System/Utilities/TrueType: Add @stbtt_GetTextWidth()

System/Utilities/TrueType.HC

@@ -50,6 +50,19 @@ U8* @stbtt_RenderText(stbtt_fontinfo* info, I32 b_w, I32 b_h, I32 l_h, I32* word
     }
 }
 
+I32 @stbtt_GetTextWidth(stbtt_fontinfo* info, I32 l_h, I32* word, I32* advance = NULL)
+{
+    U64 reg RDI rdi = info;
+    U64 reg RSI rsi = l_h;
+    U64 reg RDX rdx = word;
+    U64 reg RCX rcx = advance;
+    no_warn rdi, rsi, rdx, rcx;
+    asm {
+        MOV RAX, STBTT_GETTEXTWIDTH
+        CALL RAX
+    }
+}
+
 U8* @stbtt_GetFontNameDefault(stbtt_fontinfo* font, I32* length)
 {
     U64 reg RDI rdi = font;

scripts/build-all

@@ -209,6 +209,7 @@ def generate_iso_c_file():
 
     truetype_hc_fixup('STBTT_INITFONT', 'stbtt_InitFont', truetype_bin_path, truetype_hc_path)
     truetype_hc_fixup('STBTT_RENDERTEXT', 'stbtt_RenderText', truetype_bin_path, truetype_hc_path)
+    truetype_hc_fixup('STBTT_GETTEXTWIDTH', 'stbtt_GetTextWidth', truetype_bin_path, truetype_hc_path)
     truetype_hc_fixup('STBTT_GETFONTNAMEDEFAULT', 'stbtt_GetFontNameDefault', truetype_bin_path, truetype_hc_path)
 
     # Fixup addresses for Tlse.HC

src/truetype/truetype.c

@@ -55,4 +55,52 @@ unsigned char* stbtt_RenderText(stbtt_fontinfo* info, int b_w, int b_h, int l_h,
     return bitmap;
 }
 
+int stbtt_GetTextWidth(stbtt_fontinfo* info, int l_h, int* word, int* advance)
+{
+    // https://github.com/justinmeiners/stb-truetype-example
+
+    /* calculate font scaling */
+    float scale = stbtt_ScaleForPixelHeight(info, l_h);
+
+    int x = 0;
+
+    int ascent, descent, lineGap;
+    stbtt_GetFontVMetrics(info, &ascent, &descent, &lineGap);
+
+    ascent = roundf(ascent * scale);
+    descent = roundf(descent * scale);
+
+    int i = 0;
+    while (word[i]) {
+        /* how wide is this character */
+        int ax;
+        int lsb;
+        stbtt_GetCodepointHMetrics(info, word[i], &ax, &lsb);
+        /* (Note that each Codepoint call has an alternative Glyph version which caches the work required to lookup the character word[i].) */
+
+        /* get bounding box for character (may be offset to account for chars that dip above or below the line) */
+        int c_x1, c_y1, c_x2, c_y2;
+        stbtt_GetCodepointBitmapBox(info, word[i], scale, scale, &c_x1, &c_y1, &c_x2, &c_y2);
+
+        /* compute y (different characters have different heights) */
+        int y = ascent + c_y1;
+
+        /* advance x */
+        x += roundf(ax * scale);
+
+        /* add kerning */
+        int kern;
+        kern = stbtt_GetCodepointKernAdvance(info, word[i], word[i + 1]);
+        x += roundf(kern * scale);
+
+        if (advance) {
+            advance[i] = x;
+        }
+
+        ++i;
+    }
+
+    return x;
+}
+
 int main() { return 0; }