b612
2bf8478639
- 新增日月食中心带、偏食带、阴影足迹、等时线、食分线及升落边界计算，支持极区与混合食拓扑 - 新增日食单时刻阴影求解器、站心状态查询、批量采样和 ΔT 覆盖接口 - 重构恒星与行星月掩路径，补充有限盘面接触、站心修正、掩带宽度、极区投影及升落边界 - 扩展 SVG 与 GeoJSON 输出，支持详细面板、全球/极区/地球投影、边界闭合、时间标记和拓扑签名 - 扩展日月食候选搜索、局地搜索、沙罗序列预计算与范围外推，补充系列锚点和成员一致性校验 - 补齐古历纪年、儒略历独有闰日、多公历候选、历法改革跨日及精确日期运算接口 - 优化 ΔT、章动、恒星时、月球地平线、事件根搜索和本地星历缓存，降低重复计算开销并提升边界稳定
559 lines
20 KiB
Go
559 lines
20 KiB
Go
package svg
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import (
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"math"
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"time"
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eclipsecore "b612.me/astro/eclipse"
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"b612.me/astro/internal/svgchart"
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"b612.me/astro/internal/svgmap"
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)
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// 数据块的表头高度与行字号：取值与 internal/svgchart 的排版常量相同，这里只用它们反推行距下限。
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const (
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solarEclipsePanelHeaderHeight = 30.0
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solarEclipsePanelRowFontSize = 10.5
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)
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// solarEclipsePanelRowSpacingMin 是数据块行距下限：低于它相邻两行文字必然压叠。
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func solarEclipsePanelRowSpacingMin() float64 {
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above, below := svgchart.EstimatedTextExtents(solarEclipsePanelRowFontSize)
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return above + below
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}
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// solarEclipseMinPanelHeight 是容下 count 行文字的数据块高度下限；0.5 px 是等分行高时浮点取整的余量。
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func solarEclipseMinPanelHeight(count int) float64 {
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return solarEclipsePanelHeaderHeight + float64(count)*solarEclipsePanelRowSpacingMin() + 0.5
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}
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// solarEclipsePanelCell 是一个数据块的矩形与内容：占位与绘制共用同一份几何。
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type solarEclipsePanelCell struct {
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title string
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rows []svgchart.PanelRow
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box svgchart.LabelBox
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}
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// solarEclipsePanelCells 给出该版式下全部数据块矩形。
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func solarEclipsePanelCells(layout solarEclipseMapLayout, blocks solarEclipsePanelBlocks) []solarEclipsePanelCell {
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if layout.landscape {
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order := solarEclipseLandscapeBlockOrder(blocks)
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cells := make([]solarEclipsePanelCell, 0, len(order)+1)
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for index, block := range order {
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if len(block.rows) == 0 {
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continue
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}
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box, ok := solarEclipseLandscapeCellBox(layout, index)
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if !ok {
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continue
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}
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cells = append(cells, solarEclipsePanelCell{title: block.title, rows: block.rows, box: box})
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}
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if len(blocks.libration.rows) > 0 && layout.stripHeight > 0 {
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cells = append(cells, solarEclipsePanelCell{
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title: blocks.libration.title, rows: blocks.libration.rows,
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box: svgchart.LabelBox{
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X: layout.margin, Y: layout.bottomY,
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Width: solarEclipseLandscapeCellWidth, Height: layout.stripHeight,
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},
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})
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}
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return cells
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}
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if !layout.nasa {
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return nil
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}
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columnWidth := solarEclipsePortraitColumnWidth(layout)
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cells := make([]solarEclipsePanelCell, 0, 5)
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for column, block := range []solarEclipsePanelBlock{blocks.penumbra, blocks.circumstances, blocks.umbra} {
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if len(block.rows) == 0 {
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continue
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}
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cells = append(cells, solarEclipsePanelCell{title: block.title, rows: block.rows, box: svgchart.LabelBox{
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X: solarEclipsePortraitColumnX(layout, column), Y: layout.panelY,
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Width: columnWidth, Height: layout.panelHeight,
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}})
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}
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second := [2]struct {
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column int
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block solarEclipsePanelBlock
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}{{0, blocks.ephemeris}, {2, blocks.libration}}
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for _, entry := range second {
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if len(entry.block.rows) == 0 {
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continue
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}
