Qt: Fix handling of display window size in hidpi

src/duckstation-qt/d3d11displaywindow.cpp

@@ -0,0 +1,406 @@
+#include "d3d11displaywindow.h"
+#include "YBaseLib/Log.h"
+#include "common/d3d11/shader_compiler.h"
+#include <array>
+#include <imgui.h>
+#include <imgui_impl_dx11.h>
+Log_SetChannel(D3D11DisplayWindow);
+
+class D3D11DisplayWindowTexture : public HostDisplayTexture
+{
+public:
+  template<typename T>
+  using ComPtr = Microsoft::WRL::ComPtr<T>;
+
+  D3D11DisplayWindowTexture(ComPtr<ID3D11Texture2D> texture, ComPtr<ID3D11ShaderResourceView> srv, u32 width, u32 height,
+                          bool dynamic)
+    : m_texture(std::move(texture)), m_srv(std::move(srv)), m_width(width), m_height(height), m_dynamic(dynamic)
+  {
+  }
+  ~D3D11DisplayWindowTexture() override = default;
+
+  void* GetHandle() const override { return m_srv.Get(); }
+  u32 GetWidth() const override { return m_width; }
+  u32 GetHeight() const override { return m_height; }
+
+  ID3D11Texture2D* GetD3DTexture() const { return m_texture.Get(); }
+  ID3D11ShaderResourceView* GetD3DSRV() const { return m_srv.Get(); }
+  bool IsDynamic() const { return m_dynamic; }
+
+  static std::unique_ptr<D3D11DisplayWindowTexture> Create(ID3D11Device* device, u32 width, u32 height, const void* data,
+                                                         u32 data_stride, bool dynamic)
+  {
+    const CD3D11_TEXTURE2D_DESC desc(DXGI_FORMAT_R8G8B8A8_UNORM, width, height, 1, 1, D3D11_BIND_SHADER_RESOURCE,
+                                     dynamic ? D3D11_USAGE_DYNAMIC : D3D11_USAGE_DEFAULT,
+                                     dynamic ? D3D11_CPU_ACCESS_WRITE : 0, 1, 0, 0);
+    const D3D11_SUBRESOURCE_DATA srd{data, data_stride, data_stride * height};
+    ComPtr<ID3D11Texture2D> texture;
+    HRESULT hr = device->CreateTexture2D(&desc, data ? &srd : nullptr, texture.GetAddressOf());
+    if (FAILED(hr))
+      return {};
+
+    const CD3D11_SHADER_RESOURCE_VIEW_DESC srv_desc(D3D11_SRV_DIMENSION_TEXTURE2D, DXGI_FORMAT_R8G8B8A8_UNORM, 0, 1, 0,
+                                                    1);
+    ComPtr<ID3D11ShaderResourceView> srv;
+    hr = device->CreateShaderResourceView(texture.Get(), &srv_desc, srv.GetAddressOf());
+    if (FAILED(hr))
+      return {};
+
+    return std::make_unique<D3D11DisplayWindowTexture>(std::move(texture), std::move(srv), width, height, dynamic);
+  }
+
+private:
+  ComPtr<ID3D11Texture2D> m_texture;
+  ComPtr<ID3D11ShaderResourceView> m_srv;
+  u32 m_width;
+  u32 m_height;
+  bool m_dynamic;
+};
+
+D3D11DisplayWindow::D3D11DisplayWindow(QtHostInterface* host_interface, QWindow* parent)
+  : QtDisplayWindow(host_interface, parent)
+{
+  
+}
+
+D3D11DisplayWindow::~D3D11DisplayWindow() = default;
+
+HostDisplay::RenderAPI D3D11DisplayWindow::GetRenderAPI() const
+{
+  return HostDisplay::RenderAPI::D3D11;
+}
+
+void* D3D11DisplayWindow::GetRenderDevice() const
