【代理DLL汉化研究】 [C++] Overlay sample 覆盖代码实例

shane007

用于在全屏游戏上画东西，写字。

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http://www.gamedev.net/community/forums/topic.asp?topic_id=359319

A lot of people seem interested in knowing how to render content over full-screen applications, like XFire and Co, judging by the number of posts about it. Here’s an unmanaged overlaying sample. Visual Studio 2003 and 2005 solutions are included.
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The sample uses DirectDraw overlays to render a black 256x64 box to the top-left of the screen, with some text in it. I would’ve shown you a screenshot, but I can’t, due to the way overlays work. Overlays are displayed as the device is painting the monitor from the primary surface. If it’s painting a location where an overlay exists, it paints the monitor with its color instead of the primary surface. Consequently, you can’t capture that in an image.
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Back to the sample. The files of interest are:
( ?; H8 D( q# ~Overlay.cpp: Window creation (auto-generated, nothing interesting) and the main loop (important).
overlay_renderer.h, overlay_renderer.cpp: The core of the sample. The code is fairly self-explanatory, though.

* w2 P3 C' n* H/ V; T* W, y! TOne important thing to keep in mind is that overlay support comes with a set of limitations. The following limitations are not checked or accounted for in the sample:
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dwAlignSizeSrc
dwAlignBoundaryDest
dwAlignSizeDest
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dwMinOverlayStretch
2 u2 ~& }- k5 O7 ]7 rdwMaxOverlayStretch

4 z" P) a5 _% ~6 l1 o+ S: xThe limitations are hardware-dependent. For example, my X300 doesn’t impose any alignment restrictions for the source or destination overlay rectangles. In a product, however, you’d want to make sure you check for these and abide by them. Use CapsViewer to find out the limitations of your hardware quickly. I don’t know if the October SDK caps database includes DirectDraw caps or not, but consider checking it out.

The limitations (and overlays in general) are documented under “DirectDraw->DirectDraw Essentials->Surfaces->Overlay Surfaces” in the DX7 documentation. It’s available at icarusIndie.

I might write a managed port, if someone’s interested. All feedback’s welcome.