public class

BoxView

extends CompositeView
java.lang.Object
   ↳ javax.swing.text.View
     ↳ javax.swing.text.CompositeView
       ↳ javax.swing.text.BoxView
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

A view that arranges its children into a box shape by tiling its children along an axis. The box is somewhat like that found in TeX where there is alignment of the children, flexibility of the children is considered, etc. This is a building block that might be useful to represent things like a collection of lines, paragraphs, lists, columns, pages, etc. The axis along which the children are tiled is considered the major axis. The orthoginal axis is the minor axis.

Layout for each axis is handled separately by the methods layoutMajorAxis and layoutMinorAxis. Subclasses can change the layout algorithm by reimplementing these methods. These methods will be called as necessary depending upon whether or not there is cached layout information and the cache is considered valid. These methods are typically called if the given size along the axis changes, or if layoutChanged is called to force an updated layout. The layoutChanged method invalidates cached layout information, if there is any. The requirements published to the parent view are calculated by the methods calculateMajorAxisRequirements and calculateMinorAxisRequirements. If the layout algorithm is changed, these methods will likely need to be reimplemented.

Summary

[Expand]
Inherited Constants
From class javax.swing.text.View
From interface javax.swing.SwingConstants
Public Constructors
BoxView(Element elem, int axis)
Constructs a BoxView.
Public Methods
float getAlignment(int axis)
Determines the desired alignment for this view along an axis.
int getAxis()
Fetches the tile axis property.
Shape getChildAllocation(int index, Shape a)
Fetches the allocation for the given child view.
int getHeight()
Returns the current height of the box.
float getMaximumSpan(int axis)
Determines the maximum span for this view along an axis.
float getMinimumSpan(int axis)
Determines the minimum span for this view along an axis.
float getPreferredSpan(int axis)
Determines the preferred span for this view along an axis.
int getResizeWeight(int axis)
Gets the resize weight.
int getWidth()
Returns the current width of the box.
void layoutChanged(int axis)
Invalidates the layout along an axis.
Shape modelToView(int pos, Shape a, Position.Bias b)
Provides a mapping from the document model coordinate space to the coordinate space of the view mapped to it.
void paint(Graphics g, Shape allocation)
Renders the BoxView using the given rendering surface and area on that surface.
void preferenceChanged(View child, boolean width, boolean height)
This is called by a child to indicate its preferred span has changed.
void replace(int index, int length, View[] elems)
Invalidates the layout and resizes the cache of requests/allocations.
void setAxis(int axis)
Sets the tile axis property.
void setSize(float width, float height)
Sets the size of the view.
int viewToModel(float x, float y, Shape a, Bias[] bias)
Provides a mapping from the view coordinate space to the logical coordinate space of the model.
Protected Methods
void baselineLayout(int targetSpan, int axis, int[] offsets, int[] spans)
Computes the location and extent of each child view in this BoxView given the targetSpan, which is the width (or height) of the region we have to work with.
SizeRequirements baselineRequirements(int axis, SizeRequirements r)
Calculates the size requirements for this BoxView by examining the size of each child view.
SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r)
Calculates the size requirements for the major axis axis.
SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r)
Calculates the size requirements for the minor axis axis.
void childAllocation(int index, Rectangle alloc)
Allocates a region for a child view.
boolean flipEastAndWestAtEnds(int position, Position.Bias bias)
Determines in which direction the next view lays.
void forwardUpdate(DocumentEvent.ElementChange ec, DocumentEvent e, Shape a, ViewFactory f)
Forwards the given DocumentEvent to the child views that need to be notified of the change to the model.
int getOffset(int axis, int childIndex)
Fetches the offset of a particular child's current layout.
int getSpan(int axis, int childIndex)
Fetches the span of a particular childs current layout.
View getViewAtPoint(int x, int y, Rectangle alloc)
Fetches the child view at the given coordinates.
boolean isAfter(int x, int y, Rectangle innerAlloc)
Determines if a point falls after an allocated region.
boolean isAllocationValid()
Are the allocations for the children still valid?
boolean isBefore(int x, int y, Rectangle innerAlloc)
Determines if a point falls before an allocated region.
boolean isLayoutValid(int axis)
Determines if the layout is valid along the given axis.
void layout(int width, int height)
Perform layout on the box
void layoutMajorAxis(int targetSpan, int axis, int[] offsets, int[] spans)
Performs layout for the major axis of the box (i.e.
void layoutMinorAxis(int targetSpan, int axis, int[] offsets, int[] spans)
Performs layout for the minor axis of the box (i.e.
void paintChild(Graphics g, Rectangle alloc, int index)
Paints a child.
[Expand]
Inherited Methods
From class javax.swing.text.CompositeView
From class javax.swing.text.View
From class java.lang.Object

