Rewind improvements

[mgba-emu]

Rewind improvements

[endrift]

Very unlikely this is going to happen in 0.3.0 now.

[tony971]

Customizable rewind speed is easiest to understand as a ratio of playing speed e.g. "1/2x, 1x, 2x" Listing the time between jumps in milliseconds is more direct but less meaningful. Users will convert this to playing speed in their heads, anyway. Think of it like you would driving. The fuel gauge shows the remaining gallons of gasoline but drivers convert it into a distance range in their heads. The remaining gallons of gasoline is more direct, but less meaningful.

If a user selects a desired rewind speed (in relation to playing speed), time between interval jumps can be calculated in the background fairly easily. Here's the formula for determining this value:

[ 1000ms * (frames between intervals) ] / [ (desired FPS) * (desired rewind speed) ]

So let's say that someone plays at 60fps and records a rewind interval every 6 frames. They want to rewind at 2x playing speed. Their time between rewinding intervals would be this:

(1000 * 6) / (60 * 2) = 50ms between interval jumps.

If they wanted to change it to 1/3 playback speed, it would become this:

(1000 * 6) / (60 * (1/3)) = 300ms between interval jumps.

Throw in some rounding protection for non-integers and this formula can be extrapolated for any combination of desired fps, time between intervals, and desired rewind speeds.

An additional benefit to doing it like this is that the menu will match the fast forward speed selectors, save the unbounded option. Having rewind work similarly to fast forward will help with usability and cleanliness of the UI.

[tony971]

In the same interest of getting rewind to work like fast forward, the "Rewind" button in the emulation tab should rewind gradually rather than one single jump. Users expecting the same effect as the "Fast Forward" button are left confused when their game jumps however many seconds or minutes backwards without warning. This change would effectively make the rewind option the same as the held rewind option, except with toggling instead of holding.

[endrift]

I fixed the menu bar issue.

[tony971]

Thanks, I updated my comments to reflect the current state.

[endrift]

Most of this should land tonight.