macOS: sharp ImGui menu text on Retina at every menu scale (#714)

* macOS: sharp ImGui menu text on Retina at every menu scale

On a HiDPI display the ImGui overlay renders into a 2x framebuffer, but
the glyph atlas is rasterized at the logical point size and stretched up
by DisplayFramebufferScale, so all menu text looks fuzzy.

Set ImFontConfig::RasterizerDensity on the game fonts and the merged
FontAwesome icons: glyphs rasterize at higher resolution without
changing logical size or layout. Baked at retinaScale (2.0) times the
Menu Scale slider's maximum (2.0) so the runtime FontGlobalScale only
ever downsamples a high-res atlas instead of stretching a low-res one,
keeping text crisp at every Menu Scale setting. Standard-DPI displays
just get a supersampled atlas (identical layout, slightly sharper).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Shorten the RasterizerDensity comment

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/src/port/Engine.cpp b/src/port/Engine.cpp
index 5120c82a2..3d516130e 100644
--- a/src/port/Engine.cpp
+++ b/src/port/Engine.cpp
@@ -587,11 +587,21 @@ uint8_t GameEngine::GetBankIdByName(const std::string& name) {
 ImFont* GameEngine::CreateFontWithSize(float size, std::string fontPath) {
     auto mImGuiIo = &ImGui::GetIO();
     ImFont* font;
+    // Rasterize the glyph atlas at higher density so menu text stays sharp on HiDPI/Retina
+    // displays. Bake at retinaScale * maxMenuScale so the runtime Menu Scale setting
+    // (FontGlobalScale) only ever downsamples the atlas rather than stretching it blurry.
+    float rasterDensity = 1.0f;
+#if defined(__APPLE__)
+    constexpr float kRetinaScale = 2.0f;  // Retina backing scale
+    constexpr float kMaxMenuScale = 2.0f; // keep in sync with the gSettings.Menu.Scale slider Max
+    rasterDensity = kRetinaScale * kMaxMenuScale;
+#endif
     if (fontPath == "") {
         ImFontConfig fontCfg = ImFontConfig();
         fontCfg.OversampleH = fontCfg.OversampleV = 1;
         fontCfg.PixelSnapH = true;
         fontCfg.SizePixels = size;
+        fontCfg.RasterizerDensity = rasterDensity;
         font = mImGuiIo->Fonts->AddFontDefault(&fontCfg);
     } else {
         auto initData = std::make_shared<Ship::ResourceInitData>();
@@ -603,7 +613,9 @@ ImFont* GameEngine::CreateFontWithSize(float size, std::string fontPath) {
             Ship::Context::GetInstance()->GetResourceManager()->LoadResource(fontPath, false, initData));
         char* fontDataPtr = (char*) malloc(fontData->DataSize);
         memcpy(fontDataPtr, fontData->Data, fontData->DataSize);
-        font = mImGuiIo->Fonts->AddFontFromMemoryTTF(fontDataPtr, fontData->DataSize, size);
+        ImFontConfig fontCfg = ImFontConfig();
+        fontCfg.RasterizerDensity = rasterDensity;
+        font = mImGuiIo->Fonts->AddFontFromMemoryTTF(fontDataPtr, fontData->DataSize, size, &fontCfg);
     }
     // FontAwesome fonts need to have their sizes reduced by 2.0f/3.0f in order to align correctly
     float iconFontSize = size * 2.0f / 3.0f;
@@ -612,6 +624,7 @@ ImFont* GameEngine::CreateFontWithSize(float size, std::string fontPath) {
     iconsConfig.MergeMode = true;
     iconsConfig.PixelSnapH = true;
     iconsConfig.GlyphMinAdvanceX = iconFontSize;
+    iconsConfig.RasterizerDensity = rasterDensity;
     mImGuiIo->Fonts->AddFontFromMemoryCompressedBase85TTF(fontawesome_compressed_data_base85, iconFontSize,
                                                           &iconsConfig, sIconsRanges);
     return font;