feat: Get all of Rostamian's old pages working (#44)

Implements the pivot parameter to the Geometry applet and numerous new construction methods.
Resolves #36.

Reviewed-on: #44
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Co-committed-by: Glen Whitney <glen@studioinfinity.org>

etc/deps/geotypes/api.ts

@@ -101,7 +101,7 @@ export interface AppletObject {
   getXcoord(objName: string): number;
   getYcoord(objName: string): number;
   getZcoord(objName: string): number;
-  setCoords(objName: string, x: number, y: number, z: number): void;
+  setCoords(objName: string, x: number, y: number, z?: number): void;
   getValue(objName: string): number;
   getVersion(): string;
   getScreenshotBase64(callback: (data: string) => void, scale?: number): void;

etc/options.html

@@ -18,8 +18,12 @@
   Alter execution of the translated applet: <br/>
   <label for="showall">Show all applet entities, even hidden ones</label>
   <input type="checkbox" id="showall"><br/>
-  <label for="showaux">Show geogebra auxiliaries (not in applet)</label>
+  <label for="showaux">Show GeoGebra auxiliaries (not in applet)</label>
   <input type="checkbox" id="showaux">
+  <br/>
+  <br/>
+  <label for="algebra">Show the GeoGebra algebra pane</label>
+  <input type="checkbox" id="algebra">
   <script src="options.js" type="module"></script>
 </body>
 

src/adapptext.civet

@@ -64,7 +64,7 @@ document.addEventListener "DOMContentLoaded", async =>
             use3d = true
             break
       codebase .= browser.runtime.getURL 'deps/GeoGebra/HTML5/5.0/'
-      codebase += use3d ? 'web3d' : 'webSimple'
+      codebase += (use3d or config.algebra) ? 'web3d' : 'webSimple'
       adapParams: AdapParams := {codebase, config, joyceApplets }
       apars := JSON.stringify(adapParams)
       addScriptTag(browser.runtime.getURL 'deps/GeoGebra/deployggb.js').then =>

src/adapptlet.civet

@@ -35,6 +35,42 @@ type Description
 // with the otherName property:
 type JoyceElements = Record<AnyName, Description>
 
+adapptScript := findAdappt() as HTMLScriptElement
+
+function findAdappt()
+  scripts := document.querySelectorAll 'script'
+  for scrip of scripts
+     src := scrip.getAttribute 'src'
+     if src and src.includes 'adapptlet'
+        return scrip
+
+adapParams: AdapParams :=
+   typeof GGBApplet is 'undefined'
+      ? {loader: 'https://www.geogebra.org/apps/deployggb.js', joyceApplets: []}
+      : JSON.parse(adapptScript.dataset.params ?? '') as AdapParams
+
+type ConstructionData
+  id: string
+  bg: RGB
+  is3d: boolean
+  width: number
+  height: number
+  elements: JoyceElements
+  pivot: string
+
+// Global data setup for pivoting (ugh, but necessary because the api
+// is not passed to the callback, so we have to look up the slider in
+// a global list):
+
+type PivotData
+  api: AppletObject
+  pivot: string
+  lastAngle: number
+  rotatable: string[]
+  fixed: Record<string, boolean>
+
+pivotData: Record<string, PivotData> := {}
+
 function postApplets(jApplets: AppletDescription[], codebase = '')
    for each jApp of jApplets
       params := {
@@ -44,11 +80,9 @@ function postApplets(jApplets: AppletDescription[], codebase = '')
          jApp.width,
          jApp.height,
          appletOnLoad: (api: AppletObject) =>
-            elements: JoyceElements := {}
+            is3d := contains3d jApp.params
-            backgroundRGB := [255, 255, 255] as RGB
+            if is3d
-            config3d := contains3d jApp.params
+               api.enable3D true
-            if config3d
-               worked := api.enable3D true
                api.setPerspective 'T'
                // Get rid of the xy-plane indicator
                xml .= api.getXML()
@@ -56,10 +90,26 @@ function postApplets(jApplets: AppletDescription[], codebase = '')
                api.setXML xml
             else if codebase.includes 'web3d'
                api.setPerspective 'G'
+            if adapParams.config?.algebra
+               api.setPerspective '+A'
+            elements := {}
+            pivot .= ''
+            if 'pivot' in jApp.params
+               if is3d
+                  console.warn('Geometry Applet "pivot" only supported for '
+                     + '2D constrcutions. Ignoring.')
+               else
+                  pivot = geoname(jApp.id, elements, 'point') + 'Pivot'
+                  pivotData[pivot] = {
+                     api, jApp.params.pivot,
+                     lastAngle: 0, rotatable: [], 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, elements, backgroundRGB, config3d
+                  api, name, value, cdata
-            if config3d
+            if is3d
                depth .= jApp.width
                if jApp.height > depth then depth = jApp.height
                api.setCoordSystem
@@ -78,22 +128,6 @@ function postApplets(jApplets: AppletDescription[], codebase = '')
       if codebase then geoApp.setHTML5Codebase codebase
       geoApp.inject jApp.id
 
