[desktop] More qt_common reorganization (#3916)

Ported from QML branch.

Main "big" change is that EmuThread is now a shared state in QtCommon,
not individually managed/passed around by GRenderWindow and MainWindow.

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3916
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/qt_common/render/context.h

@@ -0,0 +1,107 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <QSurface>
+#include "common/logging.h"
+#include "common/settings.h"
+#include "core/frontend/graphics_context.h"
+
+#ifdef HAS_OPENGL
+#include <QOffscreenSurface>
+#include <QOpenGLContext>
+#endif
+
+#ifdef HAS_OPENGL
+class OpenGLSharedContext : public Core::Frontend::GraphicsContext {
+public:
+    /// Create the original context that should be shared from
+    explicit OpenGLSharedContext(QSurface* surface_) : surface{surface_} {
+        QSurfaceFormat format;
+        format.setVersion(4, 6);
+        format.setProfile(QSurfaceFormat::CompatibilityProfile);
+        format.setOption(QSurfaceFormat::FormatOption::DeprecatedFunctions);
+        if (Settings::values.renderer_debug) {
+            format.setOption(QSurfaceFormat::FormatOption::DebugContext);
+        }
+        // TODO: expose a setting for buffer value (ie default/single/double/triple)
+        format.setSwapBehavior(QSurfaceFormat::DefaultSwapBehavior);
+        format.setSwapInterval(0);
+
+        context = std::make_unique<QOpenGLContext>();
+        context->setFormat(format);
+        if (!context->create()) {
+            LOG_ERROR(Frontend, "Unable to create main openGL context");
+        }
+    }
+
+    /// Create the shared contexts for rendering and presentation
+    explicit OpenGLSharedContext(QOpenGLContext* share_context, QSurface* main_surface = nullptr) {
+
+        // disable vsync for any shared contexts
+        auto format = share_context->format();
+        const int swap_interval =
+            Settings::values.vsync_mode.GetValue() == Settings::VSyncMode::Immediate ? 0 : 1;
+
+        format.setSwapInterval(main_surface ? swap_interval : 0);
+
+        context = std::make_unique<QOpenGLContext>();
+        context->setShareContext(share_context);
+        context->setFormat(format);
+        if (!context->create()) {
+            LOG_ERROR(Frontend, "Unable to create shared openGL context");
+        }
+
+        if (!main_surface) {
+            offscreen_surface = std::make_unique<QOffscreenSurface>(nullptr);
+            offscreen_surface->setFormat(format);
+            offscreen_surface->create();
+            surface = offscreen_surface.get();
+        } else {
+            surface = main_surface;
+        }
+    }
+
+    ~OpenGLSharedContext() {
+        DoneCurrent();
+    }
+
+    void SwapBuffers() override {
+        context->swapBuffers(surface);
+    }
+
+    void MakeCurrent() override {
+        // We can't track the current state of the underlying context in this wrapper class because
+        // Qt may make the underlying context not current for one reason or another. In particular,
+        // the WebBrowser uses GL, so it seems to conflict if we aren't careful.
+        // Instead of always just making the context current (which does not have any caching to
+        // check if the underlying context is already current) we can check for the current context
+        // in the thread local data by calling `currentContext()` and checking if its ours.
+        if (QOpenGLContext::currentContext() != context.get()) {
+            context->makeCurrent(surface);
+        }
+    }
+
+    void DoneCurrent() override {
+        context->doneCurrent();
+    }
+
+    QOpenGLContext* GetShareContext() {
+        return context.get();
+    }
+
+    const QOpenGLContext* GetShareContext() const {
+        return context.get();
+    }
+
+private:
+    // Avoid using Qt parent system here since we might move the QObjects to new threads
+    // As a note, this means we should avoid using slots/signals with the objects too
+    std::unique_ptr<QOpenGLContext> context;
+    std::unique_ptr<QOffscreenSurface> offscreen_surface{};
+    QSurface* surface;
+};
+#endif
+
+class DummyContext : public Core::Frontend::GraphicsContext {};

