BUG: Improve placement of CallTipWidget

Only the vertical placement of the CallTipWidget was being checked.
Now add checks for horizontal placement as well.

IPython/frontend/qt/console/call_tip_widget.py

@@ -157,17 +157,49 class CallTipWidget(QtGui.QLabel):
         self.resize(self.sizeHint())
 
         # Locate and show the widget. Place the tip below the current line
-        # unless it would be off the screen. In that case, place it above
-        # the current line.
+        # unless it would be off the screen.  In that case, decide the best
+        # location based trying to minimize the  area that goes off-screen.
         padding = 3 # Distance in pixels between cursor bounds and tip box.
         cursor_rect = text_edit.cursorRect(cursor)
         screen_rect = QtGui.qApp.desktop().screenGeometry(text_edit)
         point = text_edit.mapToGlobal(cursor_rect.bottomRight())
         point.setY(point.y() + padding)
         tip_height = self.size().height()
+        tip_width = self.size().width()
+
+        vertical = 'bottom'
+        horizontal = 'Right'
         if point.y() + tip_height > screen_rect.height():
-            point = text_edit.mapToGlobal(cursor_rect.topRight())
+            point_ = text_edit.mapToGlobal(cursor_rect.topRight())
+            # If tip is still off screen, check if point is in top or bottom
+            # half of screen.
+            if point_.y() - tip_height < padding:
+                # If point is in upper half of screen, show tip below it.
+                # otherwise above it.
+                if 2*point.y() < screen_rect.height():
+                    vertical = 'bottom'
+                else:
+                    vertical = 'top'
+            else:
+                vertical = 'top'
+        if point.x() + tip_width > screen_rect.width():
+            point_ = text_edit.mapToGlobal(cursor_rect.topRight())
+            # If tip is still off-screen, check if point is in the right or
+            # left half of the screen.
+            if point_.x() - tip_width < padding:
+                if 2*point.x() < screen_rect.width():
+                    horizontal = 'Right'
+                else:
+                    horizontal = 'Left'
+            else:
+                horizontal = 'Left'
+        pos = getattr(cursor_rect, '%s%s' %(vertical, horizontal))
+        point = text_edit.mapToGlobal(pos())
+        if vertical == 'top':
             point.setY(point.y() - tip_height - padding)
+        if horizontal == 'Left':
+            point.setX(point.x() - tip_width - padding)
+
         self.move(point)
         self.show()
         return True