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Previous part: Geometric algebra in 2D and 3D

Disclaimer: there will be NO proofs or rigorous explanations here, just some results and notes on how to use the library

Projective geometric algebra in 2D

Lines

We start with lines. As you can remember, the equation for a line in 2D looks like this:

Disclaimer: this is not a textbook, this is just a short explanation, so you can use this library

Geometric algebra in 2D

Let's say we have a 2d-vector:

$$ v = (v_1, v_2) $$

Data oriented UI (part 3)

In the previous part (Part 2) I created hover and click behaviours, so we could make buttons or just any hover elements. But how to use them in the game? I don't want to store a pointer to the button. UI library could reorder elements or delete them as it wishes, I don't want this hard constraint, especially with no way to check is my pointer valid or not.

Accessing elements in the game code

Introducing `ui::handle`

Data oriented input in games

Many game engines implement inputs in a more OOP style: you have an object, that represents an input device, and you can query its state. Something like this:

class input_device {};

class mouse : public input_device
{

Data oriented UI (part 2)

Last time (Part 1) I finished by drawing a couple of rectangles on the screen. But I missed the bug, so let's fix it. Let's have a look at the code below, can you spot it?

void draw(system *s)
{
    // ...

Data oriented UI (part 1)

Some time ago I read the @lisyarus' post about his UI library. In his blog post he compares existing UI frameworks, analyses reasons why they don't work to them, and shows how he created his own library to build in-game UI.

His blog post immediately inspired me: how would I build my UI library?


	#define IEEE754_32BIT_MANTISSA_MASK 0x7fffff
	#define IEEE754_32BIT_MANTISSA_NBITS 23
	#define IEEE754_32BIT_MANTISSA_SHIFT 0

	#define IEEE754_32BIT_EXPONENT_MASK 0xff
	#define IEEE754_32BIT_EXPONENT_NBITS 8
	#define IEEE754_32BIT_EXPONENT_SHIFT 23

	#define IEEE754_32BIT_SIGN_BIT_MASK 0x1

	#include <stdint.h>

	#define WIN32_LEAN_AND_MEAN
	#include <windows.h>
	#include <GL/gl.h>

	#define WGL_DRAW_TO_WINDOW_ARB 0x2001
	#define WGL_ACCELERATION_ARB 0x2003
	#define WGL_SUPPORT_OPENGL_ARB 0x2010
	#define WGL_DOUBLE_BUFFER_ARB 0x2011

	#include <stdint.h>

	#define WIN32_LEAN_AND_MEAN
	#include <windows.h>
	#include <GL/gl.h>

	#define WGL_DRAW_TO_WINDOW_ARB 0x2001
	#define WGL_ACCELERATION_ARB 0x2003
	#define WGL_SUPPORT_OPENGL_ARB 0x2010
	#define WGL_DOUBLE_BUFFER_ARB 0x2011

	#include <stdio.h>
	#include <sys/mman.h>
	#include <sys/stat.h>
	#include <fcntl.h>
	#include <string.h>
	#include <errno.h>
	#include <semaphore.h>
	#include <unistd.h>
	#include <sys/types.h>