From 16697c0503bf398aec153b498cd4fb8217d09d52 Mon Sep 17 00:00:00 2001
From: Leon Styhre <leon@leonstyhre.com>
Date: Sun, 4 Aug 2024 12:46:57 +0200
Subject: [PATCH] Added sharing of glyph atlas entries between shaped glyph
 entries that need the same texture

---
 es-core/src/resources/Font.cpp | 15 ++++++++++++++-
 es-core/src/resources/Font.h   |  6 ++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/es-core/src/resources/Font.cpp b/es-core/src/resources/Font.cpp
index f7f446ef1..88ae99c51 100644
--- a/es-core/src/resources/Font.cpp
+++ b/es-core/src/resources/Font.cpp
@@ -1109,7 +1109,20 @@ Font::Glyph* Font::getGlyphByIndex(const unsigned int id, hb_font_t* fontArg, in
     FontTexture* tex {nullptr};
     glm::ivec2 cursor {0, 0};
     const glm::ivec2 glyphSize {glyphSlot->bitmap.width, glyphSlot->bitmap.rows};
-    getTextureForNewGlyph(glyphSize, tex, cursor);
+
+    // Check if there is already a texture entry for the glyph, otherwise create it.
+    // This makes sure we don't create multiple identical glyph atlas entries and waste VRAM.
+    auto it2 = mGlyphTextureMap.find(std::make_pair(id, fontArg));
+    if (it2 != mGlyphTextureMap.end()) {
+        tex = (*it2).second.texture;
+        cursor = (*it2).second.cursor;
+    }
+    else {
+        getTextureForNewGlyph(glyphSize, tex, cursor);
+        GlyphTexture& glyphTexture {mGlyphTextureMap[std::make_pair(id, returnedFont)]};
+        glyphTexture.texture = tex;
+        glyphTexture.cursor = cursor;
+    }
 
     // This should (hopefully) never occur as size constraints are enforced earlier on.
     if (tex == nullptr) {
diff --git a/es-core/src/resources/Font.h b/es-core/src/resources/Font.h
index 0df5b9732..608db3c12 100644
--- a/es-core/src/resources/Font.h
+++ b/es-core/src/resources/Font.h
@@ -182,6 +182,11 @@ private:
         int rows;
     };
 
+    struct GlyphTexture {
+        FontTexture* texture;
+        glm::ivec2 cursor;
+    };
+
     struct FallbackFontCache {
         std::string path;
         std::shared_ptr<FontFace> face;
@@ -240,6 +245,7 @@ private:
     std::vector<std::unique_ptr<FontTexture>> mTextures;
     std::map<unsigned int, Glyph> mGlyphMap;
     std::map<std::tuple<unsigned int, hb_font_t*, int>, Glyph> mGlyphMapByIndex;
+    std::map<std::pair<unsigned int, hb_font_t*>, GlyphTexture> mGlyphTextureMap;
 
     const std::string mPath;
     hb_font_t* mFontHB;