Merged the SDL and Qt frontends together into a single unified executable

src/citra_sdl/emu_window/emu_window_sdl2.cpp

@@ -0,0 +1,252 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <cstdlib>
+#include <string>
+#define SDL_MAIN_HANDLED
+#include <SDL.h>
+#include "citra_sdl/emu_window/emu_window_sdl2.h"
+#include "common/logging/log.h"
+#include "common/scm_rev.h"
+#include "core/core.h"
+#include "input_common/keyboard.h"
+#include "input_common/main.h"
+#include "input_common/motion_emu.h"
+#include "network/network.h"
+
+void EmuWindow_SDL2::OnMouseMotion(s32 x, s32 y) {
+    TouchMoved((unsigned)std::max(x, 0), (unsigned)std::max(y, 0));
+    InputCommon::GetMotionEmu()->Tilt(x, y);
+}
+
+void EmuWindow_SDL2::OnMouseButton(u32 button, u8 state, s32 x, s32 y) {
+    if (button == SDL_BUTTON_LEFT) {
+        if (state == SDL_PRESSED) {
+            TouchPressed((unsigned)std::max(x, 0), (unsigned)std::max(y, 0));
+        } else {
+            TouchReleased();
+        }
+    } else if (button == SDL_BUTTON_RIGHT) {
+        if (state == SDL_PRESSED) {
+            InputCommon::GetMotionEmu()->BeginTilt(x, y);
+        } else {
+            InputCommon::GetMotionEmu()->EndTilt();
+        }
+    }
+}
+
+std::pair<unsigned, unsigned> EmuWindow_SDL2::TouchToPixelPos(float touch_x, float touch_y) const {
+    int w, h;
+    SDL_GetWindowSize(render_window, &w, &h);
+
+    touch_x *= w;
+    touch_y *= h;
+
+    return {static_cast<unsigned>(std::max(std::round(touch_x), 0.0f)),
+            static_cast<unsigned>(std::max(std::round(touch_y), 0.0f))};
+}
+
+void EmuWindow_SDL2::OnFingerDown(float x, float y) {
+    // TODO(NeatNit): keep track of multitouch using the fingerID and a dictionary of some kind
+    // This isn't critical because the best we can do when we have that is to average them, like the
+    // 3DS does
+
+    const auto [px, py] = TouchToPixelPos(x, y);
+    TouchPressed(px, py);
+}
+
+void EmuWindow_SDL2::OnFingerMotion(float x, float y) {
+    const auto [px, py] = TouchToPixelPos(x, y);
+    TouchMoved(px, py);
+}
+
+void EmuWindow_SDL2::OnFingerUp() {
+    TouchReleased();
+}
+
+void EmuWindow_SDL2::OnKeyEvent(int key, u8 state) {
+    if (state == SDL_PRESSED) {
+        InputCommon::GetKeyboard()->PressKey(key);
+    } else if (state == SDL_RELEASED) {
+        InputCommon::GetKeyboard()->ReleaseKey(key);
+    }
+}
+
+bool EmuWindow_SDL2::IsOpen() const {
+    return is_open;
+}
+
+void EmuWindow_SDL2::RequestClose() {
+    is_open = false;
+}
+
+void EmuWindow_SDL2::OnResize() {
+    int width, height;
+    SDL_GL_GetDrawableSize(render_window, &width, &height);
+    UpdateCurrentFramebufferLayout(width, height);
+}
+
+void EmuWindow_SDL2::Fullscreen() {
+    if (SDL_SetWindowFullscreen(render_window, SDL_WINDOW_FULLSCREEN) == 0) {
+        return;
+    }
+
+    LOG_ERROR(Frontend, "Fullscreening failed: {}", SDL_GetError());
+
+    // Try a different fullscreening method
+    LOG_INFO(Frontend, "Attempting to use borderless fullscreen...");
+    if (SDL_SetWindowFullscreen(render_window, SDL_WINDOW_FULLSCREEN_DESKTOP) == 0) {
+        return;
+    }
+
+    LOG_ERROR(Frontend, "Borderless fullscreening failed: {}", SDL_GetError());
+
+    // Fallback algorithm: Maximise window.
+    // Works on all systems (unless something is seriously wrong), so no fallback for this one.
+    LOG_INFO(Frontend, "Falling back on a maximised window...");
+    SDL_MaximizeWindow(render_window);
+}
+
+EmuWindow_SDL2::EmuWindow_SDL2(Core::System& system_, bool is_secondary)
+    : EmuWindow(is_secondary), system(system_) {}
+
+EmuWindow_SDL2::~EmuWindow_SDL2() {
+    SDL_Quit();
+}
+
+void EmuWindow_SDL2::InitializeSDL2() {
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMECONTROLLER) < 0) {
+        LOG_CRITICAL(Frontend, "Failed to initialize SDL2: {}! Exiting...", SDL_GetError());
+        exit(1);
+    }
+
+    InputCommon::Init();
+    Network::Init();
+
+    SDL_SetMainReady();
+}
+
+u32 EmuWindow_SDL2::GetEventWindowId(const SDL_Event& event) const {
+    switch (event.type) {
+    case SDL_WINDOWEVENT:
