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1 <HTML
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2 ><HEAD
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3 ><TITLE
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4 >SDL_LockSurface</TITLE
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5 ><META
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6 NAME="GENERATOR"
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.61
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8 "><LINK
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9 REL="HOME"
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10 TITLE="SDL Library Documentation"
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11 HREF="index.html"><LINK
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12 REL="UP"
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13 TITLE="Video"
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14 HREF="video.html"><LINK
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15 REL="PREVIOUS"
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16 TITLE="SDL_FreeSurface"
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17 HREF="sdlfreesurface.html"><LINK
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18 REL="NEXT"
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19 TITLE="SDL_UnlockSurface"
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20 HREF="sdlunlocksurface.html"></HEAD
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21 ><BODY
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22 CLASS="REFENTRY"
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23 BGCOLOR="#FFF8DC"
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24 TEXT="#000000"
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25 LINK="#0000ee"
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26 VLINK="#551a8b"
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27 ALINK="#ff0000"
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28 ><DIV
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29 CLASS="NAVHEADER"
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30 ><TABLE
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31 WIDTH="100%"
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32 BORDER="0"
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33 CELLPADDING="0"
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34 CELLSPACING="0"
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35 ><TR
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36 ><TH
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37 COLSPAN="3"
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38 ALIGN="center"
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39 >SDL Library Documentation</TH
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40 ></TR
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41 ><TR
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42 ><TD
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43 WIDTH="10%"
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44 ALIGN="left"
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45 VALIGN="bottom"
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46 ><A
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47 HREF="sdlfreesurface.html"
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48 >Prev</A
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49 ></TD
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50 ><TD
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51 WIDTH="80%"
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52 ALIGN="center"
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53 VALIGN="bottom"
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54 ></TD
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55 ><TD
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56 WIDTH="10%"
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57 ALIGN="right"
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58 VALIGN="bottom"
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59 ><A
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60 HREF="sdlunlocksurface.html"
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61 >Next</A
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62 ></TD
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63 ></TR
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64 ></TABLE
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65 ><HR
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66 ALIGN="LEFT"
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67 WIDTH="100%"></DIV
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68 ><H1
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69 ><A
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70 NAME="SDLLOCKSURFACE"
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71 >SDL_LockSurface</A
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72 ></H1
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73 ><DIV
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74 CLASS="REFNAMEDIV"
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75 ><A
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76 NAME="AEN1435"
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77 ></A
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78 ><H2
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79 >Name</H2
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80 >SDL_LockSurface -- Lock a surface for directly access.</DIV
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81 ><DIV
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82 CLASS="REFSYNOPSISDIV"
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83 ><A
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84 NAME="AEN1438"
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85 ></A
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86 ><H2
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87 >Synopsis</H2
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88 ><DIV
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89 CLASS="FUNCSYNOPSIS"
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90 ><A
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91 NAME="AEN1439"
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92 ></A
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93 ><P
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94 ></P
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95 ><PRE
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96 CLASS="FUNCSYNOPSISINFO"
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97 >#include "SDL.h"</PRE
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98 ><P
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99 ><CODE
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100 ><CODE
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101 CLASS="FUNCDEF"
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102 >int <B
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103 CLASS="FSFUNC"
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104 >SDL_LockSurface</B
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105 ></CODE
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106 >(SDL_Surface *surface);</CODE
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107 ></P
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108 ><P
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109 ></P
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110 ></DIV
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111 ></DIV
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112 ><DIV
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113 CLASS="REFSECT1"
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114 ><A
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115 NAME="AEN1445"
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116 ></A
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117 ><H2
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118 >Description</H2
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119 ><P
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120 ><TT
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121 CLASS="FUNCTION"
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122 >SDL_LockSurface</TT
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123 > sets up a surface for directly
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124 accessing the pixels. Between calls to <TT
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125 CLASS="FUNCTION"
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126 >SDL_LockSurface</TT
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127 >
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128 and <TT
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129 CLASS="FUNCTION"
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130 >SDL_UnlockSurface</TT
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131 >, you can write to and read from
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132 <TT
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133 CLASS="PARAMETER"
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134 ><I
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135 >surface-><TT
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136 CLASS="STRUCTFIELD"
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137 ><I
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138 >pixels</I
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139 ></TT
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140 ></I
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141 ></TT
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142 >, using the pixel format stored in
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143 <TT
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144 CLASS="PARAMETER"
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145 ><I
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146 >surface-><TT
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147 CLASS="STRUCTFIELD"
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148 ><I
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149 >format</I
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150 ></TT
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151 ></I
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152 ></TT
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153 >. Once you are done accessing the
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154 surface, you should use <TT
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155 CLASS="FUNCTION"
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156 >SDL_UnlockSurface</TT
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157 > to release it.</P
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158 ><P
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159 >Not all surfaces require locking.
