* 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.
*
* @author Timothy Prinzing
*/
public class BoxView extends CompositeView {
/**
* Constructs a BoxView.
*
* @param elem the element this view is responsible for
* @param axis either View.X_AXIS or View.Y_AXIS
*/
public BoxView(Element elem, int axis) {
super(elem);
tempRect = new Rectangle();
this.majorAxis = axis;
majorOffsets = new int[0];
majorSpans = new int[0];
majorReqValid = false;
majorAllocValid = false;
minorOffsets = new int[0];
minorSpans = new int[0];
minorReqValid = false;
minorAllocValid = false;
}
/**
* Fetches the tile axis property. This is the axis along which
* the child views are tiled.
*
* @return the major axis of the box, either
* View.X_AXIS or View.Y_AXIS
*
* @since 1.3
*/
public int getAxis() {
return majorAxis;
}
/**
* Sets the tile axis property. This is the axis along which
* the child views are tiled.
*
* @param axis either View.X_AXIS or View.Y_AXIS
*
* @since 1.3
*/
public void setAxis(int axis) {
boolean axisChanged = (axis != majorAxis);
majorAxis = axis;
if (axisChanged) {
preferenceChanged(null, true, true);
}
}
/**
* 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).
*
* @param axis either View.X_AXIS or View.Y_AXIS
*
* @since 1.3
*/
public void layoutChanged(int axis) {
if (axis == majorAxis) {
majorAllocValid = false;
} else {
minorAllocValid = false;
}
}
/**
* Determines if the layout is valid along the given axis.
*
* @param axis either View.X_AXIS or View.Y_AXIS
*
* @since 1.4
*/
protected boolean isLayoutValid(int axis) {
if (axis == majorAxis) {
return majorAllocValid;
} else {
return minorAllocValid;
}
}
/**
* Paints a child. By default
* that is all it does, but a subclass can use this to paint
* things relative to the child.
*
* @param g the graphics context
* @param alloc the allocated region to paint into
* @param index the child index, >= 0 && < getViewCount()
*/
protected void paintChild(Graphics g, Rectangle alloc, int index) {
View child = getView(index);
child.paint(g, alloc);
}
// --- View methods ---------------------------------------------
/**
* 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.
*
* @param index the starting index into the child views to insert
* the new views; this should be a value >= 0 and <= getViewCount
* @param length the number of existing child views to remove;
* This should be a value >= 0 and <= (getViewCount() - offset)
* @param elems the child views to add; this value can be
* nullto indicate no children are being added
* (useful to remove)
*/
public void replace(int index, int length, View[] elems) {
super.replace(index, length, elems);
// invalidate cache
int nInserted = (elems != null) ? elems.length : 0;
majorOffsets = updateLayoutArray(majorOffsets, index, nInserted);
majorSpans = updateLayoutArray(majorSpans, index, nInserted);
majorReqValid = false;
majorAllocValid = false;
minorOffsets = updateLayoutArray(minorOffsets, index, nInserted);
minorSpans = updateLayoutArray(minorSpans, index, nInserted);
minorReqValid = false;
minorAllocValid = false;
}
/**
* Resizes the given layout array to match the new number of
* child views. The current number of child views are used to
* produce the new array. The contents of the old array are
* inserted into the new array at the appropriate places so that
* the old layout information is transferred to the new array.
*
* @param oldArray the original layout array
* @param offset location where new views will be inserted
* @param nInserted the number of child views being inserted;
* therefore the number of blank spaces to leave in the
* new array at location offset
* @return the new layout array
*/
int[] updateLayoutArray(int[] oldArray, int offset, int nInserted) {
int n = getViewCount();
int[] newArray = new int[n];
System.arraycopy(oldArray, 0, newArray, 0, offset);
System.arraycopy(oldArray, offset,
newArray, offset + nInserted, n - nInserted - offset);
return newArray;
}
/**
* 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.