+        return event.window.windowID;
+    case SDL_KEYDOWN:
+    case SDL_KEYUP:
+        return event.key.windowID;
+    case SDL_MOUSEMOTION:
+        return event.motion.windowID;
+    case SDL_MOUSEBUTTONDOWN:
+    case SDL_MOUSEBUTTONUP:
+        return event.button.windowID;
+    case SDL_MOUSEWHEEL:
+        return event.wheel.windowID;
+    case SDL_FINGERDOWN:
+    case SDL_FINGERMOTION:
+    case SDL_FINGERUP:
+        return event.tfinger.windowID;
+    case SDL_TEXTEDITING:
+        return event.edit.windowID;
+    case SDL_TEXTEDITING_EXT:
+        return event.editExt.windowID;
+    case SDL_TEXTINPUT:
+        return event.text.windowID;
+    case SDL_DROPBEGIN:
+    case SDL_DROPFILE:
+    case SDL_DROPTEXT:
+    case SDL_DROPCOMPLETE:
+        return event.drop.windowID;
+    case SDL_USEREVENT:
+        return event.user.windowID;
+    default:
+        // Event is not for any particular window, so we can just pretend it's for this one.
+        return render_window_id;
+    }
+}
+
+void EmuWindow_SDL2::PollEvents() {
+    SDL_Event event;
+    std::vector<SDL_Event> other_window_events;
+
+    // SDL_PollEvent returns 0 when there are no more events in the event queue
+    while (SDL_PollEvent(&event)) {
+        if (GetEventWindowId(event) != render_window_id) {
+            other_window_events.push_back(event);
+            continue;
+        }
+
+        switch (event.type) {
+        case SDL_WINDOWEVENT:
+            switch (event.window.event) {
+            case SDL_WINDOWEVENT_SIZE_CHANGED:
+            case SDL_WINDOWEVENT_RESIZED:
+            case SDL_WINDOWEVENT_MAXIMIZED:
+            case SDL_WINDOWEVENT_RESTORED:
+            case SDL_WINDOWEVENT_MINIMIZED:
+                OnResize();
+                break;
+            case SDL_WINDOWEVENT_CLOSE:
+                RequestClose();
+                break;
+            }
+            break;
+        case SDL_KEYDOWN:
+        case SDL_KEYUP:
+            OnKeyEvent(static_cast<int>(event.key.keysym.scancode), event.key.state);
+            break;
+        case SDL_MOUSEMOTION:
+            // ignore if it came from touch
+            if (event.button.which != SDL_TOUCH_MOUSEID)
+                OnMouseMotion(event.motion.x, event.motion.y);
+            break;
+        case SDL_MOUSEBUTTONDOWN:
+        case SDL_MOUSEBUTTONUP:
+            // ignore if it came from touch
+            if (event.button.which != SDL_TOUCH_MOUSEID) {
+                OnMouseButton(event.button.button, event.button.state, event.button.x,
+                              event.button.y);
+            }
+            break;
+        case SDL_FINGERDOWN:
+            OnFingerDown(event.tfinger.x, event.tfinger.y);
+            break;
+        case SDL_FINGERMOTION:
+            OnFingerMotion(event.tfinger.x, event.tfinger.y);
+            break;
+        case SDL_FINGERUP:
+            OnFingerUp();
+            break;
+        case SDL_QUIT:
+            RequestClose();
+            break;
+        default:
+            break;
+        }
+    }
+    for (auto& e : other_window_events) {
+        // This is a somewhat hacky workaround to re-emit window events meant for another window
+        // since SDL_PollEvent() is global but we poll events per window.
+        SDL_PushEvent(&e);
+    }
+    if (!is_secondary) {
+        UpdateFramerateCounter();
+    }
+}
+
+void EmuWindow_SDL2::OnMinimalClientAreaChangeRequest(std::pair<u32, u32> minimal_size) {
+    SDL_SetWindowMinimumSize(render_window, minimal_size.first, minimal_size.second);
+}
+
+void EmuWindow_SDL2::UpdateFramerateCounter() {
+    const u32 current_time = SDL_GetTicks();
+    if (current_time > last_time + 2000) {
+        const auto results = system.GetAndResetPerfStats();
+        const auto title =
+            fmt::format("Citra {} | {}-{} | FPS: {:.0f} ({:.0f}%)", Common::g_build_fullname,
+                        Common::g_scm_branch, Common::g_scm_desc, results.game_fps,
+                        results.emulation_speed * 100.0f);
+        SDL_SetWindowTitle(render_window, title.c_str());
+        last_time = current_time;
+    }
+}

