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java.awt
public enum class: Component.BaselineResizeBehavior [javadoc | source]
java.lang.Enum
   java.awt.Component$BaselineResizeBehavior
Enumeration of the common ways the baseline of a component can change as the size changes. The baseline resize behavior is primarily for layout managers that need to know how the position of the baseline changes as the component size changes. In general the baseline resize behavior will be valid for sizes greater than or equal to the minimum size (the actual minimum size; not a developer specified minimum size). For sizes smaller than the minimum size the baseline may change in a way other than the baseline resize behavior indicates. Similarly, as the size approaches Integer.MAX_VALUE and/or Short.MAX_VALUE the baseline may change in a way other than the baseline resize behavior indicates.
Field Summary
public  BaselineResizeBehavior CONSTANT_ASCENT    Indicates the baseline remains fixed relative to the y-origin. That is, getBaseline returns the same value regardless of the height or width. For example, a JLabel containing non-empty text with a vertical alignment of TOP should have a baseline type of CONSTANT_ASCENT
public  BaselineResizeBehavior CONSTANT_DESCENT    Indicates the baseline remains fixed relative to the height and does not change as the width is varied. That is, for any height H the difference between H and getBaseline(w, H) is the same. For example, a JLabel containing non-empty text with a vertical alignment of BOTTOM should have a baseline type of CONSTANT_DESCENT
public  BaselineResizeBehavior CENTER_OFFSET    Indicates the baseline remains a fixed distance from the center of the component. That is, for any height H the difference between getBaseline(w, H) and H / 2 is the same (plus or minus one depending upon rounding error).

Because of possible rounding errors it is recommended you ask for the baseline with two consecutive heights and use the return value to determine if you need to pad calculations by 1. The following shows how to calculate the baseline for any height:

  Dimension preferredSize = component.getPreferredSize();
  int baseline = getBaseline(preferredSize.width,
                             preferredSize.height);
  int nextBaseline = getBaseline(preferredSize.width,
                                 preferredSize.height + 1);
  // Amount to add to height when calculating where baseline
  // lands for a particular height:
  int padding = 0;
  // Where the baseline is relative to the mid point
  int baselineOffset = baseline - height / 2;
  if (preferredSize.height % 2 == 0 &&
      baseline != nextBaseline) {
      padding = 1;
  }
  else if (preferredSize.height % 2 == 1 &&
           baseline == nextBaseline) {
      baselineOffset--;
      padding = 1;
  }
  // The following calculates where the baseline lands for
  // the height z:
  int calculatedBaseline = (z + padding) / 2 + baselineOffset;
 
public  BaselineResizeBehavior OTHER    Indicates the baseline resize behavior can not be expressed using any of the other constants. This may also indicate the baseline varies with the width of the component. This is also returned by components that do not have a baseline.