plot: add stacked series composition

.github/workflows/ci-freebsd.yml

@@ -16,9 +16,11 @@ jobs:
         include:
           - name: QRhi (FreeBSD)
             text: OFF
+            benchmark: OFF
             examples: OFF
           - name: QRhi+Text (FreeBSD)
             text: ON
+            benchmark: ON
             examples: ON
     steps:
       - name: Checkout repository
@@ -28,24 +30,30 @@ jobs:
         uses: vmactions/freebsd-vm@v1
         env:
           TEXT: ${{ matrix.text }}
+          BENCHMARK: ${{ matrix.benchmark }}
           EXAMPLES: ${{ matrix.examples }}
         with:
           release: "15.0"
           usesh: true
-          envs: 'TEXT EXAMPLES'
+          envs: 'TEXT BENCHMARK EXAMPLES'
           prepare: |
             pkg bootstrap -fy
             mkdir -p /usr/local/etc/pkg/repos
             echo 'FreeBSD-ports: { enabled: no }' > /usr/local/etc/pkg/repos/FreeBSD-ports.conf
             echo 'FreeBSD: { url: https://pkg.FreeBSD.org/${ABI}/latest }' > /usr/local/etc/pkg/repos/FreeBSD.conf
             pkg update -f
-            pkg install -y git cmake pkgconf qt6-base qt6-declarative qt6-shadertools
+            pkg install -y git cmake pkgconf python311 qt6-base qt6-declarative qt6-shadertools xauth xorg-vfbserver
           run: |
+            set -e
+            mkdir -p build
             cmake -S . -B build \
               -DCMAKE_BUILD_TYPE=Release \
               -DVNM_PLOT_ENABLE_TEXT=${TEXT} \
               -DVNM_PLOT_BUILD_TESTS=ON \
+              -DVNM_PLOT_BUILD_BENCHMARK=${BENCHMARK} \
               -DVNM_PLOT_BUILD_EXAMPLES=${EXAMPLES} \
               -DVNM_PLOT_BUILD_FUNCTION_PLOTTER=OFF
             cmake --build build --config Release
-            cd build && env QT_QPA_PLATFORM=offscreen ctest --output-on-failure
+            Xvfb :99 -screen 0 1280x1024x24 >/tmp/vnm-plot-xvfb.log 2>&1 &
+            export DISPLAY=:99
+            (cd build && ctest --output-on-failure)

.github/workflows/ci-linux.yml

@@ -12,9 +12,14 @@ defaults:
 
 env:
   CMAKE_BUILD_TYPE: Release
+  # Hosted Xvfb uses Mesa's CPU renderer. Bound its worker count to the job
+  # memory limit and use its GL 3.3 rasterizer without selecting a QRhi API.
+  GALLIUM_DRIVER: softpipe
+  LP_NUM_THREADS: "1"
   LINUX_SYSTEM_DEPS: >-
     libgl-dev libx11-dev libxrandr-dev libxinerama-dev libxcursor-dev
     libxi-dev libxext-dev libwayland-dev libxkbcommon-dev libvulkan-dev
+    xvfb xauth
 
 jobs:
   build-rhi:
@@ -65,9 +70,7 @@ jobs:
 
       - name: Run tests
         working-directory: build
-        env:
-          QT_QPA_PLATFORM: offscreen
-        run: ctest --output-on-failure
+        run: xvfb-run -a ctest --output-on-failure
 
       - name: Build summary
         run: |

.github/workflows/ci-windows.yml

@@ -57,8 +57,6 @@ jobs:
 
       - name: Run tests
         working-directory: build
-        env:
-          QT_QPA_PLATFORM: offscreen
         run: ctest --output-on-failure -C ${CMAKE_BUILD_TYPE}
 
