HunterZ wrote:(since on real hardware it would appear only in the CRT overscan area).
robertmo wrote:Btw - is there actually any use for the boarder? I noticed that Crystal Caves displays a text box after you have picked up the last crystal. And you cannot close the box by accident, cause you have to press "esc" key for that. So boarder colour notification is not needed in this game.
vasyl wrote:I was afraid of something like that. It means that the game sets non-zero border color but it still black and carries no useful load. Two possible solutions: detect complete (or nearly complete) black and ignore it as well OR set no border as DOSBox default because it is only needed by a handful of games. In ideal case, shortcut key -- I just did not want to touch that part of the code until the feature gets debugged and proven.
VileRancour wrote:About CGA borders (and by extension, PCjr, Tandy, and 200-line EGA modes. VGA is different as noted):
I don't have my sources handy right now, but the total visible area - including borders - should be 240 pixels tall, and 720 hi-res pixels wide (=360 low-res pixels); this agrees with NTSC timings which CGA is based on.
At least a small part of this overscan area is normally obscured by the monitor or TV bezel, though you could probably conveniently ignore that.
- The active image area isn't necessarily centered within the total visible area; the exact position should be determined according to the relevant MC6845 register values (the attached PDF may help). Emulating this in DOSBox would enable some "screen shaking" effects that don't currently work, as well as H-position adjustment in games like Atarisoft's Gremlins or Moon Patrol.
NY00123 wrote:I should probably add the fact I've hoped it should be possible to let a simple app written in ASM extract data from the CRTC registers, right after setting a video mode with "int 10h".
Unfortunately, it seems like at least some of the useful registers are write-only, although they may still be readable in practice (as it seems to be with DOSBox, at least for one emulated video card). The other alternatives, I guess, are manual measurements of the borders (as done above by Hierophant) and extractions of ROM data (which have their...problems).
NY00123 wrote:VileRancour wrote:I don't have my sources handy right now, but the total visible area - including borders - should be 240 pixels tall, and 720 hi-res pixels wide (=360 low-res pixels); this agrees with NTSC timings which CGA is based on.
So the composite case is different from what you get with non-composite CGA monitors? At least, based on Hierophant's reply from 2009, the visible area, including the borders, has the width of 912-80=832 high-res (or 416 low-res) pixels and the height of 262-16=246 pixels.
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