-adapptScript := findAdappt() as HTMLScriptElement
-
-function findAdappt()
-  scripts := document.querySelectorAll 'script'
-  for scrip of scripts
-     src := scrip.getAttribute 'src'
-     if src and src.includes 'adapptlet'
-        return scrip
-
-console.log 'In script', document.currentScript, adapptScript
-
-adapParams: AdapParams :=
-   typeof GGBApplet is 'undefined'
-      ? {loader: 'https://www.geogebra.org/apps/deployggb.js', joyceApplets: []}
-      : JSON.parse(adapptScript.dataset.params ?? '') as AdapParams
-
 // Always use the final joyceApplets if there are any:
 if joyceApplets.length
    adapParams.joyceApplets = joyceApplets
@@ -135,7 +169,7 @@ type ClassHandler = (
    method: string,
    args: JoyceArguments,
    index: number,
-   is3d: boolean) => Commander
+   cdata: ConstructionData) => Commander
 type RGB = [number, number, number]
 type XYZ = RGB
 
@@ -146,28 +180,26 @@ function dispatchJcommand(
       api: AppletObject,
       name: string,
       value: string,
-      elements: JoyceElements
+      cdata: ConstructionData): void
-      backgroundRGB: RGB,
-      is3d: boolean): void
    switch name
       'background'
-         newback := joyce2rgb value, backgroundRGB
+         cdata.bg = joyce2rgb value, cdata.bg
          if adapParams.config?.commands
             console.log 'Setting background to', value, 'interpreted as',
-               newback
+               cdata.bg
-         for i of [0..2]
+         api.setGraphicsOptions 1, bgColor: colorsea(cdata.bg).hex()
-            backgroundRGB[i] = newback[i]
-         api.setGraphicsOptions 1, bgColor: colorsea(backgroundRGB).hex()
       'title'
          if adapParams.config?.commands
             console.log 'Setting title to', value
-         corner := is3d ? 'Corner(-1,1)' : 'Corner(1,1)'
+         corner := cdata.is3d ? 'Corner(-1,1)' : 'Corner(1,1)'
          api.evalCommand `TitlePoint = ${corner}
             Text("${value}", TitlePoint + (2,5))`
+      'pivot'
+         return  // already handled in postApplets
       /e\[\d+\]/
          num := parseInt(name.slice(2))
          {commands, callbacks, parts} :=
-            jToG value, elements, num, backgroundRGB, is3d
+            jToG value, num, cdata
          if commands.length
             lastTried .= 0
             if commands.filter((&)).every (cmd) =>
@@ -180,16 +212,14 @@ function dispatchJcommand(
                 (part of translation of '${value}')
                 failed.`
          else console.warn `Could not parse command '${value}'`
-      else console.warn `Unkown param ${name} = ${value}`
+      else console.warn `Unknown param ${name} = ${value}`
 
