Action area. The viewer in which interactive user operations create and manipulate the graphical scene. The action area appears below the control panel or in a separate associated viewer if the user so desires.

Alignment line. A greyed straight line or circle for use during an operation which requires precision, such as dragging, rotating, scaling, and rubberbanding. Which lines appear depends on the objects in the scene which generate the lines (explicitly hot objects and objects chosen by heuristics based on the operation being performed), and which types of alignment objects the user has activated on the control panel. Alignment lines are gravity active.

Anchor. The center of rotation and the center of scaling. Currently appears as shown below. The anchor is oriented, gravity-active and hot; it generates alignment slope lines, a single alignment angle line, alignment radius circles, and alignment parallel distance line, all relative to its orientation. See caret.

Caret. The V shaped object (often pointing up) which appears during most interactive operations. The caret is used as the first endpoint of new segments, the insertion point for new text strings, the center of new circles, -- in general, the start point of new graphical objects. It also acts as a kind of tugboat, pulling selected objects toward some object to which it is attracted by gravity. The caret is oriented, usually with the caret normal perpendicular to the tangent of whatever curve it is on, or with vertical normal in free space. The anchor is always created at the caret position, with anchor normal aligned to the caret normal.

Cluster. A hierarchical collection of graphical objects. Clusters are multi-level and may be constructed of other clusters, outlines, or leaf objects. Clusters are made and unmade by user action. All the elements of a cluster may be simultaneously selected and operated on as a unit.

Control Panel. The set of buttons and menus above the action area or in a separate associated viewer if the user so desires.

Control point. Curved segments have points associated with them, called control points, which define their shape. Control points are drawn in Gargoyle as small solid squares which are normally invisible, become solid white squares as needed for attracting the caret or when a related object is selected, and become solid black squares when they are selected.

Edit Constraints. Constraints that determine how the control points of adjacent Bezier curve segments will behave as one of the segments, or its parts, are dragged. The currently available constraints are none, tangent and length. Performing a drag while in a constrained mode will cause the affected joint to maintain shape; thus if tangent continuity existed at the joint before the drag, it will afterwards. Higher order continuity is not preserved.

Feedback Line. A one line label at the bottom of the control panel in which Gargoyle displays feedback and error messages for the user.

Fence. See Holes.

Frozen. A cluster may be frozen or thawed by user action. Frozen clusters will not allow editing of the individual elements of the cluster. Freezing of clusters is NYI.

Gravity Active. An object is gravity active if the caret will "snap" to that object during a caret positioning operation or an operation using caret motion such as dragging, rotating, scaling, and rubberbanding. All objects in a scene which are not themselves in motion will be gravity active, all alignment lines are gravity active, and some intersection points among alignment lines and scene objects are gravity active.

Gravity Extent. The farthest the cursor can be from a gravity active object and still map the caret onto that object. The user interactively sets the gravity extent.

Gravity. The mapping from cursor position to caret position. This mapping often "snaps" the caret onto a trajectory or an alignment line in the scene; the caret is "snapped" to a gravity active object when the cursor moves to within the gravity extent of that object. Two types of gravity are available, called PreferPoints gravity and PreferLines gravity. The user interactively chooses the desired type. The user may also turn gravity off completely, even while an interactive operation (like dragging) is in progress.

Holes. An outline may consist of a single closed object (a fence), and a number of subsidiary closed objects called holes. The fence and its holes are rendered using wrap numbers; the graphical effect is that of a window or hole through the opaque fence through which scene objects behind the fence appear. See Holes in the Edit menu below.

Hot Objects. A joint or segment is hot if it triggers alignment objects. Hot joints can trigger slope lines, and alignment circles. Hot segments can trigger angle lines and parallel "distance" lines. The anchor acts as a hot joint and as a special hot segment. Segments and joints are made hot or cold by explicit user actions and, when enabled, by heuristics based on the operation being performed. Hot joints are drawn in Gargoyle as white squares larger than the squares used to show control points.

Joint. An endpoint of a segment. Every segment has two joints. Joints are drawn in Gargoyle as small squares which are normally invisible, become solid white squares with a dot in the center as needed for attracting the caret or when a related object is selected, and become solid black squares when they are selected.

NYI. Not yet implemented.

NLI. No longer implemented.

Outline. A set of objects considered as a group for rendering purposes. Most outlines contain a single trajectory (open or closed), but a closed trajectory with holes in it is represented by a single outline composed of several closed objects. Trajectories never appear alone; they are always contained in an outline.

Point. The noun, not the verb. One point is 1/72 (0.01388889) of an inch.

Scene. The set of graphical objects currently in the Gargoyle viewer. The scene includes the graphical objects created by the user and alignment lines created by Gargoyle for the user.

Segment. A single straight line segment, circular arc, piece of a conic, cubic Bezier curve, or interpolating spline. A segment has two endpoints called joints. Also called a stroke.

Select. the act of initiating or extending the selection. Selecting is usually done via pointing and clicking, though some menu operations and keyboard accelerators perform selection actions. Selections occur at certain levels, described in the Interactive Features section, below.

