From 2050c0e0576f05156f192aa4caf48834d2f28b14 Mon Sep 17 00:00:00 2001
From: fschildt <florian.schildt@protonmail.com>
Date: Fri, 22 Aug 2025 15:23:11 +0200
Subject: first commit

---
 src/client/font.c | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 src/client/font.c

(limited to 'src/client/font.c')

diff --git a/src/client/font.c b/src/client/font.c
new file mode 100644
index 0000000..fd4915d
--- /dev/null
+++ b/src/client/font.c
@@ -0,0 +1,142 @@
+#include "basic/basic.h"
+#include <os/os.h>
+#include <client/font.h>
+#include <assert.h>
+
+#include <stb/stb_truetype.h>
+#include <stb/stb_image.h>
+#include <stb/stb_image_write.h>
+
+#include <string.h>
+#include <math.h>
+
+f32
+font_get_string32_cursor_xoff(Font *font, String32 *str, u32 cursor) {
+    f32 xoff = 0.0f;
+    u32 x = 0;
+    while (x < cursor) {
+        Glyph *glyph = font_get_glyph(font, str->codepoints[x]);
+        xoff += glyph->advance_width;
+        x++;
+    }
+    return xoff;
+}
+
+f32
+font_get_string32_width(Font *font, String32 *str)
+{
+    // @Todo: also consider left_side_bearing and kerning?
+    f32 width = 0.0f;
+    for (u64 i = 0; i < str->len; i++) {
+        Glyph *glyph = font_get_glyph(font, str->codepoints[i]);
+        width += glyph->advance_width;
+    }
+    return width;
+}
+
+f32
+font_get_height(Font *font)
+{
+    return font->y_advance;
+}
+
+Glyph *
+font_get_glyph(Font *font, u32 codepoint)
+{
+    assert(codepoint >= ' ' && codepoint <= '~');
+    i32 index = codepoint - ' ';
+    Glyph *glyph = &font->glyphs[index];
+    return glyph;
+}
+
+b32
+font_init(Font *font, char *path, int font_size)
+{
+    arena_init(&font->arena, MEBIBYTES(4));
+
+    size_t len;
+    u8 *ttf = (u8*)os_file_read_as_string(&font->arena, path, &len);
+    if (!ttf) {
+        arena_deinit(&font->arena);
+        return false;
+    }
+
+
+    // set font info
+    if (!stbtt_InitFont(&font->info, ttf, 0))
+    {
+        printf("stbtt_InitFont failed\n");
+        arena_deinit(&font->arena);
+        return false;
+    }
+
+
+    // set scale
+    f32 scale = stbtt_ScaleForPixelHeight(&font->info, font_size);
+
+
+    // get font vmetrics
+    i32 baseline, ascent, descent, line_gap;
+    stbtt_GetFontVMetrics(&font->info, &ascent, &descent, &line_gap);
+    baseline = scale * -descent;
+    ascent   = scale * ascent;
+    descent  = scale * descent;
+    line_gap = scale * line_gap;
+
+
+    font->scale = scale;
+    font->baseline = baseline;
+    font->y_advance = ascent - descent + line_gap;
+
+
+    // make glyphs
+    u32 glyph_count = '~' - ' ' + 1;
+    for (u32 it = 0; it < glyph_count; ++it)
+    {
+        Glyph *glyph = font->glyphs + it;
+        char c = it + ' ';
+
+
+        int bbx0, bby0, bbx1, bby1;
+        stbtt_GetCodepointBitmapBox(&font->info, c, scale, scale, &bbx0, &bby0, &bbx1, &bby1);
+        int width = bbx1 - bbx0;
+        int height = bby1 - bby0;
+
+
+        u8 *bitmap_correct = arena_push(&font->arena, width * height);
+        u32 arena_save_pos = font->arena.size_used;
+        u8 *bitmap_flipped = arena_push(&font->arena, width * height);
+
+
+        stbtt_MakeCodepointBitmap(&font->info, bitmap_flipped, width, height, width, scale, scale, c);
+
+        // @Speed: Adjust projection and don't execute this at all?
+        u8 *dest = bitmap_correct;
+        for (u32 y = 0; y < height; ++y)
+        {
+            u8 *src = bitmap_flipped + (height-1-y)*width;
+            for (u32 x = 0; x < width; ++x)
+            {
+                *dest++ = *src++;
+            }
+        }
+
+        i32 advance_width;
+        i32 left_side_bearing;
+        stbtt_GetCodepointHMetrics(&font->info, c, &advance_width, &left_side_bearing);
+        advance_width = scale * advance_width;
+        left_side_bearing = scale * left_side_bearing;
+
+
+        glyph->xoff = scale * bbx0 + left_side_bearing;
+        glyph->yoff = -bby1;
+        glyph->advance_width = advance_width;
+        glyph->bitmap.width  = width;
+        glyph->bitmap.height = height;
+        glyph->bitmap.data.grayscale = bitmap_correct;
+        font->arena.size_used = arena_save_pos;
+    }
+
+    return true;
+}
+
-- 
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