 // Parses a Joyce element-creating command, extending the elements
 // by side effect:
 function jToG(
       jCom: string,
-      elements: JoyceElements,
       index: number,
-      backgroundRGB: RGB
+      cdata: ConstructionData): Commander
-      is3d: boolean): Commander
    [jname, klass, method, data, ...colors] := jCom.split ';'
    if adapParams.config?.commands
       console.log 'Defining', jname, 'as a', klass, 'constructed by',
@@ -199,7 +229,9 @@ function jToG(
       console.warn `Unknown entity class ${klass}`
       return cmdr
    assertJoyceClass klass  // shouldn't need to do that :-/
-   name := if /^\p{L}\w*$/u.test jname then jname else geoname jname, elements
+   isPivot := !!cdata.pivot and jname is pivotData[cdata.pivot].pivot
+   name := geoname jname, cdata.elements, klass
+   if isPivot then pivotData[cdata.pivot].pivot = name
    args: JoyceArguments := {}
    usesCaptions := []
    for each jdep of data.split ','
@@ -207,17 +239,17 @@ function jToG(
       if scalar is scalar // not NaN
          (args.scalar ?= []).push scalar
          continue
-      unless jdep in elements
+      unless jdep in cdata.elements
          console.warn `Reference to unknown geometric entity ${jdep} in $jCom}`
          return cmdr
       usesCaptions.push jdep
-      {klass: depKlass, otherName: depGeo, ends} := elements[jdep]
+      {klass: depKlass, otherName: depGeo, ends} := cdata.elements[jdep]
       (args[depKlass] ?= []).push depGeo
       if depKlass is 'point'
          (args.subpoints ?= []).push depGeo
       else if depKlass is 'line'
          (args.subpoints ?= []).push ...ends ?? []
-   cmdr = classHandler[klass] name, method, args, index, is3d
+   cmdr = classHandler[klass] name, method, args, index, cdata
    unless name is jname then cmdr.callbacks.push (api: AppletObject) =>
       api.setCaption name, jname
       api.setLabelStyle name, 3  // style CAPTION = 3
@@ -225,7 +257,27 @@ function jToG(
       cmdr.callbacks.push (api: AppletObject) =>
          for each aux of cmdr.auxiliaries
             api.setAuxiliary aux, true
+            api.setLabelVisible aux, false
             api.setVisible aux,false
+
+   // set up the pivot if there is one
+   if isPivot
+      unless klass is 'point'
+         console.warn(`Can only pivot around a point, not the ${klass}`
+            + `named ${jname}. Ignoring.`)
+         cdata.pivot = ''
+      cmdr.commands.push(`${cdata.pivot} = `
+         + `Slider(0°,360°,1°,1,${cdata.width/3},true,true,false,false)`)
+      cmdr.callbacks.push (api: AppletObject) =>
+         api.setCaption cdata.pivot, 'Rotate Display'
+         api.setLabelStyle cdata.pivot, 3
+         api.setCoords(cdata.pivot, 2*cdata.width/3, cdata.height-10)
+         // Not sure how to let TypeScript deal with putting a new function
+         // on the global window object, so punting at least for now:
+         // @ts-ignore
+         window.pivotListener = pivotListener
+         api.registerObjectUpdateListener(cdata.pivot, 'pivotListener')
+
    // Create callback to assign colors
    if colors.length is 4 and colors.every (color) => invisible color
       cmdr.callbacks.push (api: AppletObject) => api.setVisible name, false
@@ -243,11 +295,11 @@ function jToG(
                    console.log 'Fading out interior of', face if trace
                    // hide the interior by making it transparent
                    api.setFilling face, 0
-                else if face not in elements
+                else if face not in cdata.elements
                    console.log 'Hiding face', face if trace
                    api.setVisible face, false
          else
-            faceRGB := joyce2rgb(colors[3] or 'brighter', backgroundRGB)
+            faceRGB := joyce2rgb(colors[3] or 'brighter', cdata.bg)
             deep := ['circle', 'polygon', 'sector']
             filling := deep.includes(klass) ? 0.7 : 0.2
             for each face of parts[2]
@@ -259,28 +311,30 @@ function jToG(
          // Lines default to black:
          if invisible colors[2]
             for each line of parts[1]
-                if line is name or line not in elements
+                if line is name or line not in cdata.elements
                    console.log 'Hiding line', line if trace
                    api.setVisible line, false
          else
-            lineRGB := joyce2rgb(colors[2] or 'black', backgroundRGB)
+            lineRGB := joyce2rgb(colors[2] or 'black', cdata.bg)
             for each line of parts[1]
                console.log 'Coloring line', line, 'to', colors[2] if trace
                api.setVisible line, true
                api.setColor line, ...lineRGB
 