src/citra_sdl/emu_window/emu_window_sdl2.h

@@ -0,0 +1,91 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <utility>
+#include "common/common_types.h"
+#include "core/frontend/emu_window.h"
+
+union SDL_Event;
+struct SDL_Window;
+
+namespace Core {
+class System;
+}
+
+class EmuWindow_SDL2 : public Frontend::EmuWindow {
+public:
+    explicit EmuWindow_SDL2(Core::System& system_, bool is_secondary);
+    ~EmuWindow_SDL2();
+
+    /// Initializes SDL2
+    static void InitializeSDL2();
+
+    /// Presents the most recent frame from the video backend
+    virtual void Present() {}
+
+    /// Polls window events
+    void PollEvents() override;
+
+    /// Whether the window is still open, and a close request hasn't yet been sent
+    bool IsOpen() const;
+
+    /// Close the window.
+    void RequestClose();
+
+protected:
+    /// Gets the ID of the window an event originated from.
+    u32 GetEventWindowId(const SDL_Event& event) const;
+
+    /// Called by PollEvents when a key is pressed or released.
+    void OnKeyEvent(int key, u8 state);
+
+    /// Called by PollEvents when the mouse moves.
+    void OnMouseMotion(s32 x, s32 y);
+
+    /// Called by PollEvents when a mouse button is pressed or released
+    void OnMouseButton(u32 button, u8 state, s32 x, s32 y);
+
+    /// Translates pixel position (0..1) to pixel positions
+    std::pair<unsigned, unsigned> TouchToPixelPos(float touch_x, float touch_y) const;
+
+    /// Called by PollEvents when a finger starts touching the touchscreen
+    void OnFingerDown(float x, float y);
+
+    /// Called by PollEvents when a finger moves while touching the touchscreen
+    void OnFingerMotion(float x, float y);
+
+    /// Called by PollEvents when a finger stops touching the touchscreen
+    void OnFingerUp();
+
+    /// Called by PollEvents when any event that may cause the window to be resized occurs
+    void OnResize();
+
+    /// Called when user passes the fullscreen parameter flag
+    void Fullscreen();
+
+    /// Called when a configuration change affects the minimal size of the window
+    void OnMinimalClientAreaChangeRequest(std::pair<u32, u32> minimal_size) override;
+
+    /// Called when polling to update framerate
+    void UpdateFramerateCounter();
+
+    /// Is the window still open?
+    bool is_open = true;
+
+    /// Internal SDL2 render window
+    SDL_Window* render_window;
+
+    /// Internal SDL2 window ID
+    u32 render_window_id{};
+
+    /// Fake hidden window for the core context
+    SDL_Window* dummy_window;
+
+    /// Keeps track of how often to update the title bar during gameplay
+    u32 last_time = 0;
+
+    Core::System& system;
+};

