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Move with the keyboard

You want an object to move while the player holds the arrow keys.

#include <brasa/brasa.hpp>
using namespace brasa;


class Player : public Entity {
public:
    void onUpdate() override {
        const float speed = 2.0f;  // pixels per step
        if (held(Key::Left) || held(Key::A))  x -= speed;
        if (held(Key::Right) || held(Key::D)) x += speed;
        if (held(Key::Up) || held(Key::W))    y -= speed;
        if (held(Key::Down) || held(Key::S))  y += speed;
    }
};
BRASA_ENTITY(Player);

How it works

Section titled “How it works”
  • onUpdate runs 60 times per second. Each time, the code checks the keyboard.
  • held(Key::Left) is true while the key is held down.
  • x grows to the right and y grows downwards. That’s why “up” is y -= speed.
  • || means or: the arrow and the letter do the same thing.

Variations

Section titled “Variations”

Move diagonally at the same speed. Adding the two directions, the diagonal ends up faster. Keep the direction in dx/dy and fix it with 0.7071 (that’s how it is in the tutorial):

if (dx != 0.0f && dy != 0.0f) { dx *= 0.7071f; dy *= 0.7071f; }

Don’t go through walls. Mark the wall object as Sólido (solid) in the Inspector and move with moveAndStop, which stops when it touches a solid:

float dx = 0, dy = 0;
if (held(Key::Left))  dx -= 2;
if (held(Key::Right)) dx += 2;
moveAndStop(dx, dy);

One action per tap. To jump or open a menu, use pressed, which is true only on the step when the key was pressed:

if (pressed(Key::Space)) vspeed = -6;  // jump

See also

Section titled “See also”