more accurate computation of transaction fees.

gui/gui_classic.py

@@ -795,6 +795,10 @@ class ElectrumWindow(QMainWindow):
             self.show_message(str(e))
             return
 
+        if tx.requires_fee(self.wallet.verifier) and fee == 0:
+            QMessageBox.warning(self, _('Error'), _("This transaction requires a fee, or it will not be propagated by the network."), _('OK'))
+            return
+
         self.run_hook('send_tx', tx)
 
         if label: 
@@ -1928,8 +1932,8 @@ class ElectrumWindow(QMainWindow):
         fee_e = QLineEdit()
         fee_e.setText("%s"% str( Decimal( self.wallet.fee)/100000000 ) )
         grid_wallet.addWidget(fee_e, 0, 2)
-        msg = _('Fee per transaction input. Transactions involving multiple inputs tend to require a higher fee.') + ' ' \
-            + _('Recommended value') + ': 0.001'
+        msg = _('Fee per kilobyte of transaction.') + ' ' \
+            + _('Recommended value') + ': 0.0001'
         grid_wallet.addWidget(HelpButton(msg), 0, 3)
         fee_e.textChanged.connect(lambda: numbify(fee_e,False))
         if not self.config.is_modifiable('fee'):

gui/gui_gtk.py

@@ -198,7 +198,7 @@ def run_settings_dialog(wallet, parent):
     fee_entry.connect('changed', numbify, False)
     fee_entry.show()
     fee.pack_start(fee_entry,False,False, 10)
-    add_help_button(fee, 'Fee per transaction input. Transactions involving multiple inputs tend to have a higher fee. Recommended value:0.0005')
+    add_help_button(fee, 'Fee per kilobyte of transaction. Recommended value:0.0001')
     fee.show()
     vbox.pack_start(fee, False,False, 5)
             
@@ -843,6 +843,11 @@ class ElectrumWindow:
         except BaseException, e:
             self.show_message(str(e))
             return
+
+        if tx.requires_fee(self.wallet.verifier) and fee == 0:
+            self.show_message( "This transaction requires a fee, or it will not be propagated by the network." )
+            return
+
             
         if label: 
             self.wallet.labels[tx.hash()] = label