NAME¶
Graphic, FullGraphic - structured graphic abstract base class and subclass that
stores a complete set of graphics state attributes
SYNOPSIS¶
#include <Unidraw/Graphic/graphic.h>
DESCRIPTION¶
Graphic is an abstract base class for structured graphics objects.
Graphic objects maintain graphics state and geometric information, which lets
them draw themselves on demand and support hit detection.
Graphic subclasses can implement graphical objects such as lines, rectangles,
ellipses, and polygons. Subclasses can also support hierarchical composition
of Graphic instances, thus providing an object-oriented rendition of
traditional structured graphics functionality.
GRAPHIC PUBLIC OPERATIONS¶
- virtual void Draw(Canvas*)
- virtual void Draw(Canvas*, Coord, Coord, Coord, Coord)
- virtual void DrawClipped(Canvas*, Coord, Coord, Coord, Coord)
- virtual void Erase(Canvas*)
- virtual void Erase(Canvas*, Coord, Coord, Coord, Coord)
- virtual void EraseClipped(Canvas*, Coord, Coord, Coord, Coord)
- Draw or erase the graphic on the given canvas. The one-parameter Draw and
Erase operations draw and erase the graphic in its entirety. The
five-parameter forms take four coordinates defining a rectangular area
with which to cull drawing. Composite graphics in particular can use this
information to avoid drawing children falling entirely outside the given
area. DrawClipped and EraseClipped draw the graphic strictly within a
rectangular area. All Coord parameters are in canvas coordinates.
- virtual void FillBg(boolean)
- virtual void SetBrush(PSBrush*)
- virtual void SetColors(PSColor* fg, PSColor* bg)
- virtual void SetFont(PSFont*)
- virtual void SetPattern(PSPattern*)
- virtual int BgFilled()
- virtual PSBrush* GetBrush()
- virtual PSColor* GetFgColor()
- virtual PSColor* GetBgColor()
- virtual PSFont* GetFont()
- virtual PSPattern* GetPattern()
- Set and get the graphic's graphic state attributes analogous to those
defined for Painters. The base class implements the operations for setting
and getting the fill mode and colors; the other operations should be
redefined in subclasses that need them.
- void Translate(float dx, float dy)
- void Scale(float x, float y, float cx = 0.0, float cy = 0.0)
- void Rotate(float angle, float cx = 0.0, float cy = 0.0)
- void SetTransformer(Transformer*)
- Transformer* GetTransformer()
- void TotalTransformation(Transformer& t)
- Coordinates passed to drawing operations are transformed according to the
current translation, rotation, and scale factor. Optionally, scaling and
rotation can be performed relative to a point ( cx, cy). The
base class stores a transformer _t that can be directly set and
accessed with SetTransformer and GetTransformer. The default transformer
is nil, meaning no transformations are performed. TotalTransformation uses
concatTransformer (described below) to concatenate t (usually the
identity transformation) and the transformers of the graphic's parents to
obtain the graphic's total transformation, which it then stores in
t.
Unless otherwise noted, input and output coordinates are affected by the
concatentation of this's transformer, its parent's transformer, its
parent's parent's, and so on up to the root of the graphic instance
hierarchy. Prior to transformation, coordinates reflect the graphic's
coordinate system. Following transformation, the coordinates reflect
the canvas coordinate system (i.e., they are canvas coordinates). The
coordinates that Graphic subclass constructors require are normally in
graphic coordinates, while operations for returning a graphic's bounding
box (see below) are in canvas coordinates.
- void Align(Alignment, Graphic*, Alignment)
- Position the given graphic relative to this, which stays fixed,
while the graphic supplied as the argument is translated appropriately.
The first Alignment parameter specifies the alignment with respect to
this, while the second specifies the alignment with respect to the
given graphic.
- virtual void GetBounds(
- float& left, float& bottom, float& right, float&
top
- )
-
Return the exact coordinates of the smallest box circumscribing the graphic.
The return values are in canvas coordinates.
