Sdl event loop Call the function SDL_WaitEvent () to wait for events, and call the function SDL_PollEvent () to poll. The game loop designing. I am developing app GUI on RPI Zero 2 (so UNIX port) with framebuffer as display driver and evdev touchscreen driver. You typically keep polling events until there are no more events. A type that encapsulates SDL event-pumping functions. – lmNt. It is not a big deal but I'd love to sort this out. We can grab this event from the queue by using the SDL_PollEvent, and then passing it to OnEvent to handle it accordingly. SDL_PushEvent -- Pushes an event onto the event queue If you move SDL_RenderPresent outside of your event loop, you'll be able to process as many events are there are available in the queue, and when you are done you present the frame and wait for vsync. return(0); if ( event->type == SDL_MOUSEMOTION ) { printf("Mouse moved to (%d,%d)\n", event->motion. . Handling SDL events inside Win32 window. When I comment out the event loop, the emulator runs super fast. So many of these events are being inserted in the event queue and all of this happens in one frame of rendering or one iteration of the loop I said above, but on each frame I remove only one event from the queue. Viewed 214 times 1 I know this question has been asked before but most of the time answer was just to add delay or an event loop. Polls for currently pending events, and returns 1 if there are any pending events, or 0 if there are none available. It's also normal to just ignore events you don't care about in your event loop without calling this function. Follow answered Apr 13, 2021 at 12:27. This will unconditionally remove any events from the queue that are in the range of minType to maxType, inclusive. SDL (C)- Window Won't Appear without Event Loop. I am still not sure how to "integrate" the SDL-events into my application, though. Start(); But this code is wrong in case of somebody else registering an event. md for details */ SDL_EVENT_TERMINATING, /**< The application is being SDL_AddTimer is a problem here. I'm trying to execute the while ( SDL_PollEvent( &amp;TOE_sdlevent ) ) loop in a SDL_Thread. sdl2 0. For personal use, I'm coding an additional layer on SDL2, which includes an event manager. The queue was just not started! I though the queue runs the SDL2 automatically when initializing I have added SDL_StartEventLoop(); call into the main function and it works now - almost five hours of my live are gone with such a SDL Window does not show even with Event Loop. But it could be useful, for example, if you have an application that only does UI, because you only need to Description. Setup. To do this, I attempted to pass in the SDL_Event object to my scene manager every frame, which would then pass it to my scene where I could detect input. Now, I know you can get the events with SDL like OnKeyPressed, OnKeyReleased, OnKeyHit, etc, but I . Initializes the SDL library. Commented Jan 21, 2021 at 8:34. The following code is an example of an event loop that waits for events: SDL_Event To poll events off the queue, use the SDL_PollEvent function. Thread Safety. Using functions like SDL_PollEvent and SDL_PeepEvents you can observe and handle waiting input events. Vumaq, I think that in most cases, you do not need to use SDL_PumpEvent, as it is used by SDL internally. xrel and This is my current code : All the include. View Full Course Free, unlimited access. while(SDL_PollEvent(&test_event)) {The SDL_PollEvent function take a pointer to an SDL SDL_PollEvent returns events whose type field contains values that are incorrect. SDL_PollEvent -- Polls for currently pending events. This event happens when ever you press a key on the keyboard. g SDL_QUIT, SDL_WINDOWEVENT, SDL_KEYDOWN) to other areas of code. Now, as you poll/pop all events there, act on what you can (like Window-related events), but store the inputs on a public (static) vector on your own I'm in the process of wrapping SDL into C++ objects. I am a little bit confused with the lack of visible event loop in examples like this one. h> #include <SDL2/SDL. Let’s update our Image class to make use of this. md and README-android. Oh wow okay, thats definitely gonna make things much more difficult, okay – asdfgodsia123 e890dik. One advanced scenario to avoid the hypothetical SDL_PollEvent gridlock is to call SDL_PumpEvents() once in the outer loop and then repeatedly call SDL_PeepEvents() to look at the events in the Our SDL_PollEvent(&Event) statement will update our Event object with any mouse action that the user performs. SDL_QUIT vs SDL_Quit() Using Attributes in the Event Loop. You have two options: Using SDL_Thread, but I prefere to not use threads when another solution is possible (because you may have to deal with semaphores or mutexes); Using SDL_TimerCallback (some would say that too much timers kill the flow of the code, but it's what we gonna use); Here is a code sample (NB: 2) The action your program takes after catching a specific event will trigger other events, like when using SDL_RaiseWindow, which may trigger a multitude of focus and window related subsequent events, especially if you have more than one SDL window. task_handler() sleep_ms(100) which seems to work. SDL_PumpEvents. h> #include <iostream> SDL will detect this and put two events in the queue, one for a key press and one for a mouse move. The only argument it takes is a