citra_qt: Allow enabling frame advance before emulation start

Effectively allows starting emulation as paused.

src/citra_qt/bootmanager.cpp

@@ -21,6 +21,7 @@
 #include "core/3ds.h"
 #include "core/core.h"
 #include "core/frontend/scope_acquire_context.h"
+#include "core/perf_stats.h"
 #include "core/settings.h"
 #include "input_common/keyboard.h"
 #include "input_common/main.h"
@@ -55,6 +56,13 @@ void EmuThread::run() {
 
     emit LoadProgress(VideoCore::LoadCallbackStage::Complete, 0, 0);
 
+    if (Core::System::GetInstance().frame_limiter.IsFrameAdvancing()) {
+        // Usually the loading screen is hidden after the first frame is drawn. In this case
+        // we hide it immediately as we need to wait for user input to start the emulation.
+        emit HideLoadingScreen();
+        Core::System::GetInstance().frame_limiter.WaitOnce();
+    }
+
     // Holds whether the cpu was running during the last iteration,
     // so that the DebugModeLeft signal can be emitted before the
     // next execution step.

src/citra_qt/bootmanager.h

@@ -122,6 +122,8 @@ signals:
     void ErrorThrown(Core::System::ResultStatus, std::string);
 
     void LoadProgress(VideoCore::LoadCallbackStage stage, std::size_t value, std::size_t total);
+
+    void HideLoadingScreen();
 };
 
 class OpenGLWindow : public QWindow {

src/citra_qt/main.cpp

@@ -1048,6 +1048,8 @@ void GMainWindow::BootGame(const QString& filename) {
 
     connect(emu_thread.get(), &EmuThread::LoadProgress, loading_screen,
             &LoadingScreen::OnLoadProgress, Qt::QueuedConnection);
+    connect(emu_thread.get(), &EmuThread::HideLoadingScreen, loading_screen,
+            &LoadingScreen::OnLoadComplete);
 
     // Update the GUI
     registersWidget->OnDebugModeEntered();
@@ -1082,6 +1084,13 @@ void GMainWindow::BootGame(const QString& filename) {
         movie_record_author.clear();
     }
 
+    if (ui->action_Enable_Frame_Advancing->isChecked()) {
+        ui->action_Advance_Frame->setEnabled(true);
+        Core::System::GetInstance().frame_limiter.SetFrameAdvancing(true);
+    } else {
+        ui->action_Advance_Frame->setEnabled(false);
+    }
+
     if (video_dumping_on_start) {
         Layout::FramebufferLayout layout{
             Layout::FrameLayoutFromResolutionScale(VideoCore::GetResolutionScaleFactor())};
@@ -1155,8 +1164,6 @@ void GMainWindow::ShutdownGame() {
     ui->action_Load_Amiibo->setEnabled(false);
     ui->action_Remove_Amiibo->setEnabled(false);
     ui->action_Report_Compatibility->setEnabled(false);
-    ui->action_Enable_Frame_Advancing->setEnabled(false);
-    ui->action_Enable_Frame_Advancing->setChecked(false);
     ui->action_Advance_Frame->setEnabled(false);
     ui->action_Capture_Screenshot->setEnabled(false);
     render_window->hide();
@@ -1564,7 +1571,6 @@ void GMainWindow::OnStartGame() {
     ui->action_Cheats->setEnabled(true);
     ui->action_Load_Amiibo->setEnabled(true);
     ui->action_Report_Compatibility->setEnabled(true);
-    ui->action_Enable_Frame_Advancing->setEnabled(true);
     ui->action_Capture_Screenshot->setEnabled(true);
 
     discord_rpc->Update();

src/citra_qt/main.ui

@@ -349,9 +349,6 @@
    <property name="checkable">
     <bool>true</bool>
    </property>
-   <property name="enabled">
-    <bool>false</bool>
-   </property>
    <property name="text">
     <string>Enable Frame Advancing</string>
    </property>

src/core/perf_stats.cpp

@@ -169,6 +169,10 @@ void FrameLimiter::DoFrameLimiting(microseconds current_system_time_us) {
     previous_walltime = now;
 }
 
+bool FrameLimiter::IsFrameAdvancing() const {
+    return frame_advancing_enabled;
+}
+
 void FrameLimiter::SetFrameAdvancing(bool value) {
     const bool was_enabled = frame_advancing_enabled.exchange(value);
     if (was_enabled && !value) {

src/core/perf_stats.h

@@ -90,6 +90,7 @@ public:
 
     void DoFrameLimiting(std::chrono::microseconds current_system_time_us);
 
+    bool IsFrameAdvancing() const;
     /**
      * Sets whether frame advancing is enabled or not.
      * Note: The frontend must cancel frame advancing before shutting down in order