Extract fill modes, preview runtime pockets, and brush item UI

src/legacy_node_stroke_preview_runtime_services.cpp

@@ -24,6 +24,79 @@
 
 namespace pp::panopainter {
 
+void execute_legacy_node_stroke_preview_background_capture_pass(
+    const LegacyNodeStrokePreviewBackgroundCaptureRequest& request)
+{
+    if (!request.draw_checkerboard) {
+        return;
+    }
+
+    const float aspect = request.size.x / request.size.y;
+    pp::panopainter::setup_legacy_canvas_draw_merge_checkerboard_shader(
+        pp::panopainter::LegacyCanvasDrawMergeCheckerboardUniforms {
+            .mvp = glm::ortho(-.5f, .5f, -.5f / aspect, .5f / aspect, -1.f, 1.f),
+            .colorize = request.colorize,
+        });
+    request.draw_checkerboard();
+    const auto copy_status = pp::paint_renderer::copy_stroke_preview_result_to_texture(
+        [&] {
+            request.background_texture.bind();
+        },
+        [](
+            int src_x,
+            int src_y,
+            int dst_x,
+            int dst_y,
+            int width,
+            int height) {
+            copy_framebuffer_to_texture_2d(src_x, src_y, dst_x, dst_y, width, height);
+        },
+        pp::paint_renderer::StrokePreviewCopySize {
+            .width = static_cast<int>(request.size.x),
+            .height = static_cast<int>(request.size.y),
+        });
+    assert(copy_status.ok());
+}
+
+std::vector<LegacyNodeStrokePreviewFrame> plan_legacy_node_stroke_preview_stroke_frames(
+    const LegacyNodeStrokePreviewStrokeComputeRequest& request)
+{
+    auto samples = const_cast<Stroke&>(request.stroke).compute_samples();
+    StrokeSample previous_sample = request.stroke.m_prev_sample;
+    previous_sample.size *= request.zoom;
+    for (auto& sample : samples) {
+        sample.size *= request.zoom;
+    }
+
+    return pp::panopainter::plan_legacy_canvas_stroke_frames(
+        pp::panopainter::LegacyCanvasStrokeComputeRequest {
+            .previous_sample = previous_sample,
+            .samples = samples,
+            .zoom = 1.0f,
+            .mixer_size = request.mixer_size,
+        },
+        [](
+            std::array<vertex_t, 4>& brush_quad,
+            bool /*project_3d*/,
+            glm::mat4 /*model_view*/) {
+            return brush_quad;
+        },
+        [](
+            glm::vec4 mixer_rect,
+            glm::vec4 color,
+            float flow,
+            float opacity,
+            std::array<vertex_t, 4>&& shapes) -> LegacyNodeStrokePreviewFrame {
+            return LegacyNodeStrokePreviewFrame {
+                .col = color,
+                .flow = flow,
+                .opacity = opacity,
+                .shapes = std::move(shapes),
+                .mixer_rect = mixer_rect,
+            };
+        });
+}
+
 bool execute_legacy_node_stroke_preview_immediate_runtime(
     const LegacyNodeStrokePreviewImmediateRuntimeRequest& request)
 {