Ive got an program using DirectDraw in a window. Everything initializes correctly, DD object, the front and back buffers, and clipper (All this is on the window's OnInitDialog).
My question is how do I get the primary surface to draw to the window?
Say i do some drawing on the back buffer... then I Blit it to the front buffer (since flipping doesnt work in windowed), shouldnt the surface be drawn on the window?
Sorry, if this question seems obvious, Im new to DX.
Your backbuffer should be an offscreen surface that is the same size as your client area and not an attached surface and your primary will be a regular primary surface with NO backbuffers attached. Each loop blit a DDBLTFX color fill of black to clear your backbuffer, blit your graphics to your backbuffer, then blit your backbuffer to your primary surface.
Last edited by jdinger; 06-13-2002 at 02:50 PM.
Does this code do it right?
Code:HRESULT r; r = DirectDrawCreateEx (0,(void**)&ddMain,IID_IDirectDraw7,0); if FAILED(r) return false; r = ddMain->SetCooperativeLevel( m_hWnd, DDSCL_NORMAL ); if FAILED(r) return false; // Create the primary surface DDSURFACEDESC2 ddsd; ZeroMemory( &ddsd, sizeof( ddsd ) ); ddsd.dwSize = sizeof( ddsd ); ddsd.dwFlags = DDSD_CAPS; ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE; r = ddMain->CreateSurface(&ddsd,&dsFront,NULL); if FAILED(r) return false; //--------------------------- // Create the backbuffer surface ddsd.dwFlags = DDSD_CAPS | DDSD_WIDTH | DDSD_HEIGHT; ddsd.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN | DDSCAPS_3DDEVICE; ddsd.dwWidth = dwWidth; ddsd.dwHeight = dwHeight; r = ddMain->CreateSurface(&ddsd,&dsBack,NULL); if FAILED(r) return false; //------------------------------
As far as initialization code is concerned, yes that is right. Assuming that all your variables are initialized with valid values (dwWidth, m_hWnd, etc.) then that will set them up. But you would still need at least one other additional surface to hold your image(s).
But this will handle just initialization. Do you have a main program loop that handles your blitting?
Right now, all I need is to update the screen a few times every second, so I have a timer set to 250 milliseconds and the OnTimer code is simply:
dsFront->Blt( NULL, dsBack, NULL, DDBLT_WAIT, NULL );
Im kinda gettin it to work. My next question is this... I have another thread plotting pixels to dsBack by doin Lock(), then writing to the video memory, and then Unlock() (is there any other way?). This process takes 5-20sec usually, so I wanna redraw the screen a few times during this. However blitting the back buffer to the front doesn't work while its locked does it? Is there any way I could go about this without Locking/Unlocking the back buffer after every pixel, thats just unpractical.
Could I skip this whole back buffer/front buffer thing and simply plot pixels directly to the front one. Will the screen still update while front buffer is locked??
Also... do I need to set the clipper to the back surface as well??
Thanks for all the help too, btw.
Last edited by phatslug; 06-13-2002 at 09:16 PM.
It's an unfortunate fact that locking/unlocking surfaces slows things down quite a bit. The only other way that I know of to plot pixels would be using GDI which would be slower than DirectX. And, no, you don't need (or want for that matter) a clipper on the backbuffer.
