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<!DOCTYPE language SYSTEM "klayout_doc.dtd">

<doc>

  <title>Partial Editing</title>
  <keyword name="Editing"/>
  <keyword name="Partial mode"/>

  <p>
  When objects have to be modified after the have been created, partial editing comes into play. 
  "Partial" refers to the fact that just parts of a polygon or path are edited. For example, just one
  vertex or an edge of a polygon can be moved. Partial editing mode also allows deleting single vertices or
  edges or to insert new ones. In partial editing mode, multiple edges or vertices can be selected, even a 
  whole shape can be selected and can then be moved or deleted.
  </p>

  <p>
  When moving the selected parts, the movement direction constraint applies. 
  See <link href="/manual/editor_options.xml"/> for details about the modes
  available. For example, in manhattan mode, only horizontal and vertical movements of parts are allowed.
  Again, the global movement constraint can be overridden by pressing Shift (orthogonal), Ctrl (diagonal) or 
  both Shift and Ctrl (any angle) while moving the mouse.
  </p>

  <p>
  To enter partial mode, click on the "Partial" button in the toolbar.
  Parts (edges or vertices) can then be selected either by simply clicking at them or by dragging a selection rectangle.
  As in normal selection mode, the modifier buttons Shift and Ctrl can be used to add a selection to
  the existing one or to remove elements from the existing selection. Partial selection is subject to the 
  "top level only" constraint (see <link href="/manual/editor_options.xml"/> for a description of the top level selection mode).
  </p>

  <p>
  Simply clicking at an item immediately enters "move" mode. In this mode, you can position the element at the desired
  target location and place it there by left-clicking at the position. Press "ESC" to cancel the operation.
  When a complex selection is made, move mode is entered by clicking at one of the selected items (the edges
  or vertices, not the shape to which they belong). While you move, two edit boxes are shown at the top of 
  the layout view. Press the Tab key to enter these edit fields. You can specify explicit move distances there.
  Press the Enter key to apply them or the Escape key to leave these edit fields.
  </p>

  <p>
  When moving parts, certain constraints apply, i.e. single edges can only be moved perpendicular to their
  current position. In addition, the movement is confined to the editing grid.
  </p>

  <p>
  The selected items can be deleted by using the "Delete" function from the "Edit" menu or pressing the "Delete"
  key. If not enough vertices remain to form a valid object, the object is deleted (i.e. a polygon with
  less then 3 points). 
  </p>

  <p>
  By double-clicking at an edge or path segment, an additional point is created on this edge at the 
  cursor's position. You can create a "bend" on a path by placing two new vertices on that segment
  and moving the connecting segment between these vertices away from the former center line. This basically
  requires two double-clicks on the path's centerline, a single click on the newly formed segment and
  a single click to drop it at the new position.
  </p>

</doc>