*
* @param ec changes to the element this view is responsible
* for (may be null if there were no changes)
* @param e the change information from the associated document
* @param a the current allocation of the view
* @param f the factory to use to rebuild if the view has children
* @see #insertUpdate
* @see #removeUpdate
* @see #changedUpdate
* @since 1.3
*/
protected void forwardUpdate(DocumentEvent.ElementChange ec,
DocumentEvent e, Shape a, ViewFactory f) {
boolean wasValid = isLayoutValid(majorAxis);
super.forwardUpdate(ec, e, a, f);
// determine if a repaint is needed
if (wasValid && (! isLayoutValid(majorAxis))) {
// Repaint is needed because one of the tiled children
// have changed their span along the major axis. If there
// is a hosting component and an allocated shape we repaint.
Component c = getContainer();
if ((a != null) && (c != null)) {
int pos = e.getOffset();
int index = getViewIndexAtPosition(pos);
Rectangle alloc = getInsideAllocation(a);
if (majorAxis == X_AXIS) {
alloc.x += majorOffsets[index];
alloc.width -= majorOffsets[index];
} else {
alloc.y += minorOffsets[index];
alloc.height -= minorOffsets[index];
}
c.repaint(alloc.x, alloc.y, alloc.width, alloc.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.
*
* @param child the child view
* @param width true if the width preference should change
* @param height true if the height preference should change
*/
public void preferenceChanged(View child, boolean width, boolean height) {
boolean majorChanged = (majorAxis == X_AXIS) ? width : height;
boolean minorChanged = (majorAxis == X_AXIS) ? height : width;
if (majorChanged) {
majorReqValid = false;
majorAllocValid = false;
}
if (minorChanged) {
minorReqValid = false;
minorAllocValid = false;
}
super.preferenceChanged(child, width, height);
}
/**
* Gets the resize weight. A value of 0 or less is not resizable.
*
* @param axis may be either View.X_AXIS or
* View.Y_AXIS
* @return the weight
* @exception IllegalArgumentException for an invalid axis
*/
public int getResizeWeight(int axis) {
checkRequests(axis);
if (axis == majorAxis) {
if ((majorRequest.preferred != majorRequest.minimum) ||
(majorRequest.preferred != majorRequest.maximum)) {
return 1;
}
} else {
if ((minorRequest.preferred != minorRequest.minimum) ||
(minorRequest.preferred != minorRequest.maximum)) {
return 1;
}
}
return 0;
}
/**
* Sets the size of the view along an axis. This should cause
* layout of the view along the given axis.
*
* @param axis may be either View.X_AXIS or
* View.Y_AXIS
* @param span the span to layout to >= 0
*/
void setSpanOnAxis(int axis, float span) {
if (axis == majorAxis) {
if (majorSpan != (int) span) {
majorAllocValid = false;
}
if (! majorAllocValid) {
// layout the major axis
majorSpan = (int) span;
checkRequests(majorAxis);
layoutMajorAxis(majorSpan, axis, majorOffsets, majorSpans);
majorAllocValid = true;
// flush changes to the children
updateChildSizes();
}
} else {
if (((int) span) != minorSpan) {
minorAllocValid = false;
}
if (! minorAllocValid) {
// layout the minor axis
minorSpan = (int) span;
checkRequests(axis);
layoutMinorAxis(minorSpan, axis, minorOffsets, minorSpans);
minorAllocValid = true;
// flush changes to the children
updateChildSizes();
}
}
}
/**
* Propagates the current allocations to the child views.
*/
void updateChildSizes() {
int n = getViewCount();
if (majorAxis == X_AXIS) {
for (int i = 0; i < n; i++) {
View v = getView(i);
v.setSize((float) majorSpans[i], (float) minorSpans[i]);
}
} else {
for (int i = 0; i < n; i++) {
View v = getView(i);
v.setSize((float) minorSpans[i], (float) majorSpans[i]);
}
}
}
/**
* Returns the size of the view along an axis. This is implemented
* to return zero.
*
* @param axis may be either View.X_AXIS or
* View.Y_AXIS
* @return the current span of the view along the given axis, >= 0
*/
float getSpanOnAxis(int axis) {
if (axis == majorAxis) {
return majorSpan;
} else {
return minorSpan;
}
}
/**
* 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.
*
* @param width the width >= 0
* @param height the height >= 0
*/
public void setSize(float width, float height) {
layout(Math.max(0, (int)(width - getLeftInset() - getRightInset())),
Math.max(0, (int)(height - getTopInset() - getBottomInset())));
}
/**
* 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.
