SDL video Subsystem

The most common subsystem in SDL is the video subsystem. The video here refers not to movies we normally play, but to things that are displayed on the screen. If you need to show pictures and texts on the screen, you must use the video subsystem, otherwise, nothing can be seen. The video subsystem supports: Setting the video mode or creating a video window; supporting direct image frame buffering; supporting Alpha pixel mixing; supporting Blit bit Block Transmission and hardware acceleration ); supports window management and graphic rendering.

To use the video subsystem, you must first create an SDL window or set the display mode of SDL:

/*
Function: Create an SDL display surface.
Parameter: int width. The window width is measured in pixels.
Int height window height in pixels
The number of pixels in the int bpp window. If it is 0, the default Prime Number of the current window is used.
Unit32 flags, indicating window features
Returned value: SDL_Surface *. The window pointer is returned successfully; otherwise, NULL is returned.
*/

　　SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags);

To create a window, you must click it to display everything in the future. The Return Value of the function is SDL_Surface *, and SDL_Surface is also called a surface or a skin). It is something to be displayed. It may be an image or a string. We may need to display a lot of things in our applications, so we may create a lot of surfaces, but remember that no matter how many surfaces there are, but only useSurface Generated by SDL_SetVideoMode FunctionOr window) to display, any other surface must be flushed to this window to display, this is very important. For example, this window is like a whiteboard. You need to paste the display items on the whiteboard to display them, and the pasted items will overwrite the previous items. The following code creates a display window:

/* Function: Create an SDL display window by csl Date: 2012-5-4 */# include <stdio. h> # include <stdlib. h> # include "SDL. h "SDL_Surface * gpScreen; // display surface int main (int argc, char * argv []) {if (SDL_Init (SDL_INIT_VIDEO) =-1 )) // initialize the video subsystem {printf ("Unable to init SDL: % s \ n", SDL_GetError (); exit (-1);} atexit (SDL_Quit ); // register SDL_Quit and call it upon exit so that the program is automatically cleared upon exit // create a 32-bit 600*480 window gpScreen = SDL_SetVideoMode (600,480, 32, SDL_HWSURFACE | SDL_HWPALETTE | SDL_DOUBLEBUF); if (! GpScreen) {exit (1);} SDL_Delay (3000); // pause SDL_FreeSurface (gpScreen) for 3 seconds; // system ("pause") must be released before exiting the program "); return 0 ;}

GpScreen is the pointer to the display window, a global variable. The display window is created in Row 3. flags is a bid indicating the window features. Common labels are already displayed in bold:

SDL_SWSURFACE	Create a surface in system memory
SDL_HWSURFACE	On the Display memory creation Surface
Sdl_asyncb.pdf	Displays asynchronous updates on the table, which reduces the performance of the cpu but increases the speed on the multi-processor.
SDL_ANYFORMAT	Generally, if the pixel depth on the surface is not available, for example, you specify 64, but not on your machine), SDL will simulate a shadow surface. This flag prohibits this practice. This will enable SDL to use this surface without considering bpp
SDL_DOUBLEBUF	Use double buffering
SDL_FULLSCREEN	Full Screen mode
SDL_OPENGL	Create an OpenGL rendering environment
SDL_RESIZABLE	Create a variable size window
SDL_NOFRAME	Create a window without borders and titles.

These constants can be used in combination. For example, SDL_FULLSCREEN | SDL_DOUBLEBUF | SDL_HWSURFACE indicates creating a full screen window in the video memory and using double buffering. Note: Dual buffering is generally used in full screen mode, and dual buffering is also used if it is used in the display memory creation surface. We recommend that you use SDL_HWSURFACE | SDL_DOUBLEBUF. If an error occurs, try SDL_SWSURFACE.

After calling the function, check whether gpScreen is empty. If it is empty, end the program. Before exiting the program, you must call SDL_FreeSurface to release the window resource referred to by gpScreen.

The SDL_Surface details are described in detail in the basic concepts of the video subsystem.

This article is from the "Learning Joy" blog, please be sure to keep this source http://chengshaolei.blog.51cto.com/1994169/1291966