This video demonstrates the slowness of the new Windows 7 GUI.
Windows Display Drivers Model used in both Vista and 7 doesn't include the neccesary hardware accelerated 2D functions to make the graphics generated by GDI and GDI+ as fast as in Windows XP.
Microsoft chose software render because they found too difficult to combine the new graphical engine with the old one. If you want to learn more about it read this: http://blogs.msdn.co...in-windows.aspx
GDI has dozens of functions: http://msdn.microsof...203(VS.85).aspx
GDI hardware acceleration in Windows 7 using WDDM 1.1 drivers has only these functions hardware accelerated: http://msdn.microsof...y/dd434692.aspx
WDDM 1.1 drivers makes mandatory this new "partial" GDI hardware acceleration. So any driver which claims to be 1.1 is already accelerating as much as it ever will.
Too bad, the results I got were based on WDDM 1.1 drivers (both from nvidia and Microsoft itself).
2D results in Windows 7 seem poor compared to previous versions of Windows, why is this?
Different Windows applications use different methods of drawing to the screen. Some applications render directly to the window, which is the same method used in the vector tests in PerformanceTest (GDI+ to a hWnd). These application will likely suffer a performance hit in Win7. Other applications render to a buffer in main memory and then use a method known as bitblt to push the final image to the screen buffer (GDI+ to a DIB section then bitblt). This method is known as double buffering. Most large commercial applications (such as Word and Photoshop) use this later method and will not suffer much if any performance degradation in Win7. There is a discussion of this on Microsoft's graphics performance blog.
DWM redirects window draw routines to an offscreen buffer and then re-draw them back to the main screen. That means for any window, DWM is redrawing their contents... twice. Coupled this with slower GDI performance than Windows XP. On the other hand, DWM will ensure the contents of the window fit in before it redraws the whole window, so when you drag the window around, it won't cause graphical glitches because now the window will only be redrawn when it's complete.
On the other hand, not using DWM will free up a lot of CPU resources. But still not enough to make GDI render operations as fast and responsive as Windows XP, as XP has more CPU free to do other tasks. If there is a fix for this, I would love to know, too... but it seems like this is already an integral part of Windows 7. The driver model has had to be rewritten to accomodate the new driver device interface (DDI) of DirectX 10 and beyond, and they had to shaft GDI hardware acceleration to accomplish that. They chose to remove GDI hardware acceleration as they found it hard to combine both driver model features. So there is no likely fix in the future except for a whole new edition of Windows.
Edited by robertcollier4, 31 August 2013 - 02:31 PM.