A
JTextCanvas
is the Swing version of the custom Yoix component that is sometimes used
to display, scroll, and otherwise manage text messages.
Yoix programs normally interact with a
JTextCanvas
using event handlers and by reading or writing the following fields:
| alignment |
An
int
that controls the positioning of the text in the textcanvas.
The value should be
LEFT,
CENTER,
or
RIGHT,
which are all defined in
yoix.swing.
Reading returns the current alignment.
Writing immediately repaints the text using the new alignment.
| | autotrim |
An
int
that is
1
when white space is automatically trimmed from both ends of every string
read from or written to the
text
field, and
0
otherwise.
| | background |
The
Color
that is used to paint the background of the textcanvas.
Reading returns a snapshot of the current color.
Writing immediately changes the background to the new color.
Storing
NULL
in
background
is special and means use the background of the nearest component
that contains the textcanvas and was assigned a background color other than
NULL;
if no component qualifies the textcanvas uses
VM.screen.background.
| | border |
An
Object
that should be a
Border,
Insets,
Number,
or
String
that describes the border that is drawn around this textcanvas.
A
NULL
value, which is the default, means no border.
A
border
that is an
Insets
or
Number
is handled differently than most other Swing components,
because it is used, in combination with the
insets
field, to set the extent of the highlighted border,
in units of 72 dots per inch, that is drawn around the textcanvas.
A
border
that is a
String
is a quick way to surround this textcanvas with a border that uses the
String
as its title.
Reading returns a snapshot of the current border.
Writing immediately sets the textcanvas's border to the new value.
| | bordercolor |
The base
Color
that is used to pick the shadow colors for the highlighted border.
The textcanvas's background is used when bordercolor is
NULL.
Reading returns a snapshot of the current color.
Writing immediately changes the bordercolor to the new color.
| | cellsize |
A
Dimension
that measures distances in units of 72 dots per inch
with a
height
field that is the distance between adjacent lines of text,
and a
width
that is an estimate of the distance between adjacent characters.
Reading returns a snapshot of the current cellsize.
Writing is not allowed and will result in an
invalidaccess
error.
| | columns |
An
int
that specifies the number of columns in a textcanvas.
Layout managers usually get the final say, so setting
columns
should be viewed as a request that will not always be honored.
Reading returns the number of columns currently used by the textcanvas.
Writing tries to change the number of columns used by the textcanvas.
| | cursor |
An
Object
that should be an
int,
Image,
or
String
that selects the cursor shown when the pointer is over the textcanvas.
A
cursor
that is an
int
should be one of the cursors defined in the
yoix.awt.Cursor
dictionary.
A
cursor
that is an
Image
can describe the cursor using its
size
and
hotspot
fields and often draws it using its
paint
function.
A
cursor
that is a
String
should be the name of a cursor that is already defined in
yoix.awt.Cursor
or the name a local a file or URL that contains a GIF or JPEG image
that will be used as the cursor.
Reading returns the current cursor.
Writing immediately changes the textcanvas's cursor to the new value.
Storing
STANDARD_CURSOR
(the default) or
NULL
in
cursor
is special and means use the cursor assigned to the nearest component
that contains the textcanvas and was assigned a cursor other than
STANDARD_CURSOR;
if no component qualifies the textcanvas uses
DEFAULT_CURSOR.
| | doublebuffered |
An
int
that is
1
when the textcanvas uses double-buffering to draw itself,
0
when it does not, and starts with a default value that is
selected by Java for the textcanvas.
Reading returns the current double-buffering behavior.
Writing immediately sets the textcanvas's double-buffering behavior to the new value.
Note that double-buffering may be required when transparent components are used.
| | dragenabled |
An
int
that should be set to
1
when this textcanvas wants to use the automatic drag handling that Swing provides
for some components, and
0
(the default)
when it does not.
Components that do not provide automatic drag handling always return
0
when their
dragenabled
field is read, so storing
1
in
dragenabled
should only be viewed as a request for a service that may not be available.
Swing components can always take complete control of their drag and drop
handling using their
transferhandler
field or special drag and drop event handlers.
| | enabled |
An
Object
that is
1
when the textcanvas can respond to user input,
0
when it can not respond, and
NULL
(the default)
when the textcanvas inherits the value from the nearest lightweight container,
like a
JPanel,
that contains the textcanvas and has its
enabled
field set to something other than
NULL.
The top-level application window that contains the textcanvas always gets the
final say, so disabling that window always disables the textcanvas.
Reading returns the current state.
