From b2a6cb29a188522d3fce3e08c8101fd2d8a23f8d Mon Sep 17 00:00:00 2001
From: Ioannis Makris <imak@imak.gr>
Date: Wed, 21 Oct 2026 11:12:12 +0200
Subject: [PATCH] Reuse axis candidate storage and transfer prepared segment
 spans

---
 src/core/layout_calculator.cpp | 19 ++++++++++---------
 src/core/series_renderer.cpp   |  8 +++++---
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/core/layout_calculator.cpp b/src/core/layout_calculator.cpp
index 4ad1206..00c49c7 100644
--- a/src/core/layout_calculator.cpp
+++ b/src/core/layout_calculator.cpp
@@ -646,6 +646,14 @@ Layout_calculator::result_t Layout_calculator::calculate(const parameters_t& par
             return params.format_timestamp_func(timestamp_ns, seconds_to_ns(step_seconds));
         };
 
+        struct candidate_t
+        {
+            std::int64_t t;
+            float        x0;
+            float        x1;
+            float        x_anchor;
+        };
+        std::vector<candidate_t> candidates;
         std::vector<std::pair<float, float>> accepted;
         std::vector<std::pair<float, float>> level;
 
@@ -677,14 +685,6 @@ Layout_calculator::result_t Layout_calculator::calculate(const parameters_t& par
                 }
             }
 
-            struct cand
-            {
-                std::int64_t t;
-                float        x0;
-                float        x1;
-                float        x_anchor;
-            };
-            std::vector<cand> candidates;
             float right_vis             = 0.0f;
             float pixel_step            = 0.0f;
             float optimistic_width      = 0.0f;
@@ -695,6 +695,7 @@ Layout_calculator::result_t Layout_calculator::calculate(const parameters_t& par
                 VNM_PLOT_PROFILE_SCOPE(
                     profiler,
                     "renderer.frame.calculate_layout.impl.cache_miss.pass1.horizontal_axis.step_prep");
+                candidates.clear();
                 candidates.reserve(64);
 
                 right_vis = float(params.usable_width + params.vbar_width);
@@ -789,7 +790,7 @@ Layout_calculator::result_t Layout_calculator::calculate(const parameters_t& par
                         break;
                     }
 
-                    cand candidate{t, x, x, x};
+                    candidate_t candidate{t, x, x, x};
                     // Use conservative width estimate for skip optimization.
                     // Must be at least as large as actual label width to avoid skipping visible labels.
                     const float skip_width = std::max(last_width, estimated_label_width);
diff --git a/src/core/series_renderer.cpp b/src/core/series_renderer.cpp
index 6214dd6..0ccfb18 100644
--- a/src/core/series_renderer.cpp
+++ b/src/core/series_renderer.cpp
@@ -2266,19 +2266,21 @@ bool Series_renderer::rhi_prepare_series_primitive(
     if (count == 0) {
         return false;
     }
-    const std::vector<builtin_segment_span_t> segment_spans =
+    std::vector<builtin_segment_span_t> computed_segment_spans =
         is_dots
             ? std::vector<builtin_segment_span_t>{}
             : builtin_segment_spans(window);
-    const bool has_segment_span = !segment_spans.empty();
+    const bool has_segment_span = !computed_segment_spans.empty();
     if (!is_dots && !has_segment_span) {
         return false;
     }
     // Hand the computed spans to the caller so the record pass can reuse them
     // (empty for DOTS, which draw per-sample instances).
     if (out_segment_spans) {
-        *out_segment_spans = segment_spans;
+        *out_segment_spans = std::move(computed_segment_spans);
     }
+    const std::vector<builtin_segment_span_t>& segment_spans =
+        out_segment_spans ? *out_segment_spans : computed_segment_spans;
 
     QRhiRenderTarget* rt = ctx.render_target;