src/citra_sdl/emu_window/emu_window_sdl2_gl.cpp

@@ -0,0 +1,167 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <cstdlib>
+#include <string>
+#define SDL_MAIN_HANDLED
+#include <SDL.h>
+#include <glad/glad.h>
+#include "citra_sdl/emu_window/emu_window_sdl2_gl.h"
+#include "common/scm_rev.h"
+#include "common/settings.h"
+#include "core/core.h"
+#include "video_core/gpu.h"
+#include "video_core/renderer_base.h"
+
+class SDLGLContext : public Frontend::GraphicsContext {
+public:
+    using SDL_GLContext = void*;
+
+    SDLGLContext() {
+        window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 0, 0,
+                                  SDL_WINDOW_HIDDEN | SDL_WINDOW_OPENGL);
+        context = SDL_GL_CreateContext(window);
+    }
+
+    ~SDLGLContext() override {
+        SDL_GL_DeleteContext(context);
+        SDL_DestroyWindow(window);
+    }
+
+    void MakeCurrent() override {
+        SDL_GL_MakeCurrent(window, context);
+    }
+
+    void DoneCurrent() override {
+        SDL_GL_MakeCurrent(window, nullptr);
+    }
+
+private:
+    SDL_Window* window;
+    SDL_GLContext context;
+};
+
+static SDL_Window* CreateGLWindow(const std::string& window_title, bool gles) {
+    if (gles) {
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
+    } else {
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+    }
+    return SDL_CreateWindow(window_title.c_str(),
+                            SDL_WINDOWPOS_UNDEFINED, // x position
+                            SDL_WINDOWPOS_UNDEFINED, // y position
+                            Core::kScreenTopWidth,
+                            Core::kScreenTopHeight + Core::kScreenBottomHeight,
+                            SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
+}
+
+EmuWindow_SDL2_GL::EmuWindow_SDL2_GL(Core::System& system_, bool fullscreen, bool is_secondary)
+    : EmuWindow_SDL2{system_, is_secondary} {
+    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
+    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
+    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);
+    // Enable debug context
+    if (Settings::values.renderer_debug) {
+        SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
+    }
+
+    std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_fullname,
+                                           Common::g_scm_branch, Common::g_scm_desc);
+
+    // First, try to create a context with the requested type.
+    render_window = CreateGLWindow(window_title, Settings::values.use_gles.GetValue());
+    if (render_window == nullptr) {
+        // On failure, fall back to context with flipped type.
+        render_window = CreateGLWindow(window_title, !Settings::values.use_gles.GetValue());
+        if (render_window == nullptr) {
+            LOG_CRITICAL(Frontend, "Failed to create SDL2 window: {}", SDL_GetError());
+            exit(1);
+        }
+    }
+
+    strict_context_required = std::strcmp(SDL_GetCurrentVideoDriver(), "wayland") == 0;
+
+    dummy_window = SDL_CreateWindow(NULL, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 0, 0,
+                                    SDL_WINDOW_HIDDEN | SDL_WINDOW_OPENGL);
+
+    if (fullscreen) {
+        Fullscreen();
+    }
+
+    window_context = SDL_GL_CreateContext(render_window);
+    core_context = CreateSharedContext();
+    last_saved_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);
+    }
+
+    render_window_id = SDL_GetWindowID(render_window);
+
+    int profile_mask = 0;
+    SDL_GL_GetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, &profile_mask);
+    auto gl_load_func =
+        profile_mask == SDL_GL_CONTEXT_PROFILE_ES ? gladLoadGLES2Loader : gladLoadGLLoader;
+
+    if (!gl_load_func(static_cast<GLADloadproc>(SDL_GL_GetProcAddress))) {
+        LOG_CRITICAL(Frontend, "Failed to initialize GL functions: {}", SDL_GetError());
+        exit(1);
+    }
+
+    OnResize();
+    OnMinimalClientAreaChangeRequest(GetActiveConfig().min_client_area_size);
+    SDL_PumpEvents();
+}
+
+EmuWindow_SDL2_GL::~EmuWindow_SDL2_GL() {
+    core_context.reset();
+    SDL_DestroyWindow(render_window);
+    SDL_GL_DeleteContext(window_context);
+}
+
+std::unique_ptr<Frontend::GraphicsContext> EmuWindow_SDL2_GL::CreateSharedContext() const {
+    return std::make_unique<SDLGLContext>();
+}
+
+void EmuWindow_SDL2_GL::MakeCurrent() {
+    core_context->MakeCurrent();
+}
+
+void EmuWindow_SDL2_GL::DoneCurrent() {
+    core_context->DoneCurrent();
+}
+
+void EmuWindow_SDL2_GL::SaveContext() {
+    last_saved_context = SDL_GL_GetCurrentContext();
+}
+
+void EmuWindow_SDL2_GL::RestoreContext() {
+    SDL_GL_MakeCurrent(render_window, last_saved_context);
+}
+
+void EmuWindow_SDL2_GL::Present() {
+    SDL_GL_MakeCurrent(render_window, window_context);
+    SDL_GL_SetSwapInterval(1);
+    while (IsOpen()) {
+        system.GPU().Renderer().TryPresent(100, is_secondary);
+        SDL_GL_SwapWindow(render_window);
+    }
+    SDL_GL_MakeCurrent(render_window, nullptr);
+}

