@Override
public void layout() {
ScrollBar scrollBar = (ScrollBar) getComponent();
int width = getWidth();
int height = getHeight();
int start = scrollBar.getStart();
int end = scrollBar.getEnd();
int extent = scrollBar.getExtent();
int value = scrollBar.getValue();
int maxLegalRealValue = end - extent;
int numLegalRealValues = maxLegalRealValue - start + 1;
float extentPercentage = (float) extent / (float) (end - start);
if (scrollBar.getOrientation() == Orientation.HORIZONTAL) {
scrollUpButton.setSize(scrollUpButton.getPreferredWidth(-1), height);
scrollUpButton.setLocation(0, 0);
scrollDownButton.setSize(scrollDownButton.getPreferredWidth(-1), height);
scrollDownButton.setLocation(width - scrollDownButton.getWidth(), 0);
if (scrollBar.isEnabled()) {
// Calculate the handle width first, as it dictates how much
// room is left to represent the range of legal values. Note
// that the handle may overlap each scroll button by 1px so
// that its borders merge into the borders of the scroll buttons
int availableWidth = width - scrollUpButton.getWidth() - scrollDownButton.getWidth() + 2;
int handleWidth =
Math.max(minimumHandleLength, Math.round(extentPercentage * availableWidth));
// Calculate the position of the handle by calculating the
// scale that maps logical value to pixel value
int numLegalPixelValues = availableWidth - handleWidth + 1;
float valueScale = (float) numLegalPixelValues / (float) numLegalRealValues;
int handleX = (int) (value * valueScale) + scrollUpButton.getWidth() - 1;
if (handleWidth > availableWidth) {
// If we can't fit the handle, we hide it
handle.setVisible(false);
} else {
handle.setVisible(true);
handle.setSize(handleWidth, height);
handle.setLocation(handleX, 0);
}
} else {
handle.setVisible(false);
}
} else {
scrollUpButton.setSize(width, scrollUpButton.getPreferredHeight(-1));
scrollUpButton.setLocation(0, 0);
scrollDownButton.setSize(width, scrollDownButton.getPreferredHeight(-1));
scrollDownButton.setLocation(0, height - scrollDownButton.getHeight());
if (scrollBar.isEnabled()) {
// Calculate the handle height first, as it dictates how much
// room is left to represent the range of legal values. Note
// that the handle may overlap each scroll button by 1px so
// that its borders merge into the borders of the scroll buttons
int availableHeight =
height - scrollUpButton.getHeight() - scrollDownButton.getHeight() + 2;
int handleHeight =
Math.max(minimumHandleLength, Math.round(extentPercentage * availableHeight));
// Calculate the position of the handle by calculating the
// scale maps logical value to pixel value
int numLegalPixelValues = availableHeight - handleHeight + 1;
float valueScale = (float) numLegalPixelValues / (float) numLegalRealValues;
int handleY = (int) (value * valueScale) + scrollUpButton.getHeight() - 1;
if (handleHeight > availableHeight) {
// If we can't fit the handle, we hide it
handle.setVisible(false);
} else {
handle.setVisible(true);
handle.setSize(width, handleHeight);
handle.setLocation(0, handleY);
}
} else {
handle.setVisible(false);
}
}
}
