[fix] avoid PRIME offload on NVIDIA primary displays, refs #137

apps/desktop/src/platform/linux/gui/cuda_graphics.cpp

@@ -2,12 +2,62 @@
 
 #include <cstdlib>
 #include <initializer_list>
+#include <memory>
+#include <string_view>
+
+#include <X11/Xlib.h>
+#include <X11/extensions/Xrandr.h>
 
 #include "rd_log.h"
 
 #include "platform/common/gui/cuda_opengl_interop.h"
 
 namespace crossdesk {
+namespace {
+
+#if USE_CUDA && (defined(__x86_64__) || defined(__amd64__))
+bool HasNvidiaOffloadProvider() {
+  // CUDA availability says nothing about the X server's PRIME topology.
+  // In particular, NVIDIA-0 is a normal display provider, not an offload
+  // GPU screen. Forcing offload in that configuration can render into a GL
+  // buffer successfully while leaving the actual window blank.
+  const char* display_name = std::getenv("DISPLAY");
+  if (!display_name || display_name[0] == '\0') return false;
+  std::unique_ptr<Display, decltype(&XCloseDisplay)> display(
+      XOpenDisplay(display_name), XCloseDisplay);
+  if (!display) return false;
+
+  int major = 0, minor = 0;
+  if (!XRRQueryVersion(display.get(), &major, &minor) || major < 1 ||
+      (major == 1 && minor < 4)) return false;
+
+  const auto root = XDefaultRootWindow(display.get());
+  std::unique_ptr<XRRScreenResources, decltype(&XRRFreeScreenResources)> screen(
+      XRRGetScreenResourcesCurrent(display.get(), root), XRRFreeScreenResources);
+  std::unique_ptr<XRRProviderResources, decltype(&XRRFreeProviderResources)>
+      providers(XRRGetProviderResources(display.get(), root),
+                XRRFreeProviderResources);
+  if (!screen || !providers) return false;
+
+  for (int i = 0; i < providers->nproviders; ++i) {
+    std::unique_ptr<XRRProviderInfo, decltype(&XRRFreeProviderInfo)> provider(
+        XRRGetProviderInfo(display.get(), screen.get(), providers->providers[i]),
+        XRRFreeProviderInfo);
+    if (!provider || !provider->name || provider->nameLen <= 0) continue;
+    const std::string_view name(provider->name, provider->nameLen);
+    // NVIDIA documents offload GPU screens as NVIDIA-G0, NVIDIA-G1, etc.
+    // Their RandR capability mask can be zero, so SourceOffload is not a
+    // reliable test for the proprietary driver's offload support.
+    constexpr std::string_view prefix = "NVIDIA-G";
+    if (name.size() > prefix.size() && name.substr(0, prefix.size()) == prefix &&
+        name.find_first_not_of("0123456789", prefix.size()) ==
+            std::string_view::npos) return true;
+  }
+  return false;
+}
+#endif
+
+}  // namespace
 
 void ConfigureLinuxCudaGraphics() {
 #if USE_CUDA && (defined(__x86_64__) || defined(__amd64__))
@@ -28,6 +78,11 @@ void ConfigureLinuxCudaGraphics() {
     }
   }
 
+  if (!HasNvidiaOffloadProvider()) {
+    LOG_INFO("Keeping default Linux graphics selection: no NVIDIA PRIME "
+             "offload GPU screen");
+    return;
+  }
   if (!IsCudaDeviceAvailable()) {
     return;
   }