consult@physc1.byu.edu (03/28/90)
Is there a standard way to detect the number of lines an EGA or VGA display adapter is currently using? It seems to me that there should be an address in the ROM data area that contains this info... Anybody know where? What about querying the ansi/nansi/(etc) driver? Thanks in advance. robin@ernie.cs.byu.edu
jmerrill@jarthur.Claremont.EDU (Confusion Reigns) (03/28/90)
In article <58consult@physc1.byu.edu> consult@physc1.byu.edu writes: > Is there a standard way to detect the number of lines an EGA or VGA display >adapter is currently using? It seems to me that there should be an address in >the ROM data area that contains this info... Anybody know where? What about >querying the ansi/nansi/(etc) driver? Yes. Check memory location 0040:0084; it contains the number of screen lines minus 1 (a 25-line display is 18 hex, a 50-line display is 31 hex). NOTE to users of DESQview 2.26: When DESQview forces a program to remain in 50-line mode, it fails to set this byte properly. I discovered this when using MS-Kermit's Tek emulation; when I came out, the display would only cover the top half of the screen. As it turns out, Kermit sets 40:84 to 18 as it leaves Tek mode, and DESQview doesn't set it back. -- Jason Merrill jmerrill@jarthur.claremont.edu
Ralf.Brown@B.GP.CS.CMU.EDU (03/28/90)
In article <58consult@physc1.byu.edu>, consult@physc1.byu.edu wrote: } Is there a standard way to detect the number of lines an EGA or VGA display }adapter is currently using? It seems to me that there should be an address in }the ROM data area that contains this info... Anybody know where? What about If an EGA or higher is present (check with INT 10h/AH=12h/BL=10h), then the byte at 0040h:0084h contains the number of the last row on the screen (total lines less one). -- UUCP: {ucbvax,harvard}!cs.cmu.edu!ralf -=- 412-268-3053 (school) -=- FAX: ask ARPA: ralf@cs.cmu.edu BIT: ralf%cs.cmu.edu@CMUCCVMA FIDO: Ralf Brown 1:129/46 "How to Prove It" by Dana Angluin Disclaimer? I claimed something? 16. proof by cosmology: The negation of the proposition is unimaginable or meaningless. Popular for proofs of the existence of God.
frisk@rhi.hi.is (Fridrik Skulason) (03/29/90)
In article <5534@jarthur.Claremont.EDU> jmerrill@jarthur.Claremont.EDU (Confusion Reigns) writes: >In article <58consult@physc1.byu.edu> consult@physc1.byu.edu writes: >> Is there a standard way to detect the number of lines an EGA or VGA display >>adapter is currently using? >Yes. Check memory location 0040:0084; it contains the number of screen >lines minus 1 (a 25-line display is 18 hex, a 50-line display is 31 hex). Just make sure first that the program is really running on a machine with EGA or VGA. On a computer with CGA or Hercules 40:84 is undefined. -- Fridrik Skulason University of Iceland | Technical Editor of the Virus Bulletin (UK) | Reserved for future expansion E-Mail: frisk@rhi.hi.is Fax: 354-1-28801 |