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160 If <TT
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161 CLASS="LITERAL"
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162 >SDL_MUSTLOCK</TT
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163 >(<TT
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164 CLASS="PARAMETER"
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165 ><I
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166 >surface</I
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167 ></TT
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168 >)
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169 evaluates to <SPAN
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170 CLASS="RETURNVALUE"
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171 >0</SPAN
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172 >, then you can read and write to the
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173 surface at any time, and the pixel format of the surface will not change. </P
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174 ><P
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175 >No operating system or library calls should be made between lock/unlock
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176 pairs, as critical system locks may be held during this time.</P
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177 ><P
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178 >It should be noted, that since SDL 1.1.8 surface locks are recursive. This means that you can lock a surface multiple times, but each lock must have a match unlock.
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179 <PRE
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180 CLASS="PROGRAMLISTING"
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181 > .
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182 .
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183 SDL_LockSurface( surface );
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184 .
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185 /* Surface is locked */
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186 /* Direct pixel access on surface here */
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187 .
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188 SDL_LockSurface( surface );
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189 .
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190 /* More direct pixel access on surface */
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191 .
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192 SDL_UnlockSurface( surface );
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193 /* Surface is still locked */
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194 /* Note: Is versions < 1.1.8, the surface would have been */
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195 /* no longer locked at this stage */
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196 .
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197 SDL_UnlockSurface( surface );
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198 /* Surface is now unlocked */
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199 .
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200 .</PRE
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201 >
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202 </P
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203 ></DIV
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204 ><DIV
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205 CLASS="REFSECT1"
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206 ><A
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207 NAME="AEN1463"
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208 ></A
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209 ><H2
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210 >Return Value</H2
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211 ><P
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212 ><TT
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213 CLASS="FUNCTION"
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214 >SDL_LockSurface</TT
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215 > returns <SPAN
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216 CLASS="RETURNVALUE"
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217 >0</SPAN
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218 >,
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219 or <SPAN
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220 CLASS="RETURNVALUE"
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221 >-1</SPAN
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222 > if the surface couldn't be locked.</P
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223 ></DIV
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224 ><DIV
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225 CLASS="REFSECT1"
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226 ><A
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227 NAME="AEN1469"
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228 ></A
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229 ><H2
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230 >See Also</H2
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231 ><P
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232 ><A
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233 HREF="sdlunlocksurface.html"
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234 ><TT
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235 CLASS="FUNCTION"
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236 >SDL_UnlockSurface</TT
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237 ></A
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238 ></P
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239 ></DIV
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240 ><DIV
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241 CLASS="NAVFOOTER"
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242 ><HR
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243 ALIGN="LEFT"
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244 WIDTH="100%"><TABLE
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245 WIDTH="100%"
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246 BORDER="0"
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247 CELLPADDING="0"
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248 CELLSPACING="0"
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249 ><TR
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250 ><TD
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251 WIDTH="33%"
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252 ALIGN="left"
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253 VALIGN="top"
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254 ><A
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255 HREF="sdlfreesurface.html"
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256 >Prev</A
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257 ></TD
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258 ><TD
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259 WIDTH="34%"
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260 ALIGN="center"
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261 VALIGN="top"
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262 ><A
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263 HREF="index.html"
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264 >Home</A
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265 ></TD
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266 ><TD
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267 WIDTH="33%"
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268 ALIGN="right"
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269 VALIGN="top"
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270 ><A
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271 HREF="sdlunlocksurface.html"
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272 >Next</A
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273 ></TD
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274 ></TR
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275 ><TR
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276 ><TD
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277 WIDTH="33%"
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278 ALIGN="left"
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279 VALIGN="top"
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280 >SDL_FreeSurface</TD
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281 ><TD
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282 WIDTH="34%"
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283 ALIGN="center"
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284 VALIGN="top"
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285 ><A
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286 HREF="video.html"
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287 >Up</A
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288 ></TD
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289 ><TD
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290 WIDTH="33%"
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291 ALIGN="right"
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292 VALIGN="top"
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293 >SDL_UnlockSurface</TD
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294 ></TR
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295 ></TABLE
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296 ></DIV
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297 ></BODY
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298 ></HTML
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299 > |