src/citra_sdl/emu_window/emu_window_sdl2_gl.h

@@ -0,0 +1,39 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "citra_sdl/emu_window/emu_window_sdl2.h"
+
+struct SDL_Window;
+
+namespace Core {
+class System;
+}
+
+class EmuWindow_SDL2_GL : public EmuWindow_SDL2 {
+public:
+    explicit EmuWindow_SDL2_GL(Core::System& system_, bool fullscreen, bool is_secondary);
+    ~EmuWindow_SDL2_GL();
+
+    void Present() override;
+    std::unique_ptr<GraphicsContext> CreateSharedContext() const override;
+    void MakeCurrent() override;
+    void DoneCurrent() override;
+    void SaveContext() override;
+    void RestoreContext() override;
+
+private:
+    using SDL_GLContext = void*;
+
+    /// The OpenGL context associated with the window
+    SDL_GLContext window_context;
+
+    /// Used by SaveContext and RestoreContext
+    SDL_GLContext last_saved_context;
+
+    /// The OpenGL context associated with the core
+    std::unique_ptr<Frontend::GraphicsContext> core_context;
+};

src/citra_sdl/emu_window/emu_window_sdl2_sw.cpp

@@ -0,0 +1,108 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <cstdlib>
+#include <string>
+#define SDL_MAIN_HANDLED
+#include <SDL.h>
+#include <SDL_rect.h>
+#include "citra_sdl/emu_window/emu_window_sdl2_sw.h"
+#include "common/scm_rev.h"
+#include "common/settings.h"
+#include "core/core.h"
+#include "core/frontend/emu_window.h"
+#include "video_core/gpu.h"
+#include "video_core/renderer_software/renderer_software.h"
+
+class DummyContext : public Frontend::GraphicsContext {};
+
+EmuWindow_SDL2_SW::EmuWindow_SDL2_SW(Core::System& system_, bool fullscreen, bool is_secondary)
+    : EmuWindow_SDL2{system_, is_secondary}, system{system_} {
+    std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_fullname,
+                                           Common::g_scm_branch, Common::g_scm_desc);
+    render_window =
+        SDL_CreateWindow(window_title.c_str(),
+                         SDL_WINDOWPOS_UNDEFINED, // x position
+                         SDL_WINDOWPOS_UNDEFINED, // y position
+                         Core::kScreenTopWidth, Core::kScreenTopHeight + Core::kScreenBottomHeight,
+                         SDL_WINDOW_SHOWN);
+
+    if (render_window == nullptr) {
+        LOG_CRITICAL(Frontend, "Failed to create SDL2 window: {}", SDL_GetError());
+        exit(1);
+    }
+
+    window_surface = SDL_GetWindowSurface(render_window);
+    renderer = SDL_CreateSoftwareRenderer(window_surface);
+
+    if (renderer == nullptr) {
+        LOG_CRITICAL(Frontend, "Failed to create SDL2 software renderer: {}", SDL_GetError());
+        exit(1);
+    }
+
+    if (fullscreen) {
+        Fullscreen();
+    }
+
+    render_window_id = SDL_GetWindowID(render_window);
+
+    OnResize();
+    OnMinimalClientAreaChangeRequest(GetActiveConfig().min_client_area_size);
+    SDL_PumpEvents();
+}
+
+EmuWindow_SDL2_SW::~EmuWindow_SDL2_SW() {
+    SDL_DestroyRenderer(renderer);
+    SDL_DestroyWindow(render_window);
+}
+
+std::unique_ptr<Frontend::GraphicsContext> EmuWindow_SDL2_SW::CreateSharedContext() const {