Writing immediately sets the textcanvas's state to the new value.
| | extent |
A
Dimension
that measures distances in units of 72 dots per inch
with a
height
field that is the vertical size of all the lines of text,
and a
width
that is the horizontal size of the longest line of text.
Reading returns a snapshot of the current extent.
Writing is not allowed and will result in an
invalidaccess
error.
| | focusable |
An
int
that is non-zero (the default)
when the textcanvas can accept the keyboard focus and zero
when it can not.
Reading returns the textcanvas's current focusable state.
Writing immediately changes the textcanvas's focusable state to the new value,
which means the focus is automatically transferred if the new value is zero
and the textcanvas is the current focus owner.
| | focusowner |
A read-only
int
that is non-zero when the textcanvas has the focus.
| | font |
The
Font,
or font name if it is a
String,
used to paint the text displayed by the textcanvas.
Reading returns a snapshot of the current font.
Writing immediately repaints the text in the new font.
| | foreground |
The
Color
used to paint the text displayed by the textcanvas.
Reading returns a snapshot of the current color.
Writing immediately repaints the text in the new color.
Storing
NULL
in
foreground
is special and means use the foreground of the nearest component
that contains the textcanvas and was assigned a foreground color other than
NULL;
if no component qualifies the textcanvas uses
VM.screen.foreground.
| | insets |
An
Object,
usually an
Insets
or
Number,
that sets margins around the textcanvas that determine how close text
comes to the edges.
In addition,
insets
also determines the maximum size of the highlighted border in any direction,
independent of the values stored in
border.
An
insets
that is a number is an easy way to describe a uniform margin.
Reading returns a snapshot of the current insets.
Writing immediately sets the insets to the new value.
| | ipad |
An
Insets
that measures distances in units of 72 dots per inch
that adjusts the vertical margins at the top and bottom of each line displayed
by the textcanvas according to the values stored in
ipad.top
and
ipad.bottom.
Adjustments corresponding to
ipad.left
and
ipad.right
have not been implemented yet.
Reading returns a snapshot of the current padding.
Writing immediately repaints the text using the new padding.
| | layer |
An
int,
often a small number between 0 and 99,
that identifies the depth of this textcanvas when it is added to a
JLayeredPane
or
JDesktopPane.
Components assigned to lower numbered layers are drawn before
the components in higher numbered layers.
Writing immediately changes the textcanvas's layer, which usually means the
JLayeredPane
or
JDesktopPane
that contains the textcanvas will be repainted.
| | location |
A
Point
that determines the location of the textcanvas
in a coordinate system that has its origin at the upper left corner
of the container closest to the textcanvas (in the component hierarchy)
that actually contains it, positive x to the right, positive y down,
and a resolution of 72 dots per inch.
Reading returns a snapshot of the current location.
Writing is allowed, but layout managers usually get the final say, so setting
location
should be viewed as a request that may not be honored.
| | nextfocus |
An
Object
that identifies the component that receives the focus after this textcanvas
when the focus traverses from one component to the next
(usually by means of the keyboard
TAB
character).
When
nextfocus
is a
String
it is assumed to be the tag associated with the target component,
which must belong to the same top-level container (e.g., the same
JFrame)
as this textcanvas.
A
NULL
value means the component that gets the focus after this textcanvas will be
selected by Java's default focus traversal policy.
Reading returns the value last stored or
NULL
if the value was a
String
that did not reference a component.
Writing immediately changes the component that gets the focus after this textcanvas.
| | opaque |
An
Object
that is
1
when the textcanvas is opaque,
0
when it is transparent, and
NULL
(the default)
when the textcanvas inherits the value from the nearest component that
contains the textcanvas and has its
opaque
field set to something other than
NULL.
| | origin |
A
Point
that is the location of the upper left corner of the printable area
(i.e., left corner plus insets) of the textcanvas in a coordinate
system that has its origin at the upper left corner of the first line
of text, positive x to the right, positive y down, and a resolution
of 72 dots per inch.
Reading returns a snapshot of the current origin.
Writing immediately sets the origin to the new value.
| | popup |
A
JPopupMenu
that is associated with the textcanvas.
Reading returns the current popup menu.
Writing immediately shows the popup menu at the point in the textcanvas's coordinate
system specified by the popup menu's
location
field, assuming of course that the textcanvas is showing on the screen.
Storing
TRUE
in the popup menu's
visible
field, which was added in release 1.2.0, is an easy way to show the
popup menu that currently belongs to the textcanvas.
| | preferredsize |
A
Dimension
that is used by layout managers when they need to know the textcanvas's
preferred size in units of 72 dots per inch.
