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Eliminate spurious video mode change (triggered by Mode X detection code)

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This commit is contained in:
Jeff Parsons 2015-12-01 20:37:43 -08:00
commit 2ec761eeda
4 changed files with 2243 additions and 2172 deletions
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10
modules/pcjs/lib/video.js
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@ -6856,11 +6856,13 @@ Video.prototype.outCRTCData = function(card, port, bOut, addrFrom)
*
* The second part of the check is required to promptly detect a switch to "Mode X"; if we assume
* that anyone switching to "Mode X" will first switch to mode 0x13, then it's a given that they
* must reprogram the VDISP_END register, and that they will change it from 0x8F to 0xDF. However,
* I'm not going to make the test that restrictive, to help catch other mode variations (but at the
* expense of triggering potentially unnecessary calls to checkMode()).
* must reprogram the VDISP_END register, and that they will probably change it from 0x8F to 0xDF.
*
* Originally, I wasn't going to check specifically for 0xDF, to help catch other "Mode X" variations,
* but if I don't, then some spurious mode changes are triggered (eg, when Windows 1.0 switches from
* CGA graphics mode 0x06 to an EGA graphics mode).
*/
if (card.regCRTIndx == Card.CRTC.MAX_SCAN.INDX && card.regCRTPrev != Card.CRTC.MAX_SCAN.INDX-1 || card.regCRTIndx == Card.CRTC.EGA.VDISP_END) {
if (card.regCRTIndx == Card.CRTC.MAX_SCAN.INDX && card.regCRTPrev != Card.CRTC.MAX_SCAN.INDX-1 || card.regCRTIndx == Card.CRTC.EGA.VDISP_END && bOut == 0xDF) {
this.checkMode(true);
}
this.checkCursor();