pointer to an SDL_Event structure which is basically an enum plus a union. Here, having a separate event loop can be used to deal with these triggered events, especially I have the typical/basic event loop for SDL2 and I'm a little confused on what to do with them or how to handle them or I guess more specifically how should I get the data from these events (e. It returns 1 if there is an event to handle, and 0 if there is not. Upon initial window creation several events are generated, like SDL_PumpEvents (3) NAME SDL_PumpEvents - Pumps the event loop, gathering events from the input devices. Stack Overflow. Source Code My SDL window is freezing IDK why I'm using PollEvent function. type = SDL_USEREVENT; SDL_PushEvent(ref sdlevent); }). Basically, what you want to do is to achieve two things at a time. Why this behaviour? c++; c; sdl; Make sure you put the delay in the outer loop, before the SDL_PollEvent(). Add the following code after the call to Dear all, after having implemented the “evdev” module in the UNIX port for Raspberry Pi, I’ve now reached the next step which is to implement a proper event loop (for example, taken care of by the lvesp32 / lvstm32 modules). The sym field is the SDLKey value of the key being pressed or released. key_states[sdl2. You could also just loop over SDL_WaitEvent() in its own thread, and have that call your callback or execute your code there. In order to get this to work with multiple displays, I have an array of display_data Timers can run in their own thread. See more SDL_PollEvent () is the favored way of receiving system events since it can be done from the main loop and does not suspend the main loop while waiting on an event to be posted. All we need now is an event loop, which is something that all SDL programs should have anyway to receive the systems quit events. However, in various First off, we create an empty SDL_Event structure. I've mentioned this before in other game related threads. Events related to the window properties will be taken care of automatically. tick_inc(1) lv. h" /* This function may run in a separate event thread */ int FilterEvents(const I'm currently using C with the gcc compiler to mess around with SDL2. Pushing Events and Custom Event Types. One assumption is that that by pressing 'D' continuously the event queue is being flood by keyboard input events. Is that possible? I'm using the SDL2 C# wrapper through FNA and I need to be able to detect when the window resizes, min/maximizes, etc. The problem is that calling the SDL_SetWindowSize() function inside the event polling loop does nothing on the screen. This function only affects currently queued events. while(SDL_PollEvent(&test_event)) {The SDL_PollEvent function take a pointer to an SDL Description. View Full Lesson. You should have added SDL_Event event; before the while loop. I sent my deltaTi Exit event loop in SDL. md for details */ SDL_EVENT_TERMINATING, /**< The application is being Sounds like it's working the way it's supposed to. typedef enum SDL_EventType {SDL_EVENT_FIRST = 0, /**< Unused (do not remove) */ /* Application events */ SDL_EVENT_QUIT = 0x100, /**< User-requested quit */ /* These application events have special meaning on iOS and Android, see README-ios. You probably want SDL_PollEvent which is non blocking. These functions might be imported by name or with the :events tag. Without calls to SDL_PumpEvents() no events would ever be placed on the queue. I have a 1st person camera, and can walk fwd, back, strafe left and right and use the mouse to look around which is great. Thirdly, using a class to handle input is unnecessary, this is more suitable: I need advice on keyboard event handling with SDL. rs. We’ve now seen two different approaches we can take to handle keyboard input. *) Header File SDL Window does not show even with Event Loop. We’ll then detect and react to those actions within the body of the loop. If you need to remove a single event type, use SDL_FlushEvent() instead. Here's how it would look in your example for anyone looking for a quick solution to it in the future. If event is not NULL, the next event is removed from the queue and stored in that area. Then I Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Here is our event loop. 0. Often the need for calls to SDL_PumpEvents() is hidden from the user since SDL_PollEvent() This question is old, but the solution I'm using doesn't seem to be mentioned anywhere else, so here it is. If you SDL has SDL_AddEventWatch(), you could set up a filter that calls your handler on SDL_QUIT. SDL_Event event; while (SDL_WaitEvent(&event)) { // handle input } If I try to do something like this, the program renders the result but after a while it stops responding: I had a typical SDL event loop calling SDL_WaitEvent, and ran into a much-discussed issue (see here and here) where my application was not able to re-draw during a resize because SDL_WaitEvent doesn't return until a resize is finished on certain platforms (Win32 & Mac OS). I used to do this with SDL_GetKeyboardState(), but I switched over to using SDL_Event and SDL_PollEvent() to have a uniform interface for Keyboard, Mouse and Joystick input (everything done with events). However, if NameTag ticks first, the Parent. Therefore you can't do graphics from timers. SYNOPSIS. You're seeing garbage window ID because you access an inactive union field. – BSasuke. Guides: Setup for Visual Studio If you want end-users to write the functions for handling the events, I would suggest relying on callbacks. ) SDL_WindowEvent. I'm working on a simple GUI, and i'm trying to use the SDL library with little success. 