GS/Qt: Represent the current frame on resize when paused

Stops the frame displayed with incorrect proportions.

pcsx2-qt/EmuThread.cpp

@@ -744,6 +744,10 @@ void Host::ResizeHostDisplay(u32 new_window_width, u32 new_window_height, float
 {
 	s_host_display->ResizeRenderWindow(new_window_width, new_window_height, new_window_scale);
 	ImGuiManager::WindowResized();
+
+	// if we're paused, re-present the current frame at the new window size.
+	if (VMManager::GetState() == VMState::Paused)
+		GetMTGS().PresentCurrentFrame();
 }
 
 void Host::RequestResizeHostDisplay(s32 width, s32 height)
@@ -755,6 +759,10 @@ void Host::UpdateHostDisplay()
 {
 	g_emu_thread->updateDisplay();
 	ImGuiManager::WindowResized();
+
+	// if we're paused, re-present the current frame at the new window size.
+	if (VMManager::GetState() == VMState::Paused)
+		GetMTGS().PresentCurrentFrame();
 }
 
 void Host::OnVMStarting()

pcsx2/Frontend/ImGuiManager.cpp

@@ -117,6 +117,10 @@ void ImGuiManager::WindowResized()
 	ImGui::GetIO().DisplaySize = ImVec2(static_cast<float>(new_width), static_cast<float>(new_height));
 
 	UpdateScale();
+
+	// restart imgui frame on the new window size to pick it up, otherwise we draw to the old size
+	ImGui::EndFrame();
+	NewFrame();
 }
 
 void ImGuiManager::UpdateScale()

pcsx2/GS.h

@@ -383,6 +383,10 @@ public:
 	/// Fully stops the thread, closing in the process if needed.
 	void ShutdownThread();
 
+	/// Re-presents the current frame. Call when things like window resizes happen to re-display
+	/// the current frame with the correct proportions. Should only be called on the GS thread.
+	void PresentCurrentFrame();
+
 	// Waits for the GS to empty out the entire ring buffer contents.
 	void WaitGS(bool syncRegs=true, bool weakWait=false, bool isMTVU=false);
 	void ResetGS(bool hardware_reset);

pcsx2/GS/GS.cpp

@@ -527,6 +527,11 @@ void GSStopGSDump()
 		g_gs_renderer->StopGSDump();
 }
 
+void GSPresentCurrentFrame()
+{
+	g_gs_renderer->PresentCurrentFrame();
+}
+
 #ifndef PCSX2_CORE
 
 void GSkeyEvent(const HostKeyEvent& e)

pcsx2/GS/GS.h

@@ -71,6 +71,7 @@ void GSvsync(u32 field, bool registers_written);
 int GSfreeze(FreezeAction mode, freezeData* data);
 void GSQueueSnapshot(const std::string& path, u32 gsdump_frames = 0);
 void GSStopGSDump();
+void GSPresentCurrentFrame();
 #ifndef PCSX2_CORE
 void GSkeyEvent(const HostKeyEvent& e);
 void GSconfigure();

pcsx2/GS/Renderers/Common/GSRenderer.cpp

@@ -745,6 +745,30 @@ void GSRenderer::StopGSDump()
 	m_dump_frames = 0;
 }
 
+void GSRenderer::PresentCurrentFrame()
+{
+	g_gs_device->ResetAPIState();
+	if (Host::BeginPresentFrame(false))
+	{
+		GSTexture* current = g_gs_device->GetCurrent();
+		if (current)
+		{
+			HostDisplay* const display = g_gs_device->GetDisplay();
+			const GSVector4 draw_rect(CalculateDrawRect(display->GetWindowWidth(), display->GetWindowHeight(),
+				current->GetWidth(), current->GetHeight(), display->GetDisplayAlignment(), display->UsesLowerLeftOrigin(), GetVideoMode() == GSVideoMode::SDTV_480P));
+
+			static constexpr ShaderConvert s_shader[5] = { ShaderConvert::COPY, ShaderConvert::SCANLINE,
+				ShaderConvert::DIAGONAL_FILTER, ShaderConvert::TRIANGULAR_FILTER,
+				ShaderConvert::COMPLEX_FILTER }; // FIXME
+
+			g_gs_device->StretchRect(current, nullptr, draw_rect, s_shader[GSConfig.TVShader], GSConfig.LinearPresent);
+		}
+
+		Host::EndPresentFrame();
+	}
+	g_gs_device->RestoreAPIState();
+}
+
 #ifndef PCSX2_CORE
 
 bool GSRenderer::BeginCapture(std::string& filename)

pcsx2/GS/Renderers/Common/GSRenderer.h

@@ -68,6 +68,7 @@ public:
 
 	void QueueSnapshot(const std::string& path, u32 gsdump_frames);
 	void StopGSDump();
+	void PresentCurrentFrame();
 
 #ifndef PCSX2_CORE
 	bool BeginCapture(std::string& filename);

pcsx2/MTGS.cpp

@@ -911,6 +911,9 @@ void SysMtgsThread::Freeze(FreezeAction mode, MTGS_FreezeData& data)
 void SysMtgsThread::RunOnGSThread(AsyncCallType func)
 {
 	SendPointerPacket(GS_RINGTYPE_ASYNC_CALL, 0, new AsyncCallType(std::move(func)));
+
+	// wake the gs thread in case it's sleeping
+	SetEvent();
 }
 
 void SysMtgsThread::ApplySettings()
@@ -993,3 +996,8 @@ bool SysMtgsThread::SaveMemorySnapshot(u32 width, u32 height, std::vector<u32>*
 	WaitGS(false, false, false);
 	return result;
 }
+
+void SysMtgsThread::PresentCurrentFrame()
+{
+	GSPresentCurrentFrame();
+}