Variable don't update from sfml event loop - c++

I am using sfml library for my graphics. During paused I want to avoid drawing on the screen. I want to intercept a spacebar press using sf::Event::MouseButtonPressed. In the debug mode, the event is successfully intercepted but failed in normal execution, why? The bool variable 'paused' don't seemed to update.
while (window.isOpen()) {
Event event;
while (window.pollEvent(event)) {
/*..*/
if (event.type = Event::KeyPressed) {
if (event.key.code == Keyboard::Space) {
if (!paused) {
paused = true;// UDATE HERE
}
else
if (paused)
{
paused = false; // UDATE HERE
}
}
}
}
if (!paused) //// UDATE DONT SEEM TO AFFECT HERE
{
/* draw here */
}
}
Edited: Even tried by declaring the variable paused as atomic, but still don't work.

Use the Event::KeyReleased instead of the Event::KeyPressed as the key press gets called every loop that a key is down leading to many enters while the Release event is only called once per click.

Related

Multiple key presses SFML

I'm trying to detect keyPress only once, but it goes for random amount of presses. I'm using keyrelease, and it work normally if I have breakpoint.
while (window.isOpen()) {
sf::Event event;
while (window.pollEvent(event)) {
if (event.type == sf::Event::Closed) {
window.close();
} else {
characterScreen.handleEvent(event, window);
}
}
bool keyReleased = event.type == sf::Event::KeyPressed;
bool rightArrowKey = event.key.code == sf::Keyboard::Right;
bool leftArrowKey = event.key.code == sf::Keyboard::Left;
if (keyReleased&&leftArrowKey)
{
if (selectedCharacter == 0)
{
selectedCharacter = characterList.size() - 1;
}
else
{
selectedCharacter--;
}
changeCharacters(characterList[selectedCharacter], font, characterScreen);
std::cout << "left pressed" << std::endl;
keyReleased = false;
std::cout << keyReleased << std::endl;
}
else if (keyReleased && rightArrowKey)
{
if (selectedCharacter == characterList.size()-1)
{
selectedCharacter = 0;
}
else
{
selectedCharacter++;
}
changeCharacters(characterList[selectedCharacter], font, characterScreen);
}
window.clear(sf::Color::White);
characterScreen.update();
characterScreen.render(window);
window.display();
}
I've tryed window.setKeyRepeatEnabled(false); and keypressed, still nothing. Tryed different keyboard aswell.
When using (C)SMFL, we generally have a main loop condition rendering the main frame (the windows) and checking events, it can be an infinite loop (such as while (1)) or a more recomanded one like your while (window.isOpen()).
It means that the windows and all events listener are refreshed / updated each loop's turn, so if you press a key on your keyboard, you will trigger your keyboard's event listener, fine, and you will continue your code until re-enter in your main loop, and re-refreshing the windows and re-updating your event listener.
What the point of explaining that ? it just means by only pressing once a key, your computer will process maybe 10, 100 or maybe 1000 iteration of your main loop (depending on it's performances and more). So it's "normal" to works fine when you use convenient features like breakpoints, but in reality you can't.
You have a lot of possibilities, bad ones (like "use delay / pause" who's not recommended since it will halt your window's refresh and can be interpreted by a crash by your OS) or good ones like tampon variables, who'll cancel the entrance of some conditions by their state:
Example:
bool tmp_var = false;
while (window.isOpen()) {
// Warn, you called your variable keyReleased but it check keyPressed
if (event.type == sf::Event::KeyPressed && tmp_var == false) {
// Check wich key is pressed and perform required actions
tmp_var = true;
} else if (event.type == sf::Event::KeyReleased) {
tmp_var = false;
}
}
Note that the code can be not correct, I wanted to point out the reasoning

Detecting if a touch pressed, not if its down?

