WaitOnBlitImageThread

Status = WaitOnBlitImageThread()

Parameters: NONE

Returns:     Status = The Status code of wait. 1=Waited, 0 = failed

The WaitOnBlitImageThread functions forces our program to wait until any previously threaded blitimage task has completed it's work, allows us to safely synchronize the main program with our secondary thread running on another CPU core . The function returns 0 when it didn't need to wait (failed) and a 1 when it had needed to wait..       When ever you use threading, then you should always call the WaitOnBlitImageThread function to make sure the thread has finished it's work. Don't assume that code that runs in parallel on your system (without wait), will operate the same on all computers, it won't ! So we always need to wait for our threads to complete. The most common usage of wait will be to synchronize our main program with the thread, where the main program is dependant upon the output of the thread. Either way, always wait !       For more information on threading see BlitImageThreadMode FACTS:       * Threading is only supported on the BlitImage commands.       * We recommend calling WaitOnBlitImageThread prior to calling END in programs that use threading. Since it's possible that our threaded job might fire up as our program is closing, which could cause a crash on exit. Same thing could occur if our program deletes an image a thread is using, while it's using it!. So some care is needed Example:

Example Source: Download This Example ; Inlude the Blit Image functions   #Include "BlitImage"       ; Create an FX image the size of the screen   Dim LightMap(2)   LIghtMap(0)               =NewImage(GetScreenWidth(),GetScreenHeight(),2)   LIghtMap(1)               =NewImage(GetScreenWidth(),GetScreenHeight(),2)      FrontImage     =0   BackImage     =1-FrontImage       ; Create a second  FX image the size of the screen ; we'll be using to blend with our other image   Backdrop=NewFXImage(GetScreenWidth(),GetScreenHeight())    ; fill the backdrop with something so we can see it   Tile=LoadNewFxImage("..\../Media/bg22.jpg")   RenderToImage Backdrop   TileImage Tile,0,0,false      LightCol=$f08040      QueueMode=true    ; -------------------------------------------------------------- ; -------------------------------------------------------------- ; Start of Demo loop ; -------------------------------------------------------------- ; --------------------------------------------------------------   Do          ; Set threading mode to capture.    ; this allows us to capture the next two blit image functions to    ; the interal 'to do' list, so both jobs can be done on the seperate thread.            If QueueMode=true         blitimagethreadmode 2      Else         blitimagethreadmode 0               EndIf    ; redirect all drawing to screen back buffer      RenderToScreen            ThisLIghtMap=LightMap(FrontImage)          ; To do combined Blit (copy) our Image.  This    ; version multiples the pixels in the blend    ; image (MyImage) with the backdrop. So it's    ; using the blend image as light map.      BlitImageAlphaMultImage(BackDrop,0,0,ThisLightMap)                  RenderToImage ThisLightMap      BlitImageClear(ThisLightMap,0,0,RGB(00,00,00))                  If QueueMode=true         blitimagethreadmode 3      EndIf            RenderToScreen      LockBuffer                ; redirect all drawing to this image      RenderToImage LightMap(BackImage)            If LeftMouseButton()<>0 Then LightCol=RndRGB()          ; draw a bunch fo circle shaped shaded polgons to represent the light      Draw_Light(100,100,150,$445566)            Draw_Light(MouseX(),MouseY(),250,LightCol)                  Draw_Light(300,200,150,$ff00000)            Draw_Light(700,400,150,$445566)                  RenderToScreen            UnLockBuffer                  SetCursor 0,0                ; make pb wait until our thread queue is done.      waitonblitimagethread()          ; Display some information about what's going on      Text 0,0 ,"Thread Queue Example (light Maps)"      Text 0,20,"Left Mouse to change light colour"      Text 0,40,"Threading:"+Str$(QueueMode)      Text 0,60,FPS()            FrontImage     =1-FrontIMage      BackImage     =1-BackImage          ; Press the spake to toggle threading on / off      If SpaceKey()         QueueMode=1-QueueMode         FlushKeys      EndIf          ; flip the back buffer to the front, so the user can see it      Sync         Loop          ; -------------------------------------------------------------- ; --[ DRAW LIGHT ]---------------------------------------------- ; --------------------------------------------------------------    Function Draw_Light(X#,y#,Radius,Colour=$ffffff)      Colour2=RGBFade(Colour,5)      Edges=12   steps#=360.0/Edges   InkMode 1+64   For lp=0 To Edges-1      Angle1#=lp*Steps#      Angle2#=WrapAngle(Angle1#,Steps#)            x1#=x#+CosRadius(angle1#,Radius)      y1#=y#+SinRadius(angle1#,Radius)            x2#=X#+CosRadius(angle2#,Radius)      y2#=y#+SinRadius(angle2#,Radius)            GouraudTri x1#,y1#,Colour2,x2#,y2#,Colour2,x#,y#,Colour         Next   InkMode 1    EndFunction

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