37. Why does my window only get shown after I use SDL_PollEvent()? Hot Network Questions Being honest with rejection vs. Here is my processEvents . #include <stdio. I need to send a quit signal to one of several instances of sdl-applications. quit structure, which has no field for window id (because SDL_QUIT is not I'm doing this tutorial about SDL in game development. Keyboard Button Events. SDL_Event test_event; SDL_PollEvent removes the next event from the event queue, if there are no events on the queue it returns 0 otherwise it returns 1. However, the actual window is not updated. The scancode field is hardware specific and should be ignored unless you know what your doing. Window state change event data (event. To workaround this, you can setup a callback in your event watcher: Exit event loop in SDL. I'm creating a game in OpenGL and having issues with SDL_PollEvent not picking up all events, for instance, if I press and hold a key, I have to wait ~1-3 seconds before the program realises what I have just done. Add a comment | Your Answer Remarks. Follow answered Dec 17, 2013 at 1:47. I've written this code: bool open = true; while (open = true) { SDL_Event event; whi Woah! Before you start pelting me with tomatoes, I need you to remember something: SDL_PollEvent() returns 0 if no events are in the queue. The issue here is that we don't know the order in which our objects' Tick() functions are called. In your programs, you will always have an event (or "game," or "main") loop that processes these events and runs your program based on the input. We must now add code to check the event loop for at least some of the above mentioned events. #include "SDL. From what I've found it seems I should use the SDL_EventFilter delegate and SDL_WindowEventID enum. md for details */ SDL_APP_TERMINATING, /**< The application is being terminated by the OS Called on iOS in applicationWillTerminate() In the previous lesson, we introduced the concept of ticking and tick functions, which allow our game objects to update on every iteration of our application loop. Inside of the SDL Event is an SDL Keyboard event which contains the information for the key event. } I'm trying to develop a robust game input system with SDL 2. gabomdq gabomdq void loop() { SDL_Event event; while(SDL_PollEvent(&event)) onEvent(&event); } Share. 0. while (1) { SDL_Event event; while (SDL_PollEvent(&event)) { // handle your event here } // do some other stuff here -- draw your app, etc. If you want 33 updates per second, then your constant timestep should be 1/33. Simple programs that collect data from only one system need only one (blocking) event loop. You use timers to send custom events that are processed in the main event loop. I used to do this with SDL_GetKeyboardState(), but I switched over to using I'm doing the same as you, using const Uint8 keystates = SDL_GetKeyboardState(nullptr);* The only difference seems to be I'm not doing it inside a while loop with SDL_PollEvent. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company typedef enum SDL_EventType {SDL_EVENT_FIRST = 0, /**< Unused (do not remove) */ /* Application events */ SDL_EVENT_QUIT = 0x100, /**< User-requested quit */ /* These application events have special meaning on iOS and Android, see README-ios. The 1 returned refers to this event, immediately stored in the SDL Event structure -- not an event to follow. Then I updated my sdl and I noticed that my game was stuck in an infinite loop. The SDL_PollEvent removes the next event from the event queue, if there are no events on the queue it returns 0 otherwise it returns 1. You should also add a SDL_Delay to your loop. Why isn't sdl window responding to when I tried to click the minimize button or tried to drag the window? Hot Network Questions Does the 'sonic tank' exist outside Dune II? I've had similar; not a huge fan of how SDL does this but nothing stops you from storing the inputs in a secondary vector. The common practice is to fully process the event queue UPDATED FOR C++23 | Step-by-step guide on creating the SDL2 application and event loops for interactive games | Clear explanations and simple code examples SDL_PollEvent () is the favored way of receiving system events since it can be done from the main loop and does not suspend the main loop while waiting on an event to be posted. If event is not NULL, the next event is removed from the queue and stored in the SDL_Event structure pointed to by event. preparing applicant for future possibility I'm building a simple game in SDL. Game loop design. SDL_SCANCODE_A] will return true whenever a is pressed. Why does my window only get shown after I use SDL_PollEvent()? 