ej.mwt

Class Widget

java.lang.Object

ej.mwt.Widget

Direct Known Subclasses:

Container, ImageWidget, Label

public abstract class Widget
extends Object

Widget is the superclass of all the user interface objects.

There are a number of important concepts involving widgets:

• Lay out.

  Lay out is the process of positioning and setting the size of the widgets on a desktop.

  This is performed by evaluating the optimal size of each widget and container in the hierarchy then, considering the layout of the containers and the optimal size of their children, setting the position and actual size of all widgets.

  The optimal size is the minimal size that allow to show correctly the content of a widget. For instance the optimal size of a label that displays a string will be the size of the string with the font defined in the style.

  The optimal size is computed by computeContentOptimalSize(Size) method. On this size are applied the boxes and dimension defined in the style, and the size of the widget is set. This size is then used by the parent container to lay out (set position and size) the widget along with its siblings.

  Whenever the state of a widget changes in a way that may affect its optimal size and the lay out of the desktop of which it is a part then the hierarchy of the widget must be ask to perform a new lay out. This can be achieved by invoking requestLayOut() on one of the parents of the widget or the desktop depending on the lay out modification.

  An application will normally invoke requestLayOut() after making a set of changes to widgets.

• Rendering.

  Any widget can be asked to render itself by invoking requestRender(). If a widget has children it will ask them to render. If the widget is transparent it will cause the relevant area of its parent to be rendered. Note that a render request does not trigger a new lay out, and the scope of the rendering that results from a call to requestRender() will never exceed the widget itself, its children (recursively), and, if it is transparent, its parent (recursively if the parent is also transparent).

For heap optimization the position and size are stored as a short and therefore are limited between -32768 and 32767.

Field Summary

Fields

Modifier and Type	Field and Description
static int	NO_CONSTRAINT A width or height hint equal to NO_CONSTRAINT means that there is no constraint on this dimension.

Constructor Summary

Constructors

Constructor and Description
Widget() Creates a widget.

Method Summary

Modifier and Type	Method and Description
void	addClassSelector(int classSelector) Adds a class selector.
protected abstract void	computeContentOptimalSize(Size size) Computes the optimal size of the widget.
boolean	contains(int x, int y) Gets whether or not a position (x,y) is in the widget's bounds.
boolean	containsWidget(Widget widget) Returns whether or not this widget contains the given widget in its hierarchy.
int	getAbsoluteX() Gets the absolute x coordinate of the widget.
int	getAbsoluteY() Gets the absolute y coordinate of the widget.
Rectangle	getContentBounds() Gets the content bounds of this widget (the bounds minus the outlines).
Desktop	getDesktop() Gets the desktop to which this widget has been added.
int	getHeight() Gets the height of this widget.
Container	getParent() Gets the parent of this widget or null if the widget is not in a hierarchy or if it is the root of its hierarchy.
Style	getStyle() Gets the current style of the widget.
Widget	getWidgetAt(int x, int y) Gets the widget at the specified position.
int	getWidth() Gets the width of this widget.
int	getX() Gets the x coordinate of this widget, relative to its parent.
int	getY() Gets the y coordinate of this widget, relative to its parent.
boolean	handleEvent(int event) Handles the given event.
boolean	hasClassSelector(int classSelector) Gets whether or not the widget has the given class selector.
boolean	isAttached() Gets whether this widget is attached or not.
boolean	isEnabled() Gets whether or not this widget is enabled.
boolean	isInState(int state) Gets whether or not the widget is in the given state.
boolean	isShown() Gets whether this widget is shown or not.
boolean	isTransparent() Tells whether or not this widget is transparent.
protected void	onAttached() This method is called as soon as: the widget is attached to a desktop that is attached, the desktop of the widget is attached.
protected void	onDetached() This method is called as soon as: the widget is detached from a desktop that is attached, the desktop of the widget is detached.
protected void	onHidden() This method is called as soon as the widget is no more visible on the display.
protected void	onLaidOut() This method is called as soon as the widget bounds are set.
protected void	onShown() This method is called as soon as the widget is visible on the display.
void	removeAllClassSelectors() Removes all the class selectors.
void	removeClassSelector(int classSelector) Removes a class selector.
void	render(GraphicsContext g) Renders the widget on the given graphics context.
protected abstract void	renderContent(GraphicsContext g, int contentWidth, int contentHeight) Renders the content of the widget without the border, margin and padding specified in the style.
void	requestLayOut() Requests a lay out of all the widgets in the sub hierarchy of this widget.
void	requestRender() Requests a render of this entire widget on the display.
void	requestRender(int x, int y, int width, int height) Requests a render of a zone of this widget on the display.
void	setClassSelectors(int[] classSelectors) Sets the class selectors.
void	setEnabled(boolean enabled) Sets this widget to be enabled or not.
void	setPosition(int x, int y) Sets the position of this widget.
void	setStyle(Style newStyle) Sets the style of the widget.
void	updateStyle() Updates the style of this widget.

