMinimumTotalFee = ui->radioCustomAtLeast->isChecked() ? ui->customFee->value() : 0;
     }
 
     fSendFreeTransactions = ui->checkBoxFreeTx->isChecked();
@@ -707,8 +710,7 @@ void SendCoinsDialog::coinControlFeatureChanged(bool checked)
     if (!checked && model) // coin control features disabled
         CoinControlDialog::coinControl->SetNull();
 
-    if (checked)
+    coinControlUpdateLabels();
-        coinControlUpdateLabels();
 }
 
 // Coin Control: button inputs -> show actual coin control dialog
@@ -782,9 +784,24 @@ void SendCoinsDialog::coinControlChangeEdited(const QString& text)
 // Coin Control: update labels
 void SendCoinsDialog::coinControlUpdateLabels()
 {
-    if (!model || !model->getOptionsModel() || !model->getOptionsModel()->getCoinControlFeatures())
+    if (!model || !model->getOptionsModel())
         return;
 
+    if (model->getOptionsModel()->getCoinControlFeatures())
+    {
+        // enable minium absolute fee UI controls
+        ui->radioCustomAtLeast->setVisible(true);
+
+        // only enable the feature if inputs are selected
+        ui->radioCustomAtLeast->setEnabled(CoinControlDialog::coinControl->HasSelected());
+    }
+    else
+    {
+        // in case coin control is disabled (=default), hide minimum absolute fee UI controls
+        ui->radioCustomAtLeast->setVisible(false);
+        return;
+    }
+
     // set pay amounts
     CoinControlDialog::payAmounts.clear();
     CoinControlDialog::fSubtractFeeFromAmount = false;