How to change view based on mouse position?

[Coakie]

I want to make a circle always in the middle of the window, but I want the view to change based on the mouse position. For example, if I move the cursor above the circle, the view will change, but the circle will still be fixed in the middle of the window.

                sf::Vector2i pixelPos = sf::Mouse::getPosition(window);
                sf::Vector2f worldPos = window.mapPixelToCoords(pixelPos);

                playerCircle.setPosition(view.getCenter());
                view.setCenter(worldPos);
 

I tried this, but it doesn't work

[Hapax]

Try setting the circle's position to the view's centre after you've correctly set the view's centre.

[Coakie]

Try setting the circle's position to the view's centre after you've correctly set the view's centre.

I tried this, but now it does the same thing as before, just moving the view around super quick. Is there a way to fix this? Here is a copy of my messy code so you can test it out for yourself; if you press the mouse then it will show the coordinates.

(click to show/hide)

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <string>
#include <cstdlib>
#include <SFML/Graphics.hpp>
#include <SFML/System.hpp>
#include <time.h>
using namespace std;

std::vector<sf::CircleShape> circles(10);
void spawnCircles(){
        for (int i = 0; i<10; ++i) {
                circles[i].setFillColor(sf::Color::Red);
                circles[i].setRadius(5);
                circles[i].setPosition(((int)rand() % 700 + 100), ((int)rand() % 700 + 100));
        }
}

int main()
{
        srand(time(NULL));
        sf::Font font;
        if (!font.loadFromFile("font.ttf")){
                // error...
        }

        sf::Vector2i screenDimensions(1000,800);
        sf::RenderWindow window(sf::VideoMode(screenDimensions.x, screenDimensions.y), "Circle Game");
        sf::View view;
        view.reset(sf::FloatRect(0, 0, screenDimensions.x, screenDimensions.y));
        view.setViewport(sf::FloatRect(0, 0, 1.0f, 1.0f));

        //Title Screen
        sf::RectangleShape nameBox(sf::Vector2f(400, 50)); //textbox
        nameBox.setPosition(200, 400);
        nameBox.setFillColor(sf::Color::Transparent);
        nameBox.setOutlineColor(sf::Color::Black); nameBox.setOutlineThickness(3);
        sf::RectangleShape goButton(sf::Vector2f(100, 100)); //press to the game
        goButton.setPosition(75, 550);
        goButton.setFillColor(sf::Color::Green);
        goButton.setOutlineColor(sf::Color::Black); goButton.setOutlineThickness(3);
        sf::CircleShape playerCircle; //player(one?)
        playerCircle.setRadius(10);
        playerCircle.setFillColor(sf::Color::Yellow);
        playerCircle.setOutlineColor(sf::Color::Black); playerCircle.setOutlineThickness(2);
        sf::CircleShape border; //world border
        border.setFillColor(sf::Color::Transparent);
        border.setOutlineThickness(7);
        border.setRadius(1500);
        border.setPosition(-1000,-1000);
        sf::Text nameInstrucs; //instructions; "Enter your name"
        nameInstrucs.setFont(font);
        nameInstrucs.setString("Enter your name");
        nameInstrucs.setFillColor(sf::Color::Black);
        nameInstrucs.setCharacterSize(24);
        nameInstrucs.setPosition(310, 350);
        sf:string str; sf::Text playerName; //player name
        playerName.setPosition(250, 410);
        playerName.setFont(font);
        playerName.setCharacterSize(24);
        playerName.setFillColor(sf::Color::Black);


        int mouseX = 0;
        int mouseY = 0;
        int drawStuff = 0; // 0: NameScreen, 1: Info Screen(?), 2: Game


        while (window.isOpen())
        {
                /////////--------------------------------------------
                sf::Vector2i pixelPos = sf::Mouse::getPosition(window);
                sf::Vector2f worldPos = window.mapPixelToCoords(pixelPos);
                mouseX = worldPos.x; mouseY = worldPos.y;