          // Now color the points:
-         console.log 'Considering point colors for', name if trace
+         if trace
+            console.log
+               'Considering point colors for', name, 'of dimension', dimension
          if invisible colors[1]
             // Hide all the dim-0 elements that are not distinct independent
             // items:
             for each point of parts[0]
-               if point is name or point not in elements
+               if point is name or point not in cdata.elements
                   console.log 'Hiding point', point if trace
                   api.setVisible point, false
          else if dimension is 0 or colors[1] // Need to color the points
-            ptRGB := colors[1] ? joyce2rgb colors[1], backgroundRGB
+            ptRGB := colors[1] ? joyce2rgb colors[1], cdata.bg
-               : pointDefaultRGB name, method
+               : pointDefaultRGB name, method, isPivot
             for each point of parts[0]
                console.log 'Coloring point', point, 'to', colors[1] if trace
                api.setVisible point, true
@@ -290,12 +344,12 @@ function jToG(
          if invisible colors[0]
             console.log 'Hiding label', name if trace
             api.setLabelVisible name, false
-         else if colors[dimension] and colors[dimension] is not colors[0]
+         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${name})`
+               when 'point' then `1.02${name}`
                when 'line'
                   (`Midpoint(${name}) + `
                   + `Rotate(Direction(${name})*Length(${name})*0.02, pi/2)`)
@@ -315,8 +369,12 @@ function jToG(
                   unless parts[0].includes ex1 then ex1 = `Centroid(${ex1})`
                   unless parts[0].includes ex2 then ex2 = `Centroid(${ex2})`
                   `(4*${ex1}+${ex2})/5`
-            api.evalCommand `${textName} = Text("${jname}", ${locationExpr})`
+            textCmd := `${textName} = Text("${jname}", ${locationExpr})`
-            api.setColor textName, ...joyce2rgb colors[0], backgroundRGB
+            textCol := joyce2rgb colors[0], cdata.bg
+            if trace
+               console.log `Making text '${textCmd}' colored`, textCol
+            api.evalCommand textCmd
+            api.setColor textName, ...textCol
             // and hide the underlying GeoGebra label
             api.setLabelVisible name, false
          else if colors[0]
@@ -331,19 +389,33 @@ function jToG(
             console.log 'Setting label vis of', name, 'to', show if trace
             api.setLabelVisible name, show
 
-//         window[hideListener] = (arg) =>
+   cdata.elements[jname] = {otherName: name, usesCaptions, klass, cmdr.ends}
-//            api.setVisible name, false
+   cdata.elements[name] = {otherName: jname, usesCaptions, klass, cmdr.ends}
-//         api.registerObjectUpdateListener name, hideListener
-   if cmdr.ends // line or sector
-      elements[jname] =
-         {otherName: name, usesCaptions, klass, cmdr.ends}
-      elements[name] =
-         {otherName: jname, usesCaptions, klass, cmdr.ends}
-   else // any other geometry
-      elements[jname] = {otherName: name, usesCaptions, klass}
-      elements[name] = {otherName: jname, usesCaptions, klass}
    cmdr
 
