show balance in sendcoins screen (issue #24)

src/qt/forms/sendcoinsdialog.ui

@@ -75,6 +75,30 @@
        </property>
       </widget>
      </item>
+     <item>
+      <layout class="QHBoxLayout" name="horizontalLayout_2">
+       <property name="spacing">
+        <number>3</number>
+       </property>
+       <item>
+        <widget class="QLabel" name="label">
+         <property name="text">
+          <string>Balance:</string>
+         </property>
+        </widget>
+       </item>
+       <item>
+        <widget class="QLabel" name="labelBalance">
+         <property name="text">
+          <string>123.456 BTC</string>
+         </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByKeyboard|Qt::TextSelectableByMouse</set>
+         </property>
+        </widget>
+       </item>
+      </layout>
+     </item>
      <item>
       <spacer name="horizontalSpacer">
        <property name="orientation">

src/qt/sendcoinsdialog.cpp

@@ -36,6 +36,9 @@ void SendCoinsDialog::setModel(WalletModel *model)
             entry->setModel(model);
         }
     }
+
+    setBalance(model->getBalance(), model->getUnconfirmedBalance());
+    connect(model, SIGNAL(balanceChanged(qint64, qint64)), this, SLOT(setBalance(qint64, qint64)));
 }
 
 SendCoinsDialog::~SendCoinsDialog()
@@ -241,3 +244,10 @@ void SendCoinsDialog::handleURL(const QUrl *url)
     }
     pasteEntry(rv);
 }
+
+void SendCoinsDialog::setBalance(qint64 balance, qint64 unconfirmedBalance)
+{
+    Q_UNUSED(unconfirmedBalance);
+    int unit = model->getOptionsModel()->getDisplayUnit();
+    ui->labelBalance->setText(BitcoinUnits::formatWithUnit(unit, balance));
+}

src/qt/sendcoinsdialog.h

@@ -37,6 +37,7 @@ public slots:
     void accept();
     SendCoinsEntry *addEntry();
     void updateRemoveEnabled();
+    void setBalance(qint64 balance, qint64 unconfirmedBalance);
 
 private:
     Ui::SendCoinsDialog *ui;