- void GetBox(Coord& left, Coord& bottom, Coord& right,
Coord& top)
- void GetBox(BoxObj&)
- Return the smallest bounding box circumscribing the graphic. The return
values are in canvas coordinates. The BoxObj represents a rectangle
defined by lower left and upper right coordinates (see geomobjs(3U) for
details).
- virtual void GetCenter(float& x, float& y)
- Return the center point of the graphic in canvas coordinates.
- virtual boolean Contains(PointObj&)
- virtual boolean Intersects(BoxObj&)
- Return whether or not the graphic contains the given point or intersects
the given rectangular area specified in canvas coordinates.
PointObj describes a point (see geomobjs(3U)). These operations are
used most often for fine-grained hit detection.
- void SetTag(void*)
- void* GetTag()
- Set or return a tag associated with the graphic.
- Graphic* Parent()
- Return the graphic's parent, if any.
- virtual void First(Iterator&)
- virtual void Last(Iterator&)
- virtual void Next(Iterator&)
- virtual void Prev(Iterator&)
- virtual boolean Done(Iterator)
- Operations for iterating over the graphic's children, if any. These
operations do nothing by default. Graphics that compose other graphics
should redefine these operations to permit traversal of their children.
First and Last initialize an iterator to point to the beginning and end of
the list of children, respectively. Next increments the iterator to point
to the following child, while Prev decrements the iterator to point to the
preceding child. Done returns whether or not the iterator points beyond
the first or last child in the list.
- Graphic* GetGraphic(Iterator)
- void SetGraphic(Graphic*, Iterator&)
- These operations do nothing by default. Subclasses that contain children
should redefine them as follows: GetGraphic should return the graphic to
which an iterator points. SetGraphic should initialize the iterator to
point to a particular graphic in the list of children; it should
initialize the iterator to point to a nil instance if the given graphic is
not a child.
- virtual void Bequeath()
- Bequeath does nothing by default. Composite graphic subclasses should
redefine it so that it propagates to the children all the graphics state
in this that can affect them. This will prevent a change in a
child's appearance should it be removed from this. Following the
call to Bequeath, this should no longer define any graphics state
attributes.
- virtual Graphic* FirstGraphicContaining(PointObj&)
- virtual Graphic* LastGraphicContaining(PointObj&)
- virtual Graphic* FirstGraphicIntersecting(BoxObj&)
- virtual Graphic* LastGraphicIntersecting(BoxObj&)
- virtual Graphic* FirstGraphicWithin(BoxObj&)
- virtual Graphic* LastGraphicWithin(BoxObj&)
- These operation do nothing by default. Composite graphic subclasses should
redefine them so that they return the first or last child that contains a
point, intersects a rectangular area, or does not extend beyond the given
rectangular area, respectively.
- virtual Graphic& operator = (Graphic&)
- Assign the given graphic's graphics state attributes to this.
- virtual Graphic* Copy()
- Return a copy of the graphic. Subclasses should redefine this operation to
return an instance of their type.
GRAPHIC PROTECTED MEMBERS¶
- Graphic(Graphic* gr = nil)
- Initialize the graphics, optionally supplying a graphic from which to
obtain an initial set of graphics state attributes. Graphic is an abstract
base class. Therefore its constructor is protected to prevent
instantiation.
- virtual void draw(Canvas*, Graphic* gs)
- virtual void drawClipped(
- Canvas*, Coord, Coord, Coord, Coord, Graphic*
- )
- virtual void erase(Canvas*, Graphic*)
- virtual void eraseClipped(
- Canvas*, Coord, Coord, Coord, Coord, Graphic*
- )
-
Graphic subclasses redefine these stateless drawing operations to
render themselves. These operations are called by the corresponding
capitalized operations, which supply them with the extra trailing Graphic
parameter gs. This parameter defines the graphics state with which
to draw the graphic. The graphic state is normally computed using the
concat functions described below. Subclasses normally use the
graphics state passed to them without ignoring or modifying it, though
they may safely do so if they must override one or more attributes.
