3 files changed, 100 insertions, 0 deletions

diff --git a/font/CMakeLists.txt b/font/CMakeLists.txt
new file mode 100644
index 0000000..6eb6fc0
--- /dev/null
+++ b/font/CMakeLists.txt
@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.0)
+
+project(font)
+
+set(CMAKE_C_STANDARD 17)
+set(CMAKE_C_STANDARD_REQUIRED On)
+set(CMAKE_C_EXTENSIONS Off)
+
+add_library(font
+  font.c)
+
+target_include_directories(font PUBLIC
+  .)
+
+target_compile_options(font PRIVATE -Wall -Wextra -Wpedantic)
diff --git a/font/font.c b/font/font.c
new file mode 100644
index 0000000..2d30c50
--- /dev/null
+++ b/font/font.c
@@ -0,0 +1,45 @@
+#include <font.h>
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static size_t GetFileSize(FILE* file) {
+  fseek(file, 0, SEEK_END);
+  const size_t size = ftell(file);
+  fseek(file, 0, SEEK_SET);
+  return size;
+}
+
+FontAtlas* LoadFontAtlas(const char* path) {
+  assert(path);
+
+  FILE*      file  = NULL;
+  FontAtlas* atlas = 0;
+
+  if ((file = fopen(path, "rb")) == NULL) {
+    goto cleanup;
+  }
+
+  const size_t size = GetFileSize(file);
+  if (size == (size_t)-1) {
+    goto cleanup;
+  }
+
+  atlas = calloc(1, size);
+  if (!atlas) {
+    goto cleanup;
+  }
+
+  if (fread(atlas, size, 1, file) != 1) {
+    free(atlas);
+    atlas = 0;
+  }
+
+cleanup:
+  if (file != NULL) {
+    fclose(file);
+  }
+  return atlas;
+}
diff --git a/font/font.h b/font/font.h
new file mode 100644
index 0000000..13ff1c3
--- /dev/null
+++ b/font/font.h
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <assert.h>
+#include <stdint.h>
+
+static const unsigned char FontGlyphStart     = 32;  // Space.
+static const unsigned char FontGlyphEnd       = 127; // One past tilde.
+static const int           FontAtlasNumGlyphs = FontGlyphEnd - FontGlyphStart;
+
+/// Font atlas header.
+typedef struct FontHeader {
+  uint16_t glyph_width;
+  uint16_t glyph_height;
+  uint16_t num_glyphs;
+} FontHeader;
+
+/// Font atlas.
+///
+/// Pixels are stored in "glyph-major" order. First the rows of the first glyph,
+/// followed by the rows of the second glyph, etc. Thus, pixels should be viewed
+/// as a linear array, not a 2d array. This arrangement allows an application to
+/// render glyphs by scanning atlas memory linearly.
+typedef struct FontAtlas {
+  FontHeader    header;
+  unsigned char pixels[1];
+} FontAtlas;
+
+/// Load a font atlas from a file.
+FontAtlas* LoadFontAtlas(const char* path);
+
+/// Get the glyph into the atlas.
+static inline const unsigned char* FontGetGlyph(
+    const FontAtlas* atlas, unsigned char c) {
+  assert(atlas);
+  const int index = c - FontGlyphStart;
+  assert(index >= 0);
+  assert(index < FontAtlasNumGlyphs);
+  return atlas->pixels +
+         index * (atlas->header.glyph_width * atlas->header.glyph_height);
+}