Java Tip: Drawing a TextLayout
==============================
Vijay Kumar <vijaykumar@bravegnu.org>

`TextLayout` objects among other things can be used to draw styled
character data. The `draw()` method of the object can be used to draw
the rendered text to a `Graphics2D` object. But the `x` and `y`
co-ordinates passed to `draw()` is not the position of the top left corner
as would be expected. The `x` and `y` coordinate is the position of
the origin.

The origin of a `TextLayout` is the intersection of the objects
baseline with its left edge. The baseline is the horizontal line on
which characters of a font are positioned. Figure (a) shows the
locations of the baseline and the origin.

.BaseLine, origin and bounds
image::text-layout.png[]

Given the position of the top left corner to draw the `TextLayout`,
the position of the origin has to be calculated. The `getBounds()`
method of `TextLayout` can be used for this purpose. The `getBounds()`
method returns the bounding rectangle of the rendered `TextLayout`
object. The top left corner of the returned bounding rectangle is
relative to the origin of the `TextLayout` as shown in figure b.

The position of the origin can be calculated as shown in the following
piece of code.

------
TextLayout layout;
Graphics2D g2;
Rectangle2D bounds;
float x, y; /* Position of top left corner to draw the TextLayout. */
float ox, oy; /* Position of origin to draw the TextLayout. */
...
...
bounds = layout.getBounds();
ox = x - bounds.getX();
oy = y - bounds.getY();
layout(g2, ox, oy);
------

The text can be centered in a rectangle `(px, py, pw, ph)` using the
following piece of code.

------
TextLayout layout;
Graphics2D g2;
Rectangle2D bounds;
float px, py, pw, ph;
float cx, cy; /* Center X, Y */
float ox, oy; /* Origin X, Y */
...
...
bounds = layout.getBounds();
cx = px + pw / 2 - bounds.getWidth() / 2;
cy = py + ph / 2 - bounds.getHeight() / 2;
ox = cx - bounds.getX();
oy = cy - bounds.getY();
layout(g2, ox, oy);
------