0. Ive simplified my main loop and event loop so that they look similar to a simple SDL tutorial. However, input events are only collected by calls to Don't declare ev as a pointer. Add a comment | Your Answer Let's give some more details on our case and few things that are bothering (running on X11) : we receive a notification from the remote RDP server that text/plain is available on the server, so we call SDL_SetClipboardData with our callback, that makes a SDL_EVENT_CLIPBOARD_UPDATE event posted;; at next loop turn, we enter our treatment Managing the Image Surface. Like user 'thebuzzsaw' noted, the best solution is to use SDL_WaitEvent to reduce the CPU usage of your event loop. This function updates the event queue and internal input device state. SDL's event queue is thread safe, you can push from any thread and you can pull from any thread. These designs are typically referred to as event So it is best to make sure you poll and process all events that are waiting each time, the while(SDL_PollEvent(&event)) loop does this. If event is NULL, it simply returns 1 if there is an event in the queue, but will not remove it. I've been through countless tutorials and I've clearly missed something as it still ignoring my Joystick completely In my constructor SDL_JoystickEventState( It's also normal to just ignore events you don't care about in your event loop without calling this function. source Ive managed to narrow it down to SDL_PollEvent. Modified 4 years, 7 months ago. Move the loop from out of your InputManager upward into your Game, call it Game::Loop or Game::ProcessEvents. When I press a key, nothing is printed. In real life, you'd just // handle the event when you get it from To a certain extent, yes. At runtime, you need libdecor. I have an event loop already and I know its working because I used cout in my input function and it just filled up the terminal. Featured Python joystick event handler. SDL_AddTimer spawns a new thread, and things won't work like you expect when using multiple threads. h> #include <stdio. Docs. I can, or I cannot use this loop in a thread? I'm having problems here of Segmentation Fault when I execute in this way. window if m_SDLEvent. Part of the course: Game Dev with SDL2. About Sadly these user events seem to just get queued up during resizing and don't make it to the main event-handling loop until you stop sizing the Although this is a question from four years ago, I still want to provide my answer to help others in need. *) Header File I've cobbled together a very basic game loop in C++ using SDL2, and I've noticed that every few seconds, SDL_PollEvent seems to be unusually slow, even when nothing is happening. Normally, you handle events in a loop like this (copied from the documentation here):. keyboard handling, update its state (second event loop). Once there are no more events in the queue, SDL_PollEvent will return false, thus exiting out of the Event queue loop. I'm developing in C language, and i can't switch to C++. Improve this answer. In our main loop we’ll want to read in every event that’s occurred since the previous frame and handle them, we can do this by putting SDL_PollEvent in a while loop, since the function will return 1 if an event was return(0); if ( event->type == SDL_MOUSEMOTION ) { printf("Mouse moved to (%d,%d)\n", event->motion. So, the main loop of my game is based on a SDL_WaitEvent type, but when the game reaches the event loop, my timer stays idle and I am not able to find a away to keep it refreshing, any tips would be very appreciated. Everythign was working fine until I made my Terrain generator class and function. I first wrote this code in windows and it all worked fine, but after switching to ubuntu, it doesn't work as expected anymore. SDL window instantly closing. SDL_PeepEvents -- Checks the event queue for messages and optionally returns them. So yes, whichever event handler you call first will eat all of the events. In past projects I tried dabbling with my own event system so I took the data from the SDL event and I'm building a simple game in SDL. Looks like this would be along the lines of mySDL_Event. yPosition values will not have been updated yet, resulting in stale data. h> #include <math. And there's not much processing going on in your loop, so it'll loop as fast as your CPU allows, printing out "A key pressed" hundreds or thousands of times per second, until you release the key. Ask Question Asked 4 years, 7 months ago. Same for the other SDL Event queue things. motion. It also bind EVENT-TYPE to the event's type (the We use a while loop to process each event in turn. // In your main loop SDL_Event event; while (SDL_PollEvent(&event)) { switch (event. This works fine, but if I want a continuous input when the Here is an example of how you could rewrite your event loop to use SDL_WaitEvent instead of SDL_PollEvent and to support both a running and a paused state in the main event The issue here is that we don't know the order in which our objects' Tick() functions are called. I'm trying to do a very basic main loop with SDL2 but the window opens and I can't close it. 0 keyboard input in pong-like game. To use an extension library, you must change a couple project settings. Hot Network Questions Comedy/Sci-Fi movie about one of the last men on Earth living in a museum/zoo on display for humanoid robots As you pointed out, SDL_WaitEvent is not suitable if you need to draw even if there are no input events. key. Edit: SDL_WaitEvent() has to be used in the thread that initialized the video system. xPosition and Parent. y); return(0); /* Drop it, we've handled it */ return(1); SDL_Event SDL_PumpEvents -- Pumps the event loop, gathering events from the input devices. We’ll add three things: An SDL_Surface* so we can remember what surface is associated with our Image object So, the main loop of my game is based on a