package lbl import "github.com/jesseduffield/lazygit/pkg/utils" func calculateOrigin(currentOrigin int, bufferHeight int, firstLineIdx int, lastLineIdx int, selectedLineIdx int, mode selectMode) int { needToSeeIdx, wantToSeeIdx := getNeedAndWantLineIdx(firstLineIdx, lastLineIdx, selectedLineIdx, mode) return calculateNewOriginWithNeededAndWantedIdx(currentOrigin, bufferHeight, needToSeeIdx, wantToSeeIdx) } // we want to scroll our origin so that the index we need to see is in view // and the other index we want to see (e.g. the other side of a line range) // is in as close to being in view as possible. func calculateNewOriginWithNeededAndWantedIdx(currentOrigin int, bufferHeight int, needToSeeIdx int, wantToSeeIdx int) int { origin := currentOrigin if needToSeeIdx < currentOrigin { origin = needToSeeIdx } else if needToSeeIdx > currentOrigin+bufferHeight { origin = needToSeeIdx - bufferHeight } bottom := origin + bufferHeight if wantToSeeIdx < origin { requiredChange := origin - wantToSeeIdx allowedChange := bottom - needToSeeIdx return origin - utils.Min(requiredChange, allowedChange) } else if wantToSeeIdx > origin+bufferHeight { requiredChange := wantToSeeIdx - bottom allowedChange := needToSeeIdx - origin return origin + utils.Min(requiredChange, allowedChange) } else { return origin } } func getNeedAndWantLineIdx(firstLineIdx int, lastLineIdx int, selectedLineIdx int, mode selectMode) (int, int) { switch mode { case LINE: return selectedLineIdx, selectedLineIdx case RANGE: if selectedLineIdx == firstLineIdx { return firstLineIdx, lastLineIdx } else { return lastLineIdx, firstLineIdx } case HUNK: return firstLineIdx, lastLineIdx default: // we should never land here panic("unknown mode") } }