fix: correct colors of labels when point color defaults (#51)

Also fixes motion of points when pivoting if they lie on a circle that only later has its center identified as the pivot point (i.e., not yet at the time the pivotable point is being defined).
Also implements the "center" method of constructing a point.

With this PR, apparently all diagrams through Book III work OK.

Reviewed-on: #51
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Co-committed-by: Glen Whitney <glen@studioinfinity.org>

src/adapptlet.civet

@@ -77,6 +77,7 @@ type PivotData
   pivot: string
   lastAngle: number
   rotatable: string[]
+  maybeRotatable: Record<string, string>
   fixed: Record<string, boolean>
 
 pivotData: Record<string, PivotData> := {}
@@ -112,13 +113,18 @@ function postApplets(jApplets: AppletDescription[], codebase = '')
                   pivot = geoname(jApp.id, elements, 'point') + 'Pivot'
                   pivotData[pivot] = {
                      api, jApp.params.pivot,
-                     lastAngle: 0, rotatable: [], fixed: {}}
+                     lastAngle: 0, rotatable: [], maybeRotatable: {}, fixed: {}}
             cdata: ConstructionData := {
                bg: ([255, 255, 255] as RGB),
                is3d, jApp.id, jApp.width, jApp.height, elements, pivot}
             for name, value in jApp.params
                dispatchJcommand
                   api, name, value, cdata
+            if pivot
+               pd := pivotData[pivot]
+               for entity, circ in pd.maybeRotatable
+                  if cdata.elements[circ].ends?[0] is pd.pivot
+                     pd.rotatable.push entity
             if is3d
                depth .= jApp.width
                if jApp.height > depth then depth = jApp.height
@@ -350,8 +356,9 @@ function jToG(
                   console.log 'Hiding point', point if traceC
                   api.setVisible point, false
          else if dimension is 0 or colors[1] // Need to color the points
-            ptRGB := colors[1] ? joyce2rgb colors[1], cdata.bg
+            if not colors[1]
-               : pointDefaultRGB name, method, isPivot
+               colors[1] = pointDefaultColorName name, method, isPivot
+            ptRGB := joyce2rgb colors[1], cdata.bg
             for each point of parts[0]
                console.log 'Coloring point', point, 'to', colors[1] if traceC
                api.setVisible point, true
@@ -361,47 +368,51 @@ function jToG(
          if invisible colors[0]
             console.log 'Hiding label', name if traceC
             api.setLabelVisible name, false
-         else if colors[dimension+1] and colors[dimension+1] is not colors[0]
-            // Have to make a text to provide the caption, since GeoGebra
-            // doesn't allow caption different color from entity.
-            textName := 'GeoText' + index
-            locationExpr := switch klass
-               when 'point' then `1.02${name}`
-               when 'line'
-                  (`Midpoint(${name}) + `
-                  + `Rotate(Direction(${name})*Length(${name})*0.02, pi/2)`)
-               when 'circle'
-                  `Center(${name}) + Radius(${name})*Vector((12/13,5/13))*1.03`
-               when 'polygon' then `Centroid(${name})`
-               when 'sector'
-                  `(5*Center(${name}) - ${cmdr.ends?[0]} - ${cmdr.ends?[1]})/3`
-               when 'plane'
-                  `Intersect(${name}, PerpendicularLine((0, 0, 0), ${name}))`
-               when 'sphere'
-                  `Center(${name})+Radius(${name})*Vector((12/13,0,5/13))*1.03`
-               when 'polyhedron'
-                  // The "ends" are faces or vertices roughly opposite
-                  // from each other
-                  [ex1, ex2] .= cmdr.ends ?? ['', '']
-                  unless parts[0].includes ex1 then ex1 = `Centroid(${ex1})`
-                  unless parts[0].includes ex2 then ex2 = `Centroid(${ex2})`
-                  `(4*${ex1}+${ex2})/5`
-            textCmd := `${textName} = Text("${jname}", ${locationExpr})`
-            textCol := joyce2rgb colors[0], cdata.bg
-            if traceC
-               console.log `Making text '${textCmd}' colored`, textCol
-            api.evalCommand textCmd
-            api.setColor textName, ...textCol
-            // and hide the underlying GeoGebra label
-            api.setLabelVisible name, false
          else if colors[0]
-            // Label gets the correct color from element
+            if colors[dimension+1] and colors[dimension+1] is not colors[0]
-            // but we had better make sure it is visible:
+               // Have to make a text to provide the caption, since GeoGebra
-            console.log 'Showing label', name if traceC
+               // doesn't allow caption different color from entity.
-            api.setLabelVisible name, true
+               textName := 'GeoText' + index
-         else
+               locationExpr := switch klass
-            // label color is defaulting. Same as element for points, invisible
+                  when 'point' then `1.02${name}`
-            // otherwise:
+                  when 'line'
+                     (`Midpoint(${name})`
+                      + ` + Rotate(Direction(${name})`
+                      +    `*Length(${name})*0.02, pi/2)`)
+                  when 'circle'
+                     (`Center(${name})`
+                      + ` + Radius(${name})*Vector((12/13,5/13))*1.03`)
+                  when 'polygon' then `Centroid(${name})`
+                  when 'sector'
+                     (`(5*Center(${name})`
+                      + ` - ${cmdr.ends?[0]} - ${cmdr.ends?[1]})/3`)
+                  when 'plane'
+                     `Intersect(${name}, PerpendicularLine((0, 0, 0), ${name}))`
+                  when 'sphere'
+                     (`Center(${name})`
+                      + ` + Radius(${name})*Vector((12/13,0,5/13))*1.03`)
+                  when 'polyhedron'
+                     // The "ends" are faces or vertices roughly opposite
+                     // from each other
+                     [ex1, ex2] .= cmdr.ends ?? ['', '']
+                     unless parts[0].includes ex1 then ex1 = `Centroid(${ex1})`
+                     unless parts[0].includes ex2 then ex2 = `Centroid(${ex2})`
+                     `(4*${ex1}+${ex2})/5`
+               textCmd := `${textName} = Text("${jname}", ${locationExpr})`
+               textCol := joyce2rgb colors[0], cdata.bg
+               if traceC
+                  console.log `Making text '${textCmd}' colored`, textCol
+               api.evalCommand textCmd
+               api.setColor textName, ...textCol
+               // and hide the underlying GeoGebra label
+               api.setLabelVisible name, false
+            else // specified label color matches the entity color
+               // So label gets the correct color from element
+               // but we had better make sure it is visible:
+               console.log 'Showing label', name if traceC
+               api.setLabelVisible name, true
+         else // label color is defaulting
+            // Make it same as the element for points, invisible otherwise:
             show := klass is 'point'
             console.log 'Setting label vis of', name, 'to', show if traceC
             api.setLabelVisible name, show
@@ -486,14 +497,15 @@ function joyce2rgb(cname: string, backgroundRGB?: RGB): RGB
          console.warn 'Could not parse color:', cname
          [128, 128, 128]
 
