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1 |
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2 /* Simple program: Fill a colormap with gray and stripe it down the screen, |
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3 Then move an alpha valued sprite around the screen. |
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4 */ |
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5 |
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6 #include <stdio.h> |
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7 #include <stdlib.h> |
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8 #include <string.h> |
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9 #include <math.h> |
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10 |
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11 #include "SDL.h" |
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12 |
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13 #define FRAME_TICKS (1000/30) /* 30 frames/second */ |
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14 |
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15 /* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */ |
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16 static void quit(int rc) |
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17 { |
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18 SDL_Quit(); |
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19 exit(rc); |
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20 } |
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21 |
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22 /* Fill the screen with a gradient */ |
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23 static void FillBackground(SDL_Surface *screen) |
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24 { |
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25 Uint8 *buffer; |
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26 Uint16 *buffer16; |
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27 Uint16 color; |
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28 Uint8 gradient; |
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29 int i, k; |
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30 |
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31 /* Set the surface pixels and refresh! */ |
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32 if ( SDL_LockSurface(screen) < 0 ) { |
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33 fprintf(stderr, "Couldn't lock the display surface: %s\n", |
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34 SDL_GetError()); |
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35 quit(2); |
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36 } |
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37 buffer=(Uint8 *)screen->pixels; |
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38 if (screen->format->BytesPerPixel!=2) { |
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39 for ( i=0; i<screen->h; ++i ) { |
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40 memset(buffer,(i*255)/screen->h, screen->w*screen->format->BytesPerPixel); |
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41 buffer += screen->pitch; |
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42 } |
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43 } |
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44 else |
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45 { |
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46 for ( i=0; i<screen->h; ++i ) { |
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47 gradient=((i*255)/screen->h); |
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48 color = (Uint16)SDL_MapRGB(screen->format, gradient, gradient, gradient); |
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49 buffer16=(Uint16*)buffer; |
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50 for (k=0; k<screen->w; k++) |
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51 { |
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52 *(buffer16+k)=color; |
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53 } |
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54 buffer += screen->pitch; |
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55 } |
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56 } |
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57 |
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58 SDL_UnlockSurface(screen); |
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59 SDL_UpdateRect(screen, 0, 0, 0, 0); |
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60 } |
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61 |
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62 /* Create a "light" -- a yellowish surface with variable alpha */ |
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63 SDL_Surface *CreateLight(int radius) |
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64 { |
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65 Uint8 trans, alphamask; |
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66 int range, addition; |
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67 int xdist, ydist; |
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68 Uint16 x, y; |
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69 Uint16 skip; |
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70 Uint32 pixel; |
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71 SDL_Surface *light; |
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72 |
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73 #ifdef LIGHT_16BIT |
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74 Uint16 *buf; |
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75 |
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76 /* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */ |
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77 /* Note: this isn't any faster than a 32 bit alpha surface */ |
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78 alphamask = 0x0000000F; |
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79 light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16, |
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80 0x0000F000, 0x00000F00, 0x000000F0, alphamask); |
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81 #else |
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82 Uint32 *buf; |
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83 |
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84 /* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */ |
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85 alphamask = 0x000000FF; |
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86 light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32, |
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87 0xFF000000, 0x00FF0000, 0x0000FF00, alphamask); |
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88 if ( light == NULL ) { |
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89 fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError()); |
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90 return(NULL); |
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91 } |
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92 #endif |
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93 |
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94 /* Fill with a light yellow-orange color */ |
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95 skip = light->pitch-(light->w*light->format->BytesPerPixel); |
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96 #ifdef LIGHT_16BIT |
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97 buf = (Uint16 *)light->pixels; |
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98 #else |
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99 buf = (Uint32 *)light->pixels; |
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100 #endif |
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101 /* Get a tranparent pixel value - we'll add alpha later */ |
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102 pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0); |
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103 for ( y=0; y<light->h; ++y ) { |
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104 for ( x=0; x<light->w; ++x ) { |
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105 *buf++ = pixel; |
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106 } |
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107 buf += skip; /* Almost always 0, but just in case... */ |
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108 } |
