refactor: remove unused withTransparentBackground theme helper

.changeset/remove-transparent-background-helper.md

@@ -0,0 +1,2 @@
+---
+---

src/ui/diff/pierre.test.ts

@@ -14,7 +14,7 @@ import { renderCodeOnlyPlannedRowText, renderDecoratedPlannedRowText } from "./r
 import { stackCellPalette } from "./rowStyle";
 import { buildReviewRenderPlan } from "./reviewRenderPlan";
 import { measureTextWidth } from "../lib/text";
-import { TRANSPARENT_BACKGROUND, resolveTheme, withTransparentBackground } from "../themes";
+import { TRANSPARENT_BACKGROUND, resolveTheme } from "../themes";
 
 function createDiffFile(): DiffFile {
   const metadata = parseDiffFromFile(
@@ -147,9 +147,17 @@ describe("Pierre diff rows", () => {
     ).toBe(true);
   });
 
-  test("keeps word-diff highlight backgrounds transparent in transparent mode", async () => {
+  test("keeps word-diff highlight backgrounds transparent when a theme uses transparent tints", async () => {
     const file = createDiffFile();
-    const theme = withTransparentBackground(resolveTheme("github-dark-default", null));
+    // Custom themes may declare "transparent" row/content tints; the renderer must not feed
+    // them into blend math and turn them into black backgrounds.
+    const theme = {
+      ...resolveTheme("github-dark-default", null),
+      addedBg: TRANSPARENT_BACKGROUND,
+      removedBg: TRANSPARENT_BACKGROUND,
+      addedContentBg: TRANSPARENT_BACKGROUND,
+      removedContentBg: TRANSPARENT_BACKGROUND,
+    };
     const highlighted = await loadHighlightedDiff(file);
     const rows = buildSplitRows(file, highlighted, theme);
     const changedRow = rows.find(

src/ui/themes.test.ts

@@ -8,7 +8,6 @@ import {
   DEFAULT_LIGHT_THEME_ID,
   resolveTheme,
   TRANSPARENT_BACKGROUND,
-  withTransparentBackground,
   withTransparentSurfaces,
 } from "./themes";
 
@@ -247,35 +246,6 @@ describe("themes", () => {
     expect(custom.syntaxColors.keyword).toBe("#ff00ff");
   });
 
-  test("withTransparentBackground only swaps painted background fields", () => {
-    const theme = resolveTheme("github-dark-default", null);
-    const transparent = withTransparentBackground(theme);
-
-    expect(transparent).toMatchObject({
-      background: TRANSPARENT_BACKGROUND,
-      panel: TRANSPARENT_BACKGROUND,
-      panelAlt: TRANSPARENT_BACKGROUND,
-      addedBg: TRANSPARENT_BACKGROUND,
-      removedBg: TRANSPARENT_BACKGROUND,
-      contextBg: TRANSPARENT_BACKGROUND,
-      addedContentBg: TRANSPARENT_BACKGROUND,
-      removedContentBg: TRANSPARENT_BACKGROUND,
-      contextContentBg: TRANSPARENT_BACKGROUND,
-      lineNumberBg: TRANSPARENT_BACKGROUND,
-      selectedHunk: TRANSPARENT_BACKGROUND,
-      noteBackground: TRANSPARENT_BACKGROUND,
-      noteTitleBackground: TRANSPARENT_BACKGROUND,
-    });
-    expect(transparent.id).toBe(theme.id);
-    expect(transparent.label).toBe(theme.label);
-    expect(transparent.text).toBe(theme.text);
-    expect(transparent.muted).toBe(theme.muted);
-    expect(transparent.addedSignColor).toBe(theme.addedSignColor);
-    expect(transparent.removedSignColor).toBe(theme.removedSignColor);
-    expect(transparent.syntaxColors).toBe(theme.syntaxColors);
-    expect(theme.background).not.toBe(TRANSPARENT_BACKGROUND);
-  });
-
   test("withTransparentSurfaces keeps added/removed row tints", () => {
     const theme = resolveTheme("github-dark-default", null);
     const transparent = withTransparentSurfaces(theme);

src/ui/themes.ts

@@ -352,30 +352,10 @@ export function bundledThemeDiffColors(themeId: string): BundledShikiThemeDiffCo
   return getBundledShikiThemeDiffColors(themeId);
 }
 
-/** Return a copy of a theme whose painted surfaces allow the terminal background through. */
-export function withTransparentBackground(theme: AppTheme): AppTheme {
-  return {
-    ...theme,
-    background: TRANSPARENT_BACKGROUND,
-    panel: TRANSPARENT_BACKGROUND,
-    panelAlt: TRANSPARENT_BACKGROUND,
-    addedBg: TRANSPARENT_BACKGROUND,
-    removedBg: TRANSPARENT_BACKGROUND,
-    contextBg: TRANSPARENT_BACKGROUND,
-    addedContentBg: TRANSPARENT_BACKGROUND,
-    removedContentBg: TRANSPARENT_BACKGROUND,
-    contextContentBg: TRANSPARENT_BACKGROUND,
-    lineNumberBg: TRANSPARENT_BACKGROUND,
-    selectedHunk: TRANSPARENT_BACKGROUND,
-    noteBackground: TRANSPARENT_BACKGROUND,
-    noteTitleBackground: TRANSPARENT_BACKGROUND,
-  };
-}
-
 /**
  * Return a copy of a theme whose neutral surfaces allow the terminal background through while
- * added/removed row tints stay painted. Static pager hosts use this so diff rows keep their
- * semantic backgrounds on translucent terminals.
+ * added/removed row tints stay painted. Both the interactive TUI and static pager hosts use
+ * this so diff rows keep their semantic backgrounds on translucent terminals.
  */
 export function withTransparentSurfaces(theme: AppTheme): AppTheme {
   return {