Update shell/common/platform_util_linux.cc

Co-authored-by: Charles Kerr <charles@charleskerr.com>

shell/browser/electron_browser_main_parts.cc

@@ -375,8 +375,24 @@ void ElectronBrowserMainParts::PostDestroyThreads() {
   fake_browser_process_->PostDestroyThreads();
 }
 
+#if defined(OS_LINUX)
+// static
+absl::optional<std::string>& ElectronBrowserMainParts::GetGDKBackend() {
+  static absl::optional<std::string> gdk_backend;
+  return gdk_backend;
+}
+#endif
+
 void ElectronBrowserMainParts::ToolkitInitialized() {
 #if defined(OS_LINUX)
+  // This is set by Chromium here:
+  // https://chromium-review.googlesource.com/c/chromium/src/+/2586184
+  // and can detrimentally affect external app behaviors, so we want to
+  // check if the user has set it so we can use it later.
+  std::string backend;
+  if (base::Environment::Create()->GetVar("GDK_BACKEND", &backend))
+    GetGDKBackend() = backend;
+
   auto linux_ui = BuildGtkUi();
   linux_ui->Initialize();
 

shell/browser/electron_browser_main_parts.h

@@ -6,6 +6,7 @@
 #define SHELL_BROWSER_ELECTRON_BROWSER_MAIN_PARTS_H_
 
 #include <memory>
+#include <string>
 
 #include "base/callback.h"
 #include "base/metrics/field_trial.h"
@@ -88,6 +89,11 @@ class ElectronBrowserMainParts : public content::BrowserMainParts {
   Browser* browser() { return browser_.get(); }
   BrowserProcessImpl* browser_process() { return fake_browser_process_.get(); }
 
+#if defined(OS_LINUX)
+  // Used by platform_util to set GDK_BACKEND.
+  static absl::optional<std::string>& GetGDKBackend();
+#endif
+
  protected:
   // content::BrowserMainParts:
   int PreEarlyInitialization() override;

shell/common/platform_util_linux.cc

@@ -19,6 +19,7 @@
 #include "dbus/bus.h"
 #include "dbus/message.h"
 #include "dbus/object_proxy.h"
+#include "shell/browser/electron_browser_main_parts.h"
 #include "shell/common/platform_util_internal.h"
 #include "ui/gtk/gtk_util.h"
 #include "url/gurl.h"
@@ -122,6 +123,16 @@ bool XDGUtil(const std::vector<std::string>& argv,
   // bring up a new terminal if necessary.  See "man mailcap".
   options.environment["MM_NOTTTY"] = "1";
 
+  // If the user set a GDK_BACKEND value of their own, use that,
+  // otherwise unset it becuase Chromium is setting GDK_BACKEND
+  // during GTK initialization and we want to respect user preference.
+  // Setting values in EnvironmentMap to an empty-string
+  // will make sure that they get unset from the environment via
+  // AlterEnvironment().
+  const absl::optional<std::string>& gdk_backend =
+      electron::ElectronBrowserMainParts::GetGDKBackend();
+  options.environment["GDK_BACKEND"] = gdk_backend ? *gdk_backend : std::string{};
+
   base::Process process = base::LaunchProcess(argv, options);
   if (!process.IsValid())
     return false;

spec-main/chromium-spec.ts

@@ -367,6 +367,66 @@ describe('web security', () => {
   });
 });
 
+ifdescribe(process.platform === 'linux')('subprocesses', () => {
+  let appProcess: ChildProcess.ChildProcessWithoutNullStreams | undefined;
+  afterEach(() => {
+    if (appProcess && !appProcess.killed) {
+      appProcess.kill();
+      appProcess = undefined;
+    }
+  });
+
+  it('does not propagate GDK_BACKEND', async () => {
+    const appPath = path.join(fixturesPath, 'api', 'gdk-backend-check');
+    appProcess = ChildProcess.spawn(process.execPath, [appPath], {
+      env: {
+        GDK_BACKEND: ''
+      }
+    });
+
+    let output = '';
+    appProcess.stdout.on('data', (data) => { output += data; });
+    let stderr = '';
+    appProcess.stderr.on('data', (data) => { stderr += data; });
+
+    const [code, signal] = await emittedOnce(appProcess, 'exit');
+    if (code !== 0) {
+      throw new Error(`Process exited with code "${code}" signal "${signal}" output "${output}" stderr "${stderr}"`);
+    }
+
+    output = output.replace(/(\r\n|\n|\r)/gm, '');
+
+    const backend = String(process.env.GDK_BACKEND);
+    expect(output).to.not.equal(backend);
+    expect(output).to.be.empty();
+  });
+
+  it('successfully honors GDK_BACKEND set in the subproc', async () => {
+    const appPath = path.join(fixturesPath, 'api', 'gdk-backend-check');
+    appProcess = ChildProcess.spawn(process.execPath, [appPath], {
+      env: {
+        GDK_BACKEND: 'wayland'
+      }
+    });
+
+    let output = '';
+    appProcess.stdout.on('data', (data) => { output += data; });
+    let stderr = '';
+    appProcess.stderr.on('data', (data) => { stderr += data; });
+
+    const [code, signal] = await emittedOnce(appProcess, 'exit');
+    if (code !== 0) {
+      throw new Error(`Process exited with code "${code}" signal "${signal}" output "${output}" stderr "${stderr}"`);
+    }
+
+    output = output.replace(/(\r\n|\n|\r)/gm, '');
+
+    const backend = String(process.env.GDK_BACKEND);
+    expect(output).to.not.equal(backend);
+    expect(output).to.equal('wayland');
+  });
+});
+
 describe('command line switches', () => {
   let appProcess: ChildProcess.ChildProcessWithoutNullStreams | undefined;
   afterEach(() => {

spec/fixtures/api/gdk-backend-check/main.js

@@ -0,0 +1,8 @@
+const { app } = require('electron');
+
+app.whenReady().then(() => {
+  process.stdout.write(String(process.env.GDK_BACKEND));
+  process.stdout.end();
+
+  app.quit();
+});

spec/fixtures/api/gdk-backend-check/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "electron-test-gdk-backend-check",
+  "main": "main.js"
+}
+