i will make a beat em up game with sfml c++ on mobilephone. So i need to use the Touch function. The problem I have is, what is the best way to detect when the Touch has been pressed, and only execute the code which should be executed when the key has been pressed once? I need it for an animation when the Player make a kick. Now its always repeating the spritesheet animation loop, i wanna fix that, here is the a piece if my code where i need it:
...
if(animHit == true){
if(plrClock.getElapsedTime().asSeconds() > 0.1)
{
animRec.x ++;
if(animRec.x * 103 >= plrtex.getSize().x)
animRec.x = 0;
plrClock.restart();
}
}
FloatRect touchButtonRect = btnSprite.getGlobalBounds();
// the Touch is pressed the button
if(touchButtonRect.contains(worldPos)){
animHit = true;
}
else
{
if(animRec.x * 412<= plrtex.getSize().x){
animHit = false;
}
}
You haven't shown the minimal amount of code needed to replicate the problem, but i think i know where the problem lies. You most likely are trying to get the touch in the while loop without any events. Events are the things that tell your program to run things at, well, a trigger of sorts. This trigger can be a mouse click, resize of window, keyboard buttons or touch events.
#include <SFML/Graphics.hpp>
#include <SFML/Window.hpp>
#include <iostream>
using namespace std;
using namespace sf;
int main()
{
// create the window
sf::RenderWindow window(sf::VideoMode(800, 600), "My window");
window.setFramerateLimit(60);
// run the program as long as the window is open
while (window.isOpen())
{
// check all the window's events that were triggered since the last iteration of the loop
sf::Event event;
while (window.pollEvent(event))
{
if(event.type == sf::Event::Closed) window.close();
if (event.type == sf::Event::TouchBegan)
{
//do something
}
if (event.type == sf::Event::TouchEnded)
{
//do something
}
if (event.type == sf::Event::TouchMoved)
{
//do something
}
}
// clear the window with black color
window.clear(sf::Color::Black);
// draw everything here...
// end the current frame
window.display();
}
return 0;
}
With events you can use the triggers really well such as a screen touch. Using touchBegan it will record the single screen touch, even if you hold down the touch it will still be considered single touch.
Hope this helped.

SDL_PollEvent() fails to catch SDL_QUIT inside class function?

trying to setup my classes to programm faster with SDL2 - so far evrything worked fine.
But in the end of my last coding session my SDL_PollEvent does no longer catch SDL_QUIT.
I´m using my own SDL_Window class to handle events and other SDL relevant Vars.
In my Window class i have the function loadEvent(), its my gameloop function, and in it i call SDL_PollEvent and right after i check if it is SDL_QUIT and if so it returns a false and ends the gameloop, otherwise it returns true. SDL_PollEvent saves into a private SDL_Event varriable of my class so i can later ask for keys pressed by looking into the event of my window class.
Any keydown event works just fine, i can end my game with esc if i want to, but i never seem to catch SDL_QUIT.
There is no error, it just does not get any SDL_QUIT back.
Any ideas what could be the problem?
Code:
class My_SDL_Window{
private:
SDL_Window* window;
SDL_Surface* surface;
SDL_Renderer* renderer;
SDL_Event sEvent;
My_Object_Node* allObj;
public:
…
bool loadEvent()
{
if(SDL_PollEvent( &sEvent ) != 0)
{
if(sEvent.type == SDL_QUIT)
{
destroy();
return false ;
}
}
return true;
}
You're only checking whether there's an event once every time the program loops.
Replace:
if(SDL_PollEvent( &sEvent ) != 0) , which only checks whether there are any events at all, where you then only act on the first event in that list, with:
while (SDL_PollEvent(&sEvent)) , which loops through every event in the event queue, where you then act on every single event that was performed since the last time you checked.
You need to change how you handle the SDL_PoolEvent() instead a if use while, with this method you will catch all events on pool not only the first one.
For example:
bool quit = false;
SDL_Event event;
while(!quit) {
// Process input
while(SDL_PollEvent(&event) > 0) {
switch(event.type) {
case SDL_QUIT: quit = true; break;
case SDL_KEYDOWN:
switch(event.key.keysym.sym) {
case SDLK_UP: go_up(); break;
case SDLK_DOWN: go_dowm(); break;
// ... other keyboard handling
}
break;
}
}
// Update state
do_game_state_update();
// Render
do_screen_render();
}

SDL_MOUSEBUTTONUP occurring even before releasing mouse button?