*
* @param g the rendering surface to use
* @param allocation the allocated region to render into
* @see View#paint
*/
public void paint(Graphics g, Shape allocation) {
Rectangle alloc = (allocation instanceof Rectangle) ?
(Rectangle)allocation : allocation.getBounds();
int n = getViewCount();
int x = alloc.x + getLeftInset();
int y = alloc.y + getTopInset();
Rectangle clip = g.getClipBounds();
for (int i = 0; i < n; i++) {
tempRect.x = x + getOffset(X_AXIS, i);
tempRect.y = y + getOffset(Y_AXIS, i);
tempRect.width = getSpan(X_AXIS, i);
tempRect.height = getSpan(Y_AXIS, i);
int trx0 = tempRect.x, trx1 = trx0 + tempRect.width;
int try0 = tempRect.y, try1 = try0 + tempRect.height;
int crx0 = clip.x, crx1 = crx0 + clip.width;
int cry0 = clip.y, cry1 = cry0 + clip.height;
// We should paint views that intersect with clipping region
// even if the intersection has no inside points (is a line).
// This is needed for supporting views that have zero width, like
// views that contain only combining marks.
if ((trx1 >= crx0) && (try1 >= cry0) && (crx1 >= trx0) && (cry1 >= try0)) {
paintChild(g, tempRect, i);
}
}
}
/**
* 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.
*
* @param index the index of the child, >= 0 && < getViewCount()
* @param a the allocation to this view
* @return the allocation to the child; or null
* if a is null;
* or null if the layout is invalid
*/
public Shape getChildAllocation(int index, Shape a) {
if (a != null) {
Shape ca = super.getChildAllocation(index, a);
if ((ca != null) && (! isAllocationValid())) {
// The child allocation may not have been set yet.
Rectangle r = (ca instanceof Rectangle) ?
(Rectangle) ca : ca.getBounds();
if ((r.width == 0) && (r.height == 0)) {
return null;
}
}
return ca;
}
return null;
}
/**
* 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.
*
* @param pos the position to convert >= 0
* @param a the allocated region to render into
* @return the bounding box of the given position
* @exception BadLocationException if the given position does
* not represent a valid location in the associated document
* @see View#modelToView
*/
public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {
if (! isAllocationValid()) {
Rectangle alloc = a.getBounds();
setSize(alloc.width, alloc.height);
}
return super.modelToView(pos, a, b);
}
/**
* Provides a mapping from the view coordinate space to the logical
* coordinate space of the model.
*
* @param x x coordinate of the view location to convert >= 0
* @param y y coordinate of the view location to convert >= 0
* @param a the allocated region to render into
* @return the location within the model that best represents the
* given point in the view >= 0
* @see View#viewToModel
*/
public int viewToModel(float x, float y, Shape a, Position.Bias[] bias) {
if (! isAllocationValid()) {
Rectangle alloc = a.getBounds();
setSize(alloc.width, alloc.height);
}
return super.viewToModel(x, y, a, bias);
}
/**
* 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).
*
* @param axis may be either View.X_AXIS
* or View.Y_AXIS
* @return 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
* @exception IllegalArgumentException for an invalid axis
*/
public float getAlignment(int axis) {
checkRequests(axis);
if (axis == majorAxis) {
return majorRequest.alignment;
} else {
return minorRequest.alignment;
}
}
/**
* Determines the preferred span for this view along an
* axis.
*
* @param axis may be either View.X_AXIS
* or View.Y_AXIS
* @return 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
* @exception IllegalArgumentException for an invalid axis type
*/
public float getPreferredSpan(int axis) {
checkRequests(axis);
float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
getTopInset() + getBottomInset();
if (axis == majorAxis) {
return ((float)majorRequest.preferred) + marginSpan;
} else {
return ((float)minorRequest.preferred) + marginSpan;
}
}
/**
* Determines the minimum span for this view along an
* axis.
