第四章 样例
注：重复的例子没有列出
最快的图像平面块传送
将图像画到屏幕上有三种方式：1.创建一个图像平面并用SDL_BlitSurface传送到屏幕；2.在系统内存创建视频平面并调用SDL_UpdateRect；3.在显存创建视频平面并调用SDL_LockSurface。最好的方法是混合方式：
#include <stdio.h>
#include <stdlib.h>
#include "SDL.h"
#include "SDL_timer.h"
void ComplainAndExit(void)
{
fprintf(stderr, "Problem: %s\n", SDL_GetError());
exit(1);
}
int main(int argc, char *argv[])
{
SDL_PixelFormat fmt;
SDL_Surface *screen, *locked;
SDL_Surface *imagebmp, *image;
SDL_Rect dstrect;
int i;
Uint8 *buffer;
/* Initialize SDL */
if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
ComplainAndExit();
}
atexit(SDL_Quit);
/* Load a BMP image into a surface */
imagebmp = SDL_LoadBMP("image.bmp");
if ( imagebmp == NULL ) {
ComplainAndExit();
}
/* Set the video mode (640x480 at native depth) */
screen = SDL_SetVideoMode(640, 480, 0, SDL_HWSURFACE|SDL_FULLSCREEN);
if ( screen == NULL ) {
ComplainAndExit();
}
/* Set the video colormap */
if ( imagebmp->format->palette != NULL ) {
SDL_SetColors(screen,
imagebmp->format->palette->colors, 0,
imagebmp->format->palette->ncolors);
}
/* Convert the image to the video format (maps colors) */
image = SDL_DisplayFormat(imagebmp);
SDL_FreeSurface(imagebmp);
if ( image == NULL ) {
ComplainAndExit();
}
/* Draw bands of color on the raw surface */
if ( SDL_MUSTLOCK(screen) ) {
if ( SDL_LockSurface(screen) < 0 )
ComplainAndExit();
}
buffer=(Uint8 *)screen->pixels;
for ( i=0; ih; ++i ) {
memset(buffer,(i*255)/screen->h,
screen->w*screen->format->BytesPerPixel);
buffer += screen->pitch;
}
if ( SDL_MUSTLOCK(screen) ) {
SDL_UnlockSurface(screen);
}
/* Blit the image to the center of the screen */
dstrect.x = (screen->w-image->w)/2;
dstrect.y = (screen->h-image->h)/2;
dstrect.w = image->w;
dstrect.h = image->h;
if ( SDL_BlitSurface(image, NULL, screen, &dstrect) < 0 ) {
SDL_FreeSurface(image);
ComplainAndExit();
}
SDL_FreeSurface(image);
/* Update the screen */
SDL_UpdateRects(screen, 1, &dstrect);
SDL_Delay(5000); /* Wait 5 seconds */
exit(0);
}
过滤和处理事件#include <stdio.h>
#include <stdlib.h>
#include "SDL.h"
/* This function may run in a separate event thread */
int FilterEvents(const SDL_Event *event) {
static int boycott = 1;
/* This quit event signals the closing of the window */
if ( (event->type == SDL_QUIT) && boycott ) {
printf("Quit event filtered out -- try again.\n");
boycott = 0;
return(0);
}
if ( event->type == SDL_MOUSEMOTION ) {
printf("Mouse moved to (%d,%d)\n",
event->motion.x, event->motion.y);
return(0); /* Drop it, we've handled it */
}
return(1);
}
int main(int argc, char *argv[])
{
SDL_Event event;
/* Initialize the SDL library (starts the event loop) */
if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
fprintf(stderr,
"Couldn't initialize SDL: %s\n", SDL_GetError());
exit(1);
}
/* Clean up on exit, exit on window close and interrupt */
atexit(SDL_Quit);
/* Ignore key events */
SDL_EventState(SDL_KEYDOWN, SDL_IGNORE);
SDL_EventState(SDL_KEYUP, SDL_IGNORE);
/* Filter quit and mouse motion events */
SDL_SetEventFilter(FilterEvents);
/* The mouse isn't much use unless we have a display for reference */
if ( SDL_SetVideoMode(640, 480, 8, 0) == NULL ) {
fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
SDL_GetError());
exit(1);
}
/* Loop waiting for ESC+Mouse_Button */
while ( SDL_WaitEvent(&event) >= 0 ) {
switch (event.type) {
case SDL_ACTIVEEVENT: {
if ( event.active.state & SDL_APPACTIVE ) {
if ( event.active.gain ) {
printf("App activated\n");
} else {
printf("App iconified\n");
}
}
}
break;
case SDL_MOUSEBUTTONDOWN: {
Uint8 *keys;
keys = SDL_GetKeyState(NULL);
if ( keys[SDLK_ESCAPE] == SDL_PRESSED ) {
printf("Bye bye...\n");
exit(0);
}
printf("Mouse button pressed\n");
}
break;