A
NULL
value means the textcanvas has no preference.
A non-positive height or width is allowed and simply means the textcanvas
has no preference for that dimension.
Reading returns the current preferred size.
Writing changes the preferred size and immediately notifies
root.layoutmanager,
which means the components contained in
root
may be repositioned and resized.
| | requestfocus |
An
int
that can be used to request or transfer the keyboard focus.
Storing a non-zero value in
requestfocus
tries to get the focus.
Storing
0
tries to transfer the focus.
Reading
requestfocus
does not currently return any useful information.
| | requestfocusenabled |
An
int
that is
1
(the default)
when actions, like mouse clicks or changes to the
requestfocus
field, can steal the keyboard focus and
0
when they can not.
Note that this field does not affect acceptance of the keyboard focus
during normal focus traversal.
Reading returns the current state.
Writing immediately sets the textcanvas's state to the new value.
| | root |
An
Object
that is automatically updated by the interpreter's layout machinery
so it is always the top-level object that contains the textcanvas.
For example, put a textcanvas in a panel and
root
will be set to that panel;
add the panel to a frame and the textcanvas's
root
field will be set to that frame.
A textcanvas's event handlers can use
root
when they need to interact with the other components in the container.
| | rows |
An
int
that specifies the number of rows in a textcanvas.
Layout managers usually get the final say, so setting
rows
should be viewed as a request that will not always be honored.
Reading returns the number of rows currently used by the textcanvas.
Writing tries to change the number of rows used by the textcanvas.
| | showing |
A read-only
int
that is non-zero when the textcanvas is showing on the screen.
| | size |
A
Dimension
that determines the size of the textcanvas
in units of 72 dots per inch.
Reading returns a snapshot of the current size.
Writing is allowed, but layout managers usually get the final say, so setting
size
should be viewed as a request that may not be honored.
| | state |
An
int
that controls how the border of the textcanvas, if there is one,
is drawn.
When state is
0
the left and top parts of the border are drawn in a brighter
color than the right and bottom parts, which makes it look like
the interior of the textcanvas is raised.
The border colors are reversed when state is
1,
which makes it look like the interior of the textcanvas is depressed.
| | subtext([int offset[, int length]]) |
A built-in that returns the current text within the given range.
When absent,
offset
defaults to the zero position and
length
defaults to the length from the offset to the end of the current text.
| | syncViewport(Rectangle viewport, Dimension extent, Dimension cellsize) |
A
Function
that is called whenever it is not
NULL
and a change, like a new font or a resize,
modifies the appearance of the text that is displayed in the textcanvas.
The function should use the
viewport,
extent,
and
cellsize
arguments to do whatever is required to synchronize other components,
like scrollbars, to the textcanvas.
| | tag |
A
String
used to identify the textcanvas that is either supplied when
the textcanvas is declared, or automatically generated otherwise.
Add a textcanvas to a container, like a
JFrame
or
JPanel,
and the interpreter's layout machinery updates the
root
field so it points at the top-level container and then adds the textcanvas, as
tag,
to the
root.components
dictionary.
| | text |
A
String
of characters that is displayed in the textcanvas.
Reading returns the current text.
Writing immediately paints the new text.
| | textmode |
An
int
that determines how lines displayed in the textcanvas are collected
from the input text.
The value should be
LINEMODE
or
WORDMODE,
which are defined in
yoix.swing.
Reading returns the current mode.
Writing immediately sets the mode to the new value.
In
LINEMODE
tabs are expanded and all characters, up to the next newline character,
are considered to be part of the next display line.
In
WORDMODE
whitespace delimited tokens are collected and then grouped into display
lines based on the value of
textwrap.
When it is
0
each token starts a new display line;
otherwise space separated tokens are added to the next display line
until there is no more room or a break is forced by the
<p>
or
<br>
tokens.
| | textwrap |
An
int
that is
1
when a line of text that is wider than the printable area of the textcanvas
can be wrapped onto the next line, and
0
when it cannot.
Reading returns the current textwrap.
Writing immediately sets the textwrap to the new value.
The
textmode
field controls what happens when a line needs to be wrapped.
In
LINEMODE
mode individual words can be split across lines;
in
WORDMODE
they cannot.
| | tooltiptext |
A
String
of characters that is displayed in a tightly sized pop-up window that
appears near the cursor whenever the cursor lingers over the textcanvas.