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cells = append(cells, solarEclipsePanelCell{title: entry.block.title, rows: entry.block.rows, box: svgchart.LabelBox{
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X: solarEclipsePortraitColumnX(layout, entry.column), Y: layout.secondPanelY,
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Width: columnWidth, Height: layout.panelHeight,
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}})
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}
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return cells
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}
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// solarEclipsePanelsOverlap 报告任一数据块内文字是否压叠；为真时调用方必须拒绝该画布。
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func solarEclipsePanelsOverlap(cells []solarEclipsePanelCell) bool {
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for _, cell := range cells {
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if len(cell.rows) == 0 || cell.box.Width <= 0 || cell.box.Height <= 0 {
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continue
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}
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if svgchart.PanelBoxOverlaps(cell.box.X, cell.box.Y, cell.box.Width, cell.box.Height, cell.title, cell.rows) {
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return true
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}
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}
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return false
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}
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func solarEclipsePortraitColumnWidth(layout solarEclipseMapLayout) float64 {
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return (layout.panelWidth - 2*layout.panelGap) / 3
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}
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func solarEclipsePortraitColumnX(layout solarEclipseMapLayout, column int) float64 {
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return layout.panelX + float64(column)*(solarEclipsePortraitColumnWidth(layout)+layout.panelGap)
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}
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func solarEclipseLandscapeCellBox(layout solarEclipseMapLayout, index int) (svgchart.LabelBox, bool) {
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row := index / solarEclipseLandscapeColumns
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column := index % solarEclipseLandscapeColumns
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if row < 0 || row >= len(layout.gridRowHeights) || layout.gridRowHeights[row] <= 0 {
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return svgchart.LabelBox{}, false
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}
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return svgchart.LabelBox{
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X: layout.gridX + float64(column)*(layout.gridCellWidth+layout.gridGapX),
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Y: layout.gridRowY[row], Width: layout.gridCellWidth, Height: layout.gridRowHeights[row],
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}, true
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}
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// solarEclipseMapLegendItem 是图例的一条：标签、图形种类、颜色与虚线。
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type solarEclipseMapLegendItem struct {
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label string
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kind string
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color string
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dash string
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}
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const (
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solarEclipseLegendFontSize = 10.0
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solarEclipseLegendLineStep = 22.0
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solarEclipseLegendIconWidth = 25.0
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solarEclipseLegendColumnGap = 12.0
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solarEclipseLegendMaxColumns = 4
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)
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// solarEclipseMapLegendItems 汇总该事件要画的图例条目，顺序即优先级。
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func solarEclipseMapLegendItems(
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partial eclipsecore.SolarEclipsePartialFootprintsInfo,
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hasCentral bool,
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hasCentralBandFootprints bool,
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options SolarEclipseMapSVGOptions,
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) []solarEclipseMapLegendItem {
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info := partial.Eclipse
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partialLabel := "偏食可见区"
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centerLineLabel := "中心线"
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if options.Language == "en" {
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partialLabel = "Partial-eclipse visibility"
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centerLineLabel = "Center line"
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}
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items := []solarEclipseMapLegendItem{{label: partialLabel, kind: "fill", color: "#f7dd93"}}
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if hasCentral || hasCentralBandFootprints {
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items = append(items, solarEclipseMapLegendItem{
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label: solarEclipseCentralPathLabel(info.Type, options.Language), kind: "fill",
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color: solarEclipseCentralPathColor(info.Type),
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})
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}
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if hasCentral {
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items = append(items, solarEclipseMapLegendItem{label: centerLineLabel, kind: "line", color: "#263f58", dash: "5 3"})
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}
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if options.PenumbralOutlineStep > 0 {
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items = append(items, solarEclipseMapLegendItem{