+{
+  return m_device.Get();
+}
+
+void* D3D11DisplayWindow::GetRenderContext() const
+{
+  return m_context.Get();
+}
+
+void* D3D11DisplayWindow::GetRenderWindow() const
+{
+  return const_cast<QWindow*>(static_cast<const QWindow*>(this));
+}
+
+void D3D11DisplayWindow::ChangeRenderWindow(void* new_window)
+{
+  Panic("Not supported");
+}
+
+std::unique_ptr<HostDisplayTexture> D3D11DisplayWindow::CreateTexture(u32 width, u32 height, const void* data,
+                                                                    u32 data_stride, bool dynamic)
+{
+  return D3D11DisplayWindowTexture::Create(m_device.Get(), width, height, data, data_stride, dynamic);
+}
+
+void D3D11DisplayWindow::UpdateTexture(HostDisplayTexture* texture, u32 x, u32 y, u32 width, u32 height, const void* data,
+                                     u32 data_stride)
+{
+  D3D11DisplayWindowTexture* d3d11_texture = static_cast<D3D11DisplayWindowTexture*>(texture);
+  if (!d3d11_texture->IsDynamic())
+  {
+    const CD3D11_BOX dst_box(x, y, 0, x + width, y + height, 1);
+    m_context->UpdateSubresource(d3d11_texture->GetD3DTexture(), 0, &dst_box, data, data_stride, data_stride * height);
+  }
+  else
+  {
+    D3D11_MAPPED_SUBRESOURCE sr;
+    HRESULT hr = m_context->Map(d3d11_texture->GetD3DTexture(), 0, D3D11_MAP_WRITE_DISCARD, 0, &sr);
+    if (FAILED(hr))
+      Panic("Failed to map dynamic host display texture");
+
+    char* dst_ptr = static_cast<char*>(sr.pData) + (y * sr.RowPitch) + (x * sizeof(u32));
+    const char* src_ptr = static_cast<const char*>(data);
+    if (sr.RowPitch == data_stride)
+    {
+      std::memcpy(dst_ptr, src_ptr, data_stride * height);
+    }
+    else
+    {
+      for (u32 row = 0; row < height; row++)
+      {
+        std::memcpy(dst_ptr, src_ptr, width * sizeof(u32));
+        src_ptr += data_stride;
+        dst_ptr += sr.RowPitch;
+      }
+    }
+
+    m_context->Unmap(d3d11_texture->GetD3DTexture(), 0);
+  }
+}
+
+void D3D11DisplayWindow::SetDisplayTexture(void* texture, s32 offset_x, s32 offset_y, s32 width, s32 height,
+                                         u32 texture_width, u32 texture_height, float aspect_ratio)
+{
+  m_display_srv = static_cast<ID3D11ShaderResourceView*>(texture);
+  m_display_offset_x = offset_x;
+  m_display_offset_y = offset_y;
+  m_display_width = width;
+  m_display_height = height;
+  m_display_texture_width = texture_width;
+  m_display_texture_height = texture_height;
+  m_display_aspect_ratio = aspect_ratio;
+  m_display_texture_changed = true;
+}
+
+void D3D11DisplayWindow::SetDisplayLinearFiltering(bool enabled)
+{
+  m_display_linear_filtering = enabled;
+}
+
+void D3D11DisplayWindow::SetDisplayTopMargin(int height)
+{
+  m_display_top_margin = height;
+}
+
+void D3D11DisplayWindow::SetVSync(bool enabled)
+{
+  m_vsync = enabled;
+}
+
+std::tuple<u32, u32> D3D11DisplayWindow::GetWindowSize() const
