Class BoxView

java.lang.Object
javax.swing.text.View
javax.swing.text.CompositeView
javax.swing.text.BoxView
All Implemented Interfaces:
SwingConstants
Direct Known Subclasses:
BlockView, FlowView, TableView, TableView.TableCell, TableView.TableRow, WrappedPlainView, ZoneView 
public class BoxView extends CompositeView
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 orthogonal 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.

Field Summary

Fields declared in class javax.swing.text.View

BadBreakWeight, ExcellentBreakWeight, ForcedBreakWeight, GoodBreakWeight, X_AXIS, Y_AXIS

Fields declared in interface javax.swing.SwingConstants

BOTTOM, CENTER, EAST, HORIZONTAL, LEADING, LEFT, NEXT, NORTH, NORTH_EAST, NORTH_WEST, PREVIOUS, RIGHT, SOUTH, SOUTH_EAST, SOUTH_WEST, TOP, TRAILING, VERTICAL, WEST

Constructor Summary

Constructor Description
BoxView(Element elem, int axis)
Constructs a BoxView.

Method Summary

Modifier and Type Method Description
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.
protected SizeRequirements baselineRequirements(int axis, SizeRequirements r)
Calculates the size requirements for this BoxView by examining the size of each child view.
protected SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r)
Calculates the size requirements for the major axis axis.
protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r)
Calculates the size requirements for the minor axis axis.
protected void childAllocation(int index, Rectangle alloc)
Allocates a region for a child view.
protected boolean flipEastAndWestAtEnds(int position, Position.Bias bias)
Determines in which direction the next view lays.
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.
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.
protected int getOffset(int axis, int childIndex)
Fetches the offset of a particular child's current layout.
float getPreferredSpan(int axis)
Determines the preferred span for this view along an axis.
int getResizeWeight(int axis)
Gets the resize weight.
protected int getSpan(int axis, int childIndex)
Fetches the span of a particular child's current layout.
protected View getViewAtPoint(int x, int y, Rectangle alloc)
Fetches the child view at the given coordinates.
int getWidth()
Returns the current width of the box.
protected boolean isAfter(int x, int y, Rectangle innerAlloc)
Determines if a point falls after an allocated region.
protected boolean isAllocationValid()
Are the allocations for the children still valid?
protected boolean isBefore(int x, int y, Rectangle innerAlloc)
Determines if a point falls before an allocated region.
protected boolean isLayoutValid(int axis)
Determines if the layout is valid along the given axis.
protected void layout(int width, int height)
Perform layout on the box
void layoutChanged(int axis)
Invalidates the layout along an axis.
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).
protected void layoutMinorAxis(int targetSpan, int axis, int[] offsets, int[] spans)
Performs layout for the minor axis of the box (i.e. the axis orthogonal to the axis that it represents).
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.
protected void paintChild(Graphics g, Rectangle alloc, int index)
Paints a child.
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, Position.Bias[] bias)
Provides a mapping from the view coordinate space to the logical coordinate space of the model.

Methods declared in class javax.swing.text.CompositeView

getBottomInset, getInsideAllocation, getLeftInset, getNextEastWestVisualPositionFrom, getNextNorthSouthVisualPositionFrom, getNextVisualPositionFrom, getRightInset, getTopInset, getView, getViewAtPosition, getViewCount, getViewIndex, getViewIndexAtPosition, loadChildren, modelToView, setInsets, setParagraphInsets, setParent

Methods declared in class javax.swing.text.View

append, breakView, changedUpdate, createFragment, forwardUpdateToView, getAttributes, getBreakWeight, getContainer, getDocument, getElement, getEndOffset, getGraphics, getParent, getStartOffset, getToolTipText, getViewFactory, getViewIndex, insert, insertUpdate, isVisible, modelToView, remove, removeAll, removeUpdate, updateChildren, updateLayout, viewToModel

