DisplayInfo

include/mostly_harmless/gui/mostlyharmless_DisplayInfo.h

@@ -0,0 +1,12 @@
+//
+// Created by Syl Morrison on 06/02/2026.
+//
+
+#ifndef GLEO_MOSTLYHARMLESS_DISPLAYINFO_H
+#define GLEO_MOSTLYHARMLESS_DISPLAYINFO_H
+#include <cstdint>
+namespace mostly_harmless::gui::display_info {
+    void getScreenDimensions(std::uint32_t* width, std::uint32_t* height);
+    double getDevicePixelRatio();
+} // namespace mostly_harmless::gui::display_info
+#endif // GLEO_MOSTLYHARMLESS_DISPLAYINFO_H

include/mostly_harmless/gui/platform/mostlyharmless_GuiHelpersMacOS.h

@@ -28,6 +28,10 @@ namespace mostly_harmless::gui::helpers::macos {
      * \param height A pointer to the height variable - the result will be written here.
      */
     void getViewSize(void* viewHandle, std::uint32_t* width, std::uint32_t* height);
+
+    void getScreenSize(std::uint32_t* width, std::uint32_t* height);
+
+    double getDevicePixelRatio();
     /**
      * Adds an NSView as a subview of another NSView.
      * \param parentViewHandle A void* to the NSView to add the child view to.

source/CMakeLists.txt

@@ -28,6 +28,7 @@ set(MOSTLYHARMLESS_SOURCES
         ${CMAKE_CURRENT_SOURCE_DIR}/gui/mostlyharmless_WebviewEditor.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/gui/mostlyharmless_Cursor.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/gui/mostlyharmless_Colour.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/gui/mostlyharmless_DisplayInfo.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/utils/mostlyharmless_TaskThread.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/utils/mostlyharmless_Timer.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/utils/mostlyharmless_OnScopeExit.cpp

source/gui/mostlyharmless_DisplayInfo.cpp

@@ -0,0 +1,24 @@
+//
+// Created by Syl Morrison on 06/02/2026.
+//
+#include "mostly_harmless/gui/platform/mostlyharmless_GuiHelpersMacOS.h"
+
+
+#include <mostly_harmless/gui/mostlyharmless_DisplayInfo.h>
+namespace mostly_harmless::gui::display_info {
+
+#if defined(MOSTLY_HARMLESS_MACOS)
+#include <mostly_harmless/gui/platform/mostlyharmless_GuiHelpersMacOS.h>
+    void getScreenDimensions(std::uint32_t* width, std::uint32_t* height) {
+        helpers::macos::getScreenSize(width, height);
+    }
+
+    double getDevicePixelRatio() {
+        return helpers::macos::getDevicePixelRatio();
+    }
+
+#else
+
+#endif
+
+} // namespace mostly_harmless::gui::display_info

source/gui/platform/mostlyharmless_GuiHelpersMacOS.mm

@@ -32,6 +32,27 @@ void getViewSize(void* viewHandle, std::uint32_t* width, std::uint32_t* height)
         *height = static_cast<std::uint32_t>(bounds.size.height);
     }
 
+    void getScreenSize(std::uint32_t* width, std::uint32_t* height) {
+        auto frame = [[NSScreen mainScreen] frame];
+        *width = static_cast<std::uint32_t>(frame.size.width);
+        *height = static_cast<std::uint32_t>(frame.size.height);
+    }
+
+    double getDevicePixelRatio() {
+        auto mainDisplayId = CGMainDisplayID();
+        auto screenSizeMm = CGDisplayScreenSize(mainDisplayId);
+        const auto widthMm = screenSizeMm.width;
+        const auto heightMm = screenSizeMm.height;
+        const auto hypMm = std::sqrt((widthMm * widthMm) + (heightMm * heightMm));
+        std::uint32_t widthPx, heightPx;
+        getScreenSize(&widthPx, &heightPx);
+        const auto pxHyp = std::sqrt((widthPx * widthPx) + (heightPx * heightPx));
+        constexpr static auto mmPerInch = 25.4;
+        const auto ratio = pxHyp / hypMm;
+        const auto dpi = ratio * mmPerInch;
+        return 1.0;
+    }
+
     void reparentView(void* hostViewHandle, void* clientViewHandle, void* childViewHandle, Colour backgroundColour) {
         auto* host = static_cast<NSView*>(hostViewHandle);
         auto* client = static_cast<NSView*>(clientViewHandle);