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dblbuffer.cpp

A demo application using "doublebuffering". It also shows hot to use ParaGUI without the built-in eventloop (using a custom one).
/* Simple program:  Move N sprites around on the screen as fast as possible */

#include "pgapplication.h"
#include "pgwidget.h"
#include "pglog.h"
#include "pgbutton.h"
#include "pglabel.h"
#include "pgcheckbutton.h"
#include "pgtheme.h"

#include <ctime>

#define NUM_SPRITES 100
#define MAX_SPEED   1

SDL_Surface *sprite;
int numsprites;
SDL_Rect *sprite_rects;
SDL_Rect *positions;
SDL_Rect *velocities;
int sprites_visible;
int done = 0;
int bForeground = 0;

bool handle_quit() {
    done = 1;
    return true;
}

bool handle_toggle() {
    bForeground = 1-bForeground;
    return true;
}

int LoadSprite(SDL_Surface *screen, char *file)
{
    /* Load the sprite image */
    sprite = PG_FileArchive::LoadSurface(file, false);
    if ( sprite == NULL ) {
        PG_LogMSG( "Couldn't load %s: %s", file, SDL_GetError());
        return(-1);
    }

    /* Set transparent pixel as the pixel at (0,0) */
    if ( sprite->format->palette ) {
        SDL_SetColorKey(sprite, (SDL_SRCCOLORKEY|SDL_RLEACCEL),
                        *(Uint8 *)sprite->pixels);
    }

    /* We're ready to roll. :) */
    return(0);
}

void MoveSprites(SDL_Surface *screen, Uint32 background)
{
    int i, nupdates;
    SDL_Rect area, *position, *velocity;

    nupdates = 0;

    SDL_SetAlpha(sprite, 0, 0);

    /* Move the sprite, bounce at the wall, and draw */
    for ( i=0; i<numsprites; ++i ) {
        position = &positions[i];
        velocity = &velocities[i];
        position->x += velocity->x;
        if ( (position->x < 0) || (position->x >= screen->w) ) {
            velocity->x = -velocity->x;
            position->x += velocity->x;
        }
        position->y += velocity->y;
        if ( (position->y < 0) || (position->y >= screen->h) ) {
            velocity->y = -velocity->y;
            position->y += velocity->y;
        }

        /* Blit the sprite onto the screen */
        area = *position;
        SDL_BlitSurface(sprite, NULL, screen, &area);
        sprite_rects[nupdates++] = area;
    }

    sprites_visible = 1;
}

/* This is a way of telling whether or not to use hardware surfaces */
Uint32 FastestFlags(Uint32 flags, int width, int height, int bpp)
{
    const SDL_VideoInfo *info;

    /* Hardware acceleration is only used in fullscreen mode */
    flags |= SDL_FULLSCREEN;

    /* Check for various video capabilities */
    info = SDL_GetVideoInfo();
    if ( info->blit_hw_CC && info->blit_fill ) {
        /* We use accelerated colorkeying and color filling */
        flags |= SDL_HWSURFACE;
    }
    /* If we have enough video memory, and will use accelerated
       blits directly to it, then use page flipping.
     */
    if ( (flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
        /* Direct hardware blitting without double-buffering
           causes really bad flickering.
         */
        if ( info->video_mem*1024 > (height*width*bpp/8) ) {
            flags |= SDL_DOUBLEBUF;
        } else {
            flags &= ~SDL_HWSURFACE;
        }
    }

    /* Return the flags */
    return(flags);
}

int main(int argc, char *argv[])
{
    SDL_Surface *screen;
    Uint8 *mem;
    int width, height;
    Uint8  video_bpp;
    Uint32 videoflags;
    Uint32 background;
    int    i;
    SDL_Event event;
    Uint32 then, now, frames;

    PG_Application app;

    numsprites = NUM_SPRITES;
    videoflags = SDL_SWSURFACE|SDL_DOUBLEBUF | SDL_ANYFORMAT;
    width = 640;
    height = 480;
    video_bpp = 16;
    while ( argc > 1 ) {
        --argc;
        if ( strcmp(argv[argc-1], "-width") == 0 ) {
            width = atoi(argv[argc]);
            --argc;
        } else
        if ( strcmp(argv[argc-1], "-height") == 0 ) {
            height = atoi(argv[argc]);
            --argc;
        } else
        if ( strcmp(argv[argc-1], "-bpp") == 0 ) {
            video_bpp = atoi(argv[argc]);
            videoflags &= ~SDL_ANYFORMAT;
            --argc;
        } else
        if ( strcmp(argv[argc], "-fast") == 0 ) {
            videoflags = FastestFlags(videoflags, width, height, video_bpp);
        } else
        if ( strcmp(argv[argc], "-hw") == 0 ) {
            videoflags ^= SDL_HWSURFACE;
        } else
        if ( strcmp(argv[argc], "-flip") == 0 ) {
            videoflags ^= SDL_DOUBLEBUF;
        } else
        if ( strcmp(argv[argc], "-fullscreen") == 0 ) {
            videoflags ^= SDL_FULLSCREEN;
        } else
        if ( isdigit(argv[argc][0]) ) {
            numsprites = atoi(argv[argc]);
        } else {
            PG_LogMSG(
    "Usage: %s [-bpp N] [-hw] [-flip] [-fast] [-fullscreen] [numsprites]",
                                argv[0]);
            exit(1);
        }
    }