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109 |
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110 /* Calculate alpha values for the surface. */ |
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111 #ifdef LIGHT_16BIT |
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112 buf = (Uint16 *)light->pixels; |
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113 #else |
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114 buf = (Uint32 *)light->pixels; |
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115 #endif |
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116 for ( y=0; y<light->h; ++y ) { |
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117 for ( x=0; x<light->w; ++x ) { |
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118 /* Slow distance formula (from center of light) */ |
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119 xdist = x-(light->w/2); |
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120 ydist = y-(light->h/2); |
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121 range = (int)sqrt(xdist*xdist+ydist*ydist); |
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122 |
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123 /* Scale distance to range of transparency (0-255) */ |
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124 if ( range > radius ) { |
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125 trans = alphamask; |
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126 } else { |
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127 /* Increasing transparency with distance */ |
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128 trans = (Uint8)((range*alphamask)/radius); |
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129 |
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130 /* Lights are very transparent */ |
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131 addition = (alphamask+1)/8; |
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132 if ( (int)trans+addition > alphamask ) { |
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133 trans = alphamask; |
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134 } else { |
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135 trans += addition; |
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136 } |
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137 } |
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138 /* We set the alpha component as the right N bits */ |
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139 *buf++ |= (255-trans); |
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140 } |
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141 buf += skip; /* Almost always 0, but just in case... */ |
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142 } |
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143 /* Enable RLE acceleration of this alpha surface */ |
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144 SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0); |
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145 |
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146 /* We're done! */ |
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147 return(light); |
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148 } |
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149 |
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150 static Uint32 flashes = 0; |
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151 static Uint32 flashtime = 0; |
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152 |
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153 void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y) |
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154 { |
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155 SDL_Rect position; |
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156 Uint32 ticks1; |
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157 Uint32 ticks2; |
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158 |
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159 /* Easy, center light */ |
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160 position.x = x-(light->w/2); |
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161 position.y = y-(light->h/2); |
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162 position.w = light->w; |
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163 position.h = light->h; |
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164 ticks1 = SDL_GetTicks(); |
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165 SDL_BlitSurface(light, NULL, screen, &position); |
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166 ticks2 = SDL_GetTicks(); |
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167 SDL_UpdateRects(screen, 1, &position); |
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168 ++flashes; |
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169 |
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170 /* Update time spend doing alpha blitting */ |
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171 flashtime += (ticks2-ticks1); |
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172 } |
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173 |
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174 static int sprite_visible = 0; |
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175 static SDL_Surface *sprite; |
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176 static SDL_Surface *backing; |
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177 static SDL_Rect position; |
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178 static int x_vel, y_vel; |
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179 static int alpha_vel; |
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180 |
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181 int LoadSprite(SDL_Surface *screen, char *file) |
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182 { |
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183 SDL_Surface *converted; |
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184 |
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185 /* Load the sprite image */ |
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186 sprite = SDL_LoadBMP(file); |
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187 if ( sprite == NULL ) { |
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188 fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError()); |
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189 return(-1); |
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190 } |
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191 |
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192 /* Set transparent pixel as the pixel at (0,0) */ |
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193 if ( sprite->format->palette ) { |
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194 SDL_SetColorKey(sprite, SDL_SRCCOLORKEY, |
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195 *(Uint8 *)sprite->pixels); |
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196 } |
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197 |
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198 /* Convert sprite to video format */ |
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199 converted = SDL_DisplayFormat(sprite); |
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200 SDL_FreeSurface(sprite); |
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201 if ( converted == NULL ) { |
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202 fprintf(stderr, "Couldn't convert background: %s\n", |
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203 SDL_GetError()); |
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204 return(-1); |
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205 } |
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206 sprite = converted; |
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207 |
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208 /* Create the background */ |
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209 backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8, |
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210 0, 0, 0, 0); |
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211 if ( backing == NULL ) { |
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212 fprintf(stderr, "Couldn't create background: %s\n", |
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213 SDL_GetError()); |
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214 SDL_FreeSurface(sprite); |
