Merge #9481: [Qt] Show more significant warning if we fall back to the default fee

7abe7bb Qt/Send: Give fallback fee a reasonable indent (Luke Dashjr)
3e4d7bf Qt/Send: Figure a decent warning colour from theme (Luke Dashjr)
c5adf8f [Qt] Show more significant warning if we fall back to the default fee (Jonas Schnelli)

Tree-SHA512: 9e85b5b398d7a49aaf6c42578d63750b1b7aa9cc9e84d008fe21d6c53f1ffe2fb69286a1a764e634ebca3286564615578eea0a1bc883e4b332be8306d9883d14

src/qt/forms/sendcoinsdialog.ui

@@ -759,11 +759,33 @@
             </item>
            </layout>
           </item>
+          <item>
+           <widget class="QLabel" name="fallbackFeeWarningLabel">
+            <property name="toolTip">
+             <string>Using the fallbackfee can result in sending a transaction that will take serval hours or days (or never) to confirm. Consider choosing your fee manually or wait until your have validated the complete chain.</string>
+            </property>
+            <property name="font">
+            <font>
+                <weight>75</weight>
+                <bold>true</bold>
+            </font>
+            </property>
+            <property name="text">
+             <string>Warning: Fee estimation is currently not possible.</string>
+            </property>
+            <property name="wordWrap">
+             <bool>false</bool>
+            </property>
+           </widget>
+          </item>
           <item>
            <spacer name="horizontalSpacer_4">
             <property name="orientation">
              <enum>Qt::Horizontal</enum>
             </property>
+            <property name="sizeType">
+             <enum>QSizePolicy::MinimumExpanding</enum>
+            </property>
             <property name="sizeHint" stdset="0">
              <size>
               <width>40</width>

src/qt/sendcoinsdialog.cpp

@@ -23,6 +23,7 @@
 #include "txmempool.h"
 #include "wallet/wallet.h"
 
+#include <QFontMetrics>
 #include <QMessageBox>
 #include <QScrollBar>
 #include <QSettings>
@@ -656,6 +657,11 @@ void SendCoinsDialog::updateSmartFeeLabel()
                                                                 std::max(CWallet::fallbackFee.GetFeePerK(), CWallet::GetRequiredFee(1000))) + "/kB");
         ui->labelSmartFee2->show(); // (Smart fee not initialized yet. This usually takes a few blocks...)
         ui->labelFeeEstimation->setText("");
+        ui->fallbackFeeWarningLabel->setVisible(true);
+        int lightness = ui->fallbackFeeWarningLabel->palette().color(QPalette::WindowText).lightness();
+        QColor warning_colour(255 - (lightness / 5), 176 - (lightness / 3), 48 - (lightness / 14));
+        ui->fallbackFeeWarningLabel->setStyleSheet("QLabel { color: " + warning_colour.name() + "; }");
+        ui->fallbackFeeWarningLabel->setIndent(QFontMetrics(ui->fallbackFeeWarningLabel->font()).width("x"));
     }
     else
     {
@@ -663,6 +669,7 @@ void SendCoinsDialog::updateSmartFeeLabel()
                                                                 std::max(feeRate.GetFeePerK(), CWallet::GetRequiredFee(1000))) + "/kB");
         ui->labelSmartFee2->hide();
         ui->labelFeeEstimation->setText(tr("Estimated to begin confirmation within %n block(s).", "", estimateFoundAtBlocks));
+        ui->fallbackFeeWarningLabel->setVisible(false);
     }
 
     updateFeeMinimizedLabel();