Merge "tweak the electron beam animation a bit" into klp-dev

    /**

     * Draws a frame where the electron beam has been stretched out into

     * a thin white horizontal line that fades as it expands outwards.

     * a thin white horizontal line that fades as it collapses inwards.

     *

     * @param stretch The stretch factor.  0.0 is no stretch / no fade,

     * 1.0 is maximum stretch / maximum fade.

     * @param stretch The stretch factor.  0.0 is maximum stretch / no fade,

     * 1.0 is collapsed / maximum fade.

     */

    private void drawHStretch(float stretch) {

        // compute interpolation scale factor

            // draw narrow fading white line

            setHStretchQuad(mVertexBuffer, mDisplayWidth, mDisplayHeight, ag);

            GLES10.glColor4f(1.0f - ag, 1.0f - ag, 1.0f - ag, 1.0f);

            GLES10.glColor4f(1.0f - ag*0.75f, 1.0f - ag*0.75f, 1.0f - ag*0.75f, 1.0f);

            GLES10.glDrawArrays(GLES10.GL_TRIANGLE_FAN, 0, 4);

            // clean up

    }

    private static void setHStretchQuad(FloatBuffer vtx, float dw, float dh, float a) {

        final float w = dw + (dw * a);

        final float w = 2 * dw * (1.0f - a);

        final float h = 1.0f;

        final float x = (dw - w) * 0.5f;

        final float y = (dh - h) * 0.5f;