GLFont.java (pixel font geometry)

package com.ulfben.asteroids.GL;
import java.util.HashMap;
/**
 * Created by Ulf Benjaminsson on 2017-03-27, www.ulfben.com
 * GLFont is a "pixel font" for OpenGL. Each glyph is made up from 1-9 quads,
 * ready to be put in a vertex-buffer and rendered as geometry.
 *
 * Example: https://media.giphy.com/media/11lKO38jQGliuY/giphy.gif
 *
 * getString(String) returns an array of GLModels. GLModel is a just glorified vertex buffer
 * so replace it with whatever you use to pass vertices into OpenGL.
 */
public class GLFont {
    public static float height = 25f;
    public static float width = 25f;
    public static float lineWidth = 5.0f;
    private static HashMap<String, GLModel> glyphMap = new HashMap<String, GLModel>();
    private GLFont(){}

    public static void init() {
        final float LW2 = lineWidth*2f; //prepare some common values
        final float LW3 = lineWidth*3f;
        final float left = 0f;
        final float top = height;
        final float bottom = 0f;
        final float right = left+width;
        final float centerY = (top/2f)+(lineWidth/2f);
        final float centerX = (right/2f)-(lineWidth/2f);
        final float[] fullLeft = quad(left, top, lineWidth, height); //prepare some common quads
        final float[] fullRight = quad(right-lineWidth, top, lineWidth, height);
        final float[] fullTop = quad(left, top, width, lineWidth);
        final float[] fullBottom = quad(left, bottom+lineWidth, width, lineWidth);
        final float[] boxOpenLeft = concat(fullLeft, fullTop, fullBottom); //C, E, G, o, 0, 8, Q, 6
        final float[] box = concat(boxOpenLeft, fullRight); //o, 0 and 8, Q
        final float[] centerLineLeft = quad(left+lineWidth, centerY, width-(LW3), lineWidth); //E, F
        final float[] centerLineRight = quad(left+LW2, centerY, width-LW2, lineWidth); //lip of G, 3
        final float[] centerLineCentered = quad(left+lineWidth, centerY, width-LW2, lineWidth); //H, B, A etc
        final float[] verticalCenter = quad(centerX, top, lineWidth, height);// I, T
        final float[] shortTop = quad(left, top, width-lineWidth, lineWidth); //B, D, P, R
        final float[] shortBottom = quad(left, bottom+lineWidth, width-lineWidth, lineWidth); //B, D