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label: solarEclipseOutlineLegendLabel("penumbra", info.Type, options.PenumbralOutlineStep, options.Language),
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kind: "line", color: "#b07a18", dash: "3 3",
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})
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}
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riseSetLabel := "初亏/食甚/复圆日升日落线"
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if options.Language == "en" {
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riseSetLabel = "Rise/set phase lines"
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}
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if len(partial.RiseSetCurves) > 0 {
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items = append(items, solarEclipseMapLegendItem{label: riseSetLabel, kind: "line", color: "#d97706", dash: "6 4"})
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}
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if len(partial.MagnitudeContours) > 0 {
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magnitudeLabel := "地方食分 0.2–0.8"
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if options.Language == "en" {
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magnitudeLabel = "Local magnitude 0.2-0.8"
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}
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items = append(items, solarEclipseMapLegendItem{label: magnitudeLabel, kind: "line", color: "#7c3aed", dash: "4 3"})
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}
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if len(partial.GreatestTimeContours) > 0 {
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isochroneLabel := "食甚时刻等时线"
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if options.Language == "en" {
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isochroneLabel = "Greatest-eclipse isochrones"
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}
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items = append(items, solarEclipseMapLegendItem{label: isochroneLabel, kind: "line", color: "#1f6fb2"})
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}
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if info.Centrality != eclipsecore.SolarEclipseNonCentral &&
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len(partial.CentralShadowFootprints) > 0 && options.CentralShadowStep > 0 {
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items = append(items, solarEclipseMapLegendItem{
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label: solarEclipseOutlineLegendLabel("central", info.Type, options.CentralShadowStep, options.Language),
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kind: "line", color: "#7b5a42",
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})
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}
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contactLabel := "P/U 影锥接触"
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hasUContacts := !partial.U1.Time.IsZero() || !partial.U2.Time.IsZero() ||
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!partial.U3.Time.IsZero() || !partial.U4.Time.IsZero()
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if !hasUContacts {
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contactLabel = "P 半影接触"
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}
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if options.Language == "en" {
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contactLabel = "P/U shadow contacts"
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if !hasUContacts {
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contactLabel = "P penumbral contacts"
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}
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}
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return append(items, solarEclipseMapLegendItem{label: contactLabel, kind: "contact", color: "#a52d70"})
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}
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// solarEclipseMapLegendRows 按可用宽度把条目分行：每行不超过四栏，栏位由实测文本宽度累加，长标签不会挤进下一栏。
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func solarEclipseMapLegendRows(items []solarEclipseMapLegendItem, available float64) [][]solarEclipseMapLegendItem {
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rows := make([][]solarEclipseMapLegendItem, 0, 2)
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current := make([]solarEclipseMapLegendItem, 0, solarEclipseLegendMaxColumns)
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used := 0.0
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flush := func() {
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if len(current) == 0 {
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return
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}
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rows = append(rows, current)
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current = make([]solarEclipseMapLegendItem, 0, solarEclipseLegendMaxColumns)
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used = 0
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}
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for _, item := range items {
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width := solarEclipseLegendIconWidth + svgchart.EstimatedTextWidth(item.label, solarEclipseLegendFontSize)
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next := width
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if len(current) > 0 {
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next = used + solarEclipseLegendColumnGap + width
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if len(current) >= solarEclipseLegendMaxColumns || next > available {
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flush()
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next = width
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}
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}
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current = append(current, item)
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used = next
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}
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flush()
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return rows
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}
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// solarEclipseMapLegendBlockHeight 由图例行数给出图例带高度：首行基线上方还要留出字高。
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func solarEclipseMapLegendBlockHeight(rows int) float64 {
