How to draw a custom shaped element? - c++

Question

I'm currently working in an app which is essentially a pong game. The game features two paddles currently in rectangular format to ease collision detection against the ball(currently square).
I'm using a "QRect" element as paddle since it provides the ".intersect" method, making it easy to check for collisions.
My implementation for a rectangular paddle is as follows:
Paddle::Paddle(int initial_x, int initial_y) {
QImage image.load(":images/paddle.png");
QRect rect = image.rect();
resetState(initial_x, initial_y);
}
I'm trying to draw an arch like paddle and hitbox, similar to what the code below provides:
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
int startAngle = 30 * 16;
int spanAngle = 120 * 16;
QPainter painter(this);
painter.drawChord(rectangle, startAngle, spanAngle);
The only problem with the code above is it only works inside a paintEvent function and that won't work for me.
paddle.h
#ifndef PADDLE_H
#pragma once
#include <QImage>
#include <QRect>
class Paddle {
public:
Paddle(int, int);
~Paddle();
public:
void resetState(int, int);
void move();
void setDx(int);
void setDy(int);
QRect getRect();
QImage & getImage();
private:
QImage image;
QRect rect;
int dx;
int dy;
static const int INITIAL_X1 = 70;
static const int INITIAL_Y1 = 350;
};
#define PADDLE_H
#endif // PADDLE_H
paddle.cpp
#include <iostream>
#include "paddle.h"
Paddle::Paddle(int initial_x, int initial_y) {
dy = 0;
image.load(":images/paddle.png");
rect = image.rect();
resetState(initial_x, initial_y);
}
Paddle::~Paddle() {
std::cout << ("Paddle deleted") << std::endl;
}
void Paddle::setDy(int y) {
dy = y;
}
void Paddle::move() {
int x = rect.x();
int y = rect.top() + dy;
rect.moveTo(x, y);
}
void Paddle::resetState(int initial_x, int initial_y) {
rect.moveTo(initial_x, initial_y);
}
QRect Paddle::getRect() {
return rect;
}
QImage & Paddle::getImage() {
return image;
}
mainGame.h
#ifndef BREAKOUT_H
#pragma once
#include <QWidget>
#include <QKeyEvent>
#include <QFrame>
#include "ball.h"
#include "brick.h"
#include "paddle.h"
class Breakout : public QFrame {
Q_OBJECT
public:
Breakout(QWidget *parent = 0);
~Breakout();
signals:
void leftScoreChanged(int leftScore);
void rightScoreChanged(int rightScore);
void ballLost(int ballsLeft);
protected:
void paintEvent(QPaintEvent *);
void timerEvent(QTimerEvent *);
void keyPressEvent(QKeyEvent *);
void keyReleaseEvent(QKeyEvent *);
void drawObjects(QPainter *);
void finishGame(QPainter *, QString);
void moveObjects();
void startGame();
void pauseGame();
void stopGame();
void victory();
void validateScoreChange(int);
void checkCollision();
private:
int x;
int timerId;
int ballsLeft;
int leftScore;
int rightScore;
static const int N_OF_BRICKS = 30;
static const int DELAY = 5;
static const int TOP_EDGE = 0;
static const int LEFT_EDGE = 0;
static const int BOTTOM_EDGE = 700;
static const int RIGHT_EDGE = 1200;
Ball *ball;
Paddle *leftPaddle;
Paddle *rightPaddle;
Brick *bricks[N_OF_BRICKS];
bool gameOver;
bool gameWon;
bool gameStarted;
bool paused;
};
#define BREAKOUT_H
#endif // BREAKOUT_H
Breakout::paintEvent()
void Breakout::paintEvent(QPaintEvent *e) {
Q_UNUSED(e);
QPainter painter(this);
if (gameOver) {
finishGame(&painter, "Game lost");
} else if(gameWon) {
finishGame(&painter, "Victory");
}
else {
drawObjects(&painter);
}
QWidget::paintEvent(e);
}

Answer 1

From what I understand you do not want to load the QImage from a .png file but you want to draw it, if so you can use QPainter to create the image as I show below:
Paddle::Paddle(int initial_x, int initial_y) {
// draw image
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
int startAngle = 30 * 16;
int spanAngle = 120 * 16;
image = QImage(QSize(100, 100), QImage::Format_ARGB32);
image.fill(Qt::transparent);
QPainter painter(&image);
painter.drawChord(rectangle, startAngle, spanAngle);
painter.end();
dy = 0;
rect = image.rect();
resetState(initial_x, initial_y);
}