fix(inkscape): use xvfb-run for headless execution

- Inkscape requires X11 display connection, causing 'GtkStyleContext without display' error
- Solution: use xvfb-run to create virtual X11 display
- Fallback: try direct inkscape if xvfb-run fails
- Add xvfb package to Dockerfile
- Update inkscape tests for new xvfb-run behavior

Fixes: Gtk-ERROR: Can't create a GtkStyleContext without a display connection

tests/converters/inkscape.test.ts

@@ -1,7 +1,117 @@
-import { test } from "bun:test";
+import { test, expect } from "bun:test";
 import { convert } from "../../src/converters/inkscape";
-import { runCommonTests } from "./helpers/commonTests";
+import type { ExecFileException } from "node:child_process";
+import { ExecFileFn } from "../../src/converters/types";
 
-runCommonTests(convert);
+// Inkscape 使用 xvfb-run 包裝，需要自訂測試
+// 模擬 xvfb-run 成功執行的情況
+
+test("convert resolves when xvfb-run succeeds", async () => {
+  const mockExecFile: ExecFileFn = (
+    cmd: string,
+    _args: string[],
+    callback: (err: ExecFileException | null, stdout: string, stderr: string) => void,
+  ) => {
+    // xvfb-run 成功
+    if (cmd === "xvfb-run") {
+      callback(null, "Conversion complete", "");
+    }
+  };
+
+  const result = await convert("input.svg", "svg", "png", "output.png", undefined, mockExecFile);
+  expect(result).toBe("Done");
+});
+
+test("convert falls back to direct inkscape when xvfb-run fails", async () => {
+  let callCount = 0;
+
+  const mockExecFile: ExecFileFn = (
+    cmd: string,
+    _args: string[],
+    callback: (err: ExecFileException | null, stdout: string, stderr: string) => void,
+  ) => {
+    callCount++;
+    if (cmd === "xvfb-run") {
+      // xvfb-run 失敗
+      callback(new Error("xvfb-run not found"), "", "");
+    } else if (cmd === "inkscape") {
+      // 直接呼叫 inkscape 成功
+      callback(null, "Direct inkscape success", "");
+    }
+  };
+
+  const result = await convert("input.svg", "svg", "png", "output.png", undefined, mockExecFile);
+  expect(result).toBe("Done");
+  expect(callCount).toBe(2); // 應該呼叫兩次（xvfb-run + inkscape）
+});
+
+test("convert rejects when both xvfb-run and inkscape fail", async () => {
+  const mockExecFile: ExecFileFn = (
+    cmd: string,
+    _args: string[],
+    callback: (err: ExecFileException | null, stdout: string, stderr: string) => void,
+  ) => {
+    if (cmd === "xvfb-run") {
+      callback(new Error("xvfb-run failed"), "", "");
+    } else if (cmd === "inkscape") {
+      callback(new Error("inkscape failed"), "", "");
+    }
+  };
+
+  await expect(
+    convert("input.svg", "svg", "png", "output.png", undefined, mockExecFile),
+  ).rejects.toMatch(/error:/);
+});
+
+test("convert logs stdout when present", async () => {
+  const originalConsoleLog = console.log;
+  let loggedMessage = "";
+  console.log = (msg: string) => {
+    if (msg.startsWith("stdout:")) {
+      loggedMessage = msg;
+    }
+  };
+
+  const mockExecFile: ExecFileFn = (
+    cmd: string,
+    _args: string[],
+    callback: (err: ExecFileException | null, stdout: string, stderr: string) => void,
+  ) => {
+    if (cmd === "xvfb-run") {
+      callback(null, "Fake stdout", "");
+    }
+  };
+
+  await convert("input.svg", "svg", "png", "output.png", undefined, mockExecFile);
+  console.log = originalConsoleLog;
+
+  expect(loggedMessage).toBe("stdout: Fake stdout");
+});
+
+test("convert logs stderr when present (non-fatal warning)", async () => {
+  const originalConsoleLog = console.log;
+  let loggedMessage = "";
+  console.log = (msg: string) => {
+    if (msg.startsWith("stderr:")) {
+      loggedMessage = msg;
+    }
+  };
+
+  const mockExecFile: ExecFileFn = (
+    cmd: string,
+    _args: string[],
+    callback: (err: ExecFileException | null, stdout: string, stderr: string) => void,
+  ) => {
+    if (cmd === "xvfb-run") {
+      // Inkscape 經常輸出警告到 stderr，但轉換仍成功
+      callback(null, "", "Gtk-WARNING: some warning");
+    }
+  };
+
+  await convert("input.svg", "svg", "png", "output.png", undefined, mockExecFile);
+  console.log = originalConsoleLog;
+
+  expect(loggedMessage).toBe("stderr: Gtk-WARNING: some warning");
+});
 
 test.skip("dummy - required to trigger test detection", () => {});