[haiku-development] Proposed Change to Common Accelerant for EDID

Currently when a mode list is built from EDID info, only the modes from the base mode list of the Common Accelerant which match both the resolution (width & height) and the refresh rate specified in the EDID info are added to the mode list being built. I'm proposing to ignore the refresh rate, and add all modes from the base mode list which have a matching width and height. By doing this, there will be fewer cases where the Screen Preferences will have to extrapolate the data of a mode to produce another mode where the refresh rate is a common rate but there is no entry for it in the mode list.
An example of the current problem is when trying to display 1152x864x60Hz. Most EDID info selects only 1152x864x75Hz; thus, whenever 1152x864@60Hz is selected via the Screen Preferences, the mode must be computed from mode 1152x864x75Hz which results in a mode which differs from the 1152x864x60Hz mode which is in the base mode list of the Common Accelerant. Most of the time this causes no problem; however, some of the ATI Mach64 chips have a problem when mode 1152x864@60Hz is extrapolated from mode 1152x864@75Hz in that there is some flickering and ripples in the display. Whereas, if mode 1152x864@60Hz from the Common Accelerant's base mode list is used when setting the mode, the ATI Mach64 chips display 1152x864@60Hz without any problems.
Unless someone can point out any problems with this solution, I will make this change. 

--Gerald

Other related posts: