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I'm unaware if this is a super-secret Microsoft formula, but it sure as heck is interesting.

There are several aspects of Windows Aero that are interesting, but the main priority is,

How does Windows Aero draw transparent glass? That is, drawing a transparent and blurred surface on the titlebar and around the windows.

First of all, how does Windows Aero draw the borders of windows? Since Windows is an operating system, it has to be optimized for computers ranging from a variety of spefications.

Let's pretend we're running a game with a blur shader programmed in. In most cases with older specifications, the framerate is likely to decrease, but it doesn't seem like the case with Windows - an operating system? I guess you could say, sure, everytime the user changes the wallpaper, create a blurred copy of the wallpaper and have each window draw a section of the wallpaper.

But Windows Aero, is more dynamic than that with it's drawing mechanisms. Let's say we move a window under an overlapping window, and the window under will move and display blurred on the overlapping window's border at a framerate not too different.

How does it actually work? Does Windows actually create a new blurred image everytime the screen updates, for display on the window's borders? Does only the mask of the borders get blurred, but even then, blurring a border more than e.g. 1024px would still sound rather performance-hungry?

Thank you in advance!

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Aero requires hardware support. The transparency and blur effects are handled by the graphics card hardware (if you don't have a sufficiently recent card, you won't get Aero at all--though I haven't seen any cards for sale in the past few years that don't support it--even the $5 after rebate cards). The operating system simply tells the graphics card where the windows are relative to each other and what the transparency and blur characteristics are and the card handles the rest--no CPU required. When the windows move, the operating system tells the graphics card the new locations and it re-renders the desktop with the new window positions (generating a new blurred image part as needed).

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