+function pivotListener(slider: string)
+   pd := pivotData[slider]
+   newval := pd.api.getValue slider
+   if newval is pd.lastAngle then return
+   rotation := newval - pd.lastAngle
+   pd.lastAngle = newval
+   pX := pd.api.getXcoord pd.pivot
+   pY := pd.api.getYcoord pd.pivot
+   relX: Record<string, number> := {}
+   relY: Record<string, number> := {}
+   for each anchor of pd.rotatable
+      relX[anchor] = pd.api.getXcoord(anchor) - pX
+      relY[anchor] = pd.api.getYcoord(anchor) - pY
+      pd.api.setFixed anchor, false
+   ct := Math.cos rotation
+   st := Math.sin rotation
+   for each anchor of pd.rotatable
+      rX := relX[anchor]*ct - relY[anchor]*st
+      rY := relY[anchor]*ct + relX[anchor]*st
+      pd.api.setCoords(anchor, rX + pX, rY + pY)
+      if pd.fixed[anchor]
+         pd.api.setFixed anchor, true
+
 function invisible(cname: string): boolean
    if adapParams.config?.showall then return false
    cname is '0' or cname is 'none'
@@ -397,8 +469,8 @@ function joyce2rgb(cname: string, backgroundRGB?: RGB): RGB
          console.warn 'Could not parse color:', cname
          [128, 128, 128]
 
-function pointDefaultRGB(name: string, method: string): RGB
+function pointDefaultRGB(name: string, method: string, isPivot: boolean): RGB
-   // Need to short-circuit with green for pivot point, once that is implemented
+   if isPivot then return joyce2rgb 'green'
    switch method
       'free'
          joyce2rgb 'red'
@@ -406,19 +478,39 @@ function pointDefaultRGB(name: string, method: string): RGB
          joyce2rgb 'orange'
       else joyce2rgb 'black'
 
-function geoname(jname: JoyceName, elements: JoyceElements): GeoName
+function geoname(
+      jname: JoyceName, elements: JoyceElements, klass: JoyceClass): GeoName
+   unless jname.substring(0,3) is 'Geo' // those might clash
+      // Names with word characters starting with a capital are always good:
+      if /^[A-Z]['\w]*$/.test jname then return jname
+      // If it's not a point, can start with any letter:
+      if klass !== 'point' and /^\p{L}['\w]*$/u.test jname then return jname
+   // GeoGebra won't deal with this name, so hash it:
    numCode .= 0n
    numCode = numCode*128n + BigInt ch.codePointAt(0) ?? 1 for each ch of jname
    return .= 'Geo' + numCode.toString(36);
    return += '1' while return.value in elements
 