+    return std::make_unique<DummyContext>();
+}
+
+void EmuWindow_SDL2_SW::Present() {
+    const auto layout{Layout::DefaultFrameLayout(
+        Core::kScreenTopWidth, Core::kScreenTopHeight + Core::kScreenBottomHeight, false, false)};
+
+    using VideoCore::ScreenId;
+
+    while (IsOpen()) {
+        SDL_SetRenderDrawColor(renderer,
+                               static_cast<Uint8>(Settings::values.bg_red.GetValue() * 255),
+                               static_cast<Uint8>(Settings::values.bg_green.GetValue() * 255),
+                               static_cast<Uint8>(Settings::values.bg_blue.GetValue() * 255), 0xFF);
+        SDL_RenderClear(renderer);
+
+        const auto draw_screen = [&](ScreenId screen_id) {
+            const auto dst_rect =
+                screen_id == ScreenId::TopLeft ? layout.top_screen : layout.bottom_screen;
+            SDL_Rect sdl_rect{static_cast<int>(dst_rect.left), static_cast<int>(dst_rect.top),
+                              static_cast<int>(dst_rect.GetWidth()),
+                              static_cast<int>(dst_rect.GetHeight())};
+            SDL_Surface* screen = LoadFramebuffer(screen_id);
+            SDL_BlitSurface(screen, nullptr, window_surface, &sdl_rect);
+            SDL_FreeSurface(screen);
+        };
+
+        draw_screen(ScreenId::TopLeft);
+        draw_screen(ScreenId::Bottom);
+
+        SDL_RenderPresent(renderer);
+        SDL_UpdateWindowSurface(render_window);
+    }
+}
+
+SDL_Surface* EmuWindow_SDL2_SW::LoadFramebuffer(VideoCore::ScreenId screen_id) {
+    const auto& renderer = static_cast<SwRenderer::RendererSoftware&>(system.GPU().Renderer());
+    const auto& info = renderer.Screen(screen_id);
+    const int width = static_cast<int>(info.width);
+    const int height = static_cast<int>(info.height);
+    SDL_Surface* surface =
+        SDL_CreateRGBSurfaceWithFormat(0, width, height, 0, SDL_PIXELFORMAT_ABGR8888);
+    SDL_LockSurface(surface);
+    std::memcpy(surface->pixels, info.pixels.data(), info.pixels.size());
+    SDL_UnlockSurface(surface);
+    return surface;
+}

src/citra_sdl/emu_window/emu_window_sdl2_sw.h

@@ -0,0 +1,43 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "citra_sdl/emu_window/emu_window_sdl2.h"
+
+struct SDL_Renderer;
+struct SDL_Surface;
+
+namespace VideoCore {
+enum class ScreenId : u32;
+}
+
+namespace Core {
+class System;
+}
+
+class EmuWindow_SDL2_SW : public EmuWindow_SDL2 {
+public:
+    explicit EmuWindow_SDL2_SW(Core::System& system, bool fullscreen, bool is_secondary);
+    ~EmuWindow_SDL2_SW();
+
+    void Present() override;
+    std::unique_ptr<GraphicsContext> CreateSharedContext() const override;
+    void MakeCurrent() override {}
+    void DoneCurrent() override {}
+
+private:
+    /// Loads a framebuffer to an SDL surface
+    SDL_Surface* LoadFramebuffer(VideoCore::ScreenId screen_id);
+
+    /// The system class.
+    Core::System& system;
+
+    /// The SDL software renderer
+    SDL_Renderer* renderer;
+
+    /// The window surface
+    SDL_Surface* window_surface;
+};

