1 files changed, 54 insertions, 0 deletions
diff --git a/symbols/symbols.h b/symbols/symbols.h
new file mode 100644
index 0000000..998ff3f
--- /dev/null
+++ b/symbols/symbols.h
@@ -0,0 +1,54 @@
+#ifndef VEGA_SYMBOLS_H
+#define VEGA_SYMBOLS_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* Symbols: glyphs and icons as outlines of quadratic curves in one file,
+ * verified once and then read where it lies (docs/design/002-symbol-format.md).
+ * An outline is a chain of points, on or off the curve, as in TrueType: two
+ * off points in a row imply the on point halfway between them. */
+enum { VEGA_SYMBOLS_HEADER = 28, VEGA_SYMBOL_BYTES = 24, VEGA_POINT_BYTES = 4 };
+typedef struct {
+    int16_t x, y;
+    bool off;  /* a control point */
+    bool move; /* starts a contour */
+} VegaPoint;
+typedef struct { float x0, y0, x1, y1, x2, y2; } VegaCurve; /* a line has its middle as control */
+typedef struct {
+    uint32_t code, first, count;          /* its points: [first, first + count) */
+    int16_t left, bottom, right, top;     /* bounds, in units, y up */
+    int16_t advance;
+} VegaSymbol;
+typedef struct {
+    const unsigned char *bytes;
+    size_t size;
+    uint16_t units; /* per em */
+    uint32_t symbols, points;
+} VegaSymbols;
+
+/* Verify bytes as a symbol file (kept, not copied); false with why. What
+ * reading needs is checked, per symbol: after this no read leaves the file
+ * or its symbol. The points themselves are not: one outside its symbol's
+ * bounds draws wrong. */
+bool vega_symbols_open(VegaSymbols *, const unsigned char *bytes, size_t size, char *error, size_t error_size);
+/* The symbol of code (a binary search), or false. */
+bool vega_symbol(const VegaSymbols *, uint32_t code, VegaSymbol *out);
+VegaSymbol vega_symbol_at(const VegaSymbols *, uint32_t index);
+VegaPoint vega_point(const VegaSymbols *, uint32_t index);
+/* The curve that point index of symbol begins, if any: an off point is the
+ * control of one, and an on point followed by another on point in the same
+ * contour starts a line. Every curve of a symbol is had once this way, from
+ * the point and its two neighbours alone (as a GPU would fetch it). */
+bool vega_symbol_curve(const VegaSymbols *, const VegaSymbol *, uint32_t index, VegaCurve *out);
+/* All of a symbol's curves, in one pass over its points; out has room for
+ * symbol->count (a symbol has no more curves than points). */
+uint32_t vega_symbol_curves(const VegaSymbols *, const VegaSymbol *, VegaCurve *out);
+/* The coverage (0 to 1) of the pixel whose center is (x, y) in units, at
+ * scale pixels per unit: the exact area the curves' outline covers. */
+double vega_coverage(const VegaCurve *, uint32_t count, double scale, double x, double y);
+/* width x height 8-bit coverage, rows top first; pixel (i, j) has its center
+ * at (left + (i + 0.5) / scale, top - (j + 0.5) / scale) in units. */
+void vega_symbol_raster(const VegaSymbols *, const VegaSymbol *, double scale, double left, double top, int width,
+                        int height, unsigned char *out);
+#endif