+// Helper for similar point/line functions:
+function cutoffExtend(
+      method: string, pt: string[], point?: string[], line?: string[]
+      ): [string, string]
+   direction .= `UnitVector(Vector(${pt[0]},${pt[1]}))`
+   if line and (not point or point[0] !== pt[0])
+      direction = `UnitVector(${line[0]})`
+   displacement := `Distance(${pt[2]}, ${pt[3]})*${direction}`
+   source := method is 'cutoff' ? pt[0] : pt[1]
+   [source, displacement]
+
 // All of the detailed semantics of each available command lies in this
 // function.
 classHandler: Record<JoyceClass, ClassHandler> :=
-   point: (name, method, args, index, is3d): Commander =>
+   point: (name, method, args, index, cdata): Commander =>
       return := freshCommander()
       {commands, callbacks, parts, auxiliaries} := return.value
+      zeroVector := cdata.is3d ? 'Vector((0,0,0))' : 'Vector((0,0))'
       aux := name + 'aUx'
+      pivotable := cdata.pivot and name !== pivotData[cdata.pivot].pivot
       parts[0].push name
       switch method
          /angle(?:Bisector|Divider)/
@@ -433,30 +525,41 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                commands.push `${destination} = Segment(${start}, ${end})`
             else destination = args.line[0]
             n := method is 'angleBisector' ? 2 : args.scalar?[0]
-            inPlane := is3d ? `, Plane(${start}, ${center}, ${end})` : ''
+            inPlane := cdata.is3d ? `, Plane(${start}, ${center}, ${end})` : ''
             commands.push
                `${aux}2 = Angle(${start}, ${center}, ${end}${inPlane})`
                `${aux}3 = If(${aux}2 > pi, ${aux}2 - 2*pi, ${aux}2)`
                `${aux}4 = Rotate(${start}, ${aux}3/${n}, ${center}${inPlane})`
                `${name} = Intersect(${destination}, Ray(${center}, ${aux}4))`
             auxiliaries.push ...[2..4].map (i) => `${aux}${i}`
-         'extend'
+         'circleSlider'
-            sp := args.subpoints
+            unless args.circle then return
-            unless sp then return
+            circ := args.circle[0]
-            direction .= `UnitVector(Vector(${sp[0]},${sp[1]}))`
+            commands.push `${name} = Point(${circ})`
-            if args.line and (
+            if (pivotable
-                  not args.point or args.point[0] !== sp[0])
+                  and cdata.elements[circ].ends?[0] // center
-               direction = `UnitVector(${args.line[0]})`
+                      is pivotData[cdata.pivot].pivot)
-            displacement := `Distance(${sp[2]}, ${sp[3]})*${direction}`
+               pivotData[cdata.pivot].rotatable.push name
-            commands.push `${name} = Translate(${sp[1]}, ${displacement})`
+            if args.scalar and args.scalar.length
+               callbacks.push (api: AppletObject) =>
+                  api.setCoords name, ...args.scalar as XYZ
+         /cutoff|extend/
+            pt := args.subpoints
+            unless pt and pt.length is 4 then return
+            [source, displacement] :=
+               cutoffExtend method, pt, args.point, args.line
+            commands.push `${name} = Translate(${source}, ${displacement})`
          'first'
             unless args.subpoints then return
             commands.push `${name} = ${args.subpoints[0]}`
          /fixed|free/
             coords := args.scalar
             unless coords then return
-            commands.push `${name} = (${coords.join ','})`
+            scoord := coords.join ','
+            if pivotable then pivotData[cdata.pivot].rotatable.push name
+            commands.push `${name} = (${scoord})`
             if method is 'fixed'
+               if pivotable then pivotData[cdata.pivot].fixed[name] = true
                callbacks.push (api: AppletObject) => api.setFixed name, true
          'foot'
             pt := args.subpoints
@@ -476,7 +579,8 @@ classHandler: Record<JoyceClass, ClassHandler> :=
             commands.push `${name} = Intersect(${l1},${e2})`
          'last'
             unless args.subpoints then return
-            commands.push `${name} = ${args.subpoints.at(-1)}`
+            commands.push
+               `${name} = ${args.subpoints.at(-1)}`
          'lineSegmentSlider'
             segment .= args.line?[0]
             unless segment
@@ -500,9 +604,26 @@ classHandler: Record<JoyceClass, ClassHandler> :=
             [center, direction] := args.subpoints
             // Note clockwise 90° rotation (3π/2) confirmed in Joyce source
             commands.push `${name} = Rotate(${direction}, 3*pi/2, ${center})`
-         'proportion'
+         /proportion|similar/
-            pt := args.subpoints
+            pt .= args.subpoints
             unless pt then return
+            // reduce the similar case to general proportion
+            if method is 'similar'
+               unless pt.length is 5 then return
+               sourcePlane .= ''
+               destPlane .= ''
+               if cdata.is3d
+                  unless args.plane then return
+                  destPlane = `, ${args.plane[0]}`
+                  if args.plane.length > 1
+                     sourcePlane = `, ${args.plane[1]}`
+                  else
+                     sourcePlane = `, Plane(${pt[2]}, ${pt[3]}, ${pt[4]})`
+               angle := `Angle(${pt[3]}, ${pt[2]}, ${pt[4]}${sourcePlane})`
+               commands.push
+                  `${aux} = Rotate(${pt[1]}, ${angle}, ${pt[0]}${destPlane})`
+               auxiliaries.push aux
+               pt = [pt[2], pt[3], pt[2], pt[4], pt[0], pt[1], pt[0], aux]
             len := `Distance(${pt[2]},${pt[3]})*Distance(${pt[4]},${pt[5]})`
                + `/ Distance(${pt[0]},${pt[1]})`
             direction := `UnitVector(Vector(${pt[6]}, ${pt[7]}))`
@@ -511,7 +632,7 @@ classHandler: Record<JoyceClass, ClassHandler> :=
             commands.push
                `${name} = Vertex(${args.polygon?[0]},${args.scalar?[0]})`
 