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if rows < 1 {
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rows = 1
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}
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above, below := svgchart.EstimatedTextExtents(solarEclipseLegendFontSize)
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return float64(rows-1)*solarEclipseLegendLineStep + above + below + 1
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}
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// solarEclipseMapLegendAvailableWidth 只由画布宽度与排布给出图例可用宽度，与竖向堆叠无关。
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func solarEclipseMapLegendAvailableWidth(options SolarEclipseMapSVGOptions) float64 {
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width, height := float64(options.Width), float64(options.Height)
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if width >= height {
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panelGap := math.Max(12, width*0.011)
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return solarEclipseLandscapeColumns*solarEclipseLandscapeCellWidth +
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float64(solarEclipseLandscapeColumns-1)*panelGap - 26
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}
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margin := math.Max(30, math.Min(52, width*0.044))
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return width - 2*margin - 26
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}
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// solarEclipseMapPointLabel 是一个点标注：图形锚点、文本、字号与落位结果。
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type solarEclipseMapPointLabel struct {
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x, y float64
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text string
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fontSize float64
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placed svgchart.LabelPlacement
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ok bool
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}
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func solarEclipseMapPlaceLabel(
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labels *svgchart.LabelTable,
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label solarEclipseMapPointLabel,
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candidates []svgchart.LabelPlacement,
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frame svgmap.Frame,
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) solarEclipseMapPointLabel {
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label.placed, label.ok = labels.Place(label.text, label.fontSize,
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labelCandidatesInsideBox(candidates, label.text, label.fontSize, solarEclipseFrameBox(frame)))
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return label
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}
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// labelCandidatesInsideBox 丢掉会让文本跑出给定区域的候选位次。
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func labelCandidatesInsideBox(
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candidates []svgchart.LabelPlacement,
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text string,
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fontSize float64,
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area svgchart.LabelBox,
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) []svgchart.LabelPlacement {
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kept := make([]svgchart.LabelPlacement, 0, len(candidates))
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for _, candidate := range candidates {
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box := svgchart.LabelTextBox(candidate.X, candidate.Y, fontSize, text, candidate.Anchor)
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if box.X < area.X || box.X+box.Width > area.X+area.Width {
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continue
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}
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if box.Y < area.Y || box.Y+box.Height > area.Y+area.Height {
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continue
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}
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kept = append(kept, candidate)
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}
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return kept
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}
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// solarEclipseFrameBox 把图框写成占位矩形。
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func solarEclipseFrameBox(frame svgmap.Frame) svgchart.LabelBox {
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return svgchart.LabelBox{X: frame.X, Y: frame.Y, Width: frame.Width, Height: frame.Height}
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}
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// solarEclipseMapPointLabels 汇总优先放置的点标注：食甚、影锥接触、太阳直射点与中心线时刻。
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type solarEclipseMapPointLabels struct {
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greatest solarEclipseMapPointLabel
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contacts []solarEclipseContactLabel
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subsolar solarEclipseMapPointLabel
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times []solarEclipseMapPointLabel
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}
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// solarEclipseContactMarker 是一个影锥接触标记：点名、位置、颜色与原位标注偏移。
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type solarEclipseContactMarker struct {
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name string
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point eclipsecore.SolarEclipsePathPoint
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color string
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labelDX float64
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labelDY float64
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textAnchor string
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}
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// solarEclipseContactLabel 是接触标记的落位结果：图形锚点与标注文本。
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type solarEclipseContactLabel struct {
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marker solarEclipseContactMarker
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x, y float64