        final float[] a = concat(fullLeft, fullTop, fullRight, centerLineCentered);
        final float[] b = concat(fullLeft, shortTop, shortBottom, centerLineCentered, quad(right-lineWidth, top-lineWidth, lineWidth, height-LW2));
        final float[] c = boxOpenLeft;
        final float[] d = concat(fullLeft, shortTop, shortBottom, quad(right-lineWidth, top-lineWidth, lineWidth, height-LW2));
        final float[] e = concat(boxOpenLeft, centerLineLeft);
        final float[] f = concat(fullLeft, fullTop, centerLineLeft);
        final float[] g = concat(boxOpenLeft, quad(right-lineWidth, centerY, lineWidth, bottom+centerY), centerLineRight);
        final float[] h = concat(fullLeft, fullRight, centerLineCentered);
        final float[] i = concat(fullTop, fullBottom, verticalCenter);
        final float[] j = concat(fullRight, fullBottom, quad(left, bottom+LW2, lineWidth, lineWidth));
        final float[] k = concat(fullLeft, centerLineLeft,
                quad(right-LW2, centerY+lineWidth, lineWidth, lineWidth),
                quad(right-lineWidth, top, lineWidth, lineWidth),
                quad(right-LW2, centerY-lineWidth, lineWidth, lineWidth),
                quad(right-lineWidth, bottom+lineWidth, lineWidth, lineWidth)
        );
        final float[] l = concat(fullLeft, fullBottom);
        final float[] m = concat(fullLeft, verticalCenter, fullRight, fullTop);
        final float[] n = concat(fullLeft, fullTop, fullRight);
        final float[] o = box;
        final float[] p = concat(fullLeft, shortTop, centerLineCentered, quad(right-lineWidth, top-lineWidth, lineWidth, LW2));
        final float[] q = concat(fullLeft, fullRight, fullTop, fullBottom, quad(centerX, bottom+LW2, lineWidth, LW3));
        final float[] r = concat(fullLeft, shortTop, centerLineCentered,
                quad(right-lineWidth, top-lineWidth, lineWidth, centerY-lineWidth),
                quad(right-LW2, centerY-lineWidth, lineWidth, lineWidth),
                quad(right-lineWidth, bottom+lineWidth, lineWidth, lineWidth)
        );
        final float[] s = concat(fullTop, fullBottom, centerLineCentered,
                quad(left, top, lineWidth, centerY),
                quad(right-lineWidth, centerY, lineWidth, centerY));
        final float[] t = concat(fullTop, verticalCenter);
        final float[] u = concat(fullLeft, fullRight, fullBottom);
        final float[] v = concat(quad(left, top, lineWidth, centerY),
                quad(right-lineWidth, top, lineWidth, centerY),
                quad(right-LW2, centerY-lineWidth, lineWidth, lineWidth),
                quad(left+lineWidth, centerY-lineWidth, lineWidth, lineWidth),
                quad(centerX, bottom+lineWidth, lineWidth, lineWidth)
        );
        final float[] w = concat(fullLeft, verticalCenter, fullRight, fullBottom);
        final float[] x = concat(
                quad(left, top, lineWidth, lineWidth), quad(right-lineWidth, top, lineWidth, lineWidth),
                quad(left+lineWidth, top-lineWidth, lineWidth, lineWidth), quad(right-LW2, top-lineWidth, lineWidth, lineWidth),
                quad(left+LW2, top-LW2, lineWidth, lineWidth), //center of x
                quad(left+lineWidth, bottom+LW2, lineWidth, lineWidth), quad(right-LW2, bottom+LW2, lineWidth, lineWidth),
                quad(left, bottom+lineWidth, lineWidth, lineWidth), quad(right-lineWidth, bottom+lineWidth, lineWidth, lineWidth)
        );
        final float[] y = concat(
                quad(left, top, lineWidth, lineWidth), quad(right-lineWidth, top, lineWidth, lineWidth),
                quad(left+lineWidth, top-lineWidth, lineWidth, lineWidth), quad(right-LW2, top-lineWidth, lineWidth, lineWidth),
                quad(left+LW2, top-LW2, lineWidth, (LW3))
        );
        final float[] z = concat(fullTop, fullBottom, quad(right-LW2, top-lineWidth, lineWidth, lineWidth),
                quad(left+LW2, top-LW2, lineWidth, lineWidth),
                quad(left+lineWidth, bottom+LW2, lineWidth, lineWidth)
        );
        final  float[] zero = box;
        final float[] one = concat(quad(centerX-lineWidth, top, lineWidth, lineWidth), verticalCenter);
        final float[] two = concat(fullTop, fullBottom, centerLineCentered, quad(left, centerY, lineWidth, centerY),
                quad(right-lineWidth, top, lineWidth, centerY));
        final  float[] three = concat(fullRight, fullTop, centerLineRight, fullBottom);
        final float[] four = concat(fullRight, centerLineCentered, quad(left, top, lineWidth, centerY));
        final float[] five = concat(fullTop, fullBottom, centerLineCentered, quad(left, top, lineWidth, centerY),
                quad(right-lineWidth, centerY, lineWidth, centerY));
        final float[] six = concat(boxOpenLeft, centerLineCentered, quad(right-lineWidth, centerY, lineWidth, centerY));
        final float[] seven = concat(fullTop, fullRight);
        final float[] eight = concat(box, centerLineCentered);
        final float[] nine = concat(fullRight, fullTop, centerLineCentered,  quad(left, top, lineWidth, centerY));
        final float[] dot = quad(left, bottom+lineWidth, lineWidth, lineWidth);
        final float[] dash = quad(left+lineWidth, centerY, width-LW2, lineWidth);
        final float[] slash = concat(quad(right-lineWidth, top, lineWidth, lineWidth),
                quad(right-LW2, top-lineWidth, lineWidth, lineWidth), quad(left+LW2, top-LW2, lineWidth, lineWidth),
                quad(left+lineWidth, bottom+LW2, lineWidth, lineWidth), quad(left, bottom+lineWidth, lineWidth, lineWidth)
        );
        addGlyph("a", a);
        addGlyph("b", b);
        addGlyph("c", c);
        addGlyph("d", d);
        addGlyph("e", e);
        addGlyph("f", f);
        addGlyph("g", g);
        addGlyph("h", h);
        addGlyph("i", i);
        addGlyph("j", j);
        addGlyph("k", k);
        addGlyph("l", l);
        addGlyph("m", m);
        addGlyph("n", n);
        addGlyph("o", o);
        addGlyph("p", p);
        addGlyph("q", q);
        addGlyph("r", r);
        addGlyph("s", s);
        addGlyph("t", t);
        addGlyph("u", u);
        addGlyph("v", v);
        addGlyph("x", x);
        addGlyph("y", y);
        addGlyph("z", z);
        addGlyph("0", zero);
        addGlyph("1", one);
        addGlyph("2", two);
        addGlyph("3", three);
        addGlyph("4", four);
        addGlyph("5", five);
        addGlyph("6", six);
        addGlyph("7", seven);
        addGlyph("8", eight);
        addGlyph("9", nine);
        addGlyph(".", dot);
        addGlyph("-", dash);
        addGlyph("/", slash);
    }

    public static GLModel[] getString(final String s){
        int length = s.length();
        GLModel[] result = new GLModel[length];
        for(int i = 0; i < length; i++){
            result[i] = GLFont.getChar(s.substring(i, i+1));
        }
        return result;
    }

    public static final GLModel getChar(final String s){
        GLModel result = glyphMap.get(s);
        if(result == null){
            return glyphMap.get(".");
        }
        return result;
    }

    private static float[] quad(float left, float top, float width, float height){
        final float z = 0.0f;
        final float right = left+width;
        final float bottom = top-height;
        return new float[]{
                left, top, z,
                left, bottom, z,
                right, bottom, z,
                right, top, z,
                left, top, z,
                right, bottom, z
        };
    }

    private static void addGlyph(final String index, final float[] vertices){
        glyphMap.put(index, new GLModel(vertices));
    }

    private static float[] concat(final float[]... arrays){
        if(arrays == null || arrays.length < 1){ throw new IllegalArgumentException(""); }
        int length = 0, pos = 0, count = arrays.length;
        for (float[] a : arrays) {
            length += a.length;
        }
        float[] result = new float[length];
        for(int i = 0; i < count; i++){
            System.arraycopy(arrays[i], 0, result, pos, arrays[i].length);
            pos += arrays[i].length;
        }
        return result;
    }
}