                sf::Event event;
                while (window.pollEvent(event))
                {
                        if (event.type == sf::Event::Closed) {
                                window.close();
                        }
                        if (event.type == sf::Event::TextEntered)
                        {
                                if (drawStuff == 0) {
                                        if (event.text.unicode == '\b' && str.size() >= 1) {
                                                str.erase(str.size() - 1, 1);
                                                cout << "ASCII character typed: Backspace" << endl;
                                                cout << "Total string: " << str << endl;
                                                playerName.setString(str);
                                        }
                                        else if (event.text.unicode < 128 && str.size() <= 30) {
                                                str += static_cast<char>(event.text.unicode);
                                                cout << "ASCII character typed: " << static_cast<char>(event.text.unicode) << endl;
                                                cout << "Total string: " << str << endl;
                                                playerName.setString(str);
                                        }
                                }
                        }
                        if (drawStuff == 0 && event.type == sf::Event::MouseButtonPressed) {
                                if (event.mouseButton.button == sf::Mouse::Left)
                                {
                                        if (mouseX > goButton.getGlobalBounds().left &&
                                                mouseY > goButton.getGlobalBounds().top &&
                                                mouseX < goButton.getGlobalBounds().left + goButton.getGlobalBounds().width &&
                                                mouseY < goButton.getGlobalBounds().top + goButton.getGlobalBounds().height) {
                                                cout << "Button pressed." << endl; //press the button to start the game
                                                drawStuff = 2;
                                        }
                                }
                        }
                        if (event.mouseButton.button == sf::Mouse::Right && event.type == sf::Event::MouseButtonReleased) {
                                spawnCircles();
                        }
                        if (event.mouseButton.button == sf::Mouse::Left && event.type == sf::Event::MouseButtonPressed) {
                                std::cout << "The left mouse button was pressed." << std::endl;
                                std::cout << "mouseX: " << mouseX << std::endl;
                                std::cout << "mouseY: " << mouseY << std::endl;
                        }
                }

                /////////---------------------------------------------

               


               
                window.setView(view);
                window.clear(sf::Color(200, 200, 200));
                if (drawStuff == 0) {
                        window.draw(nameBox);
                        window.draw(nameInstrucs);
                        window.draw(goButton);
                }
                if (drawStuff == 2) {
                        for (int n = 0; n < 10; ++n) {
                                window.draw(circles[n]);
                        }
                        window.draw(playerCircle);
                        window.draw(border);
                        view.setCenter(worldPos);
                        playerCircle.setPosition(view.getCenter());
                }
                window.draw(playerName);
                window.display();
        }

        return 0;
}

[Hapax]

I want the view to change based on the mouse position.

is unclear.

How do you intend the view to move based on the mouse movement?
Do you want it to centre on the mouse when you click or something?
Or, do you want it to move at a speed based on the mouse's offset from the centre.

If the former, the view's centre should only be updated when there has been a click.

If the latter, you get the difference between the current mouse position and the centre, then you can use that amount to offset the current view centre (move the view). This difference can be multiplied to scale the amount you want it to affect the speed. You could also use a specific view for this - one with a lower range. Then use this view to find the mouse position. This can reduce the need for scaling the result. If this view's centre is at zero, there would also be no need for any "difference" calculations.

Maybe you want something completely different but we can't know the exact thing you want without enough information.

[Coakie]

If the latter, you get the difference between the current mouse position and the centre, then you can use that amount to offset the current view centre (move the view). This difference can be multiplied to scale the amount you want it to affect the speed. You could also use a specific view for this - one with a lower range. Then use this view to find the mouse position. This can reduce the need for scaling the result. If this view's centre is at zero, there would also be no need for any "difference" calculations.

I wanted it to move similar to the way you explained it, except I want the view to move at the same speed regardless of the amount of distance between the cursor and the circle, similar to a game like "agar.io". Can you maybe give to me an example of this to get started?

[Hapax]

The second way I explained?

I think I would try to set up a view to use just for this, probably size of 2x2 and centre at (0,0). This means that the positions of the window are (-1, -1) to (1, 1). If you map your mouse position to that view, you can see which direction the mouse is from the centre of the window.
To move in that direction by a constant speed, you find the unit vector of the mouse's mapped position and then multiply that by the required speed.

Note that you may want to consider some distance from the centre as still in the centre otherwise it'll be difficult to stop the motion.