Methods inherited from class java.lang.Object

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

Field Detail

NO_CONSTRAINT

public static final int NO_CONSTRAINT

A width or height hint equal to NO_CONSTRAINT means that there is no constraint on this dimension.

See Also:

computeContentOptimalSize(Size), Constant Field Values

Constructor Detail

Widget

public Widget()

Creates a widget.

Once created, the widget is disabled. It may be enabled by calling setEnabled(boolean). Enabled widgets can handle events by overriding handleEvent(int).

Method Detail

addClassSelector

public void addClassSelector(int classSelector)

Adds a class selector.

Parameters:

classSelector - the class selector to add.

Throws:

NullPointerException - if the given class selector is null.

computeContentOptimalSize

protected abstract void computeContentOptimalSize(Size size)

Computes the optimal size of the widget.

This method does not consider the border, margin, padding and dimension specified in the style.

The given size is the available size for this widget in its parent. A width or a height equal to Widget#NO_CONSTRAINT means that there is no constraint on this dimension.

The given size is modified to set the optimal size.

Parameters:

size - the size available for the content.

contains

public boolean contains(int x,
                        int y)

Gets whether or not a position (x,y) is in the widget's bounds.

The given position is considered here as a relative position to parent.

Subclasses can override this method if the widget is not reactive to pointer events in its entire bounds. As long as this method is used to dispatch pointer events, its implementation should be as fast as possible (for example by simplifying the shape of the sensitive area).

If this method is overridden, it may be relevant to override the isTransparent() method as well.

Parameters:

x - x coordinate.

y - y coordinate.

Returns:

true if the (x,y) position is in widget bounds, false otherwise.

containsWidget

public boolean containsWidget(Widget widget)

Returns whether or not this widget contains the given widget in its hierarchy.

A widget contains an other widget if one of the children of the former contains the latter or if they reference the same widget.

Parameters:

widget - the widget to check.

Returns:

true if this widget contains the given widget, false otherwise.

getAbsoluteX

public int getAbsoluteX()

Gets the absolute x coordinate of the widget. That is, the x coordinate relative to the origin of the display.

Returns:

the absolute x coordinate of the widget.

getAbsoluteY

public int getAbsoluteY()

Gets the absolute y coordinate of the widget. That is, the y coordinate relative to the origin of the display.

Returns:

the absolute y coordinate of the widget.

getContentBounds

public Rectangle getContentBounds()

Gets the content bounds of this widget (the bounds minus the outlines).

Returns:

the content bounds of this widget.

getDesktop

public Desktop getDesktop()

Gets the desktop to which this widget has been added.

This method can only be called if this widget has been added to a desktop.

Returns:

the desktop to which this widgets has been added.

getHeight

public int getHeight()

Gets the height of this widget.

Returns:

the height.

getParent

@Nullable
public Container getParent()

Gets the parent of this widget or null if the widget is not in a hierarchy or if it is the root of its hierarchy.

Returns:

the parent of this widget or null.

getStyle

public Style getStyle()

Gets the current style of the widget.

This method should not be called before this widget is laid out.

Returns:

the current style of the widget.

See Also:

Stylesheet.getStyle(Widget)

getWidgetAt

@Nullable
public Widget getWidgetAt(int x,
                                    int y)

Gets the widget at the specified position.

If this widget does not contains(x, y), null is returned, else this widget is returned. The position is considered here as a relative position to parent.

Parameters:

x - x coordinate.

y - y coordinate.

Returns:

this widget if it contains(x, y), null otherwise.

getWidth

public int getWidth()

Gets the width of this widget.

Returns:

the width.

getX

public int getX()

Gets the x coordinate of this widget, relative to its parent.

Returns:

the x coordinate.

getY

public int getY()

Gets the y coordinate of this widget, relative to its parent.

Returns:

the y coordinate.

handleEvent

public boolean handleEvent(int event)

Handles the given event. Does nothing by default and returns false (does not consume event).

Called by the desktop event manager.

Parameters:

event - the event to handle.

Returns:

true if the widget has consumed the event, false otherwise.

hasClassSelector

public boolean hasClassSelector(int classSelector)

Gets whether or not the widget has the given class selector.

Parameters:

classSelector - the class selector to check.

Returns:

true if the widget has the given class selector, false otherwise.

isAttached

public boolean isAttached()

Gets whether this widget is attached or not.

A widget is considered as attached if it belongs to the hierarchy of an attached desktop.