src/citra_sdl/emu_window/emu_window_sdl2_vk.cpp

@@ -0,0 +1,90 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <cstdlib>
+#include <memory>
+#include <string>
+#include <SDL.h>
+#include <SDL_syswm.h>
+#include <fmt/format.h>
+#include "citra_sdl/emu_window/emu_window_sdl2_vk.h"
+#include "common/logging/log.h"
+#include "common/scm_rev.h"
+#include "core/frontend/emu_window.h"
+
+class DummyContext : public Frontend::GraphicsContext {};
+
+EmuWindow_SDL2_VK::EmuWindow_SDL2_VK(Core::System& system, bool fullscreen, bool is_secondary)
+    : EmuWindow_SDL2{system, is_secondary} {
+    const std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_fullname,
+                                                 Common::g_scm_branch, Common::g_scm_desc);
+    render_window =
+        SDL_CreateWindow(window_title.c_str(),
+                         SDL_WINDOWPOS_UNDEFINED, // x position
+                         SDL_WINDOWPOS_UNDEFINED, // y position
+                         Core::kScreenTopWidth, Core::kScreenTopHeight + Core::kScreenBottomHeight,
+                         SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
+    SDL_SysWMinfo wm;
+    SDL_VERSION(&wm.version);
+    if (SDL_GetWindowWMInfo(render_window, &wm) == SDL_FALSE) {
+        LOG_CRITICAL(Frontend, "Failed to get information from the window manager");
+        std::exit(EXIT_FAILURE);
+    }
+
+    if (fullscreen) {
+        Fullscreen();
+        SDL_ShowCursor(false);
+    }
+
+    switch (wm.subsystem) {
+#ifdef SDL_VIDEO_DRIVER_WINDOWS
+    case SDL_SYSWM_TYPE::SDL_SYSWM_WINDOWS:
+        window_info.type = Frontend::WindowSystemType::Windows;
+        window_info.render_surface = reinterpret_cast<void*>(wm.info.win.window);
+        break;
+#endif
+#ifdef SDL_VIDEO_DRIVER_X11
+    case SDL_SYSWM_TYPE::SDL_SYSWM_X11:
+        window_info.type = Frontend::WindowSystemType::X11;
+        window_info.display_connection = wm.info.x11.display;
+        window_info.render_surface = reinterpret_cast<void*>(wm.info.x11.window);
+        break;
+#endif
+#ifdef SDL_VIDEO_DRIVER_WAYLAND
+    case SDL_SYSWM_TYPE::SDL_SYSWM_WAYLAND:
+        window_info.type = Frontend::WindowSystemType::Wayland;
+        window_info.display_connection = wm.info.wl.display;
+        window_info.render_surface = wm.info.wl.surface;
+        break;
+#endif
+#ifdef SDL_VIDEO_DRIVER_COCOA
+    case SDL_SYSWM_TYPE::SDL_SYSWM_COCOA:
+        window_info.type = Frontend::WindowSystemType::MacOS;
+        window_info.render_surface = SDL_Metal_GetLayer(SDL_Metal_CreateView(render_window));
+        break;
+#endif
+#ifdef SDL_VIDEO_DRIVER_ANDROID
+    case SDL_SYSWM_TYPE::SDL_SYSWM_ANDROID:
+        window_info.type = Frontend::WindowSystemType::Android;
+        window_info.render_surface = reinterpret_cast<void*>(wm.info.android.window);
+        break;
+#endif
+    default:
+        LOG_CRITICAL(Frontend, "Window manager subsystem {} not implemented", wm.subsystem);
+        std::exit(EXIT_FAILURE);
+        break;
+    }
+
+    render_window_id = SDL_GetWindowID(render_window);
+
+    OnResize();
+    OnMinimalClientAreaChangeRequest(GetActiveConfig().min_client_area_size);
+    SDL_PumpEvents();
+}
+
+EmuWindow_SDL2_VK::~EmuWindow_SDL2_VK() = default;
+
+std::unique_ptr<Frontend::GraphicsContext> EmuWindow_SDL2_VK::CreateSharedContext() const {
+    return std::make_unique<DummyContext>();
+}

src/citra_sdl/emu_window/emu_window_sdl2_vk.h

@@ -0,0 +1,24 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "citra_sdl/emu_window/emu_window_sdl2.h"
+
+namespace Frontend {
+class GraphicsContext;
+}
+
+namespace Core {
+class System;
+}
+
+class EmuWindow_SDL2_VK final : public EmuWindow_SDL2 {
+public:
+    explicit EmuWindow_SDL2_VK(Core::System& system_, bool fullscreen, bool is_secondary);
+    ~EmuWindow_SDL2_VK() override;
+
+    std::unique_ptr<Frontend::GraphicsContext> CreateSharedContext() const override;
+};