SDL_WaitEvent type, but when the game reaches the event loop, my timer stays idle and I am not able to find a away to keep it refreshing, any tips would be very appreciated. Without calls to SDL_PumpEvents no events would ever be placed on the queue. This just means no events need to be processed. h> #define SIZE_MOVE_TIMER_ID 1 bool sizeMoveTimerRunning = Here is a rather simple program demonstrating a game event loop using SDL2: #include <SDL. Contribute to justengel/pyjoystick development by creating an account on GitHub. Ive also used the visual studio performance profiler to check, and sure enough, SDL_PollEvent is taking up ~94% of the cpu time. 1. This You probably want the SDL_EventState() function. This is because SDL_PumpEvents (which is called directly or indirectly by sdl) will not return until resizing is done, effectively blocking your thread. So my code looks like this: while(!Quit) { SDL_Event event; while(SDL_PollEvent(&event)) If you are using a single thread, setting up an event watcher using SDL_AddEventWatch is not enough. 2. You could also just loop over SDL_WaitEvent() in its own thread, and have that I am writing a program that displays an animation that is dependent on the size of the display. 2 and SDL2. Using these stale values means our NameTag's position will be based on where the #include <iostream> #include <string> #include <vector> #include <time. h> // Just a quick warning: this is a silly way to do things, but it // illustrates how event filters work. You should not trust SDL_Delay to wait for a specified duration, as it depends notably on the OS scheduling, for example you may want to wait 15 ms but it may only wait 10 ms. But if m_SDLEvent. If Parent ticks before NameTag, there's no problem. I've done that, its going more or less fine. h> #include <SDL_image. Often the need for calls to SDL_PumpEvents() is hidden from the user since SDL_PollEvent() SDL2::events - SDL Event Handling. I don't want to render in real time. You should always use SDL_GetTicks to check that it is really waiting so long and not shorter or longer. If you move that outside of the SDL event loop, does that change anything? Have you tried calling SDL_GetGlobalMouseState(&xMouse,&yMouse); without checking for a SDL_MOUSEMOTION event? So just get the mouse position in every execution of your main loop and check if that fixes the problem. I'm using SDL 2. For example, Windows applications have the message loop, POSIX network programs usually have a select/epoll/etc. This will make sure that you get relative motion data in SDL_MOUSEMOTION events. Placing events on the event queue. Skip to { // message processing loop SDL_Event event; while (SDL_PollEvent(&event)) { // check for messages So the immediate fix to send the event (BAD CODE ALERT): new Thread(() => { Thread. And THIS while_loop is within another while_loop. Remarks. It looks like SDL_PumpEvent does the work of querying the input I'm running an update() method n times per second to "update" the keyboard input from the user so I can read it later in the logic part of the program. 2,175 2 2 gold badges 17 17 silver badges 27 27 bronze badges. Let's assume our event loop looks like this: SDL has SDL_AddEventWatch(), you could set up a filter that calls your handler on SDL_QUIT. An event loop example for SDL1. #include "SDL/SDL. Both SDL_PushEvent and SDL_PeepEvents allow you to place events onto the event queue. Commented Jan 21, 2021 at 8:40. you are filtering them), then you must call SDL_PumpEvents() to force an event queue update. SDL_PumpEvents gathers all the pending input information from devices and places it on the event queue. A 0 in a while loop condition means to stop executing. 0 that will serve as example code for a bug report I am making - senquack/event-loop-example Skip to content Toggle navigation The SDL uses an event queue internally. Edit: Whoops - thought event was a pointer: The while (SDL_PollEvent(&event)) line will loop through until all pending events have been handled. @SDL_Event event; SDL will detect this and put two events in the queue, one for a key press and one for a mouse move. Version. If you want to make sure that all pending OS events are flushed, you can call SDL_PumpEvents() on the main thread immediately before the flush call. We need to register an event, get the ID, and use it. As this function implicitly calls SDL_PumpEvents(), SDL uses libdecor to draw the window decorations on Wayland. What you want to do is to use a constant timestep which you get by accumulating time deltas. Header File. (This is the legacy documentation for SDL2, the previous stable version; SDL3 is the current stable version. Since your code only polls once per second, the queue probably gets flooded by mouse movements, and the SDL_QUIT event Description. Basically, I'm just tired of seeing SDL_ in my code. Learn C++ and SDL development by creating hands on, practical projects inspired by classic retro games. WARNING: This should only be run in the thread that initialized the video subsystem, and for extra safety, you should consider only doing those things on the main thread in any case. Secondly, you can't check events if you haven't initialised an event handler. SDL2 was the previous version!) SDL_WindowEvent. type == SDL_QUIT, you have to use m_SDLEvent. #define GLEW_STATIC #include <stdlib. The returned values are consistent, but