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text string
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placed svgchart.LabelPlacement
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ok bool
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}
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func solarEclipseContactMarkerSpecs(info eclipsecore.SolarEclipsePartialFootprintsInfo) []solarEclipseContactMarker {
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return []solarEclipseContactMarker{
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{name: "P1", point: info.P1, color: "#a52d70", labelDX: -7, labelDY: 14, textAnchor: "end"},
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{name: "P2", point: info.P2, color: "#a52d70", labelDX: 7, labelDY: -7, textAnchor: "start"},
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{name: "P3", point: info.P3, color: "#a52d70", labelDX: -7, labelDY: -7, textAnchor: "end"},
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{name: "P4", point: info.P4, color: "#a52d70", labelDX: 7, labelDY: 14, textAnchor: "start"},
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{name: "U1", point: info.U1, color: "#a12c25", labelDX: -7, labelDY: -7, textAnchor: "end"},
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{name: "U2", point: info.U2, color: "#a12c25", labelDX: 7, labelDY: 14, textAnchor: "start"},
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{name: "U3", point: info.U3, color: "#a12c25", labelDX: -7, labelDY: 14, textAnchor: "end"},
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{name: "U4", point: info.U4, color: "#a12c25", labelDX: 7, labelDY: -7, textAnchor: "start"},
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}
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}
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// solarEclipseMapPlacePointLabels 按重要性放置点标注：食甚最先占位，其余标注再让开。
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func solarEclipseMapPlacePointLabels(
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partial eclipsecore.SolarEclipsePartialFootprintsInfo,
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central eclipsecore.SolarEclipsePath,
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hasCentral bool,
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frame svgmap.Frame,
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options SolarEclipseMapSVGOptions,
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labels *svgchart.LabelTable,
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) solarEclipseMapPointLabels {
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result := solarEclipseMapPointLabels{}
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if x, y, ok := frame.Project(partial.Eclipse.GreatestLongitude, partial.Eclipse.GreatestLatitude); ok {
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text := "食甚"
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if options.Language == "en" {
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text = "Greatest"
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}
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result.greatest = solarEclipseMapPlaceLabel(labels, solarEclipseMapPointLabel{x: x, y: y, text: text, fontSize: 11},
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[]svgchart.LabelPlacement{
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{X: x, Y: y - 10, Anchor: "middle"},
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{X: x, Y: y + 19, Anchor: "middle"},
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{X: x + 9, Y: y + 4, Anchor: "start"},
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{X: x - 9, Y: y + 4, Anchor: "end"},
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{X: x + 9, Y: y - 8, Anchor: "start"},
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{X: x - 9, Y: y - 8, Anchor: "end"},
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{X: x, Y: y - 24, Anchor: "middle"},
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{X: x, Y: y + 33, Anchor: "middle"},
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}, frame)
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}
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result.contacts = solarEclipseMapPlaceContactLabels(partial, frame, labels)
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result.subsolar = solarEclipseMapPlaceSubsolarLabel(partial.Eclipse, frame, options.Language, labels)
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if hasCentral {
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result.times = solarEclipseMapPlaceTimeLabels(central, frame, options, labels)
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}
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return result
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}
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func solarEclipseMapPlaceContactLabels(
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info eclipsecore.SolarEclipsePartialFootprintsInfo,
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frame svgmap.Frame,
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labels *svgchart.LabelTable,
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) []solarEclipseContactLabel {
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specs := solarEclipseContactMarkerSpecs(info)
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result := make([]solarEclipseContactLabel, 0, len(specs))
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for _, marker := range specs {
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if marker.point.Time.IsZero() {
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continue
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}
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x, y, visible := frame.Project(marker.point.Longitude, marker.point.Latitude)
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if !visible {
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continue
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}
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labelX, anchor := x+marker.labelDX, marker.textAnchor
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// 贴到图框边上的点名改到另一侧，避免被裁掉。
|
||
if labelX < frame.X+18 {
|
||
labelX, anchor = x+7, "start"
|
||
} else if labelX > frame.X+frame.Width-18 {
|
||
labelX, anchor = x-7, "end"
|
||
}
|
||
candidates := make([]svgchart.LabelPlacement, 0, 22)
|
||
candidates = append(candidates, svgchart.LabelPlacement{X: labelX, Y: y + marker.labelDY, Anchor: anchor})
|
||
candidates = append(candidates, svgchart.LabelCandidates(x+7, y+14, "start", 9)...)