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215 return(-1); |
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216 } |
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217 |
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218 /* Convert background to video format */ |
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219 converted = SDL_DisplayFormat(backing); |
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220 SDL_FreeSurface(backing); |
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221 if ( converted == NULL ) { |
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222 fprintf(stderr, "Couldn't convert background: %s\n", |
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223 SDL_GetError()); |
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224 SDL_FreeSurface(sprite); |
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225 return(-1); |
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226 } |
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227 backing = converted; |
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228 |
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229 /* Set the initial position of the sprite */ |
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230 position.x = (screen->w-sprite->w)/2; |
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231 position.y = (screen->h-sprite->h)/2; |
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232 position.w = sprite->w; |
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233 position.h = sprite->h; |
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234 x_vel = 0; y_vel = 0; |
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235 alpha_vel = 1; |
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236 |
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237 /* We're ready to roll. :) */ |
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238 return(0); |
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239 } |
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240 |
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241 void AttractSprite(Uint16 x, Uint16 y) |
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242 { |
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243 x_vel = ((int)x-position.x)/10; |
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244 y_vel = ((int)y-position.y)/10; |
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245 } |
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246 |
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247 void MoveSprite(SDL_Surface *screen, SDL_Surface *light) |
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248 { |
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249 SDL_Rect updates[2]; |
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250 int alpha; |
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251 |
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252 /* Erase the sprite if it was visible */ |
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253 if ( sprite_visible ) { |
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254 updates[0] = position; |
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255 SDL_BlitSurface(backing, NULL, screen, &updates[0]); |
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256 } else { |
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257 updates[0].x = 0; updates[0].y = 0; |
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258 updates[0].w = 0; updates[0].h = 0; |
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259 sprite_visible = 1; |
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260 } |
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261 |
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262 /* Since the sprite is off the screen, we can do other drawing |
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263 without being overwritten by the saved area behind the sprite. |
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264 */ |
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265 if ( light != NULL ) { |
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266 int x, y; |
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267 |
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268 SDL_GetMouseState(&x, &y); |
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269 FlashLight(screen, light, x, y); |
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270 } |
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271 |
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272 /* Move the sprite, bounce at the wall */ |
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273 position.x += x_vel; |
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274 if ( (position.x < 0) || (position.x >= screen->w) ) { |
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275 x_vel = -x_vel; |
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276 position.x += x_vel; |
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277 } |
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278 position.y += y_vel; |
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279 if ( (position.y < 0) || (position.y >= screen->h) ) { |
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280 y_vel = -y_vel; |
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281 position.y += y_vel; |
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282 } |
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283 |
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284 /* Update transparency (fade in and out) */ |
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285 alpha = sprite->format->alpha; |
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286 if ( (alpha+alpha_vel) < 0 ) { |
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287 alpha_vel = -alpha_vel; |
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288 } else |
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289 if ( (alpha+alpha_vel) > 255 ) { |
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290 alpha_vel = -alpha_vel; |
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291 } |
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292 SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel)); |
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293 |
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294 /* Save the area behind the sprite */ |
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295 updates[1] = position; |
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296 SDL_BlitSurface(screen, &updates[1], backing, NULL); |
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297 |
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298 /* Blit the sprite onto the screen */ |
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299 updates[1] = position; |
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300 SDL_BlitSurface(sprite, NULL, screen, &updates[1]); |
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301 |
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302 /* Make it so! */ |
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303 SDL_UpdateRects(screen, 2, updates); |
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304 } |
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305 |
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306 void WarpSprite(SDL_Surface *screen, int x, int y) |
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307 { |
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308 SDL_Rect updates[2]; |
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309 |
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310 /* Erase, move, Draw, update */ |
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311 updates[0] = position; |
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312 SDL_BlitSurface(backing, NULL, screen, &updates[0]); |
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313 position.x = x-sprite->w/2; /* Center about X */ |
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314 position.y = y-sprite->h/2; /* Center about Y */ |
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315 updates[1] = position; |
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316 SDL_BlitSurface(screen, &updates[1], backing, NULL); |
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317 updates[1] = position; |
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318 SDL_BlitSurface(sprite, NULL, screen, &updates[1]); |
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319 SDL_UpdateRects(screen, 2, updates); |
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320 } |
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321 |
