Starfield in D, uses krakjoe/dui (or any other 1:1 module)

starfield.d

import std.random;

import andlabs.libui;

struct Star {
	double X;
	double Y;
	double V;
	bool   F;
	double G;
}

Star stars[];

extern (C) {
	
	int closing(uiWindow *win, void *data) {
		uiControlDestroy(cast(uiControl*) win);
		uiQuit();
		
		return 0;
	}

	void draw(uiAreaHandler *handlers, uiArea *area, uiAreaDrawParams *params) {
		uiDrawBrush blackBrush = {uiDrawBrushTypeSolid, 0, 0, 0, 1};
		uiDrawBrush whiteBrush = {uiDrawBrushTypeSolid, 1, 1, 1, 1};

		double hWidth = params.AreaWidth / 2;
		double hHeight = params.AreaHeight / 2;

		uiDrawPath *path = uiDrawNewPath(uiDrawFillModeWinding);
		uiDrawPathAddRectangle(path, 0, 0, params.AreaWidth, params.AreaHeight);
		uiDrawPathEnd(path);

		uiDrawFill(params.Context, path, &blackBrush);

		uiDrawFreePath(path);

		for (int start = 0; start < 1024; start++) {
			Star *star = &stars[start];

			star.V -= 0.2;

			if (star.V <= 0) {
				star.X = uniform(-25, 26);
				star.Y = uniform(-25, 26);
				star.V = 128;
			}

			double px = star.X * (128 / star.V) + hWidth;
			double py = star.Y * (128 / star.V) + hHeight;

			if (px >= 0 && px <= params.AreaWidth && py >= 0 && py <= params.AreaHeight) {
				double channel = (1 - star.V / 32) * 5;

				uiDrawPath *next = uiDrawNewPath(uiDrawFillModeWinding);
				uiDrawPathNewFigureWithArc(next, px, py, channel/2, 0, uiPi*2, 0);
				uiDrawPathEnd(next);

				uiDrawBrush brush = {
					uiDrawBrushTypeSolid,
					channel,
					channel,
					channel,
					star.F && star.G++ % 3 == 0 ? uniform(0, 11)/10 : 1
				};

				uiDrawFill(params.Context, next, &brush);
				uiDrawFreePath(next);
			}
		}
	}

	void mouse(uiAreaHandler *handlers, uiArea *area, uiAreaMouseEvent *ev) {}
	
	void crossed(uiAreaHandler *handlers, int left) {}

	void drag(uiAreaHandler *handlers, uiArea *area) {}

	int key(uiAreaHandler *handlers, uiArea *area, uiAreaKeyEvent *ev) {
		return 0;
	}

	uiAreaHandler handlers = {
		&draw,
		&mouse,
		&crossed,
		&drag,
		&key
	};
}

void main()
{
    uiInitOptions o;
	uiWindow *win;
	uiBox *box;
	uiArea *area;
    const char *err = uiInit(&o);

	if (err != null) {
		uiFreeInitError(err);
		return;
	}

	win = uiNewWindow("Starfield", 640, 480, 0);
	uiWindowOnClosing(win, &closing, win);

	box = uiNewVerticalBox();
	uiWindowSetChild(win, cast(uiControl*) box);

	area = uiNewArea(&handlers);
	uiBoxAppend(box, cast(uiControl*) area, 1);

	stars = new Star[1024];

	for (int i = 0; i < 1024; i++) {
		stars[i].X = uniform(-25, 26);
		stars[i].Y = uniform(-25, 26);
		stars[i].V = uniform(1, 129);
		stars[i].F = cast(bool) uniform(0, 2);
		stars[i].G = 0;
	}

	uiControlShow(cast(uiControl*) win);	
	uiMainSteps();

	while (uiControlVisible(cast(uiControl*) win)) {
		uiAreaQueueRedrawAll(area);

		uiMainStep(1);		
	} 
    
	uiUninit();
}