diff --git a/include/glez/draw.hpp b/include/glez/draw.hpp
index 435843d..32272a3 100644
--- a/include/glez/draw.hpp
+++ b/include/glez/draw.hpp
@@ -22,8 +22,8 @@ void rect_textured(float x, float y, float w, float h, rgba color,
     float angle);
 void circle(float x, float y, float radius, rgba color, float thickness, int steps);
 
-void string(float x, float y, const std::string& string, font& font, rgba color,
+void string(float x, float y, const std::string& string, const font& font, rgba color,
     float* width, float* height);
-void outlined_string(float x, float y, const std::string& string, font& font,
+void outlined_string(float x, float y, const std::string& string, const font& font,
     rgba color, rgba outline, float* width, float* height);
 } // namespace glez::draw
diff --git a/include/glez/font.hpp b/include/glez/font.hpp
index c9b1a89..700bf7e 100644
--- a/include/glez/font.hpp
+++ b/include/glez/font.hpp
@@ -22,8 +22,8 @@ public:
     glez::font& operator=(glez::font&&);
 
     // void stringSize(std::string_view string, float* width, float* height);
-    void stringSize(const std::string& string, float* width, float* height);
-    inline bool isLoaded() { return this->m_font != nullptr && this->atlas != nullptr; };
+    void stringSize(const std::string& string, float* width, float* height) const;
+    inline bool isLoaded() const { return this->m_font != nullptr && this->atlas != nullptr; };
 
 public:
     texture_font_t* m_font = nullptr;
diff --git a/src/draw.cpp b/src/draw.cpp
index 79ddb70..699cfa4 100644
--- a/src/draw.cpp
+++ b/src/draw.cpp
@@ -21,7 +21,7 @@ static GLuint triangle[3] = { 0, 1, 2 };
 } // namespace indices
 
 void internal_draw_string(float x, float y, const std::string& string,
-    glez::font& font, glez::rgba color, float* width, float* height) {
+    const glez::font& font, glez::rgba color, float* width, float* height) {
     assert(font.isLoaded());
     auto* fnt = font.m_font;
     float pen_x = x;
@@ -202,14 +202,14 @@ void circle(float x, float y, float radius, rgba color, float thickness,
     }
 }
 
-void string(float x, float y, const std::string& string, font& font, rgba color, float* width, float* height) {
+void string(float x, float y, const std::string& string, const font& font, rgba color, float* width, float* height) {
     auto fnt = font.m_font;
     fnt->rendermode = RENDER_NORMAL;
     fnt->outline_thickness = 0.0f;
     internal_draw_string(x, y, string, font, color, width, height);
 }
 
-void outlined_string(float x, float y, const std::string& string, font& font, rgba color, rgba outline, float* width, float* height) {
+void outlined_string(float x, float y, const std::string& string, const font& font, rgba color, rgba outline, float* width, float* height) {
     auto fnt = font.m_font;
     fnt->rendermode = RENDER_OUTLINE_POSITIVE;
     fnt->outline_thickness = 1.0f;
diff --git a/src/font.cpp b/src/font.cpp
index fe8cf62..824b46d 100644
--- a/src/font.cpp
+++ b/src/font.cpp
@@ -36,7 +36,7 @@ glez::font& font::operator=(glez::font&& var) {
     var.atlas = nullptr;
     return *this;
 }
-void font::stringSize(const std::string& string, float* width, float* height) {
+void font::stringSize(const std::string& string, float* width, float* height) const {
     assert(this->isLoaded());
     float penX = 0;