       - name: Build summary

.gitignore

@@ -11,6 +11,8 @@
 
 # Benchmark output files
 inspector_benchmark_*.txt
+inspector_benchmark_*.json
+benchmark_phase_trace.jsonl
 
 # QtCreator user settings
 /examples/**/.qtcreator/
@@ -20,6 +22,7 @@ inspector_benchmark_*.txt
 # Claude workspace metadata
 .claude/
 /repo/
+__pycache__/
 
 # Windows artifacts
 /nul

CMakeLists.txt

@@ -17,7 +17,6 @@ option(VNM_PLOT_BUILD_FUNCTION_PLOTTER "Build the Qt Multimedia function_plotter
 option(VNM_PLOT_ENABLE_TEXT "Enable MSDF text rendering (requires FreeType + msdfgen)" ON)
 option(VNM_PLOT_BUILD_TESTS "Build test suite" OFF)
 option(VNM_PLOT_USE_SYSTEM_LIBS "Prefer find_package dependencies over FetchContent when available" OFF)
-set(VNM_PLOT_VNM_MSDF_TEXT_VERSION 0.2.0)
 
 include(FetchContent)
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/EmbedAssets.cmake)
@@ -169,7 +168,7 @@ if(_vnm_plot_missing_msdf_text_targets)
     _vnm_plot_has_any_msdf_text_target(_vnm_plot_has_partial_msdf_text_targets)
     if(VNM_PLOT_USE_SYSTEM_LIBS AND
        NOT _vnm_plot_has_partial_msdf_text_targets)
-        find_package(vnm_msdf_text ${VNM_PLOT_VNM_MSDF_TEXT_VERSION} CONFIG QUIET
+        find_package(vnm_msdf_text CONFIG QUIET
             COMPONENTS ${_vnm_plot_msdf_text_components})
         _vnm_plot_alias_existing_msdf_text_targets()
         _vnm_plot_missing_targets(
@@ -492,8 +491,8 @@ message(STATUS "vnm_plot: Building RHI library")
 #
 # Bake every shader in shaders/qsb/ into a multi-profile .qsb artifact and
 # embed it under :/vnm_plot/shaders/qsb/<name>.qsb. Profile set covers Vulkan
-# (SPIR-V), Metal 1.2 + 2.1, D3D11 (HLSL 5.0), and desktop GL 4.10 so RHI can
-# pick a working artifact on every supported backend.
+# (SPIR-V), Metal 1.2 + 2.1, D3D11 (HLSL 5.0), and desktop GL 3.30 + 4.10 so
+# RHI can pick a working artifact on every supported backend.
 # -----------------------------------------------------------------------------
 
 set(VNM_PLOT_QSB_SHADERS
@@ -517,10 +516,9 @@ if(VNM_PLOT_ENABLE_TEXT)
 endif()
 
 # Each input shader yields :/vnm_plot/shaders/qsb/<name>.<ext>.qsb.
-# GLSL profile is desktop 410 only; mobile GL ES is out of scope for
-# the RHI shaders. They use storage buffers that are unavailable below
-# ES 3.1, so emitting a 300 ES artifact would compile-fail at runtime
-# on a real ES 3.0 driver.
+# The RHI shaders use vertex attributes and std140 uniform blocks, so retain
+# desktop GLSL 330 for GL 3.3 contexts and GLSL 410 for existing GL 4 paths.
+# Mobile GL ES remains out of scope for this desktop renderer.
 foreach(_vnm_plot_qsb_shader IN LISTS VNM_PLOT_QSB_SHADERS)
     get_filename_component(_vnm_plot_qsb_output_dir
         "${CMAKE_CURRENT_BINARY_DIR}/.qsb/${_vnm_plot_qsb_shader}"
@@ -533,7 +531,7 @@ unset(_vnm_plot_qsb_shader)
 qt_add_shaders(vnm_plot_rhi "vnm_plot_qsb_shaders"
     PREFIX "/vnm_plot"
     BASE   "${CMAKE_CURRENT_SOURCE_DIR}"
-    GLSL   "410"
+    GLSL   "330,410"
     HLSL   "50"
     MSL    "12,21"
     OUTPUT_TARGETS VNM_PLOT_RHI_RESOURCE_TARGETS

