Puranjay Savar Mattas
6e1ffb96fd
Convert from git submodule to plain vendored copy. No push access to upstream nodes-app/swift-markdown-engine meant our local fix commit (05c1720) was stranded and unreachable from any remote on fresh clones/CI. Vendoring as plain files folds it into normal repo history instead.
72 lines
2.8 KiB
Swift
72 lines
2.8 KiB
Swift
//
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// BottomOverscrollPolicy.swift
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// MarkdownEngine
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//
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// Created by Luca Chen on 16.03.26.
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//
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// Computes the comfortable bottom-of-document slack so the caret never
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// hugs the bottom edge of the visible viewport while typing.
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//
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import AppKit
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import Foundation
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struct BottomOverscrollPolicy {
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let overscrollPercent: CGFloat
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let minOverscrollPoints: CGFloat
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let maxOverscrollPoints: CGFloat
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let activationStartFraction: CGFloat
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let activationRangeFraction: CGFloat
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init(configuration: OverscrollPolicy) {
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self.overscrollPercent = configuration.percent
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self.minOverscrollPoints = configuration.minPoints
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self.maxOverscrollPoints = configuration.maxPoints
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self.activationStartFraction = configuration.activationStartFraction
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self.activationRangeFraction = configuration.activationRangeFraction
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}
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init(
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overscrollPercent: CGFloat,
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minOverscrollPoints: CGFloat,
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maxOverscrollPoints: CGFloat,
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activationStartFraction: CGFloat = OverscrollPolicy.default.activationStartFraction,
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activationRangeFraction: CGFloat = OverscrollPolicy.default.activationRangeFraction
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) {
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self.overscrollPercent = overscrollPercent
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self.minOverscrollPoints = minOverscrollPoints
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self.maxOverscrollPoints = maxOverscrollPoints
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self.activationStartFraction = activationStartFraction
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self.activationRangeFraction = activationRangeFraction
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}
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func activeOverscroll(
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baseContentHeight: CGFloat,
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headerHeight: CGFloat = 0,
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visibleHeight: CGFloat,
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lineHeight: CGFloat
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) -> CGFloat {
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// The header band scrolls with the content, so it counts toward activation
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// and unlock; the comfortable slack stays viewport-based (the band is gone
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// once the user reaches the document bottom).
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let stackedContentHeight = baseContentHeight + headerHeight
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let activationStartHeight = visibleHeight * activationStartFraction
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let activationRange = max(visibleHeight * activationRangeFraction, 1)
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let activationProgress = min(
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max((stackedContentHeight - activationStartHeight) / activationRange, 0),
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1
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)
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guard activationProgress > 0 else { return 0 }
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var desiredSlack = visibleHeight * overscrollPercent
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desiredSlack = min(desiredSlack, maxOverscrollPoints)
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desiredSlack = max(desiredSlack, minOverscrollPoints)
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desiredSlack = max(0, floor(desiredSlack - lineHeight))
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// Start unlocking downward scroll before the stacked content fully fills
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// the viewport, then blend into the final comfortable bottom slack.
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let scrollUnlockDistance = max(visibleHeight - stackedContentHeight, 0)
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return floor((scrollUnlockDistance + desiredSlack) * activationProgress)
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}
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}
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