*
* @param axis may be either View.X_AXIS
* or View.Y_AXIS
* @return 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
* @exception IllegalArgumentException for an invalid axis type
*/
public float getMinimumSpan(int axis) {
checkRequests(axis);
float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
getTopInset() + getBottomInset();
if (axis == majorAxis) {
return ((float)majorRequest.minimum) + marginSpan;
} else {
return ((float)minorRequest.minimum) + marginSpan;
}
}
/**
* Determines the maximum span for this view along an
* axis.
*
* @param axis may be either View.X_AXIS
* or View.Y_AXIS
* @return 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
* @exception IllegalArgumentException for an invalid axis type
*/
public float getMaximumSpan(int axis) {
checkRequests(axis);
float marginSpan = (axis == X_AXIS) ? getLeftInset() + getRightInset() :
getTopInset() + getBottomInset();
if (axis == majorAxis) {
return ((float)majorRequest.maximum) + marginSpan;
} else {
return ((float)minorRequest.maximum) + marginSpan;
}
}
// --- local methods ----------------------------------------------------
/**
* Are the allocations for the children still
* valid?
*
* @return true if allocations still valid
*/
protected boolean isAllocationValid() {
return (majorAllocValid && minorAllocValid);
}
/**
* Determines if a point falls before an allocated region.
*
* @param x the X coordinate >= 0
* @param y the Y coordinate >= 0
* @param innerAlloc the allocated region; this is the area
* inside of the insets
* @return true if the point lies before the region else false
*/
protected boolean isBefore(int x, int y, Rectangle innerAlloc) {
if (majorAxis == View.X_AXIS) {
return (x < innerAlloc.x);
} else {
return (y < innerAlloc.y);
}
}
/**
* Determines if a point falls after an allocated region.
*
* @param x the X coordinate >= 0
* @param y the Y coordinate >= 0
* @param innerAlloc the allocated region; this is the area
* inside of the insets
* @return true if the point lies after the region else false
*/
protected boolean isAfter(int x, int y, Rectangle innerAlloc) {
if (majorAxis == View.X_AXIS) {
return (x > (innerAlloc.width + innerAlloc.x));
} else {
return (y > (innerAlloc.height + innerAlloc.y));
}
}
/**
* Fetches the child view at the given coordinates.
*
* @param x the X coordinate >= 0
* @param y the Y coordinate >= 0
* @param alloc the parents inner allocation on entry, which should
* be changed to the childs allocation on exit
* @return the view
*/
protected View getViewAtPoint(int x, int y, Rectangle alloc) {
int n = getViewCount();
if (majorAxis == View.X_AXIS) {
if (x < (alloc.x + majorOffsets[0])) {
childAllocation(0, alloc);
return getView(0);
}
for (int i = 0; i < n; i++) {
if (x < (alloc.x + majorOffsets[i])) {
childAllocation(i - 1, alloc);
return getView(i - 1);
}
}
childAllocation(n - 1, alloc);
return getView(n - 1);
} else {
if (y < (alloc.y + majorOffsets[0])) {
childAllocation(0, alloc);
return getView(0);
}
for (int i = 0; i < n; i++) {
if (y < (alloc.y + majorOffsets[i])) {
childAllocation(i - 1, alloc);
return getView(i - 1);
}
}
childAllocation(n - 1, alloc);
return getView(n - 1);
}
}
/**
* Allocates a region for a child view.
*
* @param index the index of the child view to
* allocate, >= 0 && < getViewCount()
* @param alloc the allocated region
*/
protected void childAllocation(int index, Rectangle alloc) {
alloc.x += getOffset(X_AXIS, index);
alloc.y += getOffset(Y_AXIS, index);
alloc.width = getSpan(X_AXIS, index);
alloc.height = getSpan(Y_AXIS, index);
}
/**
* Perform layout on the box
*
* @param width the width (inside of the insets) >= 0
* @param height the height (inside of the insets) >= 0
*/
protected void layout(int width, int height) {
setSpanOnAxis(X_AXIS, width);
setSpanOnAxis(Y_AXIS, height);
}
/**
* Returns the current width of the box. This is the width that
* it was last allocated.
* @return the current width of the box
*/
public int getWidth() {
int span;
if (majorAxis == X_AXIS) {
span = majorSpan;
} else {
span = minorSpan;
}
span += getLeftInset() - getRightInset();
return span;
}
/**
* Returns the current height of the box. This is the height that
* it was last allocated.
