[video_core] Properly disable/avoid building OpenGL when it's disabled (#3692)

- OpenGL symbols would still be included in builds without OpenGL, this pr fixes that
- Same goes for Vulkan, but now with `ENABLE_VULKAN`
- Add support to have OpenGL-only builds (why would you do this?)
- Add support for headless runs (yes you could just select NULL backend, but why not compile it headless? :)

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3692
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: DraVee <chimera@dravee.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

src/yuzu/bootmanager.cpp

@@ -1020,8 +1020,7 @@ bool GRenderWindow::InitializeOpenGL() {
 
     return true;
 #else
-    QMessageBox::warning(this, tr("OpenGL not available!"),
-                         tr("Eden has not been compiled with OpenGL support."));
+    QMessageBox::warning(this, tr("OpenGL not available!"), tr("Eden has not been compiled with OpenGL support."));
     return false;
 #endif
 }
@@ -1031,7 +1030,6 @@ bool GRenderWindow::InitializeVulkan() {
     child_widget = child;
     child_widget->windowHandle()->create();
     main_context = std::make_unique<DummyContext>();
-
     return true;
 }
 

src/yuzu/main_window.cpp

@@ -3784,14 +3784,30 @@ void MainWindow::OnToggleAdaptingFilter() {
 
 void MainWindow::OnToggleGraphicsAPI() {
     auto api = Settings::values.renderer_backend.GetValue();
-    if (api != Settings::RendererBackend::Vulkan) {
-        api = Settings::RendererBackend::Vulkan;
-    } else {
+    switch (api) {
 #ifdef HAS_OPENGL
+    case Settings::RendererBackend::Vulkan:
         api = Settings::RendererBackend::OpenGL_GLSL;
-#else
+        break;
+    case Settings::RendererBackend::OpenGL_GLSL:
+        api = Settings::RendererBackend::OpenGL_GLSL;
+        break;
+    case Settings::RendererBackend::OpenGL_SPIRV:
+        api = Settings::RendererBackend::OpenGL_GLASM;
+        break;
+    case Settings::RendererBackend::OpenGL_GLASM:
         api = Settings::RendererBackend::Null;
+        break;
+#else
+    case Settings::RendererBackend::Vulkan:
+        api = Settings::RendererBackend::Null;
+        break;
 #endif
+    case Settings::RendererBackend::Null:
+        api = Settings::RendererBackend::Vulkan;
+        break;
+    default:
+        break;
     }
     Settings::values.renderer_backend.SetValue(api);
     renderer_status_button->setChecked(api == Settings::RendererBackend::Vulkan);

src/yuzu/startup_checks.cpp

@@ -1,6 +1,10 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+// Don't move this! put it below and MSVC will get angry!
 #include "video_core/vulkan_common/vulkan_wrapper.h"
 
 #ifdef _WIN32

src/yuzu/vk_device_info.cpp

@@ -77,4 +77,5 @@ void PopulateRecords(std::vector<Record>& records, QWindow* window) try {
 } catch (const Vulkan::vk::Exception& exception) {
     LOG_ERROR(Frontend, "Failed to enumerate devices with error: {}", exception.what());
 }
+
 } // namespace VkDeviceInfo