List of articles

SDL2 A concise tutorial （ One ）： Use Cmake and Conan structure SDL2 Programming environment

SDL2 A concise tutorial （ Two ）： Create an empty window

Create an empty window

In the last article , We learned through CMake + Conan introduce SDL2 Library programming . Today we go on SDL2 teaching , Learn how to create an empty window .

Creating an empty window is very simple , Just a few lines of code ：

#if defined(__cplusplus)
extern "C" {
    
#endif
#include <SDL.h>
#if defined(__cplusplus)
};
#endif

int main(int argc, char ** argv)
{
    
    SDL_Init(SDL_INIT_VIDEO);
 
    SDL_Window * screen = SDL_CreateWindow("My SDL Empty Window",
        SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
 
    SDL_Quit();
 
    return 0;
}

In the above code ：

• SDL_Init initialization SDL, It tells SDL Which subsystems are needed , In this case SDL_INIT_VIDEO It means that video is what we need
• Call at the end of the code SDL_Quit sign out SDL, Clean up related memory and resources
• SDL_CreateWindow Used to create a window , We will the title of the window , Initialization position , The width and height of the window and flags tell SDL, It is responsible for generating a window

If you run the above code , It works , But the window stay time is very short , Cease ~ It just disappeared . We can add some code , Keep the window until it is actively closed ：

#if defined(__cplusplus)
extern "C" {
    
#endif
#include <SDL.h>
#if defined(__cplusplus)
};
#endif

int main(int argc, char *argv[]) {
    
    bool quit = false;
    SDL_Event event;

    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window *screen = SDL_CreateWindow("My SDL Empty window",
                                          SDL_WINDOWPOS_UNDEFINED,
                                          SDL_WINDOWPOS_UNDEFINED,
                                          640, 480, 0);
    for (; !quit;) {
    
        SDL_WaitEvent(&event);

        switch (event.type) {
    
        case SDL_QUIT: {
    
            quit = true;
            break;
        }
        }
    }

    SDL_Quit();
    return 0;
}

for(;!quit;) Indicates that the code is looping indefinitely until the exit condition is met .

We use SDL_WaitEvent() To wait for an event to happen （ For example, press the keyboard ）, At the same time, we will have a SDL_Event The structure is put into it . You can still use it SDL_PollEvent() To continuously acquire events , But it will consume a lot of CPU cycle .（SDL_WaitEvent() Basically, I'm sleeping , Know that an event happened , In general, it is lighter ）.

Events tell you what happened , It may be a key 、 Roller sliding 、 Mouse movement 、 Touch interaction and so on . In our example , We are only right SDL_QUIT Events of interest , This means that the user clicked the close button of the form .

OK, Now run the code , You can get an empty form , It will exist until you close it ：

Ha ha ha , It's very simple . You can start with this , Start drawing things in your window . Have a good time , Come back to more tutorials ！

summary

This article explains how to use it SDL2 Create an empty window , You can specify the position of the window , Size and other information . To keep the window alive , We introduce an infinite loop until the exit condition is satisfied , Close the window and trigger SDL_QUIT event , adopt SDL_WaitEvent Wait for this event , Then close the window .

The source code of this article can be found in sdl2_tutorial find .