-function pointDefaultRGB(name: string, method: string, isPivot: boolean): RGB
+function pointDefaultColorName(
-   if isPivot then return joyce2rgb 'green'
+            name: string, method: string, isPivot: boolean): string
+   if isPivot then return 'green'
    switch method
       'free'
-         joyce2rgb 'red'
+         'red'
       /.*[Ss]lider$/
-         joyce2rgb 'orange'
+         'orange'
-      else joyce2rgb 'black'
+      else 'black'
 
 function geoname(
       jname: JoyceName, elements: JoyceElements, klass: JoyceClass): GeoName
@@ -564,14 +576,26 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                makeAngDiv(method, args, cdata, aux, auxiliaries, commands)
             unless foot return
             commands.push `${name} = ${foot}`
+         'center'
+            entity := args.circle ? args.circle[0] : args.sphere?[0]
+            if entity
+               commands.push `${name} = Center(${entity})`
+               entityEnds := cdata.elements[entity].ends
+               if entityEnds and not entityEnds[0]
+                  entityEnds[0] = name // labeled the center
+            else
+               console.warn 'Nothing to produce center point of in',
+                  name, method, args
          'circleSlider'
             unless args.circle then return
             circ := args.circle[0]
             commands.push `${name} = Point(${circ})`
-            if (pivotable
+            if pivotable
-                  and cdata.elements[circ].ends?[0] // center
+               maybeCenter := cdata.elements[circ].ends?[0]
-                      is pivotData[cdata.pivot].pivot)
+               if maybeCenter is pivotData[cdata.pivot].pivot
-               pivotData[cdata.pivot].rotatable.push name
+                  pivotData[cdata.pivot].rotatable.push name
+               if not maybeCenter
+                  pivotData[cdata.pivot].maybeRotatable[name] = circ
             if args.scalar and args.scalar.length
                callbacks.push (api: AppletObject) =>
                   api.setCoords name, ...vertFlipped(args.scalar or [], cdata)
@@ -658,6 +682,7 @@ classHandler: Record<JoyceClass, ClassHandler> :=
          'vertex'
             commands.push
                `${name} = Vertex(${args.polygon?[0]},${args.scalar?[0]})`
+         else console.warn 'Unknown point method:', method
 
    line: (name, method, args, index, cdata) =>
       return := freshCommander()
@@ -770,15 +795,8 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                   ends[0] = pt[0]
                   ends[1] = aux
                   auxiliaries.push aux
-                  if args.line?.length is 1
+                  commands.push
-                     ln := args.line[0]
+                     `${aux} = Rotate(${pt[1]}, pi/2, ${pt[0]}${inPlane})`
-                     commands.push
-                        `${name} = Rotate(${ln}, pi/2, ${pt[0]}${inPlane})`
-                        `${aux} = Vertex(${name}, 2)`
-                     madeSegment = true
-                  else
-                     commands.push
-                        `${aux} = Rotate(${pt[1]}, pi/2, ${pt[0]}${inPlane})`
                when 3
                   return // TODO: line perpendicular to plane
                when 4