41 lines
1.0 KiB
Go
41 lines
1.0 KiB
Go
package transcode
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// ZoomResult is the result of a TimelineZoom calculation.
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type ZoomResult struct {
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Type string `json:"type"`
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Percent float64 `json:"percent"`
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ViewStart float64 `json:"viewStart"`
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ViewEnd float64 `json:"viewEnd"`
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}
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// TimelineZoom computes the visible time window for the given zoomPercentage
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// (1–100, where 100 = full duration visible) centered on zoomCenter.
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func TimelineZoom(zoomCenter, zoomPercentage, duration float64) *ZoomResult {
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visibleDuration := duration * (zoomPercentage / 100)
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half := visibleDuration / 2
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viewStart := zoomCenter - half
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viewEnd := zoomCenter + half
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// Clamp to [0, duration], shifting the window rather than just truncating
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// so the visible span stays the same size when near the edges.
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if viewStart < 0 {
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viewEnd -= viewStart
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viewStart = 0
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}
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if viewEnd > duration {
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viewStart -= viewEnd - duration
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viewEnd = duration
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}
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if viewStart < 0 {
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viewStart = 0
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}
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return &ZoomResult{
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Type: "zoom",
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Percent: zoomPercentage,
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ViewStart: viewStart,
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ViewEnd: viewEnd,
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}
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}
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