wrong, ALWAYS! I'm running code that worked correctly with older versions of the library and VC compilers. h" void SDL_PumpEvents(void); We'll cover setting up and using SDL_Image and SDL_Mixer in this lesson. In this application we're going to look for quit events to end the application. The idea is that the end-user will dictate what event handler to Look at the documentation of SDL_Event and other event types for the details. (Verify SDL_WAYLAND_LIBDECOR is enabled at the end of CMake configuration) Wayland needs you to draw something before it creates a window. keysym. SDL_PumpEvents() gathers all the pending input information from devices and places it in the event queue. I would like to know how can I detect the press of a key or release of a key in a while loop in SDL. x, event->motion. sdl2-0. Your event manager would listen/poll for events, it then dispatch (call handlers to those that matches the event). Now, in your event loop, instead of calculating the offsets yourself, simply use event. When any event occurs, like the mouse moving a few pixels, it gets added to the queue. As this function may implicitly call SDL_PumpEvents(), you can only call this function in the thread that initialized the video subsystem. When I write my application Waiting. h> #define SIZE_MOVE_TIMER_ID 1 bool sizeMoveTimerRunning = Renders the current game state using the SDL rendering functions; Additionally, it measures the time taken by each frame using SDL_GetTicks(), and if the frame time is less than the desired delay time (1000 / FPS), it delays the loop using SDL_Delay() to maintain a I really don't know what I'm doing wrong here. I have no SDL event loop, so could this be that events are being discarded because I'm not using them? In which case, how could I get SDL to filter out all events? c++ void loop() { SDL_Event event; while(SDL_PollEvent(&event)) onEvent(&event); } Share. h" #include <iostream> int main(int argc, char** argv) { SDL_Window* window = Skip to main content. When the timer fires it sends Initializes the SDL library. h> #define WIN32_LEAN_AND_MEAN #define NOMINMAX #include <Windows. Your event manager would have a lookup mapping to keep track of all the handlers to corresponding event type. The general loop looks something like The macro is a DO-style loop with an implicit NIL block, which binds EVENT to an SDL event object (a single allocation that is mutated). It correctly detects every type of event, except SDL_WINDOWEVENT_CLOSE. This question is old, but the solution I'm using doesn't seem to be mentioned anywhere else, so here it is. h> #include <stdlib. Upon further investigation I found that control was stuck inside my event loop and it wouldn't break out because of a sentin Remarks. Defined in <SDL3/SDL if you are not polling or waiting for events (e. h> using namespace std; // Gravity First off, we create an empty SDL_Event structure. I want there to be no input lag at all. 1. We use a while loop to process each event in turn. So I tried registering a user-defined event with an integer as data, but cannot get it to quit the event loop like :quit does. Functions. Skip to main content. loop at their core, pure SDL games use SDL's event loop. h> #include "SDL. That's why you use while(SDL_PollEvent()) loop to fetch event, process its contents, fetch next event, – keltar. scene manager should be called within the event loop. h> void on_render(SDL_Window* window, SDL_Renderer* renderer); int main(int argc, char** argv) { SDL_Window *mainwindow = NULL; SDL_Renderer *renderer = NULL; SDL_Event event = { 0 }; int exit = 0; // If 1, the event loop will break. The Overflow Blog We'll Be In Touch - A New Podcast From Stack Overflow! The app that fights for your data privacy rights. What do you put to figure out which buttons these are in the SDL_Event loop? I know they are usually known as button4 and button5 from assigning them in many games. This is usually used to place a SDL_USEREVENT on the event queue, however you could use it to post fake input events if you wished. The two most common event types for handling the keyboard are SDL_KEYDOWN, which is created when a button is pressed, and SDL_KEYUP, for when a SDL window freezing with event loop . Since you're already using SDL, you could use the SDL_PollEvent function to run an event loop, checking to see if the key press event was ESC. As a quick-and-dirty hack I used while True: lv. Often calls the need for SDL_PumpEvents is hidden from the user since SDL_PollEvent and SDL_WaitEvent implicitly This code works fine whit the test SDL_PollEvent(&e)!=0 but it doesn't read the SDL_KEYDOWN event when I use the test !SDL_PollEvent(&e) (but it DOES enter in the while and process the SDL_QUIT event without any problem). sym == SDLK_ESCAPE. Load 7 more related questions Show fewer related questions Sorted by: Reset to default Know someone who can answer I am trying to get the resize event like this. y); return(0); /* Drop it, we've handled it */ return(1); SDL_Event Internally, SDL stores all the events waiting to be handled in an event queue. So I find two ways of #include <SDL3/SDL. SDL 2, how use the event system and draw asynchronously. We can grab this event from the queue by using the SDL_PollEvent, and SDL2::events - SDL Event Handling. At SDL build time, you need the libdecor-dev package. Simulated action (like spinning) often takes multiple frames to complete, and