fix offset bug; we want the same image independently of the slight translation we apply on lower DPI screens

Author: Fil

src/marks/hexgrid.js

@@ -1,7 +1,7 @@
 import {create} from "../context.js";
 import {Mark} from "../mark.js";
 import {number, singleton} from "../options.js";
-import {applyChannelStyles, applyDirectStyles, applyIndirectStyles, applyTransform, offset} from "../style.js";
+import {applyChannelStyles, applyDirectStyles, applyIndirectStyles, applyTransform} from "../style.js";
 import {sqrt4_3} from "../symbol.js";
 import {ox, oy} from "../transforms/hexbin.js";
 
@@ -47,7 +47,7 @@ export class Hexgrid extends Mark {
     return create("svg:g", context)
       .datum(0)
       .call(applyIndirectStyles, this, dimensions, context)
-      .call(applyTransform, this, {}, offset + ox, offset + oy)
+      .call(applyTransform, this, {}, ox, oy)
       .call((g) => g.append("path").call(applyDirectStyles, this).call(applyChannelStyles, this, channels).attr("d", d))
       .node();
   }

src/transforms/hexbin.js

@@ -1,5 +1,6 @@
 import {map, number, valueof} from "../options.js";
 import {applyPosition} from "../projection.js";
+import {offset} from "../style.js";
 import {sqrt3} from "../symbol.js";
 import {initializer} from "./basic.js";
 import {hasOutput, maybeGroup, maybeGroupOutputs, maybeSubgroup} from "./group.js";
@@ -9,8 +10,8 @@ import {hasOutput, maybeGroup, maybeGroupOutputs, maybeSubgroup} from "./group.j
 // to be rounded up into a floating bin to the right of the plot. Therefore,
 // rather than centering the origin hexagon around ⟨0,0⟩ in screen coordinates,
 // we offset slightly to ⟨0.5,0⟩. The hexgrid mark uses the same origin.
-export const ox = 0.5,
-  oy = 0;
+export const ox = 0.5 - offset;
+export const oy = -offset;
 
 export function hexbin(outputs = {fill: "count"}, {binWidth, ...options} = {}) {
   const {z} = options;