Selection. the set of objects that have been designated by the select operation(s). The selection comprises the set of objects that will be operands to specified operations.

Slice. A graphical object which is either an outline or a member of a class of graphical objects. Clusters, outlines, text strings, boxes, circles, and pieces of Interpress files are currently implemented as slice classes. Slices define their behavior via the classing mechanism supported in the implementation of Gargoyle.

Top level object(s). An object in the scene not contained in another (parent) object.

Trajectory. A connected sequence of line segments and/or curve segments. Trajectories may be open or closed; a closed trajectory is called a fence.

Caret Position. Hold down Shift and the left mouse button while moving the cursor in the action area. The caret will appear and will follow the cursor; if the caret nears a gravity-active object it will snap to it and stick as long as Shift and the left mouse button are held down and moved near the attractor object. If gravity snaps the cursor onto an object, its joints and control points will temporarily appear as attractor feedback. The feedback line will display useful textual information about objects which attract the caret during this operation. N.B.: it is easy to confuse this operation with the Select Joint operation; the Caret Position operation will not change the current selection.

Select Joint. Hold down the left mouse button and move the cursor in the action area. If gravity snaps the cursor onto a joint or control point, the joint or control point will temporarily be highlighted (appear as a filled black square). If a point is highlighted, its related joints and control points will also appear, unhighlighted. Releasing the mouse button at this point will cause all previously selected objects to be deselected and the highlighted joint or control point to become selected. This operation is called selecting at the joint level. N.B.: it is easy to confuse this operation with the Caret Position operation.

Select Segment. Hold down the middle mouse button and move the cursor around. If gravity snaps the cursor onto a segment, its end joints will temporarily be highlighted (appear as a filled black square). If the segment is a curve its control points will appear. Releasing at this point will cause all previously selected objects to be deselected and that segment to become selected. The segment, joints, and control points will remain highlighted as selection feedback. This operation is called selecting at the segment level.

Select Trajectory. Double click the middle mouse button, holding down on the second stroke. Then move around as in Select Joint. If gravity snaps the cursor onto a graphical object, all of its parts (e.g. joints, segments, control points) become highlighted. Releasing at this point will cause all previously selected objects to be deselected and that object to become selected. This operation is called selecting at the trajectory level, for historical reasons, although objects other than trajectories (e.g. boxes, circles, text) may be selected at this level. If filled paths are present, the topmost such path (in overlap order) will be selected, unless the cursor is near an unfilled path that is even more forward (in overlap order), in which case the top level object containing that path will be selected.

Select TopLevel. Double click the left mouse button, holding down on the second stroke. Then move around as in Select Joint. If gravity snaps the cursor onto a top level object, all of its components become highlighted; a top level object is an object which is a component of no other object. Releasing at this point will cause all previously selected objects to be deselected and that top level object to become selected. A top level selection may be extended to any number of top level objects via the Extend Selection operation. If filled paths are present, the top level object that contains the topmost such path (in overlap order) will be selected, unless the cursor is near an unfilled path that is even more forward (in overlap order), in which case the top level object containing that path will be selected.

Extend Selection. Hold down the right mouse button and move around. If gravity snaps the cursor onto an object or object part which may be selected at the same level as the previous successful selection level, releasing at this point will ADD the object or part to the current selection. Extend selection may be repeated indefinitely and is usually invoked after an initial successful selection. Extend selection is often repeated to build a temporary collection of objects for use as operands to an interactive operation. Note that extending at the segment level within a single trajectory will make a new selection of all segments in that trajectory between the original selected segment and the extended segment. Since trajectories are ordered, extend segment selection may wrap around from the end to the beginning of a trajectory.

META Extend Selection. Hold down the R15 key (also known as the SWAT key from the old days) and initiate a selection operation (Select Joint/Segment/Trajectory/TopLevel) as before. When you release the mouse button and the R15 key, the selected object or object part will be ADDED to the existing selection rather than replacing the existing selection. It is thus possible to (meta)select heterogeneous objects, say a mixture of joints, segments, and trajectories, for a subsequent operation like Drag or Delete. META Extend Selection may be repeated indefinitely.

Select with Box. Position one corner of a box using the Caret Position operation (above). Move the cursor, then double click the right mouse button, holding down on the second stroke. A box will appear (originating from the caret position) which may be rubberbanded exactly as in the Add Box command (below). When the button is released, the box will disappear and all objects whose bounding box lies completely within the box will become the current selection.

Deselect Joint/Segment/Trajectory/TopLevel. Hold down Control and Shift^ to convert selection operations into deselection operations. Use the same mouse buttons as in the corresponding selection operations.

ExtendDeelection. NYI.

