it was actually not that hard

build.gradle

@@ -20,7 +20,7 @@ apply plugin: 'net.minecraftforge.gradle'
 apply plugin: 'org.parchmentmc.librarian.forgegradle'
 apply plugin: 'org.spongepowered.mixin'
 
-version = '0.7.0-dev.4'
+version = '0.7.0-dev.5'
 group = 'at.petra-k.hexcasting' // http://maven.apache.org/guides/mini/guide-naming-conventions.html
 archivesBaseName = 'hexcasting'
 

src/main/java/at/petrak/hexcasting/client/entity/WallScrollRenderer.java

@@ -1,5 +1,6 @@
 package at.petrak.hexcasting.client.entity;
 
+import at.petrak.hexcasting.HexConfig;
 import at.petrak.hexcasting.HexMod;
 import at.petrak.hexcasting.common.entities.EntityWallScroll;
 import com.mojang.blaze3d.systems.RenderSystem;
@@ -98,6 +99,7 @@ public class WallScrollRenderer extends EntityRenderer<EntityWallScroll> {
         }
 
         if (wallScroll.zappyPoints != null) {
+            var points = wallScroll.zappyPoints;
             ps.pushPose();
 
             ps.mulPose(Vector3f.YP.rotationDegrees(180f));
@@ -111,9 +113,38 @@ public class WallScrollRenderer extends EntityRenderer<EntityWallScroll> {
             var outer = 0xff_d2c8c8;
             var inner = 0xc8_322b33;
             var verts = bufSource.getBuffer(RenderType.entityCutout(WHITE));
-            theCoolerDrawLineSeq(mat, norm, light, verts, wallScroll.zappyPoints, 5, outer);
+            theCoolerDrawLineSeq(mat, norm, light, verts, points, 5, outer);
             ps.translate(0, 0, 0.01);
-            theCoolerDrawLineSeq(mat, norm, light, verts, wallScroll.zappyPoints, 2, inner);
+            theCoolerDrawLineSeq(mat, norm, light, verts, points, 2, inner);
+
+            if (wallScroll.getShowsStrokeOrder()) {
+                var animTime = wallScroll.tickCount;
+                var pointCircuit =
+                    (animTime * HexConfig.Client.patternPointSpeedMultiplier.get()) % (points.size() + 10);
+                if (pointCircuit < points.size() - 1) {
+                    var pointMacro = Mth.floor(pointCircuit);
+                    var pointMicro = pointCircuit - pointMacro;
+
+                    var p1 = points.get(pointMacro);
+                    var p2 = points.get((pointMacro + 1) % points.size());
+                    var drawPos = new Vec2(
+                        (float) (p1.x + (p2.x - p1.x) * pointMicro),
+                        (float) (p1.y + (p2.y - p1.y) * pointMicro)
+                    );
+                    
+                    ps.translate(0, 0, 0.01);
+                    theCoolerDrawSpot(mat, norm, light, verts, drawPos, 2.6666f, 0xff_cfa0f3);
+                    ps.translate(0, 0, 0.01);
+                    theCoolerDrawSpot(mat, norm, light, verts, drawPos, 2f, 0xff_8d6acc);
+                } else {
+                    ps.translate(0, 0, 0.02);
+                }
+
+                ps.translate(0, 0, 0.01);
+                theCoolerDrawSpot(mat, norm, light, verts, points.get(0), 3f, 0xff_4946d3);
+                ps.translate(0, 0, 0.01);
+                theCoolerDrawSpot(mat, norm, light, verts, points.get(0), 2f, 0xff_5b7bd7);
+            }
 
             ps.popPose();
         }
@@ -203,4 +234,21 @@ public class WallScrollRenderer extends EntityRenderer<EntityWallScroll> {
             prevYLo = yLo;
         }
     }
+
+    private static void theCoolerDrawSpot(Matrix4f mat, Matrix3f normal, int light, VertexConsumer verts,
+        Vec2 point, float radius, int color) {
+        var fracOfCircle = 6;
+        for (int i = 0; i < fracOfCircle; i++) {
+            // We do need rects, irritatingly
+            // so we do fake triangles
+            vertexCol(mat, normal, light, verts, color, point.x, point.y);
+            vertexCol(mat, normal, light, verts, color, point.x, point.y);
+            for (int j = 0; j <= 1; j++) {
+                var theta = (i - j) / (float) fracOfCircle * Mth.TWO_PI;
+                var rx = Mth.cos(theta) * radius + point.x;
+                var ry = Mth.sin(theta) * radius + point.y;
+                vertexCol(mat, normal, light, verts, color, rx, ry);
+            }
+        }
+    }
 }

