FontCache: Use map for efficient glyph lookup

This patch updates CachedFont to now use an std::map for cached glyphs,
instead of an std::vector. std::map allows O(log n) lookup, whereas
std::vector only allows O(n) lookup.

Note: std::unordered_map technically has better lookup complexity here,
with amortized O(1) lookup. However, hashmaps have a higher inherent
overhead than red-black trees so this would only be viable when going
above around 100 entries, which should never happen here for ASCII
glyphs.

include/JGL/FontCache.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <array>
+#include <map>
 #include <vector>
 #include <glad/glad.h>
 
@@ -26,7 +27,7 @@ public:
 
 class JGL::CachedFont {
 private:
-    std::vector<CachedGlyph*> glyphs{};
+    std::map<char, CachedGlyph*> glyphs;
     GLuint texture = 0;
     GLsizei texture_width = 0, texture_height = 0;
     unsigned int font_size = 0;
@@ -36,7 +37,7 @@ public:
     unsigned int getFontSize();
     unsigned int getFontIndex();
     CachedGlyph* getGlyph(char c);
-    std::vector<CachedGlyph*> getGlyphs();
+    std::map<char, CachedGlyph*> getGlyphs();
     const GLuint* getTexture();
     const GLsizei getTextureWidth() const;
     const GLsizei getTextureHeight() const;

src/FontCache.cpp

@@ -26,7 +26,7 @@ CachedGlyph::CachedGlyph(char c, std::array<GLfloat, 12> texcoords, float x2offs
 //Because most things shown would be english characters. We can cut down on the iteration time significantly
 //by putting each english character at the beginning of the list in order of how often they usually occur in text.
 void JGL::CachedFont::appendGlyph(JGL::CachedGlyph* glyph) {
-    glyphs.push_back(glyph);
+    glyphs.emplace(glyph->getCharacter(), glyph);
 }
 
 unsigned int JGL::CachedFont::getFontSize() {
@@ -38,9 +38,9 @@ unsigned int JGL::CachedFont::getFontIndex() {
 }
 
 CachedGlyph* JGL::CachedFont::getGlyph(char c) {
-    for (const auto& g : glyphs)
-        if (c == g->getCharacter())
-            return g;
+    auto it = glyphs.find(c);
+    if (it != glyphs.end())
+        return it->second;
     return nullptr;
 }
 
@@ -52,7 +52,7 @@ CachedFont::CachedFont(GLuint texture_id, GLsizei texture_width, GLsizei texture
     this->font_index = font_index;
 }
 
-std::vector<CachedGlyph*> CachedFont::getGlyphs() {
+std::map<char, CachedGlyph*> CachedFont::getGlyphs() {
     return glyphs;
 }