Using mouse for editing

TpX hot keys could be learned from the main menu. However, some editing tasks could only be done with mouse. The list follows:

• Click object:  Select object (current selection would be lost)
• Shift-click object:  Add object to selection (current selection would be maintained)
• Double-click object:  Edit object properties
• Drag object:  Move object
• Drag control point:  Move control point of selected object to reshape it
• Ctrl-drag object:  Copy object and drag the copy
• Ctrl-click object/control point:  Add/delete control point of selected object
• Ctrl-Alt-click object:  Break path, making graphical object disjoint
• Wheel:  Move viewport vertically
• Shift-wheel:  Move viewport horizontally
• Ctrl-wheel:  Zoom viewport
• Alt-drag round control point of Bezier curve:   Determines whether the joint is kept smooth.