Add a separate thread for rendering and add texture mailbox and shared context to SDL

src/citra/citra.cpp

@@ -35,6 +35,7 @@
 #include "core/file_sys/cia_container.h"
 #include "core/frontend/applets/default_applets.h"
 #include "core/frontend/framebuffer_layout.h"
+#include "core/frontend/scope_acquire_context.h"
 #include "core/gdbstub/gdbstub.h"
 #include "core/hle/service/am/am.h"
 #include "core/hle/service/cfg/cfg.h"
@@ -347,7 +348,7 @@ int main(int argc, char** argv) {
     Core::System::GetInstance().RegisterImageInterface(std::make_shared<LodePNGImageInterface>());
 
     std::unique_ptr<EmuWindow_SDL2> emu_window{std::make_unique<EmuWindow_SDL2>(fullscreen)};
-
+    Frontend::ScopeAcquireContext scope(*emu_window);
     Core::System& system{Core::System::GetInstance()};
 
     const Core::System::ResultStatus load_result{system.Load(*emu_window, filepath)};
@@ -411,9 +412,11 @@ int main(int argc, char** argv) {
         system.VideoDumper().StartDumping(dump_video, "webm", layout);
     }
 
+    std::thread render_thread([&emu_window] { emu_window->Present(); });
     while (emu_window->IsOpen()) {
         system.RunLoop();
     }
+    render_thread.join();
 
     Core::Movie::GetInstance().Shutdown();
     if (system.VideoDumper().IsDumping()) {

src/citra/emu_window/emu_window_sdl2.cpp

@@ -20,6 +20,28 @@
 #include "input_common/motion_emu.h"
 #include "input_common/sdl/sdl.h"
 #include "network/network.h"
+#include "video_core/renderer_base.h"
+#include "video_core/video_core.h"
+
+SharedContext_SDL2::SharedContext_SDL2() {
+    window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 0, 0,
+                              SDL_WINDOW_HIDDEN | SDL_WINDOW_OPENGL);
+    context = SDL_GL_CreateContext(window);
+}
+
+SharedContext_SDL2::~SharedContext_SDL2() {
+    DoneCurrent();
+    SDL_GL_DeleteContext(context);
+    SDL_DestroyWindow(window);
+}
+
+void SharedContext_SDL2::MakeCurrent() {
+    SDL_GL_MakeCurrent(window, context);
+}
+
+void SharedContext_SDL2::DoneCurrent() {
+    SDL_GL_MakeCurrent(window, nullptr);
+}
 
 void EmuWindow_SDL2::OnMouseMotion(s32 x, s32 y) {
     TouchMoved((unsigned)std::max(x, 0), (unsigned)std::max(y, 0));
@@ -135,6 +157,10 @@ EmuWindow_SDL2::EmuWindow_SDL2(bool fullscreen) {
     SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
     SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
     SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 0);
+    // Enable context sharing for the shared context
+    SDL_GL_SetAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
+    // Enable vsync
+    SDL_GL_SetSwapInterval(1);
 
     std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_fullname,
                                            Common::g_scm_branch, Common::g_scm_desc);
@@ -150,16 +176,24 @@ EmuWindow_SDL2::EmuWindow_SDL2(bool fullscreen) {
         exit(1);
     }
 
+    dummy_window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 0, 0,
+                                    SDL_WINDOW_HIDDEN | SDL_WINDOW_OPENGL);
+
     if (fullscreen) {
         Fullscreen();
     }
 
-    gl_context = SDL_GL_CreateContext(render_window);
+    window_context = SDL_GL_CreateContext(render_window);
+    core_context = CreateSharedContext();
 
-    if (gl_context == nullptr) {
+    if (window_context == nullptr) {
         LOG_CRITICAL(Frontend, "Failed to create SDL2 GL context: {}", SDL_GetError());
         exit(1);
     }
+    if (core_context == nullptr) {
+        LOG_CRITICAL(Frontend, "Failed to create shared SDL2 GL context: {}", SDL_GetError());
+        exit(1);
+    }
 
     auto gl_load_func = Settings::values.use_gles ? gladLoadGLES2Loader : gladLoadGLLoader;
 