+{
+  const QSize s = size();
+  return std::make_tuple(static_cast<u32>(s.width()), static_cast<u32>(s.height()));
+}
+
+void D3D11DisplayWindow::WindowResized()
+{
+}
+
+void D3D11DisplayWindow::onWindowResized(int width, int height)
+{
+  QtDisplayWindow::onWindowResized(width, height);
+
+  m_swap_chain_rtv.Reset();
+
+  HRESULT hr = m_swap_chain->ResizeBuffers(0, 0, 0, DXGI_FORMAT_UNKNOWN, 0);
+  if (FAILED(hr))
+    Log_ErrorPrintf("ResizeBuffers() failed: 0x%08X", hr);
+
+  if (!createSwapChainRTV())
+    Panic("Failed to recreate swap chain RTV after resize");
+}
+
+bool D3D11DisplayWindow::createDeviceContext(QThread* worker_thread)
+{
+  const bool debug = true;
+
+  UINT create_flags = 0;
+  if (debug)
+    create_flags |= D3D11_CREATE_DEVICE_DEBUG;
+
+  DXGI_SWAP_CHAIN_DESC swap_chain_desc = {};
+  swap_chain_desc.BufferDesc.Width = m_window_width;
+  swap_chain_desc.BufferDesc.Height = m_window_height;
+  swap_chain_desc.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
+  swap_chain_desc.SampleDesc.Count = 1;
+  swap_chain_desc.BufferCount = 3;
+  swap_chain_desc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
+  swap_chain_desc.OutputWindow = syswm.info.win.window;
+  swap_chain_desc.Windowed = TRUE;
+  swap_chain_desc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
+
+  HRESULT hr = D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, create_flags, nullptr, 0,
+                                             D3D11_SDK_VERSION, &swap_chain_desc, m_swap_chain.GetAddressOf(),
+                                             m_device.GetAddressOf(), nullptr, m_context.GetAddressOf());
+
+  if (FAILED(hr))
+  {
+    Log_WarningPrintf("Failed to create a flip-discard swap chain, trying discard.");
+    swap_chain_desc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;
+  }
+
+  if (FAILED(hr))
+  {
+    Log_ErrorPrintf("D3D11CreateDeviceAndSwapChain failed: 0x%08X", hr);
+    return false;
+  }
+
+#if 0
+  ComPtr<ID3D11InfoQueue> info;
+  hr = m_device.As(&info);
+  if (SUCCEEDED(hr))
+  {
+    info->SetBreakOnSeverity(D3D11_MESSAGE_SEVERITY_ERROR, TRUE);
+    info->SetBreakOnSeverity(D3D11_MESSAGE_SEVERITY_WARNING, TRUE);
+  }
+#endif
+
+  return true;
+}
+
+bool D3D11DisplayWindow::CreateSwapChainRTV()
+{
+  ComPtr<ID3D11Texture2D> backbuffer;
+  HRESULT hr = m_swap_chain->GetBuffer(0, IID_PPV_ARGS(backbuffer.GetAddressOf()));
+  if (FAILED(hr))
+  {
+    Log_ErrorPrintf("GetBuffer for RTV failed: 0x%08X", hr);
+    return false;
+  }
+
+  D3D11_TEXTURE2D_DESC backbuffer_desc;
+  backbuffer->GetDesc(&backbuffer_desc);
+
+  CD3D11_RENDER_TARGET_VIEW_DESC rtv_desc(D3D11_RTV_DIMENSION_TEXTURE2D, backbuffer_desc.Format, 0, 0,
+                                          backbuffer_desc.ArraySize);
+  hr = m_device->CreateRenderTargetView(backbuffer.Get(), &rtv_desc, m_swap_chain_rtv.GetAddressOf());
+  if (FAILED(hr))
+  {
