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GraphicView(3U) InterViews Reference Manual GraphicView(3U)


GraphicView, GraphicViews - base classes for graphical component views


#include <Unidraw/Components/grview.h>


GraphicView is an abstract base class for graphical views of GraphicComp objects. GraphicView is derived from ComponentView and adds operations for manipulating its graphical attributes. GraphicViews is a non-abstract subclass of GraphicView for composite graphical component views.


GraphicView objects can (un)interpret the following command:

AlignToGridCmd aligns the graphical component to the grid that affects the view. Interpret uses AlignToGridCmd::Align to carry out the alignment, while Uninterpret uses AlignToGridCmd::Unalign to reverse Interpret's effects.

Operations for displaying and hiding the view's selection handles. All use CreateHandles (described below) to create component-specific rubberbands that draw the handles if they do not already exist. The rubberband is stored in the _handles protected member. DrawHandles makes the handles visible if they are not already visible. RedrawHandles forces the handles to draw themselves even if they are already drawn, which may make them disappear if the rubberband draws them in XOR mode. InitHandles deletes and recreates the rubberband defining the handles if it existed when InitHandles was called. EraseHandles erases the handles and deletes the rubberband.
Operations that define how the GraphicView reacts when it is manipulated by a tool and how the tool affects that component following manipulation. They effectively override the tool's default behavior if the tool defers manipulator creation and interpretation to the view. This allows the same tool to behave differently depending on the component it manipulates.

CreateManipulator creates a manipulator that is appropriate for the given tool. It receives the viewer in which the manipulation will take place, an event with which to initialize the manipulator if necessary, and the coordinate transformation that maps canvas coordinates into the subject's coordinate space. InterpretManipulator is called following manipulation and defines how to construct a command that carries out the manipulation's desired effect. GraphicView objects create and interpret manipulators for the following tools:

GraphicCompTool will let the user position a fixed-sized outline reflecting the view's bounding box on the screen. Interpretation will produce a command that inserts a copy of the subject into the editor's component at the specified position. Placement will be constrained by gravity, if active.

MoveTool will let the user move a fixed-sized outline reflecting the view's bounding box on the screen. Interpretation will produce a command that moves the subject to the specified position. Holding down the Shift key will constrain the movement to purely horizontal or vertical, and movement will be constrained by gravity.

ScaleTool will let the user drag a scaling rectangular outline corresponding to the view's scale following manipulation with the tool. Scaling will be constrained by gravity.

StretchTool will let the user drag a variable-sized rectangular outline corresponding to a two-dimensional stretch that the component will undergo following manipulation. Holding the Shift key down will constrain the stretch to one dimension. Stretching will be constrained by gravity.

RotateTool will let the user rotate a fixed-sized rectangular outline reflecting the view's bounding box. The rotation of the outline corresponds to the rotation that the component will undergo following manipulation. Rotation will be constrained by gravity.

Return the graphic that defines the GraphicView's appearance. Often this graphic is a copy of that in the subject, but it needn't be.
Return the viewer (if any) that displays the view.
Return the view's subject.
A convenience function that returns whether or not the GraphicView includes the given view, that is, whether the view is a child of this.
A convenience function that returns the view of the given component (if any) that appears in the same viewer as this.
These operations do nothing by default. Subclasses that contain children should redefine them as follows: GetView should return the GraphicView to which an iterator points. SetView should initialize the iterator to point to a particular GraphicView in the list of children; it should initialize the iterator to point to a nil instance if the given GraphicView is not a child.

These convenience operations do nothing by default. Subclasses containing children should redefine them to do the following: SelectAll should return a selection object containing (pointers to) all its children; ViewContaining should return the last (visibly topmost) child view containing the given point, while ViewsContaining should return all children containing the point; ViewIntersecting should return the last (visibly topmost) child view intersecting a rectangular area, while ViewsIntersecting should return all such children; ViewsWithin should return all the child views falling strictly within a rectangular area; and ConnectorIntersecting should return the child ConnectorView (if any) that intersects a rectangular area.


The constructor is protected to guard against instantiation. It takes the view's subject as an optional argument, passing it to the ComponentView constructor.
Set the GraphicView's graphic to the given one, and store this in the graphic using Graphic::SetTag. This makes it possible to obtain the GraphicView that owns the graphic from the graphic itself, e.g., after hit detection.
Initialize the _handles member with a rubberband that will draw the appropriate handles. By default, CreateHandles creates a RubberHandles object with eight handles around the periphery of the view's bounding box.

A convenience function that returns the index of the point closest to (px, py) in an array of n points.
Convenience functions that return the GraphicView in a UList element and the GraphicView associated with a graphic, respectively.
Helper functions used by CreateManipulator and InterpretManipulator to create and interpret the manipulators associated with GraphicCompTool and StretchTool.
GraphicViews should incur damage in response to a change in their appearance, which generally happens in their Update function. AddDamage and IncurDamage produce damage by calling the related operations on the enclosing viewer's damage object. Subclasses can use these functions for convenience to avoid accessing the enclosing viewer's damage object directly.
A convenience function that unselects the given view, which entails erasing its handles and removing it from the enclosing editor's selection object.
Unimplemented operations that composite subclasses should redefine for modifying the their (conceptual) list of children. Note that subclasses needn't necessarily store their children in a list data structure, but a list maps closely to the semantics of these operations. These operations are not public because only the view itself knows how to keep its structure consistent with that of the subject and/or its semantics.

Add adds a GraphicView to the end of the list of children. InsertBefore inserts a GraphicView before the GraphicView pointed to by the iterator. Remove removes a view to which the given iterator refers from the list without deleting it, while DeleteView removes it and deletes it. Remove and DeleteView should advance the iterator to point to the following view as a side effect.


The constructor creates a GraphicViews, optionally supplying the subject. The destructor deletes the GraphicViews' children.
GraphicViews objects interpret the following command:

AlignToGridCmd aligns the graphical component to the grid that affects the view. The overall alignment is based on how the first leaf subcomponent aligns itself: Interpret aligns the first leaf subcomponent to the grid and then moves all other subcomponents by the amount that the leaf moved.

Automatically update the GraphicViews' state and structure to match the subject's. Update will not necessarily detect restructurings or state modifications made to the subject's children more than one level deep. Update uses GVUpdater to do its work.
Return the GraphicViews' graphic, which (like its subject's graphic) is a Picture.
Return the subject.


A convenience function for extracting a UList from an iterator.


Command(3U), ComponentView(3U), Connector(3U), Damage(3U), GVUpdater(3U), GraphicComp(3U), GraphicCompTool(3U), Grid(3U), Event(3I), Manipulator(3U), MoveTool(3U), Picture(3U), RotateTool(3U), Rubband(3I), ScaleTool(3U), Selection(3U), StretchTool(3U), Transformer(3I), Viewer(3U), align(3U)

18 January 1991 Unidraw