helix-view: Fix jumpy cursor on vertical center #10795
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I just noticed the use of scrolloff in horizontal offset underneath (https://github.com/helix-editor/helix/pull/10795/files#diff-18195c1eaadd7a2747b6556008c6022d79f814d64624e9e69d0735a3e0bbe296R292-R298) that I didn't update. This causes a bug with horizontal scrolling. @pascalkuthe could you explain why scrolloff is used on those lines? How does scrolloff (which I always assumed was vertical) relate to horizontal offset? |
Previously, in the case where a high scrolloff was configured in order to center the cursor vertically, the scrolloff would be clamped to a maximum value - the number of lines above and below the center line. The problem with this approach is that in the case where there are an even number of lines in the view, there are two center lines, and so the cursor would be allowed to visit them both without shifting the view. To remedy the issue, dedicate the topmost center line as the true center, by splitting the scrolloff value into a top and bottom component where the bottom is one higher than the top. In all other cases, the behaviour remains the same by setting both components to the same value as the original scrolloff.
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I fixed the issue above by using the original scrolloff (scrolloff_top) for the horiontal calculations. This works fine and could be merged now, but perhaps I could clean it up with a better understanding of the usage there. |
| } else if (viewport.height % 2) == 1 { | ||
| (max_scrolloff, max_scrolloff) | ||
| } else { | ||
| (max_scrolloff.saturating_sub(1), max_scrolloff) |
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Probably useful to keep the comment there for the last two blocks of the if
Previously, in the case where a high scrolloff was configured in order to center the cursor vertically, the scrolloff would be clamped to a maximum value - the number of lines above and below the center line.
The problem with this approach is that in the case where there are an even number of lines in the view, there are two center lines, and so the cursor would be allowed to visit them both without shifting the view.
To remedy the issue, dedicate the topmost center line as the true center, by splitting the scrolloff value into a top and bottom component where the bottom is one higher than the top.
In all other cases, the behaviour remains the same by setting both components to the same value as the original scrolloff.