+    Log_ErrorPrintf("CreateRenderTargetView for swap chain failed: 0x%08X", hr);
+    return false;
+  }
+
+  return true;
+}
+
+bool D3D11DisplayWindow::CreateD3DResources()
+{
+  static constexpr char fullscreen_quad_vertex_shader[] = R"(
+cbuffer UBOBlock : register(b0)
+{
+  float4 u_src_rect;
+};
+
+void main(in uint vertex_id : SV_VertexID,
+          out float2 v_tex0 : TEXCOORD0,
+          out float4 o_pos : SV_Position)
+{
+  float2 pos = float2(float((vertex_id << 1) & 2u), float(vertex_id & 2u));
+  v_tex0 = u_src_rect.xy + pos * u_src_rect.zw;
+  o_pos = float4(pos * float2(2.0f, -2.0f) + float2(-1.0f, 1.0f), 0.0f, 1.0f);
+}
+)";
+
+  static constexpr char display_pixel_shader[] = R"(
+Texture2D samp0 : register(t0);
+SamplerState samp0_ss : register(s0);
+
+void main(in float2 v_tex0 : TEXCOORD0,
+          out float4 o_col0 : SV_Target)
+{
+  o_col0 = samp0.Sample(samp0_ss, v_tex0);
+}
+)";
+
+  HRESULT hr;
+
+  m_display_vertex_shader =
+    D3D11::ShaderCompiler::CompileAndCreateVertexShader(m_device.Get(), fullscreen_quad_vertex_shader, false);
+  m_display_pixel_shader =
+    D3D11::ShaderCompiler::CompileAndCreatePixelShader(m_device.Get(), display_pixel_shader, false);
+  if (!m_display_vertex_shader || !m_display_pixel_shader)
+    return false;
+
+  if (!m_display_uniform_buffer.Create(m_device.Get(), D3D11_BIND_CONSTANT_BUFFER, DISPLAY_UNIFORM_BUFFER_SIZE))
+    return false;
+
+  CD3D11_RASTERIZER_DESC rasterizer_desc = CD3D11_RASTERIZER_DESC(CD3D11_DEFAULT());
+  rasterizer_desc.CullMode = D3D11_CULL_NONE;
+  hr = m_device->CreateRasterizerState(&rasterizer_desc, m_display_rasterizer_state.GetAddressOf());
+  if (FAILED(hr))
+    return false;
+
+  CD3D11_DEPTH_STENCIL_DESC depth_stencil_desc = CD3D11_DEPTH_STENCIL_DESC(CD3D11_DEFAULT());
+  depth_stencil_desc.DepthEnable = FALSE;
+  depth_stencil_desc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ZERO;
+  hr = m_device->CreateDepthStencilState(&depth_stencil_desc, m_display_depth_stencil_state.GetAddressOf());
+  if (FAILED(hr))
+    return false;
+
+  CD3D11_BLEND_DESC blend_desc = CD3D11_BLEND_DESC(CD3D11_DEFAULT());
+  hr = m_device->CreateBlendState(&blend_desc, m_display_blend_state.GetAddressOf());
+  if (FAILED(hr))
+    return false;
+
+  CD3D11_SAMPLER_DESC sampler_desc = CD3D11_SAMPLER_DESC(CD3D11_DEFAULT());
+  sampler_desc.Filter = D3D11_FILTER_MIN_MAG_MIP_POINT;
+  hr = m_device->CreateSamplerState(&sampler_desc, m_point_sampler.GetAddressOf());
+  if (FAILED(hr))
+    return false;
+
+  sampler_desc.Filter = D3D11_FILTER_MIN_MAG_LINEAR_MIP_POINT;
+  hr = m_device->CreateSamplerState(&sampler_desc, m_linear_sampler.GetAddressOf());
+  if (FAILED(hr))
+    return false;
+
+  return true;
+}
+
+bool D3D11DisplayWindow::CreateImGuiContext()
+{
+  if (!ImGui_ImplSDL2_InitForD3D(m_window) || !ImGui_ImplDX11_Init(m_device.Get(), m_context.Get()))
+    return false;