- void update(Graphic* gs)
- Graphics ultimately use a Painter to draw themselves. The Graphic class
maintains a protected static painter _p that subclasses can use to
draw themselves. The update operation sets _p's graphics state
attributes to match those of the given graphic to ensure that the painter
will generate graphics with the proper color, font, etc. Subclasses should
call update in their stateless drawing operations (normally supplying the
graphic they were passed) before they call any drawing operations on
_p. The graphics that _p generates, therefore, will reflect
the graphics state that was passed to the stateless drawing
operation.
- virtual void getExtent(
- float& left, float& bottom, float& cx, float&
cy,
- float& tol, Graphic* gs
- )
- void GetExtent(Extent&)
- A graphic's extent defines its physical boundaries. Subclasses
redefine getExtent to return this boundary information based on the
graphics state supplied in gs. The left, bottom,
cx, and cy parameters define the graphic's lower left corner
and center, respectively, in canvas coordinates. The tol parameter
specifies a fixed amount of space around the boundary to account for parts
of the graphic's appearance that do not scale linearly (e.g., brush
width). The relationship between getExtent and GetExtent is the same as
that between draw and Draw: getExtent is the stateless version of
GetExtent, which concatenates the parent's graphics state and calls
getExtent with the result.
- void getBounds(
- float& left, float& bottom, float& right, float&
top,
- Graphic* gs
- )
- void getBox(
- Coord& left, Coord& bottom, Coord& right, Coord&
top,
- Graphic*
- )
- void getBox(BoxObj&, Graphic*)
- Stateless versions of the corresponding capitalized bounding box
operations, which call the stateless versions with the cumulative graphics
state of this's ancestors. These operations are defined in terms of
getExtent and therefore should not be reimplemented by subclasses.
- virtual boolean contains(PointObj&, Graphic* gs)
- virtual boolean intersects(BoxObj&, Graphic*)
- Stateless versions of the corresponding capitalized operations for
fine-grained hit detection. By default, these operations return true if
the argument is contained in or intersects this's bounding box.
Subclasses can redefine these operations to make a more discerning
decision.
- Graphic* getRoot()
- void totalGS(Graphic& g)
- void parentXform(Transformer& t)
- Helper functions for parent-related operations. getRoot returns the root
graphic in this's hierarchy. totalGS uses concat (described below)
to concatenate the graphics state of this and all its ancestors,
returning the result in g. Any graphics state that g stored
initially will be lost. The parentXform operation uses concatTransform
(described below) to concatenate the transformations of all ancestors of
this, returning the result in t. Any transformations that
t stored initially will be lost.
- void setParent(Graphic* g, Graphic* parent)
- void unsetParent(Graphic* g)
- Operations for setting and getting the value of another graphic's (
g's) parent as stored in the _parent protected member
variable. Normally only composite graphics change this attribute of
another graphic, usually a newly-acquired child.
- void cachingOn()
- void cachingOff()
- virtual boolean extentCached()
- virtual void uncacheExtent()
- virtual void uncacheParents()
- virtual void uncacheChildren()
- virtual void invalidateCaches()
- Operations that support extent caching. Some Graphic subclasses may cache
extent information when it is computed for the first time, thereby
improving performance. For example, it may be expensive to compute the
extent for composite graphics that have many children; thus caching the
extent will improve performance if the extent does not change often.
cachingOn and cachingOff change the value of _caching, a protected
static boolean member of Graphic that indicates whether caching is active
on a global basis. Extent-caching subclasses should check this member to
avoid caching when it is false. Caching subclasses should redefine
extentCached to return whether or not they have cached their extent (in
whatever form they store it). They should redefine uncacheExtent to
discard any extent information they've cached. By default, uncacheParents
simply calls uncacheExtent on each ancestor of this, while
uncacheChildren does nothing by default. Subclasses should redefine
uncacheChildren to make any children uncache their extents.