* @return the current height of the box
*/
public int getHeight() {
int span;
if (majorAxis == Y_AXIS) {
span = majorSpan;
} else {
span = minorSpan;
}
span += getTopInset() - getBottomInset();
return span;
}
/**
* 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.
*
* @param targetSpan the total span given to the view, which
* would be used to layout the children
* @param axis the axis being layed out
* @param 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
* @param spans the span of each child view; this is a return
* value and is filled in by the implementation of this method
*/
protected void layoutMajorAxis(int targetSpan, int axis, int[] offsets, int[] spans) {
/*
* first pass, calculate the preferred sizes
* and the flexibility to adjust the sizes.
*/
long preferred = 0;
int n = getViewCount();
for (int i = 0; i < n; i++) {
View v = getView(i);
spans[i] = (int) v.getPreferredSpan(axis);
preferred += spans[i];
}
/*
* Second pass, expand or contract by as much as possible to reach
* the target span.
*/
// determine the adjustment to be made
long desiredAdjustment = targetSpan - preferred;
float adjustmentFactor = 0.0f;
int[] diffs = null;
if (desiredAdjustment != 0) {
long totalSpan = 0;
diffs = new int[n];
for (int i = 0; i < n; i++) {
View v = getView(i);
int tmp;
if (desiredAdjustment < 0) {
tmp = (int)v.getMinimumSpan(axis);
diffs[i] = spans[i] - tmp;
} else {
tmp = (int)v.getMaximumSpan(axis);
diffs[i] = tmp - spans[i];
}
totalSpan += tmp;
}
float maximumAdjustment = Math.abs(totalSpan - preferred);
adjustmentFactor = desiredAdjustment / maximumAdjustment;
adjustmentFactor = Math.min(adjustmentFactor, 1.0f);
adjustmentFactor = Math.max(adjustmentFactor, -1.0f);
}
// make the adjustments
int totalOffset = 0;
for (int i = 0; i < n; i++) {
offsets[i] = totalOffset;
if (desiredAdjustment != 0) {
float adjF = adjustmentFactor * diffs[i];
spans[i] += Math.round(adjF);
}
totalOffset = (int) Math.min((long) totalOffset + (long) spans[i], Integer.MAX_VALUE);
}
}
/**
* 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.
*
* @param targetSpan the total span given to the view, which
* would be used to layout the children
* @param axis the axis being layed out
* @param 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
* @param 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) {
int n = getViewCount();
for (int i = 0; i < n; i++) {
View v = getView(i);
int max = (int) v.getMaximumSpan(axis);
if (max < targetSpan) {
// can't make the child this wide, align it
float align = v.getAlignment(axis);
offsets[i] = (int) ((targetSpan - max) * align);
spans[i] = max;
} else {
// make it the target width, or as small as it can get.
int min = (int)v.getMinimumSpan(axis);
offsets[i] = 0;
spans[i] = Math.max(min, targetSpan);
}
}
}
/**
* Calculates the size requirements for the major axis
* axis.
*
* @param axis the axis being studied
* @param r the SizeRequirements object;
* if null one will be created
* @return the newly initialized SizeRequirements object
* @see javax.swing.SizeRequirements
*/
protected SizeRequirements calculateMajorAxisRequirements(int axis, SizeRequirements r) {
// calculate tiled request
float min = 0;
float pref = 0;
float max = 0;
int n = getViewCount();
for (int i = 0; i < n; i++) {
View v = getView(i);
min += v.getMinimumSpan(axis);
pref += v.getPreferredSpan(axis);
max += v.getMaximumSpan(axis);
}
if (r == null) {
r = new SizeRequirements();
}
r.alignment = 0.5f;
r.minimum = (int) min;
r.preferred = (int) pref;
r.maximum = (int) max;
return r;
}
/**
* Calculates the size requirements for the minor axis
* axis.
