--- a/libmlk-core/mlk/core/font.c	Sat Mar 04 15:10:35 2023 +0100
+++ b/libmlk-core/mlk/core/font.c	Sat Mar 04 15:39:21 2023 +0100
@@ -40,7 +40,10 @@
 }
 
 int
-mlk_font_openmem(struct mlk_font *font, const void *buffer, size_t buflen, unsigned int size)
+mlk_font_openmem(struct mlk_font *font,
+                 const void *buffer,
+                 size_t buflen,
+                 unsigned int size)
 {
 	assert(font);
 	assert(buffer);
@@ -120,8 +123,8 @@
 {
 	assert(font);
 
-	if (font->handle)
+	if (font->handle) {
 		TTF_CloseFont(font->handle);
-
-	memset(font, 0, sizeof (*font));
+		font->handle = NULL;
+	}
 }

--- a/libmlk-core/mlk/core/font.h	Sat Mar 04 15:10:35 2023 +0100
+++ b/libmlk-core/mlk/core/font.h	Sat Mar 04 15:39:21 2023 +0100
@@ -19,43 +19,159 @@
 #ifndef MLK_CORE_FONT_H
 #define MLK_CORE_FONT_H
 
+/**
+ * \file font.h
+ * \brief Basic font management
+ *
+ * Open and use fonts for rendering UTF-8 text.
+ */
+
 #include <stddef.h>
 
 struct mlk_texture;
 
+/**
+ * \enum mlk_font_style
+ * \brief Font style
+ */
 enum mlk_font_style {
+	/**
+	 * Rendered text is antialiased, default.
+	 */
 	MLK_FONT_STYLE_ANTIALIASED,
+
+	/**
+	 * Simple rendering, no antialiasing.
+	 */
 	MLK_FONT_STYLE_NONE,
+
+	/**
+	 * Last enumeration constant.
+	 */
 	MLK_FONT_STYLE_LAST
 };
 
+/**
+ * \struct mlk_font
+ * \brief Font structure
+ *
+ * You can fill font attributes before calling ::mlk_font_open or
+ * ::mlk_font_openmem.
+ */
 struct mlk_font {
+	/**
+	 * (read-write)
+	 *
+	 * Style used for rendering, can be changed at runtime.
+	 */
 	enum mlk_font_style style;
+
+	/** \cond MLK_PRIVATE_DECLS */
 	void *handle;
+	/** \endcond MLK_PRIVATE_DECLS */
 };
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
-int
-mlk_font_open(struct mlk_font *, const char *, unsigned int);
-
+/**
+ * Open a font from the file system path.
+ *
+ * \pre font != NULL
+ * \pre path != NULL
+ * \param font the font to open
+ * \param path path to the font file (e.g. .ttf, .otf, etc)
+ * \param size desired font height in pixels
+ * \return 0 on success or an error code on failure
+ */
 int
-mlk_font_openmem(struct mlk_font *, const void *, size_t, unsigned int);
+mlk_font_open(struct mlk_font *font, const char *path, unsigned int size);
 
+/**
+ * Open a font from a const binary data.
+ *
+ * The binary data must be kept alive until the font is no longer used.
+ *
+ * \pre font != NULL
+ * \param font the font to open
+ * \param data the font content
+ * \param datasz the font content length
+ * \param size desired font height in pixels
+ * \return 0 on success or an error code on failure
+ */
 int
-mlk_font_ok(const struct mlk_font *);
+mlk_font_openmem(struct mlk_font *font,
+                 const void *data,
+                 size_t datasz,
+                 unsigned int size);
+
+/**
+ * Tells if the font is usable.
+ *
+ * \param font the font to check
+ * \return non-zero if the font structure is usable
+ */
+int
+mlk_font_ok(const struct mlk_font *font);
 
+/**
+ * Render some text using the font and generate a texture.
+ *
+ * The texture destination must be deallocated once no longer used using
+ * ::mlk_texture_finish.
+ *
+ * \pre mlk_font_ok(font)
+ * \pre texture != NULL
+ * \pre text != NULL && strlen(text) > 0
+ * \param font the font to use
+ * \param texture the texture to initialize
+ * \param text the non NULL and non empty UTF-8 text
+ * \param color foreground color
+ * \return 0 on success or an error code on failure
+ */
 int
-mlk_font_render(struct mlk_font *, struct mlk_texture *, const char *, unsigned long);
+mlk_font_render(struct mlk_font *font,
+                struct mlk_texture *texture,
+                const char *text,
+                unsigned long color);
 
+/**
+ * Return the font height in pixels
+ *
+ * \pre mlk_font_ok(font)
+ * \param font the font to use
+ * \return the font height
+ */
 unsigned int
-mlk_font_height(const struct mlk_font *);
+mlk_font_height(const struct mlk_font *font);
 
+/**
+ * Query a dimension required to draw a text.
+ *
+ * Both w and h pointers can be NULL if one of the dimension isn't required.
+ *
+ * If the function fails, *w and *h are set to 0.
+ *
+ * \pre mlk_font_ok(font)
+ * \param font the font to use
+ * \param text the non NULL and non empty UTF-8 text
+ * \param w pointer receiving width (or NULL)
+ * \param h pointer receiving height (or NULL)
+ * \return 0 on success or an error code on failure
+ */
 int
-mlk_font_query(const struct mlk_font *, const char *, unsigned int *, unsigned int *);
+mlk_font_query(const struct mlk_font *font,
+               const char *text,
+               unsigned int *w,
+               unsigned int *h);
 
+/**
+ * Destroy this font.
+ *
+ * \pre mlk_font_ok(font)
+ * \param font the font to destroy
+ */
 void
 mlk_font_finish(struct mlk_font *);