I'm trying to make a video player using SDL and ffmpeg in C++. I've created two separate threads, one that renders the video on the SDL window and one that handles window events. When the user clicks and releases on the video I want it to toggle playback/pause. However, it fires multiple times and the event occurs even before I release the mouse which results in unpredictable behavior.
My code:
SDL_Event event;
while (1)
{
SDL_PollEvent(&event);
switch (event.type)
{
case SDL_QUIT:
SDL_DestroyWindow(screen);
SDL_Quit();
break;
case SDL_MOUSEBUTTONUP:
if (event.button.state == SDL_RELEASED)
{
printf("Mouse released\n");
}
break;
}
}
When I click the window and hold down I would expect it wouldn't print Mouse released until I release the button. However, it prints Mouse released the entire time I hold down the mouse button. I don't know if maybe this has to do with me using a touchpad on my laptop.
SDL_PollEvent has a return value, you are ignoring.
[It] returns 1 if there are any pending events, or 0 if there are none available.
Given your code logic, whenever there is no pending event, you keep handling the previous event over and over again, until a new event arrives. This leads to the observed behavior.
The easiest fix would be to wrap the entire event handling inside an if (SDL_PollEvent(&event)) { /* Event handling */ } conditional.
EDIT: My answer is wrong, check IInspectable's answer.
Your error is that you're not checking all the pending events given by pollEvent, just one. Try this code and tell me how many button ups you get.
#include <SDL2/SDL.h>
#include <iostream>
int main(int argc, char *argv[]) {
if(SDL_Init(SDL_INIT_VIDEO) != 0) {
throw std::runtime_error("SDL failed to initialize.\n");
}
SDL_Window *window = SDL_CreateWindow("App", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, NULL);
bool done = false;
while(!done) {
SDL_Event event;
while(SDL_PollEvent(&event)) {
if(event.type == SDL_QUIT) {
done = true;
}
if (event.type == SDL_MOUSEBUTTONUP) {
if (event.button.state == SDL_RELEASED) {
printf("Mouse released\n");
}
}
}
}
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}

SFML2 Mouse::isButtonPressed filling up event queue

First of all I'd like to say that I'm not sure if the title is appropriate but it's the only logical explanation I could find.
What I'm trying to do is move my window by clicking a sprite (sort of like simulating a titlebar).
All working fine until I let go of the mouse button the rate new mouse events are emitted is way lower and with huge 1.5~2s pauses between them.
Is it possible that sf::Mouse::isBUttonPressed is filling the queue or is it another issue?
Edit: The window class has a sf::Event object and passes it to each object's event handler.
The sprite class has an event handler of this form:
bool object::handleEvents(sf::Event& event)
{
switch(event.type)
{
case sf::Event::MouseMoved:
case sf::Event::MouseButtonPressed:
case sf::Event::MouseButtonReleased:
{
auto mouse_pos = sf::Mouse::getPosition(*this->parent);
if(this->isPointInside(mouse_pos))
{
if(event.type == sf::Event::MouseMoved)
{
this->hovering = true;
if(this->callback["onHover"])
this->callback["onHover"](this, nullptr);
return true;
}
else if(event.type == sf::Event::MouseButtonPressed)
{
this->clicked = true;
this->focused = true;
if(event.mouseButton.button == sf::Mouse::Left)
if(this->callback["onLClick"])
this->callback["onLClick"](this, ref(mouse_pos));
if(event.mouseButton.button == sf::Mouse::Right)
if(this->callback["onRClick"])
this->callback["onRClick"](this, ref(mouse_pos));
return true;
}
else if(event.type == sf::Event::MouseButtonReleased && this->clicked)
{
this->clicked = false;
if(event.mouseButton.button == sf::Mouse::Left)
if(this->callback["onLClickReleased"])
this->callback["onLClickReleased"](this, ref(mouse_pos));
if(event.mouseButton.button == sf::Mouse::Right)
if(this->callback["onRClickReleased"])
this->callback["onRClickReleased"](this, ref(mouse_pos));
return true;
}
}
else
{
if(this->hovering)
{
if(this->callback["onHoverLost"])
this->callback["onHoverLost"](this, nullptr);
this->hovering = false;
}
}
}break;
default: ;
}
return false;
}
and the code responsible for moving the window:
titlebar->callback["onLClick"] = [&](object* obj, void* data)
{
sf::Vector2i* relpos = (sf::Vector2i*)(data);
while(sf::Mouse::isButtonPressed(sf::Mouse::Left))
{
sf::Vector2i abspos = sf::Mouse::getPosition();
window.setPosition(sf::Vector2i((abspos.x - relpos->x),(abspos.y - relpos->y)));
}
titlebar->clicked = false;
};
The sf::Mouse class as well as sf::Keyboard and sf::Joystick aren't connected to the event system, but are completely independent, thus it's impossible that isButtonPressed would've any influence on the events.
The real problem in your code is the 'infinite' loop when the left mouse button is pressed. If the left mouse button is pressed, everything that happens in your application is, that the window gets moved around. There won't be any event dispatches (= processing) and every event that happens within that time, will get pilled in the event queue. Thus when you return to process the events, you'll have a longer queue than usual and will start dispatching with the oldest event.
So if you now move your window around for 2 seconds, you'll get a filled queue worth 2 seconds which can delay the further processing.
To solve this problem, you'll most probably have to dispatch all the events while you're moving the window.