*
* @param axis the axis being studied
* @param r the SizeRequirements object;
* if null one will be created
* @return the newly initialized SizeRequirements object
* @see javax.swing.SizeRequirements
*/
protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r) {
int min = 0;
long pref = 0;
int max = Integer.MAX_VALUE;
int n = getViewCount();
for (int i = 0; i < n; i++) {
View v = getView(i);
min = Math.max((int) v.getMinimumSpan(axis), min);
pref = Math.max((int) v.getPreferredSpan(axis), pref);
max = Math.max((int) v.getMaximumSpan(axis), max);
}
if (r == null) {
r = new SizeRequirements();
r.alignment = 0.5f;
}
r.preferred = (int) pref;
r.minimum = min;
r.maximum = max;
return r;
}
/**
* Checks the request cache and update if needed.
* @param axis the axis being studied
* @exception IllegalArgumentException if axis is
* neither View.X_AXIS nor View.Y_AXIS
*/
void checkRequests(int axis) {
if ((axis != X_AXIS) && (axis != Y_AXIS)) {
throw new IllegalArgumentException("Invalid axis: " + axis);
}
if (axis == majorAxis) {
if (!majorReqValid) {
majorRequest = calculateMajorAxisRequirements(axis,
majorRequest);
majorReqValid = true;
}
} else if (! minorReqValid) {
minorRequest = calculateMinorAxisRequirements(axis, minorRequest);
minorReqValid = true;
}
}
/**
* 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.
*
* @param targetSpan the total span given to the view, which
* would be used to layout the children
* @param axis the axis being studied, either
* View.X_AXIS or View.Y_AXIS
* @param offsets an empty array filled by this method with
* values specifying the location of each child view
* @param spans an empty array filled by this method with
* values specifying the extent of each child view
*/
protected void baselineLayout(int targetSpan, int axis, int[] offsets, int[] spans) {
int totalAscent = (int)(targetSpan * getAlignment(axis));
int totalDescent = targetSpan - totalAscent;
int n = getViewCount();
for (int i = 0; i < n; i++) {
View v = getView(i);
float align = v.getAlignment(axis);
float viewSpan;
if (v.getResizeWeight(axis) > 0) {
// if resizable then resize to the best fit
// the smallest span possible
float minSpan = v.getMinimumSpan(axis);
// the largest span possible
float maxSpan = v.getMaximumSpan(axis);
if (align == 0.0f) {
// if the alignment is 0 then we need to fit into the descent
viewSpan = Math.max(Math.min(maxSpan, totalDescent), minSpan);
} else if (align == 1.0f) {
// if the alignment is 1 then we need to fit into the ascent
viewSpan = Math.max(Math.min(maxSpan, totalAscent), minSpan);
} else {
// figure out the span that we must fit into
float fitSpan = Math.min(totalAscent / align,
totalDescent / (1.0f - align));
// fit into the calculated span
viewSpan = Math.max(Math.min(maxSpan, fitSpan), minSpan);
}
} else {
// otherwise use the preferred spans
viewSpan = v.getPreferredSpan(axis);
}
offsets[i] = totalAscent - (int)(viewSpan * align);
spans[i] = (int)viewSpan;
}
}
/**
* Calculates the size requirements for this BoxView
* by examining the size of each child view.