-   line: (name, method, args) =>
+   line: (name, method, args, index, cdata) =>
       return := freshCommander()
       return.value.ends = ['', '']
       {commands, callbacks, parts, auxiliaries, ends} := return.value
@@ -519,10 +640,62 @@ classHandler: Record<JoyceClass, ClassHandler> :=
       parts[1].push name
       madeSegment .= false
       switch method
+         'bichord'
+            // To match Joyce, we need to get the ordering here correct.
+            // we want the order so that start -> end sweeping past the
+            // center of the other circle is counterclockwise in the first
+            // circle
+            cr := args.circle
+            unless cr return
+            commands.push ...[1..2].map (n) =>
+              `${aux}${n} = Intersect(${cr[0]}, ${cr[1]}, ${n})`
+            inPlane := cdata.is3d ? `Plane(${cr[0]})` : ''
+            ctr := cr.map (c) => `Center(${c})`
+            condition := (`Angle(${aux}1,${ctr[0]},${ctr[1]}${inPlane})`
+               + `< Angle(${aux}2,${ctr[0]},${ctr[1]}${inPlane})`)
+            commands.push
+              `${aux}3 = If(${condition}, ${aux}2, ${aux}1)`
+              `${aux}4 = If(${condition}, ${aux}1, ${aux}2)`
+            ends[0] = aux + 3
+            ends[1] = aux + 4
+            auxiliaries.push ...[1..4].map (n) => aux + n
+         'chord'
+            // To match Joyce, we need to get the ordering here correct.
+            // The complicated condition about distances is modeled after
+            // Joyce's code, but it boils down to: take the endpoint of the
+            // chord closest to the first subpoint, unless that first
+            // subpoint is essentially at the midpoint of the chord, in
+            // which case start with the endpoint nearest the second subpoint.
+            unless args.subpoints and args.circle then return
+            // We intersect with the whole line, not just the segment:
+            line := `Line(${args.subpoints.join ','})`
+            pA := args.subpoints[0]
+            pB := args.subpoints[1]
+            commands.push ...[1..2].map (n) =>
+              `${aux}${n} = Intersect(${args.circle}, ${line}, ${n})`
+            s := `Distance(${aux}1,${aux}2)`
+            d := `Distance(${aux}1,${pA}) - Distance(${aux}2,${pA})`
+            condition := (`If(${s}/10^9 < abs(${d}), ${d} > 0,`
+               + `Distance(${aux}2,${pB}) < Distance(${aux}1,${pB}))`)
+            commands.push
+              `${aux}3 = If(${condition}, ${aux}2, ${aux}1)`
+              `${aux}4 = If(${condition}, ${aux}1, ${aux}2)`
+            ends[0] = aux + 3
+            ends[1] = aux + 4
+            auxiliaries.push ...[1..4].map (n) => aux + n
          'connect'
             unless args.subpoints and args.subpoints.length is 2 then return
             ends[0] = args.subpoints[0]
             ends[1] = args.subpoints[1]
+         /cutoff|extend/
+            pt := args.subpoints
+            unless pt and pt.length is 4 then return
+            [source, displacement] :=
+               cutoffExtend method, pt, args.point, args.line
+            ends[0] = source
+            commands.push `${aux} = Translate(${source}, ${displacement})`
+            auxiliaries.push aux
+            ends[1] = aux
          'parallel'
             unless args.subpoints then return
             [newStart, oldStart, oldEnd] := args.subpoints
@@ -538,24 +711,41 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                madeSegment = true
             else
                commands.push `${aux}2 = Translate(${oldEnd}, ${aux}1)`
-         'chord'
+         'perpendicular'
-            // To match Joyce, we need to get the ordering here correct.
+            pt := args.subpoints
-            // ends[0] should be the one closer to args.subpoints[0]
+            unless pt then return
-            unless args.subpoints and args.circle then return
+            inPlane .= ''
-            line := `Line(${args.subpoints.join ','})`
+            if cdata.is3d
-            pt := args.subpoints[0]
+               unless args.plane?.length is 1 then return
-            commands.push ...[1..2].map (n) =>
+               inPlane = `,${args.plane[0]}`
-              `${aux}${n} = Intersect(${args.circle}, ${line}, ${n})`
+            switch pt.length
-            condition := `Distance(${aux}2,${pt}) < Distance(${aux}1,${pt})`
+               when 2
-            // NOTE: Joyce's code has special case for when pt is almost
+                  ends[0] = pt[0]
-            // at midpoint of chord; in that case, it starts at endpoint
+                  ends[1] = aux
-            // closer to the second subpoint... postponing that nicety
+                  auxiliaries.push aux
+                  if args.line?.length is 1
+                     ln := args.line[0]
                      commands.push
-              `${aux}3 = If(${condition}, ${aux}2, ${aux}1)`
+                        `${name} = Rotate(${ln}, 3*pi/2, ${pt[0]}${inPlane})`
-              `${aux}4 = If(${condition}, ${aux}1, ${aux}2)`
+                        `${aux} = Vertex(${name}, 2)`
-            ends[0] = aux + 3
+                     madeSegment = true
-            ends[1] = aux + 4
+                  else
-            auxiliaries.push ...[1..4].map (n) => aux + n
+                     commands.push
+                        `${aux} = Rotate(${pt[1]}, 3*pi/2, ${pt[0]}${inPlane})`
+               when 3
+                  return // TODO: line perpendicular to plane
+               when 4
+                  ends[0] = pt[0]
+                  ends[1] = aux + 2
+                  auxiliaries.push aux+1, aux+2
+                  commands.push
+                     `${aux}1 = Rotate(${pt[1]}, 3*pi/2, ${pt[0]}${inPlane})`
+                  unitVec := `UnitVector(Vector(${pt[0]}, ${aux}1))`
+                  dist := `Distance(${pt[2]}, ${pt[3]})`
+                  commands.push
+                     `${aux}2 = Translate(${pt[0]}, ${dist}*${unitVec})`
+               else return
+
       unless madeSegment
          commands.push `${name} = Segment(${ends[0]},${ends[1]})`
       callbacks.push (api: AppletObject) => api.setLabelVisible name, true
@@ -563,14 +753,27 @@ classHandler: Record<JoyceClass, ClassHandler> :=
 