- virtual void concatGS(Graphic* a, Graphic* b, Graphic* dest)
- virtual void concatTransformer(
- Transformer* a, Transformer* b, Transformer* dest
- )
- virtual void concat(Graphic* a, Graphic* b, Graphic* dest)
- Operations for concatenting graphics state. concatGS concatenates
a's graphics state (brush, font, pattern, etc., but not
transformation matrix) with b's and assigns the result to
dest. According to the default concatenation semantics, dest
will receive graphics state attributes defined by b; dest
will receive only those attributes from a that b does not
define (i.e., those for which b returns nil). By default,
concatTransformer does a matrix multiply of a and b and
assigns the result to dest. The concat operation concatenates both
the graphics state and transformation of its arguments, assigning the
results to dest.
- void transform(Coord&, Coord&, Graphic*)
- void transform(Coord, Coord, Coord&, Coord&, Graphic*)
- void transform(float, float, float&, float&, Graphic*)
- void transformList(
- Coord[], Coord[], int, Coord[], Coord[], Graphic*
- )
- void transformRect(
- float, float, float, float,
- float&, float&, float&, float&, Graphic*
- )
- void invTransform(Coord&, Coord&, Graphic*)
- void invTransform(Coord, Coord, Coord&, Coord&,
Graphic*)
- void invTransform(float, float, float&, float&,
Graphic*)
- void invTransformList(
- Coord[], Coord[], int, Coord[], Coord[], Graphic*
- )
- void invTransformRect(
- float, float, float, float,
- float&, float&, float&, float&, Graphic*
- )
-
Convenience functions analogous to the Transformer operations of the same
name. These operations simply check if _t is nil before calling the
corresponding Transformer operation on it.
- virtual void drawGraphic(Graphic* g, Canvas*, Graphic* gs)
- virtual void drawClippedGraphic(
- Graphic* g, Canvas*, Coord, Coord, Coord, Coord, Graphic*
- )
- virtual void eraseGraphic(Graphic* g, Canvas*, Graphic*)
- virtual void eraseClippedGraphic(
- Graphic* g, Canvas*, Coord, Coord, Coord, Coord, Graphic*
- )
- virtual void getExtentGraphic(
- Graphic* g, float& left, float& bottom, float& cx,
float& cy,
- float& tol, Graphic* gs
- )
- virtual boolean containsGraphic(
- Graphic* g, PointObj&, Graphic* gs
- )
- virtual boolean intersectsGraphic(Graphic* g, BoxObj&,
Graphic*)
- virtual boolean extentCachedGraphic(Graphic* g)
- virtual void uncacheExtentGraphic(Graphic* g)
- virtual void uncacheParentsGraphic(Graphic* g)
- virtual void uncacheChildrenGraphic(Graphic* g)
- virtual void invalidateCachesGraphic(Graphic* g)
- virtual void concatGSGraphic(
- Graphic* g, Graphic* a, Graphic* b, Graphic* dest
- )
- virtual void concatTransformerGraphic(
- Graphic* g, Transformer* a, Transformer* b,
- Transformer* dest
- )
- virtual void concatGraphic(
- Graphic* g, Graphic* a, Graphic* b, Graphic* dest
- )
-
Helper functions that let graphic subclasses call the protected member
functions on instances of other subclasses that redefine them. All these
helper functions take the affected instance as their first parameter. All
are semantically identical to the corresponding functions described above
(which omit the "Graphic" suffix and the leading g
parameter). Composite graphics are the most likely users of such helper
functions, calling them on their children.
FULLGRAPHIC PUBLIC OPERATIONS¶
- FullGraphic(Graphic* = nil)
- Construct a full graphic, optionally supplying another graphic from which
to copy an initial set of graphics state attributes. FullGraphic objects
store a full complement of graphics state attributes; consequently,
FullGraphic redefines all the operations for setting and getting these
attributes. The FullGraphic class can be used as a base class from which
to derive graphics that require a complete set of graphics state and store
such state. It is also useful to instantiate FullGraphics and use them as
graphics state repositories.
SEE ALSO¶
Canvas(3I), Iterator(3U), Painter(3I) Transformer(3I), geomobjs(3U), pspaint(3U)
"Applying Object-Oriented Design to Structured Graphics," John M.
Vlissides and Mark A. Linton, in
Proceedings of the 1988 USENIX C++
Conference, Denver, CO, October 1988, pp. 81-94.