test: add unit test for display of font size

src/lib/components/ToolbarExpanded.svelte

@@ -18,7 +18,7 @@
   import type { Orientation } from '../storage/pageOrientation';
   import { pageDimsCm, PAGE_FORMAT_CM, type PageFormat } from '../storage/pageFormat';
   import { DEFAULT_HF_DISTANCES, clampHfDistance, type HfDistances } from '../storage/headerFooter';
-  import { HEADING_STYLE_OVERRIDES } from '../export/odt';
+  import { blockFontSize, DEFAULT_FONT_SIZE, type SizedBlock } from '../utils/fontSize';
   import { listContext } from '../editor/extensions/indent';
   import { findColumns, DEFAULT_COLUMN_GAP_CM } from '../editor/extensions/columns';
   import { t } from '../i18n/i18n.svelte';
@@ -129,27 +129,11 @@
     return mixed ? '' : (font ?? DEFAULT_EDITOR_FONT);
   });
 
-  // Must match the common document default; heading sizes come from the export overrides
-  // (the single source editor.css and both importers agree with).
-  const DEFAULT_FONT_SIZE = '12pt';
-  const HEADING_SIZES: Record<number, string> =
-    Object.fromEntries(HEADING_STYLE_OVERRIDES.map((h, i) => [i + 1, h.fontSize]));
   const FONT_SIZES = [8, 9, 10, 11, 12, 14, 16, 18, 20, 24, 28, 36, 48, 72];
 
-  type SizedBlock = { type: { name: string }; attrs: Record<string, unknown> } | null;
-
-  // What a block renders its unmarked text at: its paragraph-mark size (blockFontSize,
-  // set by the style gallery and by imported sized lines), else the heading/body default.
-  function blockSize(parent: SizedBlock): string {
-    const block = parent?.attrs?.fontSize;
-    if (typeof block === 'string' && block) return block;
-    if (parent?.type.name === 'heading') return HEADING_SIZES[Number(parent.attrs.level)] ?? DEFAULT_FONT_SIZE;
-    return DEFAULT_FONT_SIZE;
-  }
-
   function effectiveSize(node: { isText: boolean; marks: readonly { type: { name: string }; attrs: Record<string, string> }[] }, parent: SizedBlock): string {
     const explicit = node.marks.find(m => m.type.name === 'textStyle')?.attrs.fontSize;
-    return explicit || blockSize(parent);
+    return explicit || blockFontSize(parent);
   }
 
   let currentFontSize = $derived.by(() => {
@@ -160,7 +144,7 @@
       const marks = editor.state.storedMarks ?? head.marks();
       const explicit = marks.find(m => m.type.name === 'textStyle')?.attrs.fontSize;
       if (explicit) return explicit;
-      return blockSize(head.parent as SizedBlock);
+      return blockFontSize(head.parent as SizedBlock);
     }
     let size: string | undefined;
     let mixed = false;

src/lib/utils/fontSize.ts

@@ -0,0 +1,19 @@
+import { HEADING_STYLE_OVERRIDES } from '../export/odt';
+
+// The size a block renders its unmarked text at — what the toolbar's size box must show.
+// Keep in sync with editor.css (tests/unit/font-size-display.test.ts asserts it).
+
+export const DEFAULT_FONT_SIZE = '12pt';
+
+export const HEADING_SIZES: Record<number, string> =
+  Object.fromEntries(HEADING_STYLE_OVERRIDES.map((h, i) => [i + 1, h.fontSize]));
+
+export type SizedBlock = { type: { name: string }; attrs?: Record<string, unknown> } | null;
+
+// Paragraph-mark size (blockFontSize attr) wins, else the heading/body default.
+export function blockFontSize(block: SizedBlock): string {
+  const explicit = block?.attrs?.fontSize;
+  if (typeof explicit === 'string' && explicit) return explicit;
+  if (block?.type.name === 'heading') return HEADING_SIZES[Number(block.attrs?.level)] ?? DEFAULT_FONT_SIZE;
+  return DEFAULT_FONT_SIZE;
+}