HighDPI UI behavouir (Kenix3#467)

* Allow ImGui to scale itself by dpi and added Open Sans as default font to have a nice looking UI on HighDPI Monitors.

* - Changed OpenSans-Regular to OpenSans-Semibold witch is better readable and adjusted the font config for the new font.
- Changed the names of the new variables.
- Simplifyed the dpi stuff and moved the two new floats to the Header as private.
- Added comments to the changes.

* Run clang-format

* Removed new font

* Reworked GUI scaling by getting display dpi and apply the scale on events.

* Using ImGui_ImplWin32_GetDpiScaleForMonitor to support Windows 8.1
Get DpiScale instaed of DPI in window events

* Put SDL_GetDisplayDPI into if statement to prevent crash on Switch.

---------

Co-authored-by: Mirco <you@example.com>

src/window/gui/Gui.cpp

@@ -65,6 +65,10 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARA
 
 #endif
 
+#ifndef USER_DEFAULT_SCREEN_DPI
+#define USER_DEFAULT_SCREEN_DPI 96
+#endif
+
 namespace LUS {
 #define TOGGLE_BTN ImGuiKey_F1
 #define TOGGLE_PAD_BTN ImGuiKey_GamepadBack
@@ -279,6 +283,8 @@ void Gui::Update(WindowEvent event) {
         mNeedsConsoleVariableSave = false;
     }
 
+    float dpiScale = 0;
+
     switch (Context::GetInstance()->GetWindow()->GetWindowBackend()) {
 #ifdef __WIIU__
         case WindowBackend::GX2:
@@ -289,6 +295,21 @@ void Gui::Update(WindowEvent event) {
         case WindowBackend::SDL_METAL:
             ImGui_ImplSDL2_ProcessEvent(static_cast<const SDL_Event*>(event.Sdl.Event));
 
+            if (static_cast<const SDL_Event*>(event.Sdl.Event)->window.event == SDL_WINDOWEVENT_DISPLAY_CHANGED ||
+                mDpiInit) {
+                int display = 0;
+                if (Context::GetInstance()->GetWindow()->GetWindowBackend() == WindowBackend::SDL_OPENGL) {
+                    display = SDL_GetWindowDisplayIndex(static_cast<SDL_Window*>(mImpl.Opengl.Window));
+                } else {
+                    display = SDL_GetWindowDisplayIndex(static_cast<SDL_Window*>(mImpl.Metal.Window));
+                }
+
+                float dpi;
+                if (SDL_GetDisplayDPI(display, &dpi, nullptr, nullptr) == 0) {
+                    dpiScale = dpi / USER_DEFAULT_SCREEN_DPI;
+                }
+            }
+
 #ifdef __SWITCH__
             LUS::Switch::ImGuiProcessEvent(mImGuiIo->WantTextInput);
 #endif
@@ -301,11 +322,30 @@ void Gui::Update(WindowEvent event) {
         case WindowBackend::DX11:
             ImGui_ImplWin32_WndProcHandler(static_cast<HWND>(event.Win32.Handle), event.Win32.Msg, event.Win32.Param1,
                                            event.Win32.Param2);
+
+            if (event.Win32.Msg == WM_DPICHANGED || mDpiInit) {
+                HMONITOR monitor = MonitorFromWindow(static_cast<HWND>(event.Win32.Handle), MONITOR_DEFAULTTONEAREST);
+                dpiScale = (float)ImGui_ImplWin32_GetDpiScaleForMonitor(monitor);
+            }
             break;
 #endif
         default:
             break;
     }
+
+    if (dpiScale > 0) {
+        if (mDpiInit) {
+            mLastDpiScale = 1.f;
+            mDpiInit = false;
+        }
+
+        float diff = dpiScale / mLastDpiScale;
+        mLastDpiScale = dpiScale;
+
+        ImGui::GetStyle().ScaleAllSizes(diff);
+        ImFont* font = ImGui::GetFont();
+        font->Scale *= diff;
+    }
 }
 
 bool Gui::ImGuiGamepadNavigationEnabled() {
@@ -322,12 +362,24 @@ void Gui::UnblockImGuiGamepadNavigation() {
     }
 }
 
+float Gui::GetCurrentDpiScale() {
+    if (mLastDpiScale <= 0) {
+        return 1.f;
+    }
+
+    return mLastDpiScale;
+}
+
 void Gui::DrawMenu() {
     LUS::Context::GetInstance()->GetWindow()->GetGui()->GetGuiWindow("Console")->Update();
     ImGuiBackendNewFrame();
     ImGuiWMNewFrame();
     ImGui::NewFrame();
 
+    if (mLastDpiScale == 0) {
+        mDpiInit = true;
+    }
+
     const std::shared_ptr<Window> wnd = Context::GetInstance()->GetWindow();
     const std::shared_ptr<Config> conf = Context::GetInstance()->GetConfig();
 

src/window/gui/Gui.h

@@ -92,6 +92,7 @@ class Gui {
     bool ImGuiGamepadNavigationEnabled();
     void BlockImGuiGamepadNavigation();
     void UnblockImGuiGamepadNavigation();
+    float GetCurrentDpiScale();
 
   protected:
     void ImGuiWMInit();
@@ -111,6 +112,9 @@ class Gui {
     std::shared_ptr<GuiMenuBar> mMenuBar;
     std::map<std::string, GuiTextureMetadata> mGuiTextures;
     std::map<std::string, std::shared_ptr<GuiWindow>> mGuiWindows;
+
+    bool mDpiInit = false;
+    float mLastDpiScale = 0;
 };
 } // namespace LUS