Public Constructors

public BoxView (Element elem, int axis)

Constructs a BoxView.

Parameters
elem the element this view is responsible for
axis either View.X_AXIS or View.Y_AXIS

Public Methods

public float getAlignment (int axis)

Determines the desired alignment for this view along an axis. This is implemented to give the total alignment needed to position the children with the alignment points lined up along the axis orthoginal to the axis that is being tiled. The axis being tiled will request to be centered (i.e. 0.5f).

Parameters
axis may be either View.X_AXIS or View.Y_AXIS
Returns
  • the desired alignment >= 0.0f && <= 1.0f; this should be a value between 0.0 and 1.0 where 0 indicates alignment at the origin and 1.0 indicates alignment to the full span away from the origin; an alignment of 0.5 would be the center of the view
Throws
IllegalArgumentException for an invalid axis

public int getAxis ()

Fetches the tile axis property. This is the axis along which the child views are tiled.

Returns
  • the major axis of the box, either View.X_AXIS or View.Y_AXIS

public Shape getChildAllocation (int index, Shape a)

Fetches the allocation for the given child view. This enables finding out where various views are located. This is implemented to return null if the layout is invalid, otherwise the superclass behavior is executed.

Parameters
index the index of the child, >= 0 && < getViewCount()
a the allocation to this view
Returns
  • the allocation to the child; or null if a is null; or null if the layout is invalid

public int getHeight ()

Returns the current height of the box. This is the height that it was last allocated.

Returns
  • the current height of the box

public float getMaximumSpan (int axis)

Determines the maximum span for this view along an axis.

Parameters
axis may be either View.X_AXIS or View.Y_AXIS
Returns
  • the span the view would like to be rendered into >= 0; typically the view is told to render into the span that is returned, although there is no guarantee; the parent may choose to resize or break the view
Throws
IllegalArgumentException for an invalid axis type

public float getMinimumSpan (int axis)

Determines the minimum span for this view along an axis.

Parameters
axis may be either View.X_AXIS or View.Y_AXIS
Returns
  • the span the view would like to be rendered into >= 0; typically the view is told to render into the span that is returned, although there is no guarantee; the parent may choose to resize or break the view
Throws
IllegalArgumentException for an invalid axis type

public float getPreferredSpan (int axis)

Determines the preferred span for this view along an axis.

Parameters
axis may be either View.X_AXIS or View.Y_AXIS
Returns
  • the span the view would like to be rendered into >= 0; typically the view is told to render into the span that is returned, although there is no guarantee; the parent may choose to resize or break the view
Throws
IllegalArgumentException for an invalid axis type

public int getResizeWeight (int axis)

Gets the resize weight. A value of 0 or less is not resizable.

Parameters
axis may be either View.X_AXIS or View.Y_AXIS
Returns
  • the weight
Throws
IllegalArgumentException for an invalid axis

public int getWidth ()

Returns the current width of the box. This is the width that it was last allocated.

Returns
  • the current width of the box

public void layoutChanged (int axis)

Invalidates the layout along an axis. This happens automatically if the preferences have changed for any of the child views. In some cases the layout may need to be recalculated when the preferences have not changed. The layout can be marked as invalid by calling this method. The layout will be updated the next time the setSize method is called on this view (typically in paint).

