[haiku-development] Screen Preference Enhancement to use GTF

  • From: Gerald Zajac <zajacg@xxxxxxxxxxxxx>
  • To: haiku-development@xxxxxxxxxxxxx
  • Date: Thu, 16 Jul 2009 17:43:02 -0400

Attached is a zip file containing two new files (gtf.cpp and gtf.h) to be added to the Screen Preferences, and a diff file to modify ScreenMode.cpp to use the Generalized Timing Formula (GTF) to compute the mode timing parameters when a selected mode does not match any mode in the driver's mode list.


GTF produces better modes than the current scheme which only adjusts the pixel clock.

I have tested these changes with a modified ATI video driver which had EDID disabled and a mode list which contained only modes with a refresh rate of 85 Hz; thus, any mode with a refresh rate < 85 Hz (ie, 60, 70, 72 and 75 Hz) used GTF to setup the mode. These refresh rates were used because the three LCD monitors that I used for testing have a max refresh rate of 75 Hz.

Except for a few modes, the modes displayed correctly on the monitors that I used. The few modes that did not display correctly were offset either to the left or right or the display was blank. When a mode would not display correctly on one monitor, it would usually display correctly on a different monitor; thus, the monitor can be a factor in whether a mode displays correctly.

--Gerald

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