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322 int main(int argc, char *argv[]) |
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323 { |
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324 const SDL_VideoInfo *info; |
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325 SDL_Surface *screen; |
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326 int w, h; |
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327 Uint8 video_bpp; |
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328 Uint32 videoflags; |
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329 int i, done; |
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330 SDL_Event event; |
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331 SDL_Surface *light; |
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332 int mouse_pressed; |
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333 Uint32 ticks, lastticks; |
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334 |
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335 |
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336 /* Initialize SDL */ |
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337 if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) { |
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338 fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError()); |
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339 return(1); |
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340 } |
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341 |
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342 /* Alpha blending doesn't work well at 8-bit color */ |
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343 #ifdef _WIN32_WCE |
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344 /* Pocket PC */ |
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345 w = 240; |
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346 h = 320; |
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347 #else |
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348 w = 640; |
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349 h = 480; |
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350 #endif |
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351 info = SDL_GetVideoInfo(); |
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352 if ( info->vfmt->BitsPerPixel > 8 ) { |
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353 video_bpp = info->vfmt->BitsPerPixel; |
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354 } else { |
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355 video_bpp = 16; |
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356 fprintf(stderr, "forced 16 bpp mode\n"); |
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357 } |
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358 videoflags = SDL_SWSURFACE; |
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359 for ( i = 1; argv[i]; ++i ) { |
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360 if ( strcmp(argv[i], "-bpp") == 0 ) { |
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361 video_bpp = atoi(argv[++i]); |
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362 if (video_bpp<=8) { |
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363 video_bpp=16; |
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364 fprintf(stderr, "forced 16 bpp mode\n"); |
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365 } |
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366 } else |
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367 if ( strcmp(argv[i], "-hw") == 0 ) { |
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368 videoflags |= SDL_HWSURFACE; |
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369 } else |
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370 if ( strcmp(argv[i], "-warp") == 0 ) { |
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371 videoflags |= SDL_HWPALETTE; |
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372 } else |
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373 if ( strcmp(argv[i], "-width") == 0 && argv[i+1] ) { |
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374 w = atoi(argv[++i]); |
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375 } else |
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376 if ( strcmp(argv[i], "-height") == 0 && argv[i+1] ) { |
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377 h = atoi(argv[++i]); |
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378 } else |
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379 if ( strcmp(argv[i], "-resize") == 0 ) { |
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380 videoflags |= SDL_RESIZABLE; |
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381 } else |
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382 if ( strcmp(argv[i], "-noframe") == 0 ) { |
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383 videoflags |= SDL_NOFRAME; |
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384 } else |
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385 if ( strcmp(argv[i], "-fullscreen") == 0 ) { |
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386 videoflags |= SDL_FULLSCREEN; |
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387 } else { |
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388 fprintf(stderr, |
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389 "Usage: %s [-width N] [-height N] [-bpp N] [-warp] [-hw] [-fullscreen]\n", |
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390 argv[0]); |
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391 quit(1); |
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392 } |
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393 } |
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394 |
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395 /* Set video mode */ |
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396 if ( (screen=SDL_SetVideoMode(w,h,video_bpp,videoflags)) == NULL ) { |
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397 fprintf(stderr, "Couldn't set %dx%dx%d video mode: %s\n", |
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398 w, h, video_bpp, SDL_GetError()); |
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399 quit(2); |
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400 } |
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401 FillBackground(screen); |
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402 |
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403 /* Create the light */ |
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404 light = CreateLight(82); |
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405 if ( light == NULL ) { |
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406 quit(1); |
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407 } |
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408 |
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409 /* Load the sprite */ |
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410 if ( LoadSprite(screen, "icon.bmp") < 0 ) { |
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411 SDL_FreeSurface(light); |
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412 quit(1); |
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413 } |
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414 |
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415 /* Print out information about our surfaces */ |
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416 printf("Screen is at %d bits per pixel\n",screen->format->BitsPerPixel); |
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417 if ( (screen->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) { |
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418 printf("Screen is in video memory\n"); |
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419 } else { |
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420 printf("Screen is in system memory\n"); |
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421 } |
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422 if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) { |
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423 printf("Screen has double-buffering enabled\n"); |
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424 } |
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425 if ( (sprite->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) { |
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426 printf("Sprite is in video memory\n"); |
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427 } else { |