README.md

@@ -80,6 +80,86 @@ auto series = vnm::plot::Series_builder()
 plot_widget->add_series(0, series);
 ```
 
+### Stacked series
+
+Give two or more ordinary series the same non-zero stack group. Group `0`
+keeps a series independent.
+
+```cpp
+auto f_source = std::make_shared<vnm::plot::Vector_data_source<sample_t>>();
+f_source->set_data(std::vector<sample_t>{{0, 1.0f}, {1'000'000'000, 2.0f}});
+
+auto g_source = std::make_shared<vnm::plot::Vector_data_source<sample_t>>();
+g_source->set_data(std::vector<sample_t>{{0, 3.0f}, {1'000'000'000, 4.0f}});
+
+const auto access = vnm::plot::make_access_policy<sample_t>(
+    &sample_t::t_ns,
+    &sample_t::value);
+
+auto f = vnm::plot::Series_builder()
+    .style(vnm::plot::Display_style::AREA)
+    .stack_group(1)
+    .data_source(f_source)
+    .access(access)
+    .build_shared();
+
+auto g = vnm::plot::Series_builder()
+    .style(vnm::plot::Display_style::AREA)
+    .stack_group(1)
+    .data_source(g_source)
+    .access(access)
+    .build_shared();
+
+plot_widget->add_series(10, f); // bottom
+plot_widget->add_series(20, g); // top; cumulative value is f + g
+```
+
+Series are stacked bottom-to-top in ascending plot-ID order. Reordering a
+stack therefore also means updating the caller's plot-ID mapping and series
+registrations. `LINE` and `DOTS` draw cumulative values; `AREA` fills each
+component's band between its cumulative base and top. Preview sources and
+styles are composed the same way in the preview view.
+
+Each source retains its independently selected LOD and timestamp grid. The
+renderer uses their exact timestamp union when it fits the view's composition
+budget. Larger unions are interpolated onto a shared deterministic grid that
+targets half-pixel spacing, clipped to the common selected-source time domain.
+The grid retains both domain endpoints and is capped so one stack view never
+materializes more than 1,048,576 cumulative samples across all layers; very
+large layer counts therefore use a coarser grid. Main and preview use their own
+horizontal pixel widths and budgets. Members must use
+matching `Series_interpolation` modes and, after sample and nonfinite-policy
+handling, produce a single continuous drawable selected window with monotonic
+timestamps. A rejected group fails closed: the affected stack view is omitted
+instead of drawing misleading unstacked data, and its reason is queryable via
+`stack_status` or `get_stack_status`. When configured, the optional
+`Plot_config::log_error` callback may also receive a human-readable message.
+Bounded resampling is an accepted `ACTIVE` result, not a rejection. Features
+narrower than half a pixel may be omitted, and a `STEP_AFTER` transition may
+move to the next grid timestamp; indicators and auto-fit continue to match the
+geometry actually rendered.
+
+Stack acceptance is also queryable without installing a log callback. C++ can
+call `Plot_widget::stack_status(group, Series_view_kind::MAIN)` (or `PREVIEW`)
+and inspect its typed `state`, `reason`, and `affected_series_ids`. `PENDING`
+means no renderer result matches the current data and range, `ACTIVE` means the
+view was accepted, and `SUPPRESSED` includes the specific rejection reason. A
+singleton group is `ACTIVE` with no rejection because no composition is needed.
+QML can call `get_stack_status(group, preview)`; the returned map contains
+`group`, uppercase `view`, `state`, and `reason` strings, plus an
+`affected_series_ids` list.
+
+The final cumulative value gets an automatic line overlay two pixels thicker
+than `Plot_config::line_width_px`: `#E6DFCC` in dark mode and `#192033` in light
+mode. This applies to the main and preview views for `LINE`, `DOTS`, and `AREA`