*
* @param axis the axis being studied
* @param r the SizeRequirements object;
* if null one will be created
* @return the newly initialized SizeRequirements object
*/
protected SizeRequirements baselineRequirements(int axis, SizeRequirements r) {
SizeRequirements totalAscent = new SizeRequirements();
SizeRequirements totalDescent = new SizeRequirements();
if (r == null) {
r = new SizeRequirements();
}
r.alignment = 0.5f;
int n = getViewCount();
// loop through all children calculating the max of all their ascents and
// descents at minimum, preferred, and maximum sizes
for (int i = 0; i < n; i++) {
View v = getView(i);
float align = v.getAlignment(axis);
float span;
int ascent;
int descent;
// find the maximum of the preferred ascents and descents
span = v.getPreferredSpan(axis);
ascent = (int)(align * span);
descent = (int)(span - ascent);
totalAscent.preferred = Math.max(ascent, totalAscent.preferred);
totalDescent.preferred = Math.max(descent, totalDescent.preferred);
if (v.getResizeWeight(axis) > 0) {
// if the view is resizable then do the same for the minimum and
// maximum ascents and descents
span = v.getMinimumSpan(axis);
ascent = (int)(align * span);
descent = (int)(span - ascent);
totalAscent.minimum = Math.max(ascent, totalAscent.minimum);
totalDescent.minimum = Math.max(descent, totalDescent.minimum);
span = v.getMaximumSpan(axis);
ascent = (int)(align * span);
descent = (int)(span - ascent);
totalAscent.maximum = Math.max(ascent, totalAscent.maximum);
totalDescent.maximum = Math.max(descent, totalDescent.maximum);
} else {
// otherwise use the preferred
totalAscent.minimum = Math.max(ascent, totalAscent.minimum);
totalDescent.minimum = Math.max(descent, totalDescent.minimum);
totalAscent.maximum = Math.max(ascent, totalAscent.maximum);
totalDescent.maximum = Math.max(descent, totalDescent.maximum);
}
}
// we now have an overall preferred, minimum, and maximum ascent and descent
// calculate the preferred span as the sum of the preferred ascent and preferred descent
r.preferred = (int)Math.min((long)totalAscent.preferred + (long)totalDescent.preferred,
Integer.MAX_VALUE);
// calculate the preferred alignment as the preferred ascent divided by the preferred span
if (r.preferred > 0) {
r.alignment = (float)totalAscent.preferred / r.preferred;
}
if (r.alignment == 0.0f) {
// if the preferred alignment is 0 then the minimum and maximum spans are simply
// the minimum and maximum descents since there's nothing above the baseline
r.minimum = totalDescent.minimum;
r.maximum = totalDescent.maximum;
} else if (r.alignment == 1.0f) {
// if the preferred alignment is 1 then the minimum and maximum spans are simply
// the minimum and maximum ascents since there's nothing below the baseline
r.minimum = totalAscent.minimum;
r.maximum = totalAscent.maximum;
} else {
// we want to honor the preferred alignment so we calculate two possible minimum
// span values using 1) the minimum ascent and the alignment, and 2) the minimum
// descent and the alignment. We'll choose the larger of these two numbers.
r.minimum = Math.round(Math.max(totalAscent.minimum / r.alignment,
totalDescent.minimum / (1.0f - r.alignment)));
// a similar calculation is made for the maximum but we choose the smaller number.
r.maximum = Math.round(Math.min(totalAscent.maximum / r.alignment,
totalDescent.maximum / (1.0f - r.alignment)));
}
return r;
}
/**
* Fetches the offset of a particular child's current layout.
* @param axis the axis being studied
* @param childIndex the index of the requested child
* @return the offset (location) for the specified child
*/
protected int getOffset(int axis, int childIndex) {
int[] offsets = (axis == majorAxis) ? majorOffsets : minorOffsets;
return offsets[childIndex];
}
/**
* Fetches the span of a particular childs current layout.
* @param axis the axis being studied
* @param childIndex the index of the requested child
* @return the span (width or height) of the specified child
*/
protected int getSpan(int axis, int childIndex) {
int[] spans = (axis == majorAxis) ? majorSpans : minorSpans;
return spans[childIndex];
}
/**
* 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.
*
* @param position position into the model
* @param bias either Position.Bias.Forward or
* Position.Bias.Backward
* @return true if the Views surrounding the
* View responding for rendering
* position and bias
* are layed out in descending order; otherwise false
*/
protected boolean flipEastAndWestAtEnds(int position,
Position.Bias bias) {
if(majorAxis == Y_AXIS) {
int testPos = (bias == Position.Bias.Backward) ?
Math.max(0, position - 1) : position;
int index = getViewIndexAtPosition(testPos);
if(index != -1) {
View v = getView(index);
if(v != null && v instanceof CompositeView) {
return ((CompositeView)v).flipEastAndWestAtEnds(position,
bias);
}
}
}
return false;
}
// --- variables ------------------------------------------------
int majorAxis;
int majorSpan;
int minorSpan;
/*
* Request cache
*/
boolean majorReqValid;
boolean minorReqValid;
SizeRequirements majorRequest;
SizeRequirements minorRequest;
/*
* Allocation cache
*/
boolean majorAllocValid;
int[] majorOffsets;
int[] majorSpans;
boolean minorAllocValid;
int[] minorOffsets;
int[] minorSpans;
/** used in paint. */
Rectangle tempRect;
}