sdl ui backend

1 files changed, 81 insertions, 0 deletions

diff --git a/vendor/stb/font.c b/vendor/stb/font.c
new file mode 100644
index 00000000..6c5106f6
--- /dev/null
+++ b/vendor/stb/font.c
@@ -0,0 +1,81 @@
+// stb_truetype wrapper for ui_sdl.zig. See font.h. Compiled into the SDL UI
+// backend module alongside stb_truetype_impl.c (which defines the impl).
+#include "font.h"
+#include "stb_truetype.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+struct UIFont {
+    stbtt_fontinfo info;
+    const uint8_t *data;
+};
+
+UIFont *ui_font_new(const uint8_t *data, int32_t len) {
+    if (!data || len <= 0) return NULL;
+    UIFont *f = (UIFont *)calloc(1, sizeof(UIFont));
+    if (!f) return NULL;
+    f->data = data;
+    int offset = stbtt_GetFontOffsetForIndex(data, 0);
+    if (offset < 0 || !stbtt_InitFont(&f->info, (const unsigned char *)data, offset)) {
+        free(f);
+        return NULL;
+    }
+    return f;
+}
+
+void ui_font_free(UIFont *f) {
+    free(f);
+}
+
+float ui_font_scale_for_height(UIFont *f, float px) {
+    return stbtt_ScaleForPixelHeight(&f->info, px);
+}
+
+void ui_font_cell_metrics(UIFont *f, float scale, int32_t *cell_w, int32_t *cell_h, int32_t *ascent) {
+    int asc = 0, desc = 0, gap = 0;
+    stbtt_GetFontVMetrics(&f->info, &asc, &desc, &gap);
+    int a = (int)(asc * scale + 0.5f);
+    int d = (int)(-desc * scale + 0.5f);
+    int g = (int)(gap * scale + 0.5f);
+    *ascent = a;
+    *cell_h = a + d + g;
+    if (*cell_h < 1) *cell_h = 1;
+    // monospace advance of 'M'
+    int adv = 0, lsb = 0;
+    stbtt_GetCodepointHMetrics(&f->info, 'M', &adv, &lsb);
+    int w = (int)(adv * scale + 0.5f);
+    if (w < 1) w = 1;
+    *cell_w = w;
+}
+
+int ui_font_raster(UIFont *f, float scale, int32_t cp,
+                   uint8_t *out, int32_t stride, int32_t cell_w, int32_t cell_h,
+                   int32_t ascent) {
+    if (!out || cell_w <= 0 || cell_h <= 0) return 0;
+    // zero the cell
+    for (int y = 0; y < cell_h; y++)
+        memset(out + (size_t)y * stride, 0, (size_t)cell_w);
+
+    int w = 0, h = 0, xoff = 0, yoff = 0;
+    unsigned char *bm = stbtt_GetCodepointBitmap(&f->info, scale, scale, cp, &w, &h, &xoff, &yoff);
+    if (!bm || w <= 0 || h <= 0) {
+        if (bm) stbtt_FreeBitmap(bm, NULL);
+        return 0;
+    }
+    // origin = (0, baseline=ascent); glyph top-left = (xoff, ascent + yoff).
+    int gx = xoff;
+    int gy = ascent + yoff;
+    for (int y = 0; y < h; y++) {
+        int dy = gy + y;
+        if (dy < 0 || dy >= cell_h) continue;
+        for (int x = 0; x < w; x++) {
+            int dx = gx + x;
+            if (dx < 0 || dx >= cell_w) continue;
+            uint8_t v = bm[y * w + x];
+            if (v) out[(size_t)dy * stride + dx] = v;
+        }
+    }
+    stbtt_FreeBitmap(bm, NULL);
+    return 1;
+}