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

BoxView

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

Method Details

getAxis

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
Since:
1.3

setAxis

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
Since:
1.3

layoutChanged

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
Since:
1.3

isLayoutValid

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
Returns:
if the layout is valid along the given axis
Since:
1.4

paintChild

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()

replace

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.
Overrides:
replace in class CompositeView
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)

forwardUpdate

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.
Overrides:
forwardUpdate in class View
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
Since:
1.3
See Also:

preferenceChanged

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.
Overrides:
preferenceChanged in class View
Parameters:
child - the child view
width - true if the width preference should change
height - true if the height preference should change
See Also:

getResizeWeight

public int getResizeWeight(int axis)
Gets the resize weight. A value of 0 or less is not resizable.
Overrides:
getResizeWeight in class View
Parameters:
axis - may be either View.X_AXIS or View.Y_AXIS
Returns:
the weight
Throws:
IllegalArgumentException - for an invalid axis

setSize

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.
Overrides:
setSize in class View
Parameters:
width - the width >= 0
height - the height >= 0

paint

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.
Specified by:
paint in class View
Parameters:
g - the rendering surface to use
allocation - the allocated region to render into
See Also:

getChildAllocation

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.
Overrides:
getChildAllocation in class CompositeView
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

modelToView

public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException
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.
Overrides:
modelToView in class CompositeView
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:

viewToModel

public int viewToModel(float x, float y, Shape a, Position.Bias[] bias)
Provides a mapping from the view coordinate space to the logical coordinate space of the model.
Overrides:
viewToModel in class CompositeView
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:

getAlignment

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 orthogonal to the axis that is being tiled. The axis being tiled will request to be centered (i.e. 0.5f).
Overrides:
getAlignment in class View
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

getPreferredSpan

public float getPreferredSpan(int axis)
Determines the preferred span for this view along an axis.
Specified by:
getPreferredSpan in class View
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

getMinimumSpan

public float getMinimumSpan(int axis)
Determines the minimum span for this view along an axis.
Overrides:
getMinimumSpan in class View
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
See Also:

getMaximumSpan

public float getMaximumSpan(int axis)
Determines the maximum span for this view along an axis.
Overrides:
getMaximumSpan in class View
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
See Also:

isAllocationValid

protected boolean isAllocationValid()
Are the allocations for the children still valid?
Returns:
true if allocations still valid

isBefore

protected boolean isBefore(int x, int y, Rectangle innerAlloc)
Determines if a point falls before an allocated region.
Specified by:
isBefore in class CompositeView
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

isAfter

protected boolean isAfter(int x, int y, Rectangle innerAlloc)
Determines if a point falls after an allocated region.
Specified by:
isAfter in class CompositeView
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

getViewAtPoint

protected View getViewAtPoint(int x, int y, Rectangle alloc)
Fetches the child view at the given coordinates.
Specified by:
getViewAtPoint in class CompositeView
Parameters:
x - the X coordinate >= 0
y - the Y coordinate >= 0
alloc - the parents inner allocation on entry, which should be changed to the child's allocation on exit
Returns:
the view

childAllocation

protected void childAllocation(int index, Rectangle alloc)
Allocates a region for a child view.
Specified by:
childAllocation in class CompositeView
Parameters:
index - the index of the child view to allocate, >= 0 && < getViewCount()
alloc - the allocated region

layout

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

getWidth

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

getHeight

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

layoutMajorAxis

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

layoutMinorAxis

protected void layoutMinorAxis(int targetSpan, int axis, int[] offsets, int[] spans)
Performs layout for the minor axis of the box (i.e. the axis orthogonal 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

calculateMajorAxisRequirements

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:

calculateMinorAxisRequirements

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:

baselineLayout

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

baselineRequirements

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

getOffset

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

getSpan

protected int getSpan(int axis, int childIndex)
Fetches the span of a particular child's 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

flipEastAndWestAtEnds

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 return the value from invoking the same method on the View responsible for rendering position and bias. Otherwise this will return false.

Overrides:
flipEastAndWestAtEnds in class CompositeView
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

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https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/javax/swing/text/BoxView.html