case SDL_QUIT: {
printf("Quit requested, quitting.\n");
exit(0);
}
break;
}
}
/* This should never happen */
printf("SDL_WaitEvent error: %s\n", SDL_GetError());
exit(1);
}
打开音频设备 SDL_AudioSpec wanted;
extern void fill_audio(void *udata, Uint8 *stream, int len);
/* Set the audio format */
wanted.freq = 22050;
wanted.format = AUDIO_S16;
wanted.channels = 2; /* 1 = mono, 2 = stereo */
wanted.samples = 1024; /* Good low-latency value for callback */
wanted.callback = fill_audio;
wanted.userdata = NULL;
/* Open the audio device, forcing the desired format */
if ( SDL_OpenAudio(&wanted, NULL) < 0 ) {
fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
return(-1);
}
return(0);
播放音频 static Uint8 *audio_chunk;
static Uint32 audio_len;
static Uint8 *audio_pos;
/* The audio function callback takes the following parameters:
stream: A pointer to the audio buffer to be filled
len: The length (in bytes) of the audio buffer
*/
void fill_audio(void *udata, Uint8 *stream, int len)
{
/* Only play if we have data left */
if ( audio_len == 0 )
return;
/* Mix as much data as possible */
len = ( len > audio_len ? audio_len : len );
SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME)
audio_pos += len;
audio_len -= len;
}
/* Load the audio data ... */
;;;;;
audio_pos = audio_chunk;
/* Let the callback function play the audio chunk */
SDL_PauseAudio(0);
/* Do some processing */
;;;;;
/* Wait for sound to complete */
while ( audio_len > 0 ) {
SDL_Delay(100); /* Sleep 1/10 second */
}
SDL_CloseAudio();
列出所有CDROM #include "SDL.h"
/* Initialize SDL first */
if ( SDL_Init(SDL_INIT_CDROM) < 0 ) {
fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
exit(1);
}
atexit(SDL_Quit);
/* Find out how many CD-ROM drives are connected to the system */
printf("Drives available: %d\n", SDL_CDNumDrives());
for ( i=0; i<SDL_CDNumDrives(); ++i ) {
printf("Drive %d: \"%s\"\n", i, SDL_CDName(i));
}
打开缺省CDROM驱动器 SDL_CD *cdrom;
CDstatus status;
char *status_str;
cdrom = SDL_CDOpen(0);
if ( cdrom == NULL ) {
fprintf(stderr, "Couldn't open default CD-ROM drive: %s\n",
SDL_GetError());
exit(2);
}
status = SDL_CDStatus(cdrom);
switch (status) {
case CD_TRAYEMPTY:
status_str = "tray empty";
break;
case CD_STOPPED:
status_str = "stopped";
break;
case CD_PLAYING:
status_str = "playing";
break;
case CD_PAUSED:
status_str = "paused";
break;
case CD_ERROR:
status_str = "error state";
break;
}
printf("Drive status: %s\n", status_str);
if ( status >= CD_PLAYING ) {
int m, s, f;
FRAMES_TO_MSF(cdrom->cur_frame, &m, &s, &f);
printf("Currently playing track %d, %d:%2.2d\n",
cdrom->track[cdrom->cur_track].id, m, s);
}
列出CD上所有音轨 SDL_CD *cdrom; /* Assuming this has already been set.. */
int i;
int m, s, f;
SDL_CDStatus(cdrom);
printf("Drive tracks: %d\n", cdrom->numtracks);
for ( i=0; i<cdrom->numtracks; ++i ) {
FRAMES_TO_MSF(cdrom->track[i].length, &m, &s, &f);
if ( f > 0 )
++s;
printf("\tTrack (index %d) %d: %d:%2.2d\n", i,
cdrom->track[i].id, m, s);
}
播放CD SDL_CD *cdrom; /* Assuming this has already been set.. */
// Play entire CD:
if ( CD_INDRIVE(SDL_CDStatus(cdrom)) )
SDL_CDPlayTracks(cdrom, 0, 0, 0, 0);
// Play last track:
if ( CD_INDRIVE(SDL_CDStatus(cdrom)) ) {
SDL_CDPlayTracks(cdrom, cdrom->numtracks-1, 0, 0, 0);
}
// Play first and second track and 10 seconds of third track:
if ( CD_INDRIVE(SDL_CDStatus(cdrom)) )
SDL_CDPlayTracks(cdrom, 0, 0, 2, 10);
基于时间的游戏主循环#define TICK_INTERVAL 30
Uint32 TimeLeft(void)
{
static Uint32 next_time = 0;
Uint32 now;
now = SDL_GetTicks();
if ( next_time <= now ) {
next_time = now+TICK_INTERVAL;
return(0);
}
return(next_time-now);
}
/* main game loop
while ( game_running ) {
UpdateGameState();
SDL_Delay(TimeLeft());
}
