When you build your application visually using GridBagLayout, the
visual grid markers help you to move and drop components in the required position.
To add or move components within GridBagLayout:
Select the Swing component from the palette that you want to add
to your GridBagLayout, or click and drag the existing component that you want
to move within your GridBagLayout.
Move your mouse pointer over the position where you want to drop
or move the component:
If you point to a grid cell that is already occupied by another component,
you cannot move or drop in that position.
If you point to a grid cell that is empty, the cell turns dark grey
to indicate the valid drop position. The cursor shows the X and Y grid values
for the drop position. The first number is the X value, which represents the
column, and the second number is the Y value, which represents the row.
If you position your cursor on a grid boundary, a yellow bar indicates
that a new column or row number will be added.
If any new column or row number is being added by your placement,
the background color yellow shows on the cursor X/Y indicator and on the column
and row labels. Components that are in rows or columns with yellow circles
will be updated to reflect the new grid X/Y values.
Click or release your mouse to drop the component in the position
that you selected.