Adds drag and drop of variables onto operations

Very basic as of now, it only replaces the leftmost placeholder with the
variable's name. No type checking.

Also makes clicking an operation replace the current placeholder if one
is selected.

dat/gui/operations.py

@@ -1,14 +1,15 @@
 import re
 from PyQt4 import QtCore, QtGui
 
-from dat import variable_format
+from dat import MIMETYPE_DAT_VARIABLE, variable_format
 from dat.global_data import GlobalManager
 from dat.gui import translate
 from dat.gui.generic import CategorizedListWidget, ConsoleWidget, \
     SingleLineTextEdit
 from dat.operations import is_operator, perform_operation, \
     InvalidOperation, OperationWarning
 from dat.utils import catch_warning
+from dat.vistrail_data import VistrailManager
 
 from vistrails.core.application import get_vistrails_application
 from vistrails.core.packagemanager import get_package_manager
@@ -76,6 +77,26 @@ def focusNextPrevChild(self, forward):
                 self.setSelection(cursor.selectionStart())
             return super(MarkerHighlighterLineEdit, self).focusNextPrevChild(forward)
 
+    def focus_first_marker(self):
+        text = str(self.toPlainText())
+        marker = MarkerHighlighterLineEdit._marker_pattern.search(text)
+        if marker is not None:
+            marker = marker.span()
+            self.setSelection(marker[0], marker[1] - marker[0])
+
+    def has_markers(self):
+        text = str(self.toPlainText())
+        match = MarkerHighlighterLineEdit._marker_pattern.search(text)
+        return match is not None
+
+    def replace_first_marker(self, value):
+        text = str(self.toPlainText())
+        text = MarkerHighlighterLineEdit._marker_pattern.sub(
+                value,
+                text,
+                1)
+        self.setText(text)
+
 
 class OperationItem(QtGui.QTreeWidgetItem):
     def __init__(self, operation, category):
@@ -95,6 +116,8 @@ def __init__(self):
 
         _ = translate(OperationPanel)
 
+        self.setAcceptDrops(True)
+
         self._operations = dict() # VariableOperation -> OperationItem
 
         layout = QtGui.QVBoxLayout()
@@ -140,6 +163,38 @@ def operation_removed(self, operation):
         item = self._operations.pop(operation)
         self._list.removeItem(item, item.category)
 
+    def dragEnterEvent(self, event):
+        mimeData = event.mimeData()
+        if (mimeData.hasFormat(MIMETYPE_DAT_VARIABLE) and
+                self._input_line.has_markers() and
+                VistrailManager().get_variable(
+                    str(mimeData.data(MIMETYPE_DAT_VARIABLE))) is not None):
+            event.accept()
+        else:
+            event.ignore()
+
+    def dragMoveEvent(self, event):
+        mimeData = event.mimeData()
+        if mimeData.hasFormat(MIMETYPE_DAT_VARIABLE):
+            event.setDropAction(QtCore.Qt.CopyAction)
+            event.accept()
+        else:
+            event.ignore()
+
+    def dropEvent(self, event):
+        mimeData = event.mimeData()
+        if (mimeData.hasFormat(MIMETYPE_DAT_VARIABLE) and
+                self._input_line.has_markers()):
+            varname = str(mimeData.data(MIMETYPE_DAT_VARIABLE))
+            variable = VistrailManager().get_variable(varname)
+            if variable is not None:
+                self._input_line.replace_first_marker(varname)
+                event.accept()
+                self._input_line.setFocus(QtCore.Qt.MouseFocusReason)
+                self._input_line.focus_first_marker()
+                return
+        event.ignore()
+
     def operation_clicked(self, item, column=0):
         if not isinstance(item, OperationItem):
             return
@@ -158,7 +213,22 @@ def operation_clicked(self, item, column=0):
                 append += ')'
             else:
                 append += '\0\0)'
-        text = str(self._input_line.text()) + append
+
+        text = str(self._input_line.text())
+        cursor = self._input_line.textCursor()
+        # If a placeholder is selected
+        selection = str(cursor.selectedText())
+        marker = MarkerHighlighterLineEdit._marker_pattern.match(selection)
+        if marker is not None and marker.end() == len(selection):
+            # Replace it with the new operation
+            text = (
+                    text[:self._input_line.textCursor().selectionStart()] +
+                    append +
+                    text[self._input_line.textCursor().selectionEnd()])
+        # Else
+        else:
+            # Just append
+            text = text + append
         pos = text.find('\0')
         pos = pos, text.find('\0', pos + 1) - 1
         text = text[:pos[0]] + text[pos[0] + 1:pos[1] + 1] + text[pos[1] + 2:]