I'm currently updating some libraries for Inkscape on win32, and notice a serious UI slowdown when updating the Cairo libs. Everything works as expected with Cairo-1.11.2 (the dll we provide with the latest stable Inkscape version, 0.48.4), but the Inkscape UI becomes very slow when drawing or moving objects on canvas with a more recent Cairo version (tested with 1.12.0, 1.12.8, 1.12.14, 1.12.16 and yesterdays git version). I've also updated Pixman to 0.32.4, but noticed no regression with the Pixman update as long as I don't update Cairo too. I've tried with different compilers (TDM-GCC-4.5, TDM-GCC-4.6 and TDM-GCC-4.8.1) with no difference. Other operating systems are not affected (tested on Debian stable with Cairo-1.12.2 and Pixman-0.26, but other Inkscape users confirmed it's ok with recent Ubuntu and OS-X versions).
Tested again on another computer with an nvidia GeForce 210 (GT218) and found out it is not affected (Windows XP Virtualboxed on Debian stable). IIRC the affected computers were all running Intel graphic cards. I'm going to investigate and give details on the affected GPUs later today.
I can reproduce the bug with two computers with the following graphic cards: * Intel HD Graphics 2500 (Dell Optiplex 3010), * Intel GMA 4500 (Dell Optiplex 780).
Also reproduced with Intel 82945G Express. NOT reproduced with * ATI Mobility Radeon HD 4500 Series; * NVidia Quadro 1000M; * NVIDIA GeForce GTX 660 Ti; * Intel HD 3000 (integrated). See the Inkscape-devel mailing list thread for details (http://inkscape.13.x6.nabble.com/Devlibs-46-too-slow-tt4966631.html#none).
1.12.0 was released March 23, 2012, so if the performance was due to changes to cairo, it would show up in the changelog for prior to this period. And in fact I notice that in Feb/Mar of that year there was a considerable amount of work done in src/win32 when the win32 code was split out and rebased to the new compositor infrastructure. I don't see any noteworthy perfomance work done in win32 subsequent to March 23rd. So, guessing maybe there was some unfinished performance work, at least for certain breeds of hardware?
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