for that time other actions should not be stopped - which is very difficult to do if your action is implemented in long blocking function. However, we should note that when we’re implementing logic in a Tick() function, we don’t know how quickly our objects will tick. SDL_WaitEvent -- Waits indefinitely for the next available event. So this is my input processing function: void MainGame::processInput() { SDL_Event evnt; whi We do not need to handle all events, some SDL will take care of for us. Mouse Motion Events. Each time the event loop is run, you must A SDL event is some thing like a key press, mouse motion, joy button press, etc. Designing the game loop. Waits indefinitely for the next available event. Version So, a game loop can be divided into 3 parts: receiveInput() -- EventHandler class updateGamestate() -- Gamestate class render() -- Renderer class Since I'm working with SDL, the receiveInput() function for me is going to be an EventHandler class that will handle SDL events generated by user and network input. If I do (sdl2:push-event :quit) or (sdl2:push-quit-event) it goes to any/all of the applications, I need it to go to only one. h> #include <SDL_ttf. Lasersköld Lasersköld. source pub fn wait_event(&mut self) -> Event. Hot Network Questions In Catholic atonement theology, if God can save Mary from all sin without Christ, what was the point of Christ's death?. SDL does update the window size variables (calling SDL_GetWindowSize() in my main loop returns the updated window dimensions). When you poll for events (using SDL_PollEvent), you only get the oldest event. Everything else stays in the queue. On 05/27/2010 07:32 AM, Chris Dickinson wrote: Quote: Hi all, I have a quick question regarding using SDL_PollEvent. When the user’s mouse is Our SDL_PollEvent(&Event) statement will update our Event object with any keyboard action that the user performs. Summary. You can only access m_SDLEvent. The SDL event queue has a fixed number of entries, ~128 last time I looked. Hi! I am a begginer to LVGL and I am struggling with understanding how should I use (or not?) event loop and lv_task_handler. I've been through countless tutorials and I've clearly missed something as it still ignoring my Joystick completely In my constructor SDL_JoystickEventState( SDL Window does not show even with Event Loop. Filtering and Handling Events. That is, we do not know how much time has passed since the previous invocation of that My game was working fine before. The SDL_LoadBMP() function creates an SDL_Surface using the dimensions and colors of the file we loaded, and it returns a SDL_Surface* - that is, a pointer to the surface. . sym) { case SDLK_ESCAPE: std::cout << "I want quit game\n"; // Working break; case SDLK_p: std::cout But let's say I then press 'a' or 'd', SDL will not pick these events or even when I release 'w', SDL will not pickup the KEYUP event. SDL Window does not show even with Event Loop. Pumps the event loop, gathering events from the input devices. (This is the documentation for SDL3, which is the current stable version. The terrible wiki documentation might be able to help get you up to speed. However I I'm doing the same as you, using const Uint8 keystates = SDL_GetKeyboardState(nullptr);* The only difference seems to be I'm not doing it inside a while loop with SDL_PollEvent. That's undefined behavior. g. The mod field describes the state of Neither the event loop or the render loop are called in a while(1) loop; they'd be called once every 16ms (60fps for the render) and maybe once every 32ms (30tps for the event loop). *) Header File I know this is an older post, but I myself just came across this issue with SDL when starting up a little demo project. The basic idea, though, is that you simply set SDL_IGNORE or SDL_ENABLE depending on whether Remarks. type == SDL_WINDOWEVENT. There is an easy fix for this: surround the event processing while loop with another while loop: If there are no immediate events on startup, you might not ever make it into that loop. I'd like at least namespaces SDL::Window. When you call SDL_Init(), you likely do it from the main thread, and that's where your event queue is, so when you call SDL_PollEvent() from your timer thread, it won't have access to the internal SDL event queue, and thus will not return typedef enum SDL_EventType {SDL_FIRSTEVENT = 0, /**< Unused (do not remove) */ /* Application events */ SDL_QUIT = 0x100, /**< User-requested quit */ /* These application events have special meaning on iOS, see README-ios. When I look up my issue, almost all the answers are solved by adding an event loop. As you can see we handle closing the window as we did in the previous tutorial, then we handle an SDL_KEYDOWN event. Does it mean this ,suppose i want to execute 10 events inside this second while loop these events will be stored in event queue and corresponding frame is made and at the 11th event which is empty SDL_PollEvent() will return false and goes out of the second while loop and all the ten frame are rendered on the screen with SDL_RenderPresent() ,does it work like this ? When you run your while loop in each of your HandleInput functions, you're burning through the entire event queue up to that moment in time. I've tried attaching such an event using SDL_AddEventWatch and SDL_SetEventFilter methods, but I'm not getting any events I'm having a problem with SDL 2. The