[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/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();
+}