SDL Guide 中文译版(四)[1]

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");
            }