SDL2-based event-driven programming

In fact, there is no need to say too complicated ... is to read user input.

Follow the previous code to join the event polling.

Environment: SDL2 + vc++2015

The following code will open Background.png and event.png and will background tile the background and render the event as a foreground.

1#include <stdexcept>2#include <string>3#include <iostream>4#include"SDL.h"5#include"sdl_image.h"6 7 //Screen Width8 Const intScreen_width = the;9 Const intScreen_height = the;Ten  One //Global window and renderer ASdl_window *window =nullptr; -Sdl_renderer *renderer =nullptr; -  the //Loading Pictures -sdl_texture* LoadImage (std::stringfile) - { -sdl_texture* Tex =nullptr; +Tex =img_loadtexture (Renderer, File.c_str ()); -     if(Tex = =nullptr) +         ThrowStd::runtime_error ("Failed to load Image:"+ file +img_geterror ()); A     returnTex; at } -  - //apply a surface to the renderer - voidApplysurface (intXintY, sdl_texture *tex, Sdl_renderer *rend) - { - Sdl_rect Pos; inPos.x =x; -Pos.y =y; toSdl_querytexture (tex, NULL, NULL, &AMP;POS.W, &pos.h); +Sdl_rendercopy (Rend, Tex, NULL, &POS); - } the  * intMainintargcChar**argv) $ {Panax Notoginseng     //Initialize SDL -     if(Sdl_init (sdl_init_everything) = =-1) the     { +Std::cout << sdl_geterror () <<Std::endl; A         return 1; the     } +  -     //Create Window $window = Sdl_createwindow ("Lesson 4-event driven programming", $ sdl_windowpos_centered, sdl_windowpos_centered, - screen_width, Screen_height, sdl_window_shown); -     if(Window = =nullptr) the     { -Std::cout << sdl_geterror () <<Std::endl;Wuyi         return 2; the     } -  Wu     //Create renderer -Renderer = sdl_createrenderer (window,-1, Aboutsdl_renderer_accelerated |sdl_renderer_presentvsync); $     if(Renderer = =nullptr) -     { -Std::cout << sdl_geterror () <<Std::endl; -         return 3; A     } +  the     //create background and foreground textures -Sdl_texture *background = nullptr, *image =nullptr; $     Try { theBackground = LoadImage ("Background.png"); theImage = LoadImage ("Event.png"); the     } the     Catch(ConstStd::runtime_error &e) { -Std::cout << e.what () <<Std::endl; in         return 4; the     } the  About     BOOLQuit =false; the sdl_event E; the     //main loop (high CPU consumption) the      while(!quit) +     { -         //Poll event Stack e the          while(Sdl_pollevent (&e))Bayi         { the             //User Close Window the             if(E.type = = sdl_quit) QUIT =true; -  -             //the user presses the keyboard the             if(E.type = = sdl_keydown) quit =true; the  the             //User Click Mouse the             if(E.type = = sdl_mousebuttondown) quit =true; -  the             //Empty renderer the sdl_renderclear (renderer); the 94             //internal flush the background in the renderer the             intBW, BH; theSdl_querytexture (background, NULL, NULL, &AMP;BW, &BH); the              for(inty =0; Y <= screen_height; Y + =BH)98                  for(intx =0; x <= screen_width; X + =BW) About applysurface (x, y, background, renderer); - 101 102             //placing the foreground in the center of the renderer103             intIW, IH;104Sdl_querytexture (image, NULL, NULL, &AMP;IW, &IH); the             intx = screen_width/2-IW/2;106             inty = screen_height/2-IH/2;107 applysurface (x, y, image, renderer);108 109             //Render Renderer the sdl_renderpresent (renderer);111         } the     }113  the     //Freeing Resources the sdl_destroytexture (background); the sdl_destroytexture (image);117 sdl_destroyrenderer (renderer);118 Sdl_destroywindow (window);119  - sdl_quit ();121 122     return 0;123}

SDL2-based event-driven programming