1. Create process
1. SDL initialization
Flags can be filled in:
SDL_INIT_TIMER: timer
SDL_INIT_AUDIO: audio
SDL_INIT_VIDEO: video
SDL_INIT_JOYSTICK: Joystick
SDL_INIT_HAPTIC: touch screen
SDL_INIT_GAMECONTROLLER: game controller
SDL_INIT_EVENTS: Events
SDL_INIT_EVERYTHING: contains all the above options
SDL_INIT_NOPARACHUTE: do not catch key signals
extern DECLSPEC int SDLCALL SDL_Init(Uint32 flags);
2. Create window
title : window name
x : position on the display
y : position on the display
w : window width
h : window height
flags: Attributes of the window can be filled in:
SDL_WINDOW_FULLSCREEN = 0x00000001, /**< fullscreen window */
SDL_WINDOW_OPENGL = 0x00000002, /**< window usable with OpenGL context */
SDL_WINDOW_SHOWN = 0x00000004, /**< window is visible */
SDL_WINDOW_HIDDEN = 0x00000008, /**< window is not visible */
SDL_WINDOW_BORDERLESS = 0x00000010, /**< no window decoration */
SDL_WINDOW_RESIZABLE = 0x00000020, /**< window can be resized */
SDL_WINDOW_MINIMIZED = 0x00000040, /**< window is minimized */
SDL_WINDOW_MAXIMIZED = 0x00000080, /**< window is maximized */
SDL_WINDOW_INPUT_GRABBED = 0x00000100, /**< window has grabbed input focus */
SDL_WINDOW_INPUT_FOCUS = 0x00000200, /**< window has input focus */
SDL_WINDOW_MOUSE_FOCUS = 0x00000400, /**< window has mouse focus */
SDL_WINDOW_FULLSCREEN_DESKTOP = ( SDL_WINDOW_FULLSCREEN | 0x00001000 ),
SDL_WINDOW_FOREIGN = 0x00000800, /**< window not created by SDL */
SDL_WINDOW_ALLOW_HIGHDPI = 0x00002000, /**< window should be created in high-DPI mode if supported.
On macOS NSHighResolutionCapable must be set true in the
application's Info.plist for this to have any effect. */
SDL_WINDOW_MOUSE_CAPTURE = 0x00004000, /**< window has mouse captured (unrelated to INPUT_GRABBED) */
SDL_WINDOW_ALWAYS_ON_TOP = 0x00008000, /**< window should always be above others */
SDL_WINDOW_SKIP_TASKBAR = 0x00010000, /**< window should not be added to the taskbar */
SDL_WINDOW_UTILITY = 0x00020000, /**< window should be treated as a utility window */
SDL_WINDOW_TOOLTIP = 0x00040000, /**< window should be treated as a tooltip */
SDL_WINDOW_POPUP_MENU = 0x00080000, /**< window should be treated as a popup menu */
SDL_WINDOW_VULKAN = 0x10000000 /**< window usable for Vulkan surface */
extern DECLSPEC SDL_Window * SDLCALL SDL_CreateWindow(const char *title,
int x, int y, int w,
int h, Uint32 flags);
3. Generate a renderer
window: the window generated in the second step
index: -1
flags: use hardware or software when rendering
SDL_RENDERER_SOFTWARE = 0x00000001, /**<the renderer is a software fallback */
SDL_RENDERER_ACCELERATED = 0x00000002, /**<the renderer uses hardware
acceleration */
SDL_RENDERER_PRESENTVSYNC = 0x00000004, /**< Present is synchronized
with the refresh rate */
SDL_RENDERER_TARGETTEXTURE = 0x00000008 /**<the renderer supports
rendering to texture */
extern DECLSPEC SDL_Renderer * SDLCALL SDL_CreateRenderer(SDL_Window * window,
int index, Uint32 flags);
4. Generate material
renderer : the renderer of the third step
format: the pixel format of the material
access: whether it can be locked
w: width
h: high
extern DECLSPEC SDL_Texture * SDLCALL SDL_CreateTexture(SDL_Renderer * renderer,
Uint32 format,
int access, int w,
int h);
5. Memory data write material
texture: the fourth step material
rect:
pixels: memory data
pitch: the length of a line is calculated in bytes
extern DECLSPEC int SDLCALL SDL_UpdateTexture(SDL_Texture * texture,
const SDL_Rect * rect,
const void *pixels, int pitch);
6. Clean up the screen
extern DECLSPEC int SDLCALL SDL_RenderClear(SDL_Renderer * renderer);
7. Copy material to render
renderer: rendering
texture: material
srcrect : original image position and size
dstrect : target position and size
extern DECLSPEC int SDLCALL SDL_RenderCopy(SDL_Renderer * renderer,
SDL_Texture * texture,
const SDL_Rect * srcrect,
const SDL_Rect * dstrect);
8. Rendering
extern DECLSPEC void SDLCALL SDL_RenderPresent(SDL_Renderer * renderer);
2. Complete code
#include <iostream>
#include <sdl/SDL.h>
using namespace std;
#pragma comment(lib, "SDL2.lib")
#undef main
int sdl_flush_rgb_windows(int argc, char* argv[])
{<!-- -->
int width = 800;
int height = 900;
/* Initialize sdl */
if (SDL_Init(SDL_INIT_VIDEO))
{<!-- -->
cout << SDL_GetError() << endl;
return -1;
}
/**
para 1 window name
para 2 The position of the window in the interface
para 3 The position of the window in the interface
para 4 window itself width
para 5 window height
What operations are allowed by para 6?
*/
auto screen = SDL_CreateWindow("SDL_Test", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height,
SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
if (!screen)
{<!-- -->
cout << SDL_GetError() << endl;
return -1;
}
/* generate renderer */
/**
para 1 the window to render
para 2
para 3 use hardware rendering or software rendering
*/
auto render = SDL_CreateRenderer(screen, -1, SDL_RENDERER_ACCELERATED);
if (!render)
{<!-- -->
cout << SDL_GetError() << endl;
return -1;
}
/* generate material */
auto texture = SDL_CreateTexture(render, SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STREAMING, //can be locked
width, height);
if (!texture)
{<!-- -->
cout << SDL_GetError() << endl;
return -1;
}
/* store image data */
shared_ptr<unsigned char> rgb(new unsigned char[width * height * 4]);
auto r = rgb. get();
unsigned char tmp = 255;
while (1)
{<!-- -->
SDL_Event ev;
SDL_WaitEventTimeout( & ev, 10);
if (ev.type == SDL_QUIT)
{<!-- -->
SDL_DestroyWindow(screen);
break;
}
tmp--;
for (int i = 0; i < height; i ++ )
{<!-- -->
int b = i * width * 4;
for (int j = 0; j < width * 4; j + = 4)
{<!-- -->
r[b + j] = 255; // B
r[b + j + 1] = tmp; // G
r[b + j + 2] = 255; // R
r[b + j + 3] = 255; // A
}
}
/* Memory data write material */
SDL_UpdateTexture(texture, NULL, r, width * 4);
/* clear the screen */
SDL_RenderClear(render);
/* copy material to render */
SDL_Rect sdl_rect;
sdl_rect.x = 0;
sdl_rect.y = 0;
sdl_rect.w = width;
sdl_rect.h = height;
SDL_RenderCopy(render, texture,
NULL, //Original image position and size
& amp;sdl_rect); //target position and size
/* Specific rendering */
SDL_RenderPresent(render);
}
getchar();
return 0;
}