+
+  ImGui_ImplDX11_NewFrame();
+  ImGui_ImplSDL2_NewFrame(m_window);
+  return true;
+}
+
+std::unique_ptr<HostDisplay> D3D11DisplayWindow::Create(SDL_Window* window)
+{
+  std::unique_ptr<D3D11DisplayWindow> display = std::make_unique<D3D11DisplayWindow>(window);
+  if (!display->CreateD3DDevice() || !display->CreateSwapChainRTV() || !display->CreateD3DResources() ||
+      !display->CreateImGuiContext())
+  {
+    return nullptr;
+  }
+
+  return display;
+}
+
+void D3D11DisplayWindow::Render()
+{
+  static constexpr std::array<float, 4> clear_color = {};
+  m_context->ClearRenderTargetView(m_swap_chain_rtv.Get(), clear_color.data());
+  m_context->OMSetRenderTargets(1, m_swap_chain_rtv.GetAddressOf(), nullptr);
+
+  RenderDisplay();
+
+  ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
+
+  m_swap_chain->Present(BoolToUInt32(m_vsync), 0);
+
+  ImGui_ImplSDL2_NewFrame(m_window);
+  ImGui_ImplDX11_NewFrame();
+}
+
+void D3D11DisplayWindow::RenderDisplay()
+{
+  if (!m_display_srv)
+    return;
+
+  // - 20 for main menu padding
+  auto [vp_left, vp_top, vp_width, vp_height] =
+    CalculateDrawRect(m_window_width, std::max(m_window_height - m_display_top_margin, 1), m_display_aspect_ratio);
+  vp_top += m_display_top_margin;
+
+  m_context->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
+  m_context->VSSetShader(m_display_vertex_shader.Get(), nullptr, 0);
+  m_context->PSSetShader(m_display_pixel_shader.Get(), nullptr, 0);
+  m_context->PSSetShaderResources(0, 1, &m_display_srv);
+  m_context->PSSetSamplers(
+    0, 1, m_display_linear_filtering ? m_linear_sampler.GetAddressOf() : m_point_sampler.GetAddressOf());
+
+  const float uniforms[4] = {static_cast<float>(m_display_offset_x) / static_cast<float>(m_display_texture_width),
+                             static_cast<float>(m_display_offset_y) / static_cast<float>(m_display_texture_height),
+                             static_cast<float>(m_display_width) / static_cast<float>(m_display_texture_width),
+                             static_cast<float>(m_display_height) / static_cast<float>(m_display_texture_height)};
+  const auto map = m_display_uniform_buffer.Map(m_context.Get(), sizeof(uniforms), sizeof(uniforms));
+  std::memcpy(map.pointer, uniforms, sizeof(uniforms));
+  m_display_uniform_buffer.Unmap(m_context.Get(), sizeof(uniforms));
+  m_context->VSSetConstantBuffers(0, 1, m_display_uniform_buffer.GetD3DBufferArray());
+
+  const CD3D11_VIEWPORT vp(static_cast<float>(vp_left), static_cast<float>(vp_top), static_cast<float>(vp_width),
+                           static_cast<float>(vp_height));
+  m_context->RSSetViewports(1, &vp);
+  m_context->RSSetState(m_display_rasterizer_state.Get());
+  m_context->OMSetDepthStencilState(m_display_depth_stencil_state.Get(), 0);
+  m_context->OMSetBlendState(m_display_blend_state.Get(), nullptr, 0xFFFFFFFFu);
+
+  m_context->Draw(3, 0);
+}

