Extract canvas stroke runtime and preview draw shells

src/legacy_canvas_stroke_runtime_services.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include "legacy_canvas_stroke_execution_services.h"
+
+#include <array>
+#include <vector>
+
+class Canvas;
+
+namespace pp::panopainter {
+
+[[nodiscard]] LegacyCanvasStrokeMixPassShell make_legacy_canvas_stroke_mix_pass_shell(
+    Canvas& canvas,
+    const glm::vec2& bb_min,
+    const glm::vec2& bb_sz);
+
+void legacy_canvas_stroke_end(Canvas& canvas);
+void legacy_canvas_stroke_cancel(Canvas& canvas);
+void legacy_canvas_stroke_draw_mix(Canvas& canvas, const glm::vec2& bb_min, const glm::vec2& bb_sz);
+[[nodiscard]] std::array<std::vector<vertex_t>, 6> legacy_canvas_stroke_draw_project(
+    const Canvas& canvas,
+    std::array<vertex_t, 4>& B,
+    bool project_3d = false,
+    glm::mat4 mv = glm::mat4(1));
+void legacy_canvas_stroke_update(Canvas& canvas, glm::vec3 point, float pressure);
+void legacy_canvas_stroke_start(Canvas& canvas, glm::vec3 point, float pressure);
+
+} // namespace pp::panopainter