fix ini saving and high dpi support for imgui

Manually set imgui.ini file location to a safe place, as the default just drops
it into whatever the working directory is currently. Also set a new default
font and add support for scaling font and ui for high dpi and high pixel
density screens.

Author: notimaginative

code/def_files/data/fonts/BankGothic-BT-Light.ttf

@@ -159,6 +159,11 @@ namespace
 				case SDL_EVENT_WINDOW_RESIZED:
 					gr_screen_resize(e.window.data1, e.window.data2);
 					break;
+
+				case SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED:
+					auto vp = os::getMainViewport();
+					if (vp) vp->updateScaling();
+					break;
 			}
 
 			gr_activate(fAppActive);
@@ -442,6 +447,7 @@ void os_init(const char * wclass, const char * title, const char * app_name)
 	os::events::addEventListener(SDL_EVENT_WINDOW_FOCUS_LOST, os::events::DEFAULT_LISTENER_WEIGHT, window_event_handler);
 	os::events::addEventListener(SDL_EVENT_WINDOW_FOCUS_GAINED, os::events::DEFAULT_LISTENER_WEIGHT, window_event_handler);
 	os::events::addEventListener(SDL_EVENT_WINDOW_CLOSE_REQUESTED, os::events::DEFAULT_LISTENER_WEIGHT, window_event_handler);
+	os::events::addEventListener(SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED, os::events::DEFAULT_LISTENER_WEIGHT, window_event_handler);
 
 	os::events::addEventListener(SDL_EVENT_QUIT, os::events::DEFAULT_LISTENER_WEIGHT, quit_handler);
 

code/osapi/osapi.cpp

@@ -282,6 +282,27 @@ namespace os
 		 * @note Implementation may ignore invocations of this function
 		 */
 		virtual void restore() = 0;
+
+		/**
+		 * @brief Get coordinate scale value for high-dpi displays
+		 *
+		 * @return Scale value as float
+		 */
+		virtual float getCoordScale() { return 1.0f; }
+
+		/**
+		 * @brief Returns passed value scaled for high-dpi
+		 *
+		 * @param val The value to be scaled
+		 *
+		 * @return Scaled value as float
+		 */
+		virtual float getScaled(float val) { return val; }
+
+		/**
+		 * @brief Updates scaling setup based on dpi changes
+		 */
+		virtual void updateScaling() {};
 	};
 
 	/**

code/osapi/osapi.h

@@ -280,6 +280,10 @@ add_file_folder("Default files\\\\data\\\\effects"
 	def_files/data/effects/volumetric-f.sdr
 )
 
+add_file_folder("Default files\\\\data\\\\fonts"
+	def_files/data/fonts/BankGothic-BT-Light.ttf
+)
+
 add_file_folder("Default files\\\\data\\\\maps"
 	def_files/data/maps/app_icon.png
 	def_files/data/maps/app_icon_d.png
@@ -315,6 +319,7 @@ add_file_folder("Default files\\\\builtin"
 set(default_files_files
 	${files_Default_files_data}
 	${files_Default_files_data_effects}
+	${files_Default_files_data_fonts}
 	${files_Default_files_data_maps}
 	${files_Default_files_data_scripts}
 	${files_Default_files_data_tables}

