mg4/app/src/main/java/com/evsuite/abrp/MapLayerView.java

package com.evsuite.abrp;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.SystemClock;
import android.view.View;

/**
 * The map under "Grid with map": the roads round the car and a ground grid, straight from
 * above, heading up — drawn once into a hardware layer (a GPU texture) and then only moved and
 * turned, by the view's own translation and rotation, once per display frame. Nothing is
 * redrawn while driving until new tiles arrive or the car nears the layer's edge; then it is
 * drawn again round the car. {@link GridView} draws everything else on top.
 *
 * The layer is a square about twice the distance from the car to the farthest screen corner,
 * plus a margin, so it covers the screen at any angle; the car sits {@link #CAR_FROM_BOTTOM}
 * layout units above the bottom edge.
 */
final class MapLayerView extends View {

    /** Pixels (layout units) per metre, the car's height above the bottom edge, grid spacing. */
    static final float MAP_SCALE = 1.2f, CAR_FROM_BOTTOM = 150f;
    private static final float GRID_M = 50f;
    /** How far the car may move from the layer's centre before it is drawn again, in layout units. */
    private static final float MARGIN = 280f;

    private final MapRoads map;
    private final Paint line = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Path[] roads = new Path[RoadTile.CLASSES];
    private final Path grid = new Path();
    private int main = 0xFF18E6FF, light = 0xFFC8FCFF;

    /** The layer's centre (world tile units) and what it was drawn from. */
    private double anchorX = Double.NaN, anchorY;
    private int drawnVersion = -1;
    private float drawnScale;
    /** The car as shown, eased towards where it is (world tile units), and the heading. */
    private double shownX = Double.NaN, shownY;
    private float heading = Float.NaN;
    private boolean showing, ticking;
    /** The car's speed, from the readings; NaN when unread. */
    private float speedMps = Float.NaN;

    MapLayerView(Context context, MapRoads map) {
        super(context);
        this.map = map;
        for (int i = 0; i < roads.length; i++) roads[i] = new Path();
        line.setStyle(Paint.Style.STROKE);
        line.setStrokeJoin(Paint.Join.ROUND);
        line.setStrokeCap(Paint.Cap.ROUND);
        setLayerType(LAYER_TYPE_HARDWARE, null);
        setVisibility(INVISIBLE);
        setWillNotDraw(false);
    }

    void setColours(int main, int light) {
        this.main = main;
        this.light = light;
        invalidate();
    }

    /** Whether the map is there to be seen (a fix and roads). */
    boolean isShowing() {
        return showing;
    }

    /** Layout units, as GridView uses them, for this size. */
    private float unit() {
        View parent = (View) getParent();
        int w = parent == null ? getWidth() : parent.getWidth() - parent.getPaddingLeft() - parent.getPaddingRight();
        int h = parent == null ? getHeight() : parent.getHeight() - parent.getPaddingTop() - parent.getPaddingBottom();
        return Math.min(h / 640f, w / 1100f);
    }

    @Override
    protected void onMeasure(int widthSpec, int heightSpec) {
        int w = MeasureSpec.getSize(widthSpec), h = MeasureSpec.getSize(heightSpec);
        float u = Math.min(h / 640f, w / 1100f);
        int side = (int) (2 * (Math.hypot(w / 2f, h - CAR_FROM_BOTTOM * u) + MARGIN * u));
        setMeasuredDimension(Math.max(side, 1), Math.max(side, 1));
    }

    /** The car's speed in km/h, or null when unread; GridView passes it with every reading. */
    void setSpeed(Float kmh) {
        speedMps = kmh == null ? Float.NaN : kmh / 3.6f;
    }

    /** Starts the frame loop if it is not running; GridView calls it with every reading. */
    void kick() {
        if (!ticking && isAttachedToWindow()) {
            ticking = true;
            postOnAnimation(this::tick);
        }
    }

    /** One display frame: where the car is, which way, and the layer moved there. */
    private void tick() {
        View pane = (View) getParent();
        if (pane == null || !pane.isShown()) {
            ticking = false;
            return;
        }
        MapRoads.Fix fix = map.fix();
        boolean ready = fix != null && !map.tiles().isEmpty() && getWidth() > 0;
        if (ready != showing) {
            showing = ready;
            setVisibility(ready ? VISIBLE : INVISIBLE);
        }
        if (!ready) {
            ticking = false;
            return;
        }
        float target = Float.isNaN(fix.bearing) ? (Float.isNaN(heading) ? 0f : heading) : fix.bearing;
        if (Float.isNaN(heading)) heading = target;
        else heading = (heading + (((target - heading) % 360f + 540f) % 360f - 180f) * 0.12f + 360f) % 360f;