Add Line. Add Line creates a new straight line segment whose endpoints are the caret and the current cursor position. ShiftMiddleMouse initiates AddLine. Holding down the mouse button causes new alignment objects of the activated types to appear (if the Auto option is on) and the caret to jump to the cursor so the new endpoint can be placed with precision. The user may continue to hold down the mouse button and move the mouse; the new line will be rubberbanded accordingly. If the user selected an end joint of an open trajectory (using joint selection) before invoking AddLine, the new segment will extend the current trajectory, and the new segment will get its looks from the segment of the selected end joint. If the user did not select an end joint of an open trajectory before invoking AddLine, a new outline will be created and the new outline segment will get its looks from the current default looks, which are settable by the user.

Add Bezier. Similar to Add Line. ShiftRightMouse causes a new Bezier segment to be created. If an end joint of a bezier segment which is also the end joint of a trajectory is selected, and an edit constraint is turned on, the new bezier segment will be created tangent continuous to the selected joint and with a second joint at the cursor position when ShiftRightMouse is depressed. The user may hold down ShiftRightMouse at the desired second joint position and then move the mouse; the motion will cause the tangent vector at the "unconstrained" joint to appear; the tangent vector may be rubberbanded. The new bezier will rubberband accordingly. When Shift and RightMouse are released, the segment is completed. The entire operation can be aborted at any time up to the final completion of the bezier segment. If no edit constraints are on, or the end joint of a bezier is not selected, then the user will specify a new bezier in two stages. In the first stage, the initial joint and control point are specified. Place the caret at the desired first joint position. Hold down ShiftRightMouse and drag out the first tangent control vector. WHILE CONTINUING TO HOLD Shift DOWN, release RightMouse, then move the cursor to the desired second joint position, then hold RightMouse down again and drag out a second control vector. When Shift and RightMouse are released, the segment is completed. The entire operation can be aborted at anytime up to the final completion of the bezier segment. Legal Bezier constraint types are none, tangent, and length. Constraint tangent enforces tangent constraints as outlined above. Constraint length enforces tangent constraints and also constrains the vectors from the joint to each of the constrained control points to be the same length. Use the Curves menu to set, show, and apply the current constraint type.

Add Box. Create a new box object whose corners are the caret and the current cursor position. ShiftDoubleRightMouse initiates AddBox. Holding down the mouse button and moving the mouse causes alignment lines to appear (if the Auto option is on) and the caret to jump to the cursor corner of the box, so the new corner can be placed with precision. The user may continue to hold down the mouse button and move the mouse; the new box will be rubberbanded accordingly. Boxes may be translated/rotated/scaled as usual and will retain their box characteristics. Boxes are displayed with control points at their corners and center. Dragging a corner or an edge of a box will grow/shrink the box rectilinearly. Transforming a box selected as a trajectory or top level object will transform the entire box.

Drag. CtrlLeftMouse initiates dragging. All selected objects are translated, maintaining a constant relationship to the caret. Dragging is usually performed in stages. First, select the objects to be dragged; if parts of objects are selected, then those objects will be rubberbanded. Second, place the caret on that joint or segment which must be positioned with precision if the selection operation has not already positioned the caret for you. Next, position the cursor as desired. As the left mouse button is pushed down, the caret will snap to the cursor. Finally, continue to hold down the Control key and the mouse button and move the mouse. The caret will be attracted to gravity active objects as usual, taking all of the selected objects with it.

Rotate. CtrlMiddleMouse initiates rotation. Very much like Drag. Rotate has an optional extra preliminary step -- the Anchor can be placed to be used as a center of rotation. This can be done using the DropAnchor command in the HotSpots menu, or from the keyboard (CtrlA drops the anchor at the caret. CtrlShiftA deletes the anchor). Select the objects to be rotated; if parts of objects are selected, then those objects will be rubberbanded. Because the objects move with 1 degree of freedom while the mouse has two, the caret does not remain in a constant relationship with the objects being rotated. However, the caret does snap to the cursor when the operation begins so objects can be rotated with precision. The angle of rotation is the angle between two vectors: the Anchor to initial-caret-position vector, and the Anchor to current-caret-position vector. If no anchor is dropped, the center of the bounding box of the selected objects is used as an anchor point.

Scale. CtrlRightMouse initiates scaling. Very much like rotate. The Anchor is the center of scaling. The scaling factor is the ratio of <the current caret to Anchor distance> to <the initial caret to Anchor distance>. Scaling to zero is discouraged. If no anchor is present, the center of the bounding box of the selected objects is used as an anchor point.

Skew. CtrlDoubleRightMouse initiates an interactive skewing transformation. Skew is similar to Drag. The line of invariance is the line that passes through the anchor and is perpendicular to the line from the anchor to the initial caret position. The scene point at which the caret was placed before the operation is translated to stay with the caret, skewing everything else as necessary. This operation is experimental and will probably be bound to a different mouse button in the near future. If no anchor is present, the center of the bounding box of the selected objects is used as an anchor point, and a horizontal line through that point is used as the line of invariance.

Copy And Drag. CopyAndDrag is initiated by CtrlDoubleLeftClick. Hold down the Control key and double click. A copy of the selection is created and then selected. It may be immediately dragged by moving the mouse without releasing any button. The copy will first appear translated from the original by the vector defined by the caret and cursor when Copy And Drag is initiated.