    circle: (name, method, args) =>
       return := freshCommander()
-      {commands, callbacks, parts, auxiliaries} := return.value
+      return.value.ends = ['', '']
+      {commands, callbacks, parts, auxiliaries, ends} := return.value
       parts[2].push name
       parts[1].push name
       switch method
          'radius'
-            unless args.subpoints then return
+            pt := args.subpoints
-            [center, point] := args.subpoints
+            unless pt then return
-            commands.push `${name} = Circle(${center}, ${point})`
+            inPlane := args.plane ? `, ${args.plane[0]}` : ''
+            switch pt.length
+               when 2
+                  [center, point] := pt
+                  ends[0] = center
+                  commands.push
+                     `${name} = Circle(${center}, ${point}${inPlane})`
+               when 3
+                  center := pt[0]
+                  ends[0] = center
+                  radius := `Distance(${pt[1]}, ${pt[2]})`
+                  commands.push
+                     `${name} = Circle(${center}, ${radius}${inPlane})`
       callbacks.push (api: AppletObject) => api.setLabelVisible name, true
 
    polygon: (name, method, args, index) =>

src/adapptypes.civet

@@ -1,4 +1,5 @@
-export const flags = ['color', 'commands', 'showall', 'showaux'] as const
+export const flags = [
+   'color', 'commands', 'showall', 'showaux', 'algebra'] as const
 export type FlagType = (typeof flags)[number]
 export type ConfigType = Partial<Record<FlagType, boolean>>