Game Development Reference
In-Depth Information
use to build the geometry of our rectangle. The using block will automatically dis-
pose of the GeometrySink object for us when program execution reaches the end
of the using block.
Note
The using blocks only work with objects that implement the IDisposable in-
terface.
The next four lines calculate where each edge of our rectangle will be. For example,
the first line calculates the vertical position of the top edge of the rectangle. In this
case, we are making the rectangle's top edge be 25 percent of the way down from
the top of the screen. Then, we do the same thing for the other three sides of our
rectangle. The second group of four lines of code creates four Point objects and ini-
tializes them using the values we just calculated. These four Point objects repres-
ent the corners of our rectangle. A point is also often referred to as a vertex . When
we have more than one vertex, we call them vertices (pronounced as vert-is-ces ).
The final group of code has six lines. They use the GeometrySink and the Point
objects we just created to set up the geometry of our rectangle inside the PathGeo-
metry object. The first line uses the BeginFigure() method to begin the creation
of a new geometric figure. The next three lines each add one more line segment to
the figure by adding another point or vertex to it. With all four vertices added, we then
call the EndFigure() method to specify that we are done adding vertices. The last
line calls the Close() method to specify that we are finished adding geometric fig-
ures, since we can have more than one if we want. In this case, we are only adding
one geometric figure, our rectangle.
Drawing our rectangle
Since our rectangle never changes, we don't need to add any code to our UpdateS-
cene() method. We will override the base class's UpdateScene() method any-
way, in case we need to add some code in here later, which is given as follows:
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