Parameters
axis either View.X_AXIS or View.Y_AXIS

public Shape modelToView (int pos, Shape a, Position.Bias b)

Provides a mapping from the document model coordinate space to the coordinate space of the view mapped to it. This makes sure the allocation is valid before calling the superclass.

Parameters
pos the position to convert >= 0
a the allocated region to render into
b a bias value of either Position.Bias.Forward or Position.Bias.Backward
Returns
  • the bounding box of the given position
Throws
BadLocationException if the given position does not represent a valid location in the associated document
See Also

public void paint (Graphics g, Shape allocation)

Renders the BoxView using the given rendering surface and area on that surface. Only the children that intersect the clip bounds of the given Graphics will be rendered.

Parameters
g the rendering surface to use
allocation the allocated region to render into
See Also

public void preferenceChanged (View child, boolean width, boolean height)

This is called by a child to indicate its preferred span has changed. This is implemented to throw away cached layout information so that new calculations will be done the next time the children need an allocation.

Parameters
child the child view
width true if the width preference should change
height true if the height preference should change

public void replace (int index, int length, View[] elems)

Invalidates the layout and resizes the cache of requests/allocations. The child allocations can still be accessed for the old layout, but the new children will have an offset and span of 0.

Parameters
index the starting index into the child views to insert the new views; this should be a value >= 0 and <= getViewCount
length the number of existing child views to remove; This should be a value >= 0 and <= (getViewCount() - offset)
elems the child views to add; this value can be nullto indicate no children are being added (useful to remove)

public void setAxis (int axis)

Sets the tile axis property. This is the axis along which the child views are tiled.

Parameters
axis either View.X_AXIS or View.Y_AXIS

public void setSize (float width, float height)

Sets the size of the view. This should cause layout of the view if the view caches any layout information. This is implemented to call the layout method with the sizes inside of the insets.

Parameters
width the width >= 0
height the height >= 0

public int viewToModel (float x, float y, Shape a, Bias[] bias)

Provides a mapping from the view coordinate space to the logical coordinate space of the model.

Parameters
x x coordinate of the view location to convert >= 0
y y coordinate of the view location to convert >= 0
a the allocated region to render into
bias either Position.Bias.Forward or Position.Bias.Backward
Returns
  • the location within the model that best represents the given point in the view >= 0
See Also

Protected Methods

protected void baselineLayout (int targetSpan, int axis, int[] offsets, int[] spans)

Computes the location and extent of each child view in this BoxView given the targetSpan, which is the width (or height) of the region we have to work with.

Parameters
targetSpan the total span given to the view, which would be used to layout the children
axis the axis being studied, either View.X_AXIS or View.Y_AXIS
offsets an empty array filled by this method with values specifying the location of each child view
spans an empty array filled by this method with values specifying the extent of each child view

protected SizeRequirements baselineRequirements (int axis, SizeRequirements r)

Calculates the size requirements for this BoxView by examining the size of each child view.

Parameters
axis the axis being studied
r the SizeRequirements object; if null one will be created
Returns
  • the newly initialized SizeRequirements object

protected SizeRequirements calculateMajorAxisRequirements (int axis, SizeRequirements r)

Calculates the size requirements for the major axis axis.

Parameters
axis the axis being studied
r the SizeRequirements object; if null one will be created
Returns
  • the newly initialized SizeRequirements object
See Also

protected SizeRequirements calculateMinorAxisRequirements (int axis, SizeRequirements r)

Calculates the size requirements for the minor axis axis.

Parameters
axis the axis being studied
r the SizeRequirements object; if null one will be created
Returns
  • the newly initialized SizeRequirements object
See Also

protected void childAllocation (int index, Rectangle alloc)

Allocates a region for a child view.

Parameters
index the index of the child view to allocate, >= 0 && < getViewCount()
alloc the allocated region

protected boolean flipEastAndWestAtEnds (int position, Position.Bias bias)

Determines in which direction the next view lays. Consider the View at index n. Typically the Views are layed out from left to right, so that the View to the EAST will be at index n + 1, and the View to the WEST will be at index n - 1. In certain situations, such as with bidirectional text, it is possible that the View to EAST is not at index n + 1, but rather at index n - 1, or that the View to the WEST is not at index n - 1, but index n + 1. In this case this method would return true, indicating the Views are layed out in descending order. Otherwise the method would return false indicating the Views are layed out in ascending order.

