perf: default GSK_RENDERER=ngl on Linux

GTK >= 4.22 defaults to the Vulkan renderer. On dual-GPU laptops where the
only Vulkan ICD is NVIDIA's (common Optimus setup), every window then renders
on the discrete GPU: realization wakes it from runtime suspend (~1s added to
first frame on every launch) and keeps it awake for the app's lifetime, even
though the display runs on the integrated GPU. The GL renderer follows the
compositor's device via Mesa/EGL and avoids all of it.

Set at require time, before GTK reads the variable; setting GSK_RENDERER
yourself (including '' for GTK's own choice) takes precedence.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: romgrk

lib/index.js

@@ -2,6 +2,18 @@
  * index.js
  */
 
+/* GTK ≥ 4.22 defaults to the Vulkan renderer. On Linux dual-GPU laptops where
+ * the only Vulkan ICD is NVIDIA's (a common Optimus setup), that renders every
+ * window on the discrete GPU: window realization then wakes it from runtime
+ * suspend (~1s added to first frame, on every launch once it re-suspends) and
+ * pins it awake — and drawing battery — for the app's lifetime, even though the
+ * display runs on the integrated GPU. The GL renderer picks the compositor's
+ * device via Mesa/EGL and has none of these problems. Opt out by setting
+ * GSK_RENDERER yourself (any value, including 'vulkan' or '' for GTK's choice);
+ * this runs at require time, before GTK can read the variable. */
+if (process.platform === 'linux' && process.env.GSK_RENDERER === undefined)
+  process.env.GSK_RENDERER = 'ngl'
+
 const internal = require('./native.js')
 const moduleCache = internal.GetModuleCache()