    /* Set video mode */
    if(!app.InitScreen(width, height, video_bpp, videoflags)) {
        PG_LogERR("Couldn't set %dx%d video mode: %s",
                    width, height, SDL_GetError());
        exit(2);
    }

    PG_LogConsole::SetConsoleKey((SDLKey)0);
    
    app.SetBulkMode(true);
    app.LoadTheme("default");

    app.LoadLayout("dblbuffer.xml");
    app.SetCursor(app.GetTheme()->FindSurface("Pointer", "Pointer", "normal"));
    app.ShowCursor(PG_Application::SOFTWARE);

    // get a pointer to the "quit" button
    PG_Button* btn = app.GetWidget<PG_Button>("quit");
    btn->sigClick.connect(slot(handle_quit));

    // get the checkbutton
    PG_CheckButton* toggle = app.GetWidget<PG_CheckButton>("toggle");
    toggle->sigClick.connect(slot(handle_toggle));

    // get the label
    PG_Label* fps = app.GetWidget<PG_Label>("fps");

    screen = app.GetScreen();

    /* Load the sprite */
    if ( LoadSprite(screen, "icon.bmp") < 0 ) {
        exit(1);
    }

    /* Allocate memory for the sprite info */
    mem = (Uint8 *)malloc(4*sizeof(SDL_Rect)*numsprites);
    if ( mem == NULL ) {
        PG_LogMSG("Out of memory!");
        exit(2);
    }
    sprite_rects = (SDL_Rect *)mem;
    positions = sprite_rects;
    sprite_rects += numsprites;
    velocities = sprite_rects;
    sprite_rects += numsprites;
    srand(time(NULL));
    for ( i=0; i<numsprites; ++i ) {
        positions[i].x = rand()%screen->w;
        positions[i].y = rand()%screen->h;
        positions[i].w = sprite->w;
        positions[i].h = sprite->h;
        velocities[i].x = 0;
        velocities[i].y = 0;
        while ( ! velocities[i].x && ! velocities[i].y ) {
            velocities[i].x = (rand()%(MAX_SPEED*2+1))-MAX_SPEED;
            velocities[i].y = (rand()%(MAX_SPEED*2+1))-MAX_SPEED;
        }
    }
    background = SDL_MapRGB(screen->format, 0x00, 0x00, 0x00);

    /* Print out information about our surfaces */
    PG_LogMSG("Screen is at %d bits per pixel",screen->format->BitsPerPixel);
    if ( (screen->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
        PG_LogMSG("Screen is in video memory");
    } else {
        PG_LogMSG("Screen is in system memory");
    }
    if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) {
        PG_LogMSG("Screen has double-buffering enabled");
    }
    if ( (sprite->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
        PG_LogMSG("Sprite is in video memory");
    } else {
        PG_LogMSG("Sprite is in system memory");
    }
    /* Run a sample blit to trigger blit acceleration */
    { SDL_Rect dst;
        dst.x = 0;
        dst.y = 0;
        dst.w = sprite->w;
        dst.h = sprite->h;
        SDL_BlitSurface(sprite, NULL, screen, &dst);
        SDL_FillRect(screen, &dst, background);
    }
    if ( (sprite->flags & SDL_HWACCEL) == SDL_HWACCEL ) {
        PG_LogMSG("Sprite blit uses hardware acceleration");
    }
    if ( (sprite->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
        PG_LogMSG("Sprite blit uses RLE acceleration");
    }

    /* Loop, blitting sprites and waiting for a keystroke */
    frames = 0;
    then = SDL_GetTicks();
    done = 0;
    sprites_visible = 0;

    while ( !done ) {
        /* Check for events */
        ++frames;

        while ( SDL_PollEvent(&event) ) {
            app.PumpIntoEventQueue(&event);
        }
        now = SDL_GetTicks();
        if ( now > then+1000 ) {
                fps->SetTextFormat("%2.2f FPS",  ((double)frames*1000)/(now-then));

                if((now-then) > 1000) {
                    then = now;
                    frames=0;
                }
        }

        /* Erase all the sprites if necessary */
        if ( sprites_visible ) {
            SDL_FillRect(screen, NULL, background);
        }
        
        if(bForeground) {
            PG_Widget::BulkBlit();
            MoveSprites(screen, background);
        }
        else {
            MoveSprites(screen, background);
            PG_Widget::BulkBlit();
        }

        /* Update the screen! */
        SDL_Flip(screen);
    }
    free(mem);

    /* Print out some timing information */
    now = SDL_GetTicks();
    if ( now > then ) {
        PG_LogMSG("%2.2f frames per second",
                    ((double)frames*1000)/(now-then));
    }
    return(0);
}


The ParaGUI Project - Alexander Pipelka