Get angle of bullet after bouncing

[Bingocat4]

I'm trying to make a bullet bounce after it hits a wall. I think bouncing on the top and bottom wall works perfectly, but it won't bounce off of the left and right walls. How would I get it to bounce? This is how I get the direction the bullet it going whenever I shoot.

player.dir = GetAngle(player.mouseX, player.mouseY, player.x, player.y);

float GetAngle(float x1, float y1, float x2, float y2) {
	return atan2(y1 - y2, x1 - x2);
}

Also what I was trying to do to make the bullet bounce.

if (bullets[i].x < 10 || bullets[i].x > screenWidth - 10 ||
	bullets[i].y < 10 || bullets[i].y > screenHeight - 10) {
	if (bullets[i].type == 8)
		bullets[i].dir *= -1;
}

[keskiverto]

You don't need the angle explicitly:
http://en.wikipedia.org/wiki/Specular_reflection

[Bingocat4]

Well I tried some more and this uh almost works...

if (bullets[i].x < 10 || bullets[i].x > screenWidth - 10 ||
			bullets[i].y < 10 || bullets[i].y > screenHeight - 10) {
			if (bullets[i].type == 8) {
				if (bullets[i].dir < 0)
					bullets[i].dir += 1.5;
				else if (bullets[i].dir > 0)
					bullets[i].dir -= 1.5;
				else
					bullets[i].dir += 3;
			if (bullets[i].x < 10)
				bullets[i].x = 10;
			else if (bullets[i].x > screenWidth - 10)
				bullets[i].x = screenWidth - 10;
			if (bullets[i].y < 10)
				bullets[i].y = 10;
			else if (bullets[i].y > screenHeight - 10)
				bullets[i].y = screenHeight - 10;
			}
		}

[Bingocat4]

I tried some more code and I still can't get it working right. It kinda works on 3 walls from the right angle.

if (bullets[i].x < 10 || bullets[i].x > screenWidth - 10 ||
	bullets[i].y < 10 || bullets[i].y > screenHeight - 10) {
	if (bullets[i].type == 8) {
		float velX, velY;
		POINT newPos;
		POINT newPos2;
		newPos.x = bullets[i].x + (bullets[i].speed * 2) * cos(bullets[i].dir);
		newPos.y = bullets[i].y + (bullets[i].speed * 2) * sin(bullets[i].dir);
		velX = abs(bullets[i].x - newPos.x);
		velY = abs(bullets[i].y - newPos.y);

		if (bullets[i].x < 10) {
			bullets[i].x = 10;
			velX *= -1;
		}
		else if (bullets[i].x > screenWidth - 10) {
			bullets[i].x = screenWidth - 10;
			velX *= -1;
		}
		if (bullets[i].y < 10) {
			bullets[i].y = 10;
			velY *= -1;
		}
		else if (bullets[i].y > screenHeight - 10) {
			bullets[i].y = screenHeight - 10;
			velY *= -1;
		}
		newPos2.x = newPos.x + (bullets[i].speed * 2) * cos(GetAngle(newPos.x, newPos.y, newPos2.x, newPos2.y));
		newPos2.y = newPos.y + (bullets[i].speed * 2) * sin(GetAngle(newPos.x, newPos.y, newPos2.x, newPos2.y));
		bullets[i].dir = GetAngle(newPos.x, newPos.y, newPos2.x, newPos2.y);
	}
}