        // Between fixes the car runs on with the speed (at most 2.5 s), and what is shown glides
        // there rather than jumping with each fix.
        double mpu = MapGeometry.metresPerUnit(fix.lat);
        float ran = Float.isNaN(fix.bearing) || Float.isNaN(speedMps) ? 0f
                : speedMps * Math.min(2.5f, (SystemClock.elapsedRealtime() - fix.elapsedMs) / 1000f);
        double run = Math.toRadians(Float.isNaN(fix.bearing) ? 0f : fix.bearing);
        double carX = MapGeometry.worldX(fix.lon) + ran * Math.sin(run) / mpu;
        double carY = MapGeometry.worldY(fix.lat) - ran * Math.cos(run) / mpu;
        if (Double.isNaN(shownX) || Math.hypot(carX - shownX, carY - shownY) * mpu > 200) {
            shownX = carX;
            shownY = carY;
        } else {
            shownX += (carX - shownX) * 0.15;
            shownY += (carY - shownY) * 0.15;
        }

        float u = unit(), px = MAP_SCALE * u;
        if (drawnVersion != map.version() || Double.isNaN(anchorX) || drawnScale != px
                || Math.hypot(shownX - anchorX, shownY - anchorY) * mpu * px > MARGIN * u) {
            build(shownX, shownY, mpu);
            drawnScale = px;
            invalidate(); // the only redraw of the layer
        }

        // The car's spot in the layer goes to its spot on screen, turned round it.
        float half = getWidth() / 2f;
        float inX = half + (float) ((shownX - anchorX) * mpu) * px;
        float inY = half + (float) ((shownY - anchorY) * mpu) * px;
        float carSx = pane.getPaddingLeft() + (pane.getWidth() - pane.getPaddingLeft() - pane.getPaddingRight()) / 2f;
        float carSy = pane.getHeight() - pane.getPaddingBottom() - CAR_FROM_BOTTOM * u;
        setPivotX(inX);
        setPivotY(inY);
        setRotation(-heading);
        setTranslationX(carSx - getLeft() - inX);
        setTranslationY(carSy - getTop() - inY);
        postOnAnimation(this::tick);
    }

    /** The roads and the grid in metres east and south of an anchor at the car. */
    private void build(double atX, double atY, double mpu) {
        anchorX = atX;
        anchorY = atY;
        drawnVersion = map.version();
        float m = (float) mpu;
        for (Path p : roads) p.reset();
        float u = unit();
        double reach = getWidth() / 2f / (MAP_SCALE * u);
        double range = reach / mpu;
        for (RoadTile tile : map.tiles()) {
            double ox = (double) tile.x * MapGeometry.EXTENT - atX, oy = (double) tile.y * MapGeometry.EXTENT - atY;
            if (ox > range || oy > range || ox + MapGeometry.EXTENT < -range || oy + MapGeometry.EXTENT < -range) {
                continue;
            }
            float fx = (float) ox, fy = (float) oy;
            for (int i = 0; i < tile.points.length; i++) {
                int[] b = tile.bounds[i];
                if (fx + b[2] < -range || fx + b[0] > range || fy + b[3] < -range || fy + b[1] > range) continue;
                Path p = roads[tile.classes[i]];
                int[] pts = tile.points[i];
                p.moveTo((fx + pts[0]) * m, (fy + pts[1]) * m);
                for (int k = 2; k < pts.length; k += 2) p.lineTo((fx + pts[k]) * m, (fy + pts[k + 1]) * m);
            }
        }
        // Grid lines on whole multiples of GRID_M east and north, so they stay put on the ground.
        grid.reset();
        float r = (float) reach;
        float offE = (float) ((atX * mpu) % GRID_M), offS = (float) ((atY * mpu) % GRID_M);
        int lines = (int) (r / GRID_M) + 1;
        for (int k = -lines; k <= lines; k++) {
            float x = k * GRID_M - offE, y = k * GRID_M - offS;
            grid.moveTo(x, -r);
            grid.lineTo(x, r);
            grid.moveTo(-r, y);
            grid.lineTo(r, y);
        }
    }

    @Override
    protected void onDraw(Canvas c) {
        if (Double.isNaN(anchorX) || drawnScale <= 0f) return;
        float u = unit(), px = drawnScale;
        c.save();
        c.translate(getWidth() / 2f, getHeight() / 2f);
        c.scale(px, px);
        stroke(c, grid, AccentColor.withAlpha(main, 0x26), 1f * u / px);
        stroke(c, roads[3], AccentColor.withAlpha(main, 0xA0), 1.6f * u / px);
        stroke(c, roads[2], AccentColor.withAlpha(main, 0xD8), 2.2f * u / px);
        glow(c, roads[1], main, 2.6f * u / px);
        glow(c, roads[0], light, 3.4f * u / px);
        c.restore();
    }

    private void stroke(Canvas c, Path p, int colour, float width) {
        line.setColor(colour);
        line.setStrokeWidth(width);
        c.drawPath(p, line);
    }

    /** As GridView's glow: two wide faint strokes under a sharp one. */
    private void glow(Canvas c, Path p, int colour, float width) {
        stroke(c, p, AccentColor.withAlpha(colour, 0x18), width * 6f);
        stroke(c, p, AccentColor.withAlpha(colour, 0x40), width * 3f);
        stroke(c, p, colour, width);
    }
}