_
+-------------------------------+ ...........Y1 \
| view | . \
| (this component's child) | . > VY
| | . / = Y2-Y1
| +------------------------------+ ....Y2_/
| | viewport | | .
| | (this component) | | .
| | | | .
| | | | .
| | | | .
| | | | .
| +------------------------------+ ....Y3
| | .
| . | . .
| . | . .
+---------.---------------------+ ...........Y4
. . . .
. . . .
. . . .
X1.......X2.....................X3.......X4
\____ ___/
\/
VX = X2-X1
A viewport is, like all swing components, located at some position in
the swing component tree; that location is exactly the same as any other
components: the viewport's "bounds".
But in terms of drawing its child, the viewport thinks of itself as
covering a particular position of the view's coordinate space.
For example, the getViewPosition() method returns
the position (VX,VY) shown above, which is an position in
"view space", even though this is implemented by positioning
the underlying child at position (-VX,-VY)
computeBlit
protected boolean computeBlit(int dx,
int dy,
Point blitFrom,
Point blitTo,
Dimension blitSize,
Rectangle blitPaint) Computes the parameters for the blitting scroll method. dx
and dy specifiy the X and Y offset by which the viewport
is scrolled. All other arguments are output parameters and are filled by
this method.
blitFrom holds the position of the blit rectangle in the
viewport rectangle before scrolling, blitTo where the blitArea
is copied to.
blitSize holds the size of the blit area and
blitPaint is the area of the view that needs to be painted.
This method returns true if blitting is possible and
false if the viewport has to be repainted completetly without
blitting.
dx - the horizontal deltady - the vertical deltablitFrom - the position from where to blit; set by this methodblitTo - the position where to blit area is copied to; set by this
methodblitSize - the size of the blitted area; set by this methodblitPaint - the area that needs repainting; set by this method
true if blitting is possible,
false otherwise
getViewPosition
public Point getViewPosition()
Get the viewport's position in view space. Despite confusing name,
this really does return the viewport's (0,0) position in view space,
not the view's position.
getViewSize
public Dimension getViewSize()
Returns the viewSize when set, or the preferred size of the set
Component view. If no viewSize and no Component view is set an
empty Dimension is returned.
paint
public void paint(Graphics g)
Paints this component on the screen. The clipping region in the graphics
context will indicate the region that requires painting. This is called
whenever the component first shows, or needs to be repaired because
something was temporarily drawn on top. It is not necessary for
subclasses to call super.paint(g). Components with no area
are not painted.
- paint in interface JComponent
g - the graphics context for this paint job
repaint
public void repaint(long tm,
int x,
int y,
int w,
int h) Forward repaint to parent to make sure only one paint is performed by the
RepaintManager.
- repaint in interface JComponent
tm - number of milliseconds to defer the repaint requestx - the X coordinate of the upper left corner of the dirty areay - the Y coordinate of the upper left corner of the dirty areaw - the width of the dirty areah - the height of the dirty area
reshape
public void reshape(int x,
int y,
int w,
int h)use Component.setBounds(int,int,int,int) instead
Sets the bounding rectangle for this component to the specified values.
Note that these coordinates are relative to the parent, not to the screen.
- reshape in interface JComponent
x - the X coordinate of the upper left corner of the rectangley - the Y coordinate of the upper left corner of the rectangle
JViewport.java --
Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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