Fix Freeseer#501 Warn user about losing new talk info

When the user switches from one talk to another or creates a new talk
when the currently selected talk has unsaved changes, a window comes up
asking the user if they wish to save their changes, with the options
"Yes", "No", and "Cancel". "Yes" saves the changes and selects the new
talk; "No" selects the new talk without saving the changes; and
"Cancel" keeps the current talk selected without discarding or saving
any changes made.

Fix Freeseer#501
Close Freeseer#605

src/freeseer/frontend/talkeditor/talkeditor.py

@@ -26,6 +26,7 @@
 
 # PyQt modules
 from PyQt4.QtCore import SIGNAL
+from PyQt4.QtCore import QPersistentModelIndex
 from PyQt4.QtCore import QStringList
 from PyQt4.QtCore import Qt
 from PyQt4.QtGui import QAbstractItemView
@@ -93,6 +94,9 @@ def __init__(self, config, db):
         self.mainLayout.addWidget(self.importTalksWidget)
         # --- End Layout
 
+        # Keep track of index of the most recently selected talk
+        self.currentTalkIndex = QPersistentModelIndex()
+
         # Initialize geometry, to be used for restoring window positioning.
         self.geometry = None
 
@@ -112,9 +116,9 @@ def __init__(self, config, db):
         #
         # TableView Connections
         #
-        self.connect(self.tableView, SIGNAL('activated(const QModelIndex)'), self.talk_selected)
-        self.connect(self.tableView, SIGNAL('selected(const QModelIndex)'), self.talk_selected)
-        self.connect(self.tableView, SIGNAL('clicked(const QModelIndex)'), self.talk_selected)
+        self.connect(self.tableView, SIGNAL('activated(const QModelIndex)'), self.click_talk)
+        self.connect(self.tableView, SIGNAL('selected(const QModelIndex)'), self.click_talk)
+        self.connect(self.tableView, SIGNAL('clicked(const QModelIndex)'), self.click_talk)
 
         # Import Widget
         self.connect(self.importTalksWidget.csvRadioButton, SIGNAL('toggled(bool)'), self.toggle_import)
@@ -130,7 +134,7 @@ def __init__(self, config, db):
         self.connect(self.actionRemoveAll, SIGNAL('triggered()'), self.confirm_reset)
 
         # Command Buttons
-        self.connect(self.commandButtons.addButton, SIGNAL('clicked()'), self.show_new_talk_popup)
+        self.connect(self.commandButtons.addButton, SIGNAL('clicked()'), self.click_add_button)
         self.connect(self.commandButtons.removeButton, SIGNAL('clicked()'), self.remove_talk)
         self.connect(self.commandButtons.removeAllButton, SIGNAL('clicked()'), self.confirm_reset)
         self.connect(self.commandButtons.importButton, SIGNAL('clicked()'), self.show_import_talks_widget)
@@ -283,10 +287,54 @@ def search_talks(self):
         self.proxy.setFilterKeyColumn(-1)
         self.proxy.setFilterFixedString(self.commandButtons.searchLineEdit.text())
 
+    def show_save_prompt(self):
+        confirm = QMessageBox.question(self,
+                                       "Unsaved Changes Exist",
+                                       "Save changes to current talk?",
+                                       QMessageBox.Yes | QMessageBox.No | QMessageBox.Cancel,
+                                       QMessageBox.Yes)
+        return confirm
+
+    def click_talk(self, model):
+        log.info("User selected row %d", model.row())
+        modelRow = model.row()
+        if self.unsaved_details_exist():
+            confirm = self.show_save_prompt()
+            if confirm == QMessageBox.Yes:
+                log.info("User chose to SAVE")
+                self.tableView.selectRow(self.currentTalkIndex.row())
+                self.update_talk()
+                newModel = self.tableView.currentIndex().sibling(modelRow, 0)
+                self.select_talk(newModel)
+            elif confirm == QMessageBox.No:
+                log.info("User chose to DISCARD")
+                self.talk_selected(model)
+            else:
+                log.info("User chose to CANCEL")
+                self.tableView.selectRow(self.currentTalkIndex.row())
+        else:
+            self.talk_selected(model)
+
+    def click_add_button(self):
+        if self.unsaved_details_exist():
+            confirm = self.show_save_prompt()
+            if confirm == QMessageBox.Yes:
+                log.info("User chose to SAVE")
+                self.update_talk()
+                self.show_new_talk_popup()
+            elif confirm == QMessageBox.No:
+                log.info("User chose to DISCARD")
+                self.show_new_talk_popup()
+            else:
+                log.info("User chose to CANCEL")
+        else:
+            self.show_new_talk_popup()
+
     def talk_selected(self, model):
         self.mapper.setCurrentIndex(model.row())
         self.talkDetailsWidget.enable_input_fields()
         self.talkDetailsWidget.saveButton.setEnabled(False)
+        self.currentTalkIndex = QPersistentModelIndex(model)
 
     def toggle_import(self):
         if self.importTalksWidget.csvRadioButton.isChecked():