Returns:

true if this widget is attached, false otherwise.

isEnabled

public boolean isEnabled()

Gets whether or not this widget is enabled.

Returns:

true if this widget is enabled, false otherwise.

isInState

public boolean isInState(int state)

Gets whether or not the widget is in the given state.

Parameters:

state - the state to check.

Returns:

true if the widget is in the given state, false otherwise.

isShown

public boolean isShown()

Gets whether this widget is shown or not.

Returns:

true if this widget is shown, false otherwise.

isTransparent

public boolean isTransparent()

Tells whether or not this widget is transparent.

By default, a widget is transparent. A widget is considered as transparent if it does not draw every pixel of its bounds with maximal opacity when it is rendered. If a widget is transparent, its parent (recursively if also transparent) has to be rendered before the widget.

Returns:

true if this widget is transparent, false otherwise.

See Also:

contains(int, int)

onAttached

protected void onAttached()

This method is called as soon as:

• the widget is attached to a desktop that is attached,
• the desktop of the widget is attached.

After this call, the widget is ready to be rendered.

For example, the widget can allocate some resources useful to render it.

See Also:

Desktop.setAttached()

onDetached

protected void onDetached()

This method is called as soon as:

• the widget is detached from a desktop that is attached,
• the desktop of the widget is detached.

After this call, the resources allocated to render the widget must be disposed.

See Also:

Desktop.setDetached()

onHidden

protected void onHidden()

This method is called as soon as the widget is no more visible on the display.

After this call, all that has been allocated or started in onShown() must be disposed or stopped.

onLaidOut

protected void onLaidOut()

This method is called as soon as the widget bounds are set.

onShown

protected void onShown()

This method is called as soon as the widget is visible on the display.

For example, this method can be used to start a task that refreshes the widget periodically.

removeAllClassSelectors

public void removeAllClassSelectors()

Removes all the class selectors.

removeClassSelector

public void removeClassSelector(int classSelector)

Removes a class selector.

Parameters:

classSelector - the class selector to remove.

render

public void render(GraphicsContext g)

Renders the widget on the given graphics context.

The given graphics context is translated to the origin of the widget and clipped to the area to draw.

First, the different outlines defined in the style are applied, then, the content is rendered.

Parameters:

g - the graphics context to use to draw the widget.

See Also:

OutlineHelper.applyOutlinesAndBackground(GraphicsContext, Size, Style), renderContent(GraphicsContext, int, int)

renderContent

protected abstract void renderContent(GraphicsContext g,
                                      int contentWidth,
                                      int contentHeight)

Renders the content of the widget without the border, margin and padding specified in the style.

The given graphics context is translated and clipped according to the given bounds (the border, margin and padding are applied on this graphics context before).

Parameters:

g - the graphics context where to render the content of the widget.

contentWidth - the width of the content area.

contentHeight - the height of the content area.

requestLayOut

public void requestLayOut()

Requests a lay out of all the widgets in the sub hierarchy of this widget.

This method returns immediately and the layout of the widget is performed asynchronously in the MicroUI thread.

This method can only be called if this widget has been added to a desktop.

Nothing is done if the widget is not attached.

If the widget was not already shown, it is shown as soon as its bounds are set.

The style of all the widgets in the hierarchy is set (or updated) during this phase.

requestRender

public void requestRender()

Requests a render of this entire widget on the display. This method returns immediately and the rendering of the widget is performed asynchronously in the MicroUI thread.

If the widget is not shown, nothing is done.

See Also:

RenderPolicy

requestRender

public void requestRender(int x,
                          int y,
                          int width,
                          int height)

Requests a render of a zone of this widget on the display. This method returns immediately and the rendering of the widget is performed asynchronously in the MicroUI thread.

If the widget is not shown, nothing is done.

If the given area exceeds the bounds of the widget, only the intersection of the widget and the area will be rendered.

Parameters:

x - the relative x coordinate of the area to render.

y - the relative y coordinate of the area to render.

width - the width of the area to render.

height - the height of the area to render.

See Also:

RenderPolicy

setClassSelectors

public void setClassSelectors(int[] classSelectors)

Sets the class selectors.

If there is already some class selectors, they are removed.

Parameters:

classSelectors - the class selectors list to split.

setEnabled

public void setEnabled(boolean enabled)

Sets this widget to be enabled or not.

Parameters:

enabled - true if this widget is to be enabled, false otherwise.

setPosition

public void setPosition(int x,
                        int y)

Sets the position of this widget.

Parameters:

x - the x coordinate to set.

y - the y coordinate to set.

setStyle

public void setStyle(Style newStyle)

Sets the style of the widget.

Parameters:

newStyle - the style to set.

updateStyle

public void updateStyle()

Updates the style of this widget.

If the widget is not in a desktop, nothing is done.