mattgodbolt
Debug screen is black "in front of" the beam
Hitting a breakpoint or ctrl-HOME now yields a black screen post-the virtual CRTC beam. To repro:
- MODE 2
- ctrl-s 0 4 0 0 0
- hit ctrl-home
- notice the screen post the beam location is black.
I think this is probably a result of the improvements to the CRTC emulation, but it's convenient to see the screen when debugging :)
@richtw1 quite likes this: maybe it should be configurable? or the "remaining" screen should be like 30% faded out or something?
I don't think I'd bother keeping it TBH. If it's more useful to see the entire screen then that's what it should do. Sometimes a million configurable options just needlessly complicates!
That said, this isn't obviously easy to fix, because it's an inevitable consequence of clearing the texture at the start, instead of blanking scanlines as they're rasterised. This gave a reasonable performance gain, so it would be a shame to put it back.
Other possibilities:
- always pause when raster at the bottom of the screen (might lead to stopping in the same point in execution each time?)
- separate pause / screenshot button (which doesn't enter the debugger, just waits until the bottom of the screen and then stops until you press Go again)
Agreed it's not an easy fix. Just taking these comments:
- Not really an option as "pause" is the same as breakpoint, and when debugging things it's also useful to know what's on the screen. In particular I use this a lot when I do presentations on jsbeeb (e.g. https://mattgodbolt.github.io/bbc-micro-emulation/avast/#/18 which I run on purpose to crash on the "undefined" opcode).
- This is cool for screenshots so :+1: but less useful in general for debugging.
Keeping the "old" screen around in a debug mode might be an option. I already have some (expensive) debugging things knocking around that are disabled by default, and so "keep old screen around when debugging" might be an option. So long as I can put ?debug or something in the URL I'll be happy :)
(that said the "old" screen around could be used to e.g. do phosphor simulation)