code/source_groups.cmake

@@ -82,9 +82,40 @@ class SDLOpenGLContext: public os::OpenGLContext {
 class SDLWindowViewPort: public os::Viewport {
 	SDL_Window* _window;
 	os::ViewPortProperties _props;
+
+	float coord_scale;
+	float content_scale;
+	float scale_factor;
+	ImGuiStyle styleOrig;
+
+	void setDPIScaling() {
+		int window_w, window_h;
+		int framebuffer_w, framebuffer_h;
+
+		SDL_GetWindowSize(_window, &window_w, &window_h);
+		SDL_GetWindowSizeInPixels(_window, &framebuffer_w, &framebuffer_h);
+
+		float sx = framebuffer_w / static_cast<float>(window_w);
+		float sy = framebuffer_h / static_cast<float>(window_h);
+
+		coord_scale = std::max(sx, sy);
+		content_scale = SDL_GetWindowDisplayScale(_window);
+		scale_factor = content_scale / coord_scale;
+	}
+
+	void initDPIScaling() {
+		// save initial imgui style
+		styleOrig = ImGui::GetStyle();
+		// update dpi scaling values
+		setDPIScaling();
+		// scale imgui style
+		ImGui::GetStyle().ScaleAllSizes(scale_factor);
+	}
  public:
 	SDLWindowViewPort(SDL_Window* window, const os::ViewPortProperties& props) : _window(window), _props(props) {
 		Assertion(window != nullptr, "Invalid window specified");
+		// scaling for imgui high dpi stuff
+		initDPIScaling();
 	}
 	~SDLWindowViewPort() override {
 		SDL_DestroyWindow(_window);
@@ -136,6 +167,23 @@ class SDLWindowViewPort: public os::Viewport {
 	void restore() override {
 		SDL_RestoreWindow(_window);
 	}
+
+	float getCoordScale() override {
+		return coord_scale;
+	}
+
+	float getScaled(float val) override {
+		return val * scale_factor;
+	}
+
+	void updateScaling() override {
+		// restore original imgui style
+		ImGui::GetStyle() = styleOrig;
+		// update dpi scaling values
+		setDPIScaling();
+		// scale imgui style
+		ImGui::GetStyle().ScaleAllSizes(scale_factor);
+	}
 };
 
 SDLGraphicsOperations::SDLGraphicsOperations() {

freespace2/SDLGraphicsOperations.cpp

@@ -1820,6 +1820,8 @@ void game_init()
 	Random::seed(static_cast<unsigned int>(time(nullptr)));
 
 	ImGui::CreateContext();
+	ImGui::GetIO().IniFilename = nullptr;
+	ImGui::LoadIniSettingsFromDisk(os_get_config_path("imgui.ini").c_str());
 
 	Framerate_delay = 0;
 
@@ -1968,6 +1970,35 @@ void game_init()
 		return;
 	}
 
+	// if not standalone then setup scalable font for imgui to use
+	if ( !Is_standalone ) {
+		ImGuiIO &io = ImGui::GetIO();
+		ImFontConfig fontConfig;
+
+		// improves font clarity on high density displays
+		fontConfig.RasterizerDensity = os::getMainViewport()->getCoordScale();;
+
+		auto file = cfopen("BankGothic-BT-Light.ttf", "rb", CF_TYPE_FONT);
+
+		if (file) {
+			// clear out default font
+			io.Fonts->Clear();
+
+			const auto size = cfilelength(file);
+
+			// NOTE: ImGui will free this memory on shutdown
+			auto font = reinterpret_cast<uint8_t*>(IM_ALLOC(size * (sizeof(uint8_t))));
+
+			cfread(font, 1, size, file);
+
+			cfclose(file);
+			file = nullptr;
+
+			io.Fonts->AddFontFromMemoryTTF(font, size, os::getMainViewport()->getScaled(12.f),
+										   &fontConfig);
+		}
+	}
+
 	if (LoggingEnabled && Cmdline_debug_window) {
 		outwnd_debug_window_init();
 	}
@@ -7000,6 +7031,11 @@ int game_main(int argc, char *argv[])
 			break;
 		}
 
+		if (ImGui::GetIO().WantSaveIniSettings) {
+			ImGui::SaveIniSettingsToDisk(os_get_config_path("imgui.ini").c_str());
+			ImGui::GetIO().WantSaveIniSettings = false;
+		}
+
 		// Since tracing is always active this needs to happen in the main loop
 		tracing::process_events();
 	} 
@@ -7110,6 +7146,7 @@ void game_shutdown(void)
 		std_deinit_standalone();
 	}
 
+	ImGui::SaveIniSettingsToDisk(os_get_config_path("imgui.ini").c_str());
 	ImGui::DestroyContext();
 
 	os_cleanup();