feat: vector zoom for SVG in image viewer app

programs/src/imageviewer/svg_doc.hpp

@@ -0,0 +1,40 @@
+/*
+ * svg_doc.hpp
+ * Lazily-rasterized SVG document for the Image Viewer.
+ * Keeps the source bytes around so the rasterizer can be re-run whenever the
+ * user changes zoom, giving true vector quality at every scale.
+ * Copyright (c) 2026 Daniel Hammer
+ */
+
+#pragma once
+#include <cstdint>
+
+namespace imageviewer {
+
+struct SvgDoc {
+    uint8_t* source;       // SVG bytes (owned, freed in svgdoc_free)
+    int      source_len;
+    int      natural_w;    // intrinsic SVG dimensions
+    int      natural_h;
+    uint32_t* pixels;      // current rasterization (owned ARGB)
+    int      render_w;     // pixel dimensions of `pixels`
+    int      render_h;
+    float    render_scale; // pixels = natural * render_scale (may differ from
+                           // requested when capped by max_edge)
+};
+
+// Initialize from owned SVG source bytes. The doc takes ownership of `source`
+// and will free it via montauk::mfree on svgdoc_free. Returns false on
+// failure; on failure the caller still owns `source`.
+bool svgdoc_init(SvgDoc* doc, uint8_t* source, int source_len);
+
+// Ensure the rasterization matches `target_scale`. The longest rendered edge
+// is capped at `max_edge` pixels; if `target_scale` would exceed that, the
+// scale is clamped (render_scale will reflect the actual scale used).
+// Returns false if rasterization fails; the existing cache is left intact.
+bool svgdoc_render(SvgDoc* doc, float target_scale, int max_edge);
+
+// Free all owned memory (source bytes + raster cache).
+void svgdoc_free(SvgDoc* doc);
+
+} // namespace imageviewer