|
||
candidates = append(candidates, svgchart.LabelCandidates(x-7, y-7, "end", 9)...)
|
||
candidates = append(candidates, svgchart.LabelCandidates(x+7, y-7, "start", 16)...)
|
||
candidates = append(candidates, svgchart.LabelCandidates(x-7, y+14, "end", 16)...)
|
||
label := solarEclipseMapPlaceLabel(labels, solarEclipseMapPointLabel{x: x, y: y, text: marker.name, fontSize: 8}, candidates, frame)
|
||
result = append(result, solarEclipseContactLabel{marker: marker, x: x, y: y, text: marker.name, placed: label.placed, ok: label.ok})
|
||
}
|
||
return result
|
||
}
|
||
|
||
func solarEclipseMapPlaceSubsolarLabel(
|
||
info eclipsecore.SolarEclipseInfo,
|
||
frame svgmap.Frame,
|
||
language string,
|
||
labels *svgchart.LabelTable,
|
||
) solarEclipseMapPointLabel {
|
||
point := solarEclipseSubsolarPoint(info.GreatestEclipse)
|
||
x, y, visible := frame.Project(point.Longitude, point.Latitude)
|
||
if !visible {
|
||
return solarEclipseMapPointLabel{}
|
||
}
|
||
text := "太阳直射点"
|
||
if language == "en" {
|
||
text = "Subsolar"
|
||
}
|
||
return solarEclipseMapPlaceLabel(labels, solarEclipseMapPointLabel{x: x, y: y, text: text, fontSize: 7},
|
||
[]svgchart.LabelPlacement{
|
||
{X: x, Y: y - 9, Anchor: "middle"},
|
||
{X: x, Y: y + 16, Anchor: "middle"},
|
||
{X: x + 7, Y: y + 4, Anchor: "start"},
|
||
{X: x - 7, Y: y + 4, Anchor: "end"},
|
||
{X: x, Y: y - 22, Anchor: "middle"},
|
||
{X: x, Y: y + 29, Anchor: "middle"},
|
||
{X: x + 16, Y: y + 4, Anchor: "start"},
|
||
{X: x - 16, Y: y + 4, Anchor: "end"},
|
||
}, frame)
|
||
}
|
||
|
||
func solarEclipseMapPlaceTimeLabels(
|
||
path eclipsecore.SolarEclipsePath,
|
||
frame svgmap.Frame,
|
||
options SolarEclipseMapSVGOptions,
|
||
labels *svgchart.LabelTable,
|
||
) []solarEclipseMapPointLabel {
|
||
if options.TimeLabelStep <= 0 || len(path.CenterLine) < 2 {
|
||
return nil
|
||
}
|
||
excluded := []time.Time{path.Eclipse.CentralBeginOnEarth, path.Eclipse.CentralEndOnEarth}
|
||
markers := solarEclipseTimeMarkerPoints(path.CenterLine, options.TimeLabelStep, options.Location, excluded)
|
||
result := make([]solarEclipseMapPointLabel, 0, len(markers))
|
||
projected := make([][2]float64, 0, len(markers))
|
||
for _, marker := range markers {
|
||
x, y, visible := frame.Project(marker.Longitude, marker.Latitude)
|
||
if !visible || x < frame.X+22 || x > frame.X+frame.Width-22 || y < frame.Y+12 || y > frame.Y+frame.Height-12 {
|
||
continue
|
||
}
|
||
tooClose := false
|
||
for _, previous := range projected {
|
||
if math.Hypot(x-previous[0], y-previous[1]) < 44 {
|
||
tooClose = true
|
||
break
|
||
}
|
||
}
|
||
if tooClose {
|
||
continue
|
||
}
|
||
projected = append(projected, [2]float64{x, y})
|
||
preferredY := y - 8
|
||