src/qt_common/render/emu_thread.cpp

@@ -0,0 +1,83 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <qdebug.h>
+#include "core/core.h"
+#include "core/cpu_manager.h"
+#include "emu_thread.h"
+#include "qt_common/qt_common.h"
+#include "video_core/gpu.h"
+#include "video_core/rasterizer_interface.h"
+#include "video_core/renderer_base.h"
+
+EmuThread::EmuThread() {}
+
+EmuThread::~EmuThread() = default;
+
+void EmuThread::run() {
+    Common::SetCurrentThreadName("EmuControlThread");
+
+    auto& gpu = QtCommon::system->GPU();
+    auto stop_token = m_stop_source.get_token();
+
+    QtCommon::system->RegisterHostThread();
+
+    // Main process has been loaded. Make the context current to this thread and begin GPU and CPU
+    // execution.
+    gpu.ObtainContext();
+
+    emit LoadProgress(VideoCore::LoadCallbackStage::Prepare, 0, 0);
+    if (Settings::values.use_disk_shader_cache.GetValue()) {
+        QtCommon::system->Renderer().ReadRasterizer()->LoadDiskResources(
+            QtCommon::system->GetApplicationProcessProgramID(), stop_token,
+            [this](VideoCore::LoadCallbackStage stage, std::size_t value, std::size_t total) {
+                emit LoadProgress(stage, value, total);
+            });
+    }
+    emit LoadProgress(VideoCore::LoadCallbackStage::Complete, 0, 0);
+
+    gpu.ReleaseContext();
+    gpu.Start();
+
+    QtCommon::system->GetCpuManager().OnGpuReady();
+
+    if (QtCommon::system->DebuggerEnabled()) {
+        QtCommon::system->InitializeDebugger();
+    }
+
+    while (!stop_token.stop_requested()) {
+        std::unique_lock lk{m_should_run_mutex};
+        if (m_should_run) {
+            QtCommon::system->Run();
+            m_stopped.Reset();
+
+            m_should_run_cv.wait(lk, stop_token, [&] { return !m_should_run; });
+        } else {
+            QtCommon::system->Pause();
+            m_stopped.Set();
+
+            EmulationPaused(lk);
+            m_should_run_cv.wait(lk, stop_token, [&] { return m_should_run; });
+            EmulationResumed(lk);
+        }
+    }
+
+    // Shutdown the main emulated process
+    QtCommon::system->DetachDebugger();
+    QtCommon::system->ShutdownMainProcess();
+}
+
+// Unlock while emitting signals so that the main thread can
+// continue pumping events.
+
+void EmuThread::EmulationPaused(std::unique_lock<std::mutex>& lk) {
+    lk.unlock();
+    emit DebugModeEntered();
+    lk.lock();
+}
+
+void EmuThread::EmulationResumed(std::unique_lock<std::mutex>& lk) {
+    lk.unlock();
+    emit DebugModeLeft();
+    lk.lock();
+}

src/qt_common/render/emu_thread.h

@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <QThread>
+#include "common/logging.h"
+#include "common/thread.h"
+
+namespace Core {
+class System;
+} // namespace Core
+
+namespace VideoCore {
+enum class LoadCallbackStage;
+} // namespace VideoCore
+
+class EmuThread final : public QThread {
+    Q_OBJECT
+
+public:
+    explicit EmuThread();
+    ~EmuThread() override;
+
+    /**
+     * Start emulation (on new thread)
+     * @warning Only call when not running!
+     */
+    void run() override;
+
+    /**
+     * Sets whether the emulation thread should run or not
+     * @param should_run Boolean value, set the emulation thread to running if true
+     */
+    void SetRunning(bool should_run) {
+        // TODO: Prevent other threads from modifying the state until we finish.
+        {
+            // Notify the running thread to change state.
+            std::unique_lock run_lk{m_should_run_mutex};
+            m_should_run = should_run;
+            m_should_run_cv.notify_one();
+        }
+
+        // Wait until paused, if pausing.
+        if (!should_run) {
+            m_stopped.Wait();
+        }
+    }
+
+    /**
+     * Check if the emulation thread is running or not
+     * @return True if the emulation thread is running, otherwise false
+     */
+    bool IsRunning() const {
+        return m_should_run;
+    }
+
+    /**
+     * Requests for the emulation thread to immediately stop running
+     */
+    void ForceStop() {
+        LOG_WARNING(Frontend, "Force stopping EmuThread");
+        m_stop_source.request_stop();
+    }
+
+private:
+    void EmulationPaused(std::unique_lock<std::mutex>& lk);
+    void EmulationResumed(std::unique_lock<std::mutex>& lk);
+
+private:
+    std::stop_source m_stop_source;
+    std::mutex m_should_run_mutex;
+    std::condition_variable_any m_should_run_cv;
+    Common::Event m_stopped;
+    bool m_should_run{true};
+
+signals:
+    /**
+     * Emitted when the CPU has halted execution
+     *
+     * @warning When connecting to this signal from other threads, make sure to specify either
+     * Qt::QueuedConnection (invoke slot within the destination object's message thread) or even
+     * Qt::BlockingQueuedConnection (additionally block source thread until slot returns)
+     */
+    void DebugModeEntered();
+
+    /**
+     * Emitted right before the CPU continues execution
+     *
+     * @warning When connecting to this signal from other threads, make sure to specify either
+     * Qt::QueuedConnection (invoke slot within the destination object's message thread) or even
+     * Qt::BlockingQueuedConnection (additionally block source thread until slot returns)
+     */
+    void DebugModeLeft();
+
+    void LoadProgress(VideoCore::LoadCallbackStage stage, std::size_t value, std::size_t total);
+};