@@ -171,23 +205,30 @@ EmuWindow_SDL2::EmuWindow_SDL2(bool fullscreen) {
     OnResize();
     OnMinimalClientAreaChangeRequest(GetActiveConfig().min_client_area_size);
     SDL_PumpEvents();
-    SDL_GL_SetSwapInterval(Settings::values.vsync_enabled);
     LOG_INFO(Frontend, "Citra Version: {} | {}-{}", Common::g_build_fullname, Common::g_scm_branch,
              Common::g_scm_desc);
     Settings::LogSettings();
-
-    DoneCurrent();
 }
 
 EmuWindow_SDL2::~EmuWindow_SDL2() {
     Network::Shutdown();
     InputCommon::Shutdown();
-    SDL_GL_DeleteContext(gl_context);
+    SDL_GL_DeleteContext(window_context);
     SDL_Quit();
 }
 
-void EmuWindow_SDL2::SwapBuffers() {
-    SDL_GL_SwapWindow(render_window);
+std::unique_ptr<Frontend::GraphicsContext> EmuWindow_SDL2::CreateSharedContext() const {
+    return std::make_unique<SharedContext_SDL2>();
+}
+
+void EmuWindow_SDL2::Present() {
+    SDL_GL_MakeCurrent(render_window, window_context);
+    SDL_GL_SetSwapInterval(1);
+    while (IsOpen()) {
+        VideoCore::g_renderer->Present();
+        SDL_GL_SwapWindow(render_window);
+    }
+    SDL_GL_MakeCurrent(render_window, nullptr);
 }
 
 void EmuWindow_SDL2::PollEvents() {
@@ -256,11 +297,11 @@ void EmuWindow_SDL2::PollEvents() {
 }
 
 void EmuWindow_SDL2::MakeCurrent() {
-    SDL_GL_MakeCurrent(render_window, gl_context);
+    core_context->MakeCurrent();
 }
 
 void EmuWindow_SDL2::DoneCurrent() {
-    SDL_GL_MakeCurrent(render_window, nullptr);
+    core_context->DoneCurrent();
 }
 
 void EmuWindow_SDL2::OnMinimalClientAreaChangeRequest(std::pair<u32, u32> minimal_size) {

src/citra/emu_window/emu_window_sdl2.h

@@ -10,13 +10,29 @@
 
 struct SDL_Window;
 
+class SharedContext_SDL2 : public Frontend::GraphicsContext {
+public:
+    using SDL_GLContext = void*;
+
+    SharedContext_SDL2();
+
+    ~SharedContext_SDL2() override;
+
+    void MakeCurrent() override;
+
+    void DoneCurrent() override;
+
+private:
+    SDL_GLContext context;
+    SDL_Window* window;
+};
+
 class EmuWindow_SDL2 : public Frontend::EmuWindow {
 public:
     explicit EmuWindow_SDL2(bool fullscreen);
     ~EmuWindow_SDL2();
 
-    /// Swap buffers to display the next frame
-    void SwapBuffers() override;
+    void Present();
 
     /// Polls window events
     void PollEvents() override;
@@ -30,6 +46,9 @@ public:
     /// Whether the window is still open, and a close request hasn't yet been sent
     bool IsOpen() const;
 
+    /// Creates a new context that is shared with the current context
+    std::unique_ptr<GraphicsContext> CreateSharedContext() const override;
+
 private:
     /// Called by PollEvents when a key is pressed or released.
     void OnKeyEvent(int key, u8 state);
@@ -67,9 +86,16 @@ private:
     /// Internal SDL2 render window
     SDL_Window* render_window;
 
+    /// Fake hidden window for the core context
+    SDL_Window* dummy_window;
+
     using SDL_GLContext = void*;
+
     /// The OpenGL context associated with the window
-    SDL_GLContext gl_context;
+    SDL_GLContext window_context;
+
+    /// The OpenGL context associated with the core
+    std::unique_ptr<Frontend::GraphicsContext> core_context;
 
     /// Keeps track of how often to update the title bar during gameplay
     u32 last_time = 0;