Setting this value to
NULL
(the default)
disables the tooltip mechanism.
Reading returns the current tooltip text.
Writing immediately sets the new tooltip text.
| | transferhandler |
An
Object
that should be a
TransferHandler
or
String
that determines how the textcanvas handles data transfer operations
like drag and drop.
A value that is a
String
but not
""
means the field named by the
String
should be used as the source and sink of the data that is transferred by
the textcanvas.
The result is the same as assigning the
String
to the
property
field in a
TransferHandler
and then assigning that
TransferHandler
to
transferhandler.
The empty
String
""
is special and refers to the
TransferHandler
that Swing uses for automatic drag handling, if there is one.
Swing components that provide automatic drag handling start out with a
transferhandler
field that is not
NULL,
but the automatic drag handling is not enabled until
1
is stored in
dragenabled.
Swing components that provide their own drag and drop event handlers
currently must store
NULL
in
transferhandler
before those event handlers will start working.
| | viewport |
An
Rectangle
that completely describes the printable area of the textcanvas
in a coordinate system that has its origin at the upper left corner
of the first line of text, positive x to the right, positive y down,
and a resolution of 72 dots per inch.
In other words, the
x
and
y
fields match the corresponding fields in
origin,
while
height
and
width
give the dimensions of the printable area of the textcanvas.
Reading returns a snapshot of the current viewport.
Writing is not allowed and will result in an
invalidaccess
error.
| | visible |
An
int
that is
1
when the textcanvas is visible, and
0
otherwise.
Reading returns the current visibility.
Writing immediately sets the textcanvas's visibility to the new state.
|
Several permanent fields have not been documented and should not be
used in Yoix applications.
Event handlers are functions that must be added to a textcanvas when it is
declared.
The handlers that work with textcanvases are listed below;
the names should be familiar if you have done some Java programming.
| |
| Event Handlers: |
actionPerformed,
componentHidden,
componentMoved,
componentResized,
componentShown,
dragDropEnd,
dragEnter,
dragExit,
dragGestureRecognized,
dragMouseMoved,
dragOver,
drop,
dropActionChanged,
focusGained,
focusLost,
invocationRun,
itemStateChanged,
keyPressed,
keyReleased,
keyTyped,
mouseClicked,
mouseDragged,
mouseEntered,
mouseExited,
mouseMoved,
mousePressed,
mouseReleased,
mouseWheelMoved
| | |
| Example: |
The program,
import yoix.*.*;
JFrame f = {
Array layout = {
new JTextCanvas {
String tag = "textcanvas";
Color background = Color.white;
syncViewport(port, extent, cell) {
JScrollbar vbar = root.components.vbar;
vbar.cell = cell;
vbar.minimum = 0;
vbar.maximum =
(extent.height + port.height)/cell.height - 1;
vbar.visibleamount = port.height/cell.height;
vbar.unitincrement = 1;
vbar.blockincrement = port.height/cell.height - 1;
}
}, CENTER,
new JScrollbar {
Dimension cell;
String tag = "vbar";
adjustmentValueChanged(e) {
Point origin = root.components.textcanvas.origin;
origin.y = value*cell.height;
root.components.textcanvas.origin = origin;
}
}, EAST,
};
windowOpened(e) {
Stream stream;
if ((stream = open("http://www.att.com", "r")) != NULL) {
components.textcanvas.text = readStream(stream);
close(stream);
}
}
};
f.visible = TRUE;
is a nontrivial example that shows how a textcanvas and scrollbar
can operate together.
| | |
| See Also: |
appendText,
BevelBorder,
Border,
EmptyBorder,
EtchedBorder,
invokeLater,
JButton,
JCanvas,
JCheckBox,
JCheckBoxMenuItem,
JChoice,
JColorChooser,
JComboBox,
JDesktopPane,
JDialog,
JFileChooser,
JFileDialog,
JFrame,
JInternalFrame,
JLabel,
JLayeredPane,
JList,
JMenu,
JMenuBar,
JMenuItem,
JPanel,
JPasswordField,
JPopupMenu,
JProgressBar,
JRadioButton,
JRadioButtonMenuItem,
JScrollBar,
JScrollPane,
JSeparator,
JSlider,
JSplitPane,
JTabbedPane,
JTable,
JTextArea,
JTextField,
JTextPane,
JTextTerm,
JToggleButton,
JToolBar,
JTree,
JWindow,
LineBorder,
MatteBorder,
postEvent,
SoftBevelBorder,
TransferHandler
|
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