/**
* Gets the scale factor that allows us to translate pixel values to scroll bar values and vice
* versa. This assumes that the range of pixels spans from the last pixel of
* <tt>scrollUpButton</tt> to the first pixel of <tt>scrollDownButton</tt> and excludes the pixels
* taken up by <tt>handle</tt>.
*
* <p>To map from scroll bar values (<i>real values</i>) to pixel values, you multiply by the
* value scale. To map from pixel values back to real values, you divide by the value scale.
*
* @return <tt><number of legal pixel values> / <number of legal real values></tt>
*/
private float getValueScale() {
ScrollBar scrollBar = (ScrollBar) getComponent();
float valueScale;
int start = scrollBar.getStart();
int end = scrollBar.getEnd();
int extent = scrollBar.getExtent();
int maxLegalRealValue = end - extent;
int numLegalRealValues = maxLegalRealValue - start + 1;
int numLegalPixelValues;
if (scrollBar.getOrientation() == Orientation.HORIZONTAL) {
int availableWidth = getWidth() - scrollUpButton.getWidth() - scrollDownButton.getWidth() + 2;
numLegalPixelValues = availableWidth - handle.getWidth() + 1;
} else {
int availableHeight =
getHeight() - scrollUpButton.getHeight() - scrollDownButton.getHeight() + 2;
numLegalPixelValues = availableHeight - handle.getHeight() + 1;
}
// the number of segments is one less than the number of values
valueScale = numLegalPixelValues / ((float) numLegalRealValues - 1);
return valueScale;
}
private void scroll() {
ScrollBar scrollBar = (ScrollBar) TerraScrollBarSkin.this.getComponent();
int start = scrollBar.getStart();
int end = scrollBar.getEnd();
int extent = scrollBar.getExtent();
int value = scrollBar.getValue();
int adjustment;
if (incrementType == Mouse.ScrollType.UNIT) {
adjustment = direction * scrollBar.getUnitIncrement();
} else {
adjustment = direction * scrollBar.getBlockIncrement();
}
if (adjustment < 0) {
int newValue = Math.max(value + adjustment, start);
scrollBar.setValue(newValue);
if (stopValue != -1 && newValue < stopValue) {
// We've reached the explicit stop value
stop();
}
if (newValue == start) {
// We implicit stop at the minimum scroll bar value
stop();
}
} else {
int newValue = Math.min(value + adjustment, end - extent);
scrollBar.setValue(newValue);
if (stopValue != -1 && newValue > stopValue) {
// We've reached the explicit stop value
stop();
}
if (newValue == end - extent) {
// We implicitly stop at the maximum scroll bar value
stop();
}
}
}
@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);
}
}
}