src/main/java/at/petrak/hexcasting/common/entities/EntityWallScroll.java

@@ -1,14 +1,22 @@
 package at.petrak.hexcasting.common.entities;
 
 import at.petrak.hexcasting.client.RenderLib;
+import at.petrak.hexcasting.common.items.HexItems;
 import at.petrak.hexcasting.common.items.ItemScroll;
+import at.petrak.hexcasting.common.lib.HexSounds;
 import at.petrak.hexcasting.hexmath.HexPattern;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.protocol.Packet;
+import net.minecraft.network.syncher.EntityDataAccessor;
+import net.minecraft.network.syncher.EntityDataSerializers;
+import net.minecraft.network.syncher.SynchedEntityData;
 import net.minecraft.sounds.SoundEvents;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.entity.decoration.HangingEntity;
@@ -18,6 +26,7 @@ import net.minecraft.world.level.GameRules;
 import net.minecraft.world.level.Level;
 import net.minecraft.world.phys.HitResult;
 import net.minecraft.world.phys.Vec2;
+import net.minecraft.world.phys.Vec3;
 import net.minecraftforge.entity.IEntityAdditionalSpawnData;
 import net.minecraftforge.network.NetworkHooks;
 import org.jetbrains.annotations.Nullable;
@@ -25,6 +34,10 @@ import org.jetbrains.annotations.Nullable;
 import java.util.List;
 
 public class EntityWallScroll extends HangingEntity implements IEntityAdditionalSpawnData {
+    private static final EntityDataAccessor<Boolean> SHOWS_STROKE_ORDER = SynchedEntityData.defineId(
+        EntityWallScroll.class,
+        EntityDataSerializers.BOOLEAN);
+
     public ItemStack scroll;
     public HexPattern pattern;
     public List<Vec2> zappyPoints;
@@ -58,6 +71,20 @@ public class EntityWallScroll extends HangingEntity implements IEntityAdditional
         }
     }
 
+    @Override
+    protected void defineSynchedData() {
+        super.defineSynchedData();
+        this.entityData.define(SHOWS_STROKE_ORDER, false);
+    }
+
+    public boolean getShowsStrokeOrder() {
+        return this.entityData.get(SHOWS_STROKE_ORDER);
+    }
+
+    public void setShowsStrokeOrder(boolean b) {
+        this.entityData.set(SHOWS_STROKE_ORDER, b);
+    }
+
     @Override
     public int getWidth() {
         return 48;
@@ -82,6 +109,21 @@ public class EntityWallScroll extends HangingEntity implements IEntityAdditional
         }
     }
 
+    @Override
+    public InteractionResult interactAt(Player pPlayer, Vec3 pVec, InteractionHand pHand) {
+        var handStack = pPlayer.getItemInHand(pHand);
+        if (handStack.is(HexItems.AMETHYST_DUST.get()) && !this.getShowsStrokeOrder()) {
+            if (!pPlayer.getAbilities().instabuild) {
+                handStack.shrink(1);
+            }
+            this.setShowsStrokeOrder(true);
+
+            pPlayer.level.playSound(pPlayer, this, HexSounds.DUST_SCROLL.get(), SoundSource.PLAYERS, 1f, 1f);
+            return InteractionResult.SUCCESS;
+        }
+        return super.interactAt(pPlayer, pVec, pHand);
+    }
+
     @Override
     public void playPlacementSound() {
         this.playSound(SoundEvents.PAINTING_PLACE, 1.0F, 1.0F);
@@ -96,12 +138,15 @@ public class EntityWallScroll extends HangingEntity implements IEntityAdditional
     public void writeSpawnData(FriendlyByteBuf buf) {
         buf.writeVarInt(this.direction.ordinal());
         buf.writeItem(this.scroll);
+        buf.writeBoolean(this.getShowsStrokeOrder());
     }
 