If the receiver is laying its Views along the Y_AXIS, this will will return the value from invoking the same method on the View responsible for rendering position and bias. Otherwise this will return false.

Parameters
position position into the model
bias either Position.Bias.Forward or Position.Bias.Backward
Returns
  • true if the Views surrounding the View responding for rendering position and bias are layed out in descending order; otherwise false

protected void forwardUpdate (DocumentEvent.ElementChange ec, DocumentEvent e, Shape a, ViewFactory f)

Forwards the given DocumentEvent to the child views that need to be notified of the change to the model. If a child changed its requirements and the allocation was valid prior to forwarding the portion of the box from the starting child to the end of the box will be repainted.

Parameters
ec changes to the element this view is responsible for (may be null if there were no changes)
e the change information from the associated document
a the current allocation of the view
f the factory to use to rebuild if the view has children
See Also

protected int getOffset (int axis, int childIndex)

Fetches the offset of a particular child's current layout.

Parameters
axis the axis being studied
childIndex the index of the requested child
Returns
  • the offset (location) for the specified child

protected int getSpan (int axis, int childIndex)

Fetches the span of a particular childs current layout.

Parameters
axis the axis being studied
childIndex the index of the requested child
Returns
  • the span (width or height) of the specified child

protected View getViewAtPoint (int x, int y, Rectangle alloc)

Fetches the child view at the given coordinates.

Parameters
x the X coordinate >= 0
y the Y coordinate >= 0
alloc the parents inner allocation on entry, which should be changed to the childs allocation on exit
Returns
  • the view

protected boolean isAfter (int x, int y, Rectangle innerAlloc)

Determines if a point falls after an allocated region.

Parameters
x the X coordinate >= 0
y the Y coordinate >= 0
innerAlloc the allocated region; this is the area inside of the insets
Returns
  • true if the point lies after the region else false

protected boolean isAllocationValid ()

Are the allocations for the children still valid?

Returns
  • true if allocations still valid

protected boolean isBefore (int x, int y, Rectangle innerAlloc)

Determines if a point falls before an allocated region.

Parameters
x the X coordinate >= 0
y the Y coordinate >= 0
innerAlloc the allocated region; this is the area inside of the insets
Returns
  • true if the point lies before the region else false

protected boolean isLayoutValid (int axis)

Determines if the layout is valid along the given axis.

Parameters
axis either View.X_AXIS or View.Y_AXIS

protected void layout (int width, int height)

Perform layout on the box

Parameters
width the width (inside of the insets) >= 0
height the height (inside of the insets) >= 0

protected void layoutMajorAxis (int targetSpan, int axis, int[] offsets, int[] spans)

Performs layout for the major axis of the box (i.e. the axis that it represents). The results of the layout (the offset and span for each children) are placed in the given arrays which represent the allocations to the children along the major axis.

Parameters
targetSpan the total span given to the view, which would be used to layout the children
axis the axis being layed out
offsets the offsets from the origin of the view for each of the child views; this is a return value and is filled in by the implementation of this method
spans the span of each child view; this is a return value and is filled in by the implementation of this method

protected void layoutMinorAxis (int targetSpan, int axis, int[] offsets, int[] spans)

Performs layout for the minor axis of the box (i.e. the axis orthoginal to the axis that it represents). The results of the layout (the offset and span for each children) are placed in the given arrays which represent the allocations to the children along the minor axis.

Parameters
targetSpan the total span given to the view, which would be used to layout the children
axis the axis being layed out
offsets the offsets from the origin of the view for each of the child views; this is a return value and is filled in by the implementation of this method
spans the span of each child view; this is a return value and is filled in by the implementation of this method

protected void paintChild (Graphics g, Rectangle alloc, int index)

Paints a child. By default that is all it does, but a subclass can use this to paint things relative to the child.

Parameters
g the graphics context
alloc the allocated region to paint into
index the child index, >= 0 && < getViewCount()