program should leave the main loop when finding an input, but it does not: SDL_Window* gWindow = NULL; SDL_Surface* gScreenSurface = NULL; SDL_PumpEvents -- Pumps the event loop, gathering events from the input devices. Pump the event loop, gathering events from the input devices. window. I got my inspiration from this answer, and it doesn't use additional threads. The SDL_Event structure is the core of all event handling in SDL. Summarizing: Timer starts: 59 (seconds) . But what do I put in here to detect them? SDL_Event event; while (SDL_PollEvent(&event)) { Exit event loop in SDL. SDL_Eventis a union of all event structures used in SDL. Follow I would like to do a simple thing — in the unit with the logic of handling the window, I want to update the window (the first event loop), and then in another unit with the logic of e. This function should only be called on the main thread. This must be called before using any other SDL function. Like this. Share. Here, having a separate event loop can be used to deal with these triggered events, especially (This is the documentation for SDL3, which is the current stable version. When I write my application I know this is an older post, but I myself just came across this issue with SDL when starting up a little demo project. SDL_AddTimer is a problem here. That is not desirable for games. @lmNt I have tried this, still a delay. When I order to move to the left by pressing left arrow, it is processed by SDL_PollEvents() and responds correctly if the key was Event loop should not perform any simulations, especially not SDL_Delay and alike. Suppose you have an event manager. Often calls the need for SDL_PumpEvents is hidden from the user since SDL_PollEvent and SDL_WaitEvent implicitly As a start I settled with putting the SDL-stuff into a new QThread and run a simple while-loop in there. SDL2::events represents the library's version as three levels: major, minor, and patch level. I've written this code: bool open = true; while (open = true) { SDL_Event event; whi As such, we can remove the argument, and delete the SDL_Event variable it was based on. In each of these discussions, the technique of using SDL_SetEventFilter to get class LButton { public: //Button dimensions static constexpr int kButtonWidth = 300; static constexpr int kButtonHeight = 200; //Initializes internal variables LButton(); //Sets top left position void setPosition( float x, float y ); //Handles mouse event void handleEvent( SDL_Event* e ); //Shows button sprite void render(); private: enum eButtonSprite { eButtonSpriteMouseOut It seems I found the reason. h> #include <SDL_syswm. SDL_PumpEvents( ) Pump the event loop, gathering events from the input devices. 0 Pumps the event loop, gathering events from the input devices. Sleep(30000); SDL_Event sdlevent = new SDL_Event(); sdlevent. It is also possible to push events onto the event queue and so use it as a two-way communication path. I've managed to get an image to load and close automatically after 2 seconds, but now I want to wait until the user presses the X button at the top, or for the user to press the ESC key. Hot Network Questions Mainstream media house trying to promote political agenda But this loops through the body of the while loop until I stop it. When you call SDL_Init(), you likely do it from the main thread, and that's where your event queue is, so when you call SDL_PollEvent() from your timer thread, it won't have access to the internal SDL event queue, and thus will not return We do not need to handle all events, some SDL will take care of for us. SYNOPSIS use SDL2 qw[:events]; DESCRIPTION. h" /* This function may run in a separate event thread */ int FilterEvents(const It seems that SDL_Event has to be placed into a while loop to constantly check for events. So when i leave the 'D' button no more Hi! I am a begginer to LVGL and I am struggling with understanding how should I use (or not?) event loop and lv_task_handler. Your application can register various handlers for various events with the event manager. However, if NameTag ticks first, the Have you tried calling SDL_GetGlobalMouseState(&xMouse,&yMouse); without checking for a SDL_MOUSEMOTION event? So just get the mouse position in every I'm trying to develop a robust game input system with SDL 2. 5 on a Linux workstation (Red Hat SDL_keysym typedef struct{ Uint8 scancode; SDLKey sym; SDLMod mod; Uint16 unicode; } SDL_keysym; The SDL_keysym structure describes a key press or a key release. As always, follow the suggestions by Glenn Fiedler in his Game Physics series. h> #include <SDL. Commented Aug 7, 2014 at 14:22. And declare SDL_Event e inside of the gameLoop method, and then pass it to another functions by value or by reference, it's always done like SDL_GetWindowSurface documentation says This surface will be invalidated if the window is resized. #include <SDL. The SDL_PollEvent function takes a pointer to an SDL_Event structure that is to be filled with event information. However, after several print statements showing that everything is working BUT my SDL_PollEvent() loop, I'm I have got a small problem with my game. Another way is to use SDL_WaitEvent which sdl; event-loop; or ask your own question. type) { case SDL_KEYDOWN: { switch (event. Events vs Polling. You should be checking the return value of SDL_PollEvent. aqgz oixt zynntqol kypury rmopz ecgm osm vinlom ttvhve nvbowr