     @Override
     public void readSpawnData(FriendlyByteBuf buf) {
         this.direction = Direction.values()[buf.readVarInt()];
         var scroll = buf.readItem();
+        this.setShowsStrokeOrder(buf.readBoolean());
+
         this.loadDataFromScrollItem(scroll);
         this.setDirection(this.direction);
     }
@@ -110,6 +155,7 @@ public class EntityWallScroll extends HangingEntity implements IEntityAdditional
     public void addAdditionalSaveData(CompoundTag tag) {
         tag.putByte("direction", (byte) this.direction.ordinal());
         tag.put("scroll", this.scroll.serializeNBT());
+        tag.putBoolean("showsStrokeOrder", this.getShowsStrokeOrder());
         super.addAdditionalSaveData(tag);
     }
 
@@ -117,6 +163,8 @@ public class EntityWallScroll extends HangingEntity implements IEntityAdditional
     public void readAdditionalSaveData(CompoundTag tag) {
         this.direction = Direction.values()[tag.getByte("direction")];
         var scroll = ItemStack.of(tag.getCompound("scroll"));
+        this.setShowsStrokeOrder(tag.getBoolean("showsStrokeOrder"));
+
         super.readAdditionalSaveData(tag);
         this.setDirection(this.direction);
         this.loadDataFromScrollItem(scroll);

src/main/java/at/petrak/hexcasting/common/lib/HexSounds.java

@@ -27,6 +27,8 @@ public class HexSounds {
     public static final RegistryObject<SoundEvent> SPELL_CIRCLE_FAIL = sound("spellcircle.fail");
     public static final RegistryObject<SoundEvent> SPELL_CIRCLE_CAST = sound("spellcircle.cast");
 
+    public static final RegistryObject<SoundEvent> DUST_SCROLL = sound("scroll.dust");
+
     private static RegistryObject<SoundEvent> sound(String name) {
         return SOUNDS.register(name, () -> new SoundEvent(prefix(name)));
     }

src/main/resources/assets/hexcasting/lang/en_us.json

@@ -239,6 +239,7 @@
   "hexcasting.subtitles.spellcircle.add_pattern": "Spell circle crackles",
   "hexcasting.subtitles.spellcircle.fail": "Spell circle fizzles out",
   "hexcasting.subtitles.spellcircle.cast": "Spell circle casts",
+  "hexcasting.subtitles.scroll.dust": "Scroll covers with dust",
 
   "hexcasting.landing": "I seem to have discovered a new method of magical arts, in which one draws patterns strange and wild onto a hexagonal grid. It fascinates me. I've decided to start a journal of my thoughts and findings.$(br2)$(l:https://discord.gg/4xxHGYteWk)Discord Server Link/$",
 
@@ -372,7 +373,7 @@
   "hexcasting.page.spellbook.2": "$(italic)Wizards love words. Most of them read a great deal, and indeed one strong sign of a potential wizard is the inability to get to sleep without reading something first.",
 
   "hexcasting.entry.scroll": "Scrolls",
-  "hexcasting.page.scroll.1": "A $(item)Scroll/$ is a convenient method of sharing a pattern with others. I can copy a pattern onto one with $(l:patterns/readwrite#hexcasting:write)Scribe's Gambit/$, after which it will display in a tooltip.$(br2)I can also place them on the wall as decoration, like a Painting.",
+  "hexcasting.page.scroll.1": "A $(item)Scroll/$ is a convenient method of sharing a pattern with others. I can copy a pattern onto one with $(l:patterns/readwrite#hexcasting:write)$(action)Scribe's Gambit/$, after which it will display in a tooltip.$(br2)I can also place them on the wall as decoration, like a Painting. Using $(item)Amethyst Dust/$ on such a scroll will have it display the stroke order.",
   "hexcasting.page.scroll.2": "In addition, I can also find so-called $(item)Ancient Scrolls/$ in the dungeons and strongholds of the world. These contain the stroke order of Great Spells, powerful magicks rumored to be too powerful for the hands and minds of mortals...$(br2)If those \"mortals\" couldn't cast them, I'm not sure they deserve to know them.",
   "hexcasting.page.scroll.3": "$(italic)I write upon clean white parchment with a sharp quill and the blood of my students, divining their secrets./$",
 

src/main/resources/assets/hexcasting/sounds.json

@@ -82,5 +82,15 @@
       "hexcasting:cast_hex"
     ],
     "subtitle": "hexcasting.subtitles.spellcircle.cast"
+  },
+
+  "scroll.dust": {
+    "sounds": [
+      "minecraft:dig/sand1",
+      "minecraft:dig/sand2",
+      "minecraft:dig/sand3",
+      "minecraft:dig/sand4"
+    ],
+    "subtitle": "hexcasting.subtitles.scroll.dust"
   }
 }