first build attempt

src/graticule.h

@@ -0,0 +1,73 @@
+/*
+ * MIT License
+ * Author: Mark Allyn
+ *
+ * graticule.h — incandescent bearing graticule for PPI scopes.
+ *
+ * Renders:
+ *   - Inner and outer bearing rings (circles)
+ *   - One tick per degree; major ticks every 10 degrees
+ *   - Text labels every GRAT_LABEL_INTERVAL_DEG degrees (15°)
+ *
+ * Also renders the yellow cursor arc + crossline when
+ * renderCursor() is called.
+ *
+ * All geometry is in screen pixels (top-left origin);
+ * the graticule.vert shader converts to NDC.
+ */
+
+#pragma once
+#include <glad/glad.h>
+#include <string>
+#include <vector>
+#include "settings.h"
+
+// Forward-declared so graticule.h doesn't pull in FreeType.
+class TextRenderer;
+
+class Graticule {
+public:
+    Graticule()  = default;
+    ~Graticule();
+
+    // Call after GL context is current.
+    // cx/cy: scope centre in screen pixels (top-left origin).
+    bool init(const std::string& shaderDir,
+              TextRenderer& tr,
+              float cx, float cy, float radius);
+
+    // Render the incandescent bearing graticule.
+    // intensity: 0-1 scales the graticule brightness.
+    // bearingOffset: degrees to rotate the display (Head-up mode).
+    void render(float viewportW, float viewportH,
+                float intensity, float bearingOffset = 0.0f) const;
+
+    // Render the yellow cursor overlay.
+    // brgDeg: cursor bearing (degrees true)
+    // rngNorm: cursor range, normalised 0-1 (1 = scope edge)
+    void renderCursor(float viewportW, float viewportH,
+                      float brgDeg, float rngNorm) const;
+
+private:
+    void buildRingGeometry();
+    void buildTickGeometry();
+
+    GLuint prog_     = 0;
+    GLuint ringVAO_  = 0, ringVBO_  = 0;
+    GLuint tickVAO_  = 0, tickVBO_  = 0;
+    GLuint cursVAO_  = 0, cursVBO_  = 0;
+
+    int ringVertCount_  = 0;
+    int tickVertCount_  = 0;
+    // Cursor geometry is rebuilt each frame (small, dynamic)
+
+    float cx_  = 0.f, cy_  = 0.f, r_ = 1.f;
+    TextRenderer* tr_ = nullptr;
+
+    // Pre-computed label screen positions (one per 15-degree step)
+    struct LabelPos {
+        float x, y;
+        char  text[8];
+    };
+    std::vector<LabelPos> labels_;
+};