src/duckstation-qt/d3d11displaywindow.h

@@ -0,0 +1,95 @@
+#pragma once
+#include "YBaseLib/Windows/WindowsHeaders.h"
+#include "common/d3d11/stream_buffer.h"
+#include "common/d3d11/texture.h"
+#include "core/host_display.h"
+#include "qtdisplaywindow.h"
+#include <d3d11.h>
+#include <memory>
+#include <wrl/client.h>
+
+class D3D11DisplayWindow final : public QtDisplayWindow, private HostDisplay
+{
+  Q_OBJECT
+
+public:
+  template<typename T>
+  using ComPtr = Microsoft::WRL::ComPtr<T>;
+
+  D3D11DisplayWindow(QtHostInterface* host_interface, QWindow* parent);
+  ~D3D11DisplayWindow();
+
+  HostDisplay* getHostDisplayInterface() override;
+
+  bool createDeviceContext(QThread* worker_thread) override;
+  bool initializeDeviceContext() override;
+  void destroyDeviceContext() override;
+
+  RenderAPI GetRenderAPI() const override;
+  void* GetRenderDevice() const override;
+  void* GetRenderContext() const override;
+  void* GetRenderWindow() const override;
+
+  void ChangeRenderWindow(void* new_window) override;
+
+  std::unique_ptr<HostDisplayTexture> CreateTexture(u32 width, u32 height, const void* data, u32 data_stride,
+                                                    bool dynamic) override;
+  void UpdateTexture(HostDisplayTexture* texture, u32 x, u32 y, u32 width, u32 height, const void* data,
+                     u32 data_stride) override;
+
+  void SetDisplayTexture(void* texture, s32 offset_x, s32 offset_y, s32 width, s32 height, u32 texture_width,
+                         u32 texture_height, float aspect_ratio) override;
+  void SetDisplayLinearFiltering(bool enabled) override;
+  void SetDisplayTopMargin(int height) override;
+
+  void SetVSync(bool enabled) override;
+
+  std::tuple<u32, u32> GetWindowSize() const override;
+  void WindowResized() override;
+
+  void Render() override;
+
+  void onWindowResized(int width, int height) override;
+
+private:
+  static constexpr u32 DISPLAY_UNIFORM_BUFFER_SIZE = 16;
+
+  bool createImGuiContext() override;
+  void destroyImGuiContext() override;
+  bool createDeviceResources() override;
+  void destroyDeviceResources() override;
+
+  bool createSwapChainRTV();
+
+  void renderDisplay();
+
+  ComPtr<ID3D11Device> m_device;
+  ComPtr<ID3D11DeviceContext> m_context;
+  ComPtr<IDXGISwapChain> m_swap_chain;
+  ComPtr<ID3D11RenderTargetView> m_swap_chain_rtv;
+
+  ComPtr<ID3D11RasterizerState> m_display_rasterizer_state;
+  ComPtr<ID3D11DepthStencilState> m_display_depth_stencil_state;
+  ComPtr<ID3D11BlendState> m_display_blend_state;
+  ComPtr<ID3D11VertexShader> m_display_vertex_shader;
+  ComPtr<ID3D11PixelShader> m_display_pixel_shader;
+  ComPtr<ID3D11SamplerState> m_point_sampler;
+  ComPtr<ID3D11SamplerState> m_linear_sampler;
+
+  D3D11::Texture m_display_pixels_texture;
+  D3D11::StreamBuffer m_display_uniform_buffer;
+
+  ID3D11ShaderResourceView* m_display_srv = nullptr;
+  s32 m_display_offset_x = 0;
+  s32 m_display_offset_y = 0;
+  s32 m_display_width = 0;
+  s32 m_display_height = 0;
+  u32 m_display_texture_width = 0;
+  u32 m_display_texture_height = 0;
+  int m_display_top_margin = 0;
+  float m_display_aspect_ratio = 1.0f;
+
+  bool m_display_texture_changed = false;
+  bool m_display_linear_filtering = false;
+  bool m_vsync = false;
+};

src/duckstation-qt/hotkeysettingswidget.cpp

@@ -20,6 +20,7 @@ HotkeySettingsWidget::~HotkeySettingsWidget() = default;
 void HotkeySettingsWidget::createUi()
 {
   QGridLayout* layout = new QGridLayout(this);
+  layout->setContentsMargins(0, 0, 0, 0);
 
   m_tab_widget = new QTabWidget(this);
 

src/duckstation-qt/main.cpp

@@ -21,6 +21,9 @@ int main(int argc, char* argv[])
   InitLogging();
 
   QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+  QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
+#endif
 
