Extract canvas mask modes, preview draw pass, and node style shell

src/legacy_node_stroke_preview_draw_services.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include "brush.h"
+#include "legacy_node_stroke_preview_execution_services.h"
+#include "rtt.h"
+#include "texture.h"
+
+#include <array>
+#include <functional>
+#include <vector>
+
+namespace pp::panopainter {
+
+struct LegacyNodeStrokePreviewFrame {
+    glm::vec4 col {};
+    float flow = 0.0f;
+    float opacity = 0.0f;
+    std::array<vertex_t, 4> shapes {};
+    glm::vec4 mixer_rect {};
+};
+
+struct LegacyNodeStrokePreviewLiveRenderRequest {
+    const Brush& brush;
+    const LegacyNodeStrokePreviewPassOrchestrationPlan& pass_orchestration;
+    const LegacyNodeStrokePreviewPreparedStrokes& prepared_strokes;
+    Texture2D& stroke_texture;
+    RTT& mixer_rtt;
+    RTT& render_target;
+    Texture2D& background_texture;
+    Texture2D& dual_texture;
+    Texture2D& preview_texture;
+    Sampler& linear_sampler;
+    Sampler& repeat_sampler;
+    float zoom = 1.0f;
+    float min_flow = 0.0f;
+    bool copy_stroke_destination = false;
+    glm::vec2 size {};
+    std::function<void(const Brush&)> bind_dual_pass_textures;
+    std::function<void(bool)> capture_background;
+    std::function<std::vector<LegacyNodeStrokePreviewFrame>(const Stroke&, float)> compute_frames;
+    std::function<glm::vec4(std::array<vertex_t, 4>&, Texture2D&, bool)> draw_samples;
+    std::function<void(const glm::vec2&, const glm::vec2&)> draw_mix;
+    std::function<void()> unbind_mixer_texture;
+    std::function<void()> bind_pattern_texture;
+    std::function<void()> draw_composite;
+};
+
+[[nodiscard]] bool execute_legacy_node_stroke_preview_live_render_passes(
+    const LegacyNodeStrokePreviewLiveRenderRequest& request);
+
+} // namespace pp::panopainter