if mapTimesNear(marker.Time, path.Eclipse.GreatestEclipse, solarEclipseGreatestTimeLabelWindow(options.TimeLabelStep)) {
|
||
preferredY = y + 15
|
||
} else if preferredY < frame.Y+10 {
|
||
preferredY = y + 15
|
||
}
|
||
text := marker.Time.In(options.Location).Format("15:04")
|
||
label := solarEclipseMapPlaceLabel(labels, solarEclipseMapPointLabel{x: x, y: y, text: text, fontSize: 9},
|
||
[]svgchart.LabelPlacement{
|
||
{X: x, Y: preferredY, Anchor: "middle"},
|
||
{X: x, Y: y + 15, Anchor: "middle"},
|
||
{X: x, Y: y - 8, Anchor: "middle"},
|
||
{X: x + 11, Y: y + 4, Anchor: "start"},
|
||
{X: x - 11, Y: y + 4, Anchor: "end"},
|
||
{X: x, Y: y + 27, Anchor: "middle"},
|
||
{X: x, Y: y - 21, Anchor: "middle"},
|
||
}, frame)
|
||
result = append(result, label)
|
||
}
|
||
return result
|
||
}
|
||
|
||
// solarEclipseContourLabelCandidates 先给首选点，再沿最长支路从中间向两端取候选位次，标注始终贴着等值线。
|
||
func solarEclipseContourLabelCandidates(
|
||
segments [][]eclipsecore.SolarEclipsePathPoint,
|
||
frame svgmap.Frame,
|
||
preferredX, preferredY float64,
|
||
hasPreferred bool,
|
||
) []svgchart.LabelPlacement {
|
||
candidates := make([]svgchart.LabelPlacement, 0, 48)
|
||
if hasPreferred {
|
||
candidates = append(candidates, svgchart.LabelPlacement{X: preferredX, Y: preferredY, Anchor: "middle"})
|
||
}
|
||
longest := -1
|
||
for index, segment := range segments {
|
||
if longest < 0 || len(segment) > len(segments[longest]) {
|
||
longest = index
|
||
}
|
||
}
|
||
if longest < 0 {
|
||
return candidates
|
||
}
|
||
segment := segments[longest]
|
||
middle := len(segment) / 2
|
||
for offset := 0; offset <= middle; offset++ {
|
||
for _, index := range []int{middle + offset, middle - offset} {
|
||
if index < 0 || index >= len(segment) {
|
||
continue
|
||
}
|
||
point := segment[index]
|
||
x, y, visible := frame.Project(point.Longitude, point.Latitude)
|
||
if !visible ||
|
||
x < frame.X+30 || x > frame.X+frame.Width-30 ||
|
||
y < frame.Y+18 || y > frame.Y+frame.Height-18 {
|
||
continue
|
||
}
|
||
candidates = append(candidates, svgchart.LabelPlacement{X: x, Y: y - 6, Anchor: "middle"})
|
||
if len(candidates) >= 48 {
|
||
return candidates
|
||
}
|
||
}
|
||
}
|
||
return candidates
|
||
}
|
||
|
||
// solarEclipseScaleStep 在槽位宽度内取最大的整刻度，required 给出该刻度下刻度条加标注的总横向占用。
|
||
func solarEclipseScaleStep(target, available float64, required func(step float64) float64) float64 {
|
||
if target <= 0 || available <= 0 {
|
||
return 0
|
||
}
|
||
start := int(math.Floor(math.Log10(target)))
|
||
for exponent := start + 1; exponent >= start-4; exponent-- {
|
||
decade := math.Pow(10, float64(exponent))
|
||
for _, multiplier := range []float64{5, 2, 1} {
|
||
step := decade * multiplier
|
||
if required(step) <= available {
|
||
return step
|
||
}
|
||
}
|
||
}
|
||
return 0
|
||
}
|