   QApplication app(argc, argv);
 

src/duckstation-qt/opengldisplaywindow.cpp

@@ -191,13 +191,11 @@ void OpenGLDisplayWindow::SetVSync(bool enabled)
 
 std::tuple<u32, u32> OpenGLDisplayWindow::GetWindowSize() const
 {
-  const QSize s = size();
-  return std::make_tuple(static_cast<u32>(s.width()), static_cast<u32>(s.height()));
+  return std::make_tuple(static_cast<u32>(m_window_width), static_cast<u32>(m_window_height));
 }
 
 void OpenGLDisplayWindow::WindowResized() {}
 
-
 const char* OpenGLDisplayWindow::GetGLSLVersionString() const
 {
   return m_is_gles ? "#version 300 es" : "#version 130\n";
@@ -483,11 +481,10 @@ void OpenGLDisplayWindow::renderDisplay()
     return;
 
   // - 20 for main menu padding
-  const QSize window_size = size();
-  const auto [vp_left, vp_top, vp_width, vp_height] = CalculateDrawRect(
-    window_size.width(), std::max(window_size.height() - m_display_top_margin, 1), m_display_aspect_ratio);
+  const auto [vp_left, vp_top, vp_width, vp_height] =
+    CalculateDrawRect(m_window_width, std::max(m_window_height - m_display_top_margin, 1), m_display_aspect_ratio);
 
-  glViewport(vp_left, window_size.height() - (m_display_top_margin + vp_top) - vp_height, vp_width, vp_height);
+  glViewport(vp_left, m_window_height - (m_display_top_margin + vp_top) - vp_height, vp_width, vp_height);
   glDisable(GL_BLEND);
   glDisable(GL_CULL_FACE);
   glDisable(GL_DEPTH_TEST);
@@ -504,4 +501,3 @@ void OpenGLDisplayWindow::renderDisplay()
   glDrawArrays(GL_TRIANGLES, 0, 3);
   glBindSampler(0, 0);
 }
-

src/duckstation-qt/qtdisplaywindow.cpp

@@ -1,12 +1,14 @@
 #include "qtdisplaywindow.h"
 #include "imgui.h"
-#include "qtutils.h"
 #include "qthostinterface.h"
+#include "qtutils.h"
 #include <QtGui/QKeyEvent>
 
 QtDisplayWindow::QtDisplayWindow(QtHostInterface* host_interface, QWindow* parent)
   : QWindow(parent), m_host_interface(host_interface)
 {
+  m_window_width = static_cast<int>(static_cast<qreal>(width()) * devicePixelRatio());
+  m_window_height = static_cast<int>(static_cast<qreal>(height()) * devicePixelRatio());
 }
 
 QtDisplayWindow::~QtDisplayWindow() = default;
@@ -40,8 +42,8 @@ bool QtDisplayWindow::createImGuiContext()
   ImGui::CreateContext();
 
   auto& io = ImGui::GetIO();
-  io.DisplaySize.x = static_cast<float>(width());
-  io.DisplaySize.y = static_cast<float>(height());
+  io.DisplaySize.x = static_cast<float>(m_window_width);
+  io.DisplaySize.y = static_cast<float>(m_window_height);
 
   return true;
 }
@@ -62,6 +64,9 @@ void QtDisplayWindow::Render() {}
 
 void QtDisplayWindow::onWindowResized(int width, int height)
 {
+  m_window_width = width;
+  m_window_height = height;
+
   // imgui may not have been initialized yet
   if (!ImGui::GetCurrentContext())
     return;
@@ -90,5 +95,8 @@ void QtDisplayWindow::keyReleaseEvent(QKeyEvent* event)
 void QtDisplayWindow::resizeEvent(QResizeEvent* event)
 {
   QWindow::resizeEvent(event);
-  emit windowResizedEvent(event->size().width(), event->size().height());
+  
+  const int width = static_cast<int>(static_cast<qreal>(event->size().width()) * devicePixelRatio());
+  const int height = static_cast<int>(static_cast<qreal>(event->size().height()) * devicePixelRatio());
+  emit windowResizedEvent(width, height);
 }

src/duckstation-qt/qtdisplaywindow.h

@@ -41,4 +41,7 @@ protected:
   virtual void resizeEvent(QResizeEvent* event) override;
 
   QtHostInterface* m_host_interface;
+
+  int m_window_width = 0;
+  int m_window_height = 0;
 };