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428 printf("Sprite is in system memory\n"); |
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429 } |
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430 |
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431 /* Run a sample blit to trigger blit acceleration */ |
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432 MoveSprite(screen, NULL); |
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433 if ( (sprite->flags & SDL_HWACCEL) == SDL_HWACCEL ) { |
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434 printf("Sprite blit uses hardware alpha acceleration\n"); |
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435 } else { |
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436 printf("Sprite blit dosn't uses hardware alpha acceleration\n"); |
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437 } |
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438 |
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439 /* Set a clipping rectangle to clip the outside edge of the screen */ |
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440 { SDL_Rect clip; |
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441 clip.x = 32; |
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442 clip.y = 32; |
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443 clip.w = screen->w-(2*32); |
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444 clip.h = screen->h-(2*32); |
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445 SDL_SetClipRect(screen, &clip); |
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446 } |
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447 |
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448 /* Wait for a keystroke */ |
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449 lastticks = SDL_GetTicks(); |
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450 done = 0; |
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451 mouse_pressed = 0; |
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452 while ( !done ) { |
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453 /* Update the frame -- move the sprite */ |
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454 if ( mouse_pressed ) { |
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455 MoveSprite(screen, light); |
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456 mouse_pressed = 0; |
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457 } else { |
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458 MoveSprite(screen, NULL); |
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459 } |
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460 |
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461 /* Slow down the loop to 30 frames/second */ |
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462 ticks = SDL_GetTicks(); |
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463 if ( (ticks-lastticks) < FRAME_TICKS ) { |
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464 #ifdef CHECK_SLEEP_GRANULARITY |
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465 fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks)); |
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466 #endif |
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467 SDL_Delay(FRAME_TICKS-(ticks-lastticks)); |
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468 #ifdef CHECK_SLEEP_GRANULARITY |
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469 fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks)); |
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470 #endif |
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471 } |
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472 lastticks = ticks; |
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473 |
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474 /* Check for events */ |
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475 while ( SDL_PollEvent(&event) ) { |
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476 switch (event.type) { |
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477 case SDL_VIDEORESIZE: |
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478 screen = SDL_SetVideoMode(event.resize.w, event.resize.h, video_bpp, videoflags); |
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479 if ( screen ) { |
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480 FillBackground(screen); |
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481 } |
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482 break; |
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483 /* Attract sprite while mouse is held down */ |
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484 case SDL_MOUSEMOTION: |
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485 if (event.motion.state != 0) { |
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486 AttractSprite(event.motion.x, |
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487 event.motion.y); |
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488 mouse_pressed = 1; |
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489 } |
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490 break; |
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491 case SDL_MOUSEBUTTONDOWN: |
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492 if ( event.button.button == 1 ) { |
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493 AttractSprite(event.button.x, |
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494 event.button.y); |
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495 mouse_pressed = 1; |
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496 } else { |
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497 SDL_Rect area; |
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498 |
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499 area.x = event.button.x-16; |
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500 area.y = event.button.y-16; |
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501 area.w = 32; |
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502 area.h = 32; |
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503 SDL_FillRect(screen, &area, 0); |
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504 SDL_UpdateRects(screen,1,&area); |
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505 } |
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506 break; |
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507 case SDL_KEYDOWN: |
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508 #ifndef _WIN32_WCE |
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509 if ( event.key.keysym.sym == SDLK_ESCAPE ) { |
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510 done = 1; |
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511 } |
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512 #else |
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513 // there is no ESC key at all |
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514 done = 1; |
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515 #endif |
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516 break; |
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517 case SDL_QUIT: |
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518 done = 1; |
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519 break; |
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520 default: |
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521 break; |
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522 } |
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523 } |
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524 } |
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525 SDL_FreeSurface(light); |
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526 SDL_FreeSurface(sprite); |
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527 SDL_FreeSurface(backing); |
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528 |
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529 /* Print out some timing information */ |
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530 if ( flashes > 0 ) { |
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531 printf("%d alpha blits, ~%4.4f ms per blit\n", |
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532 flashes, (float)flashtime/flashes); |
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533 } |
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534 |
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535 SDL_Quit(); |
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536 return(0); |
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537 } |