NHL '94 (USA).sfc glitchy line on the title screen

[benderscruffy]

on the title screen when the puck comes down the screen the glitchy line appears when then puck first comes out

[jsgroth]

This is caused by not correctly handling mid-scanline writes to the Mode 7 scroll/center/parameter registers, which appear to be latched at the start of the scanline slightly before rendering starts. This also affects Battle Clash (there's a glitchy ~5-10 pixels towards the bottom-left corner of the screen during gameplay).

[jsgroth]

It seems like different emulators handle this differently, and I'm currently not sure what the correct behavior is.

Mesen appears to latch the registers at start of rendering (around H=22). This avoids the glitchy lines in NHL '94 but causes a glitchy line in Battle Clash during gameplay, which was the reason I attempted to handle mid-scanline Mode 7 register writes in the first place (and clearly did so incorrectly). Maybe that glitchy line is there on actual hardware?

bsnes/ares with the performance PPU normally latches all registers partway through the scanline (around H=128) which avoids the glitchy line in Battle Clash, but it has game-specific overrides for games that do mid-scanline PPU register writes, including NHL '94 where it renders the line around H=8.

bsnes/ares with the accuracy PPU renders pixel-by-pixel without latching any registers which causes partially glitched lines in both NHL '94 and Battle Clash.

[jsgroth]

For now at least I've changed the behavior to match what I think Mesen is doing, where mid-scanline Mode 7 register writes don't take effect until the next line. This fixes the glitchy lines in NHL '94 but does cause a glitchy line in Battle Clash during gameplay, right where the screen switches from Mode 1 to Mode 7.