+stacks.
+
+`PlotIndicator` keeps component text values raw while placing their markers on
+the cumulative rendered layers. It adds a text-only `Σ` total and the note
+"Markers show cumulative stack positions". `Plot_widget::auto_adjust_view()`
+(used by the function plotter's **Fit Vertical** button) fits current cumulative
+stack geometry, including `AREA` bases.
+
 **Thread Safety**
 `Plot_widget` renders on a separate RHI render thread. Treat `series_data_t` as immutable once added. To change series config (style, access policy, preview config, color), update a copy and call `add_series` again with the same id to replace it. Make sure your `Data_source` implementation is safe to read from the render thread.
 
@@ -188,11 +268,13 @@ cmake --build build
 
 - `vnm_plot_hello` - renders a sine wave using the example function-source helper
 - `vnm_plot_preview_config` - preview uses a separate data source and AREA style via `preview_config`
-- `function_plotter` - multiple functions, per-series styles, expression evaluation via mexce
+- `function_plotter` - expressions, per-series styles, and a stacked-series demo via mexce
 
 `function_plotter` is opt-in because it depends on Qt Multimedia and `mexce`.
 Build it with `-DVNM_PLOT_BUILD_EXAMPLES=ON -DVNM_PLOT_BUILD_FUNCTION_PLOTTER=ON`;
 point at a local mexce checkout with `-DMEXCE_LOCAL_PATH=...`.
+Use its **Σ** control to stack functions, drag a function's color accent or
+label to change bottom-to-top order, and use **Fit Vertical** to fit the stack.
 
 ## Configuration
 

benchmark/ARCHITECTURE.md

@@ -16,16 +16,18 @@ profiling report format for reproducible comparisons.
 ## Major Components
 - Ring_buffer<T>
   - Thread-safe circular buffer with overwrite semantics.
-  - Supports copy-on-snapshot via copy_to() for stable reads.
+  - Exposes split-span zero-copy views protected by a shared lock.
+  - Keeps `copy_to()` only as an explicit copying helper; snapshots do not use it.
 
 - Brownian_generator
   - Generates Bar_sample or Trade_sample using geometric Brownian motion.
   - Deterministic when seeded; timestamps advance at the configured rate.
 
 - Benchmark_data_source<T>
   - Implements vnm::plot::Data_source.
-  - Uses copy-on-snapshot to provide contiguous data for rendering.
-  - Tracks sequence numbers and computes value ranges for auto-scaling.
+  - Publishes zero-copy snapshots that may contain two ring-buffer spans.
+  - Reports logical view bytes separately from exact copied bytes (zero).
+  - Tracks the stable ring revision used by `current_sequence()`.
 
 - Benchmark_profiler
   - Implements vnm::plot::Profiler.
@@ -41,11 +43,14 @@ profiling report format for reproducible comparisons.
 - Generator thread:
   - Produces samples at the configured rate using steady_clock pacing.
   - Writes into the ring buffer only; no rendering work.
+  - A coordinated publication barrier bounds complete logical publications
+    across every series to the measurement interval.
 
 - UI/render thread:
-  - Executes paintGL() via Qt's event loop.
-  - Requests snapshots from the Data_source and renders with vnm_plot.
-  - Records profiling scopes through Plot_config::profiler.
+  - The offscreen path drives QRhi frames directly.
+  - Requests zero-copy snapshots from the Data_source and renders with vnm_plot.
+  - Records profiling scopes, render-thread CPU allocations, and QRhi buffer
+    allocations through Plot_config::profiler.
 
 ## Rendering Pipeline
 - vnm_plot Asset_loader loads embedded shaders.
@@ -81,7 +86,12 @@ Benchmark_profiler produces a stable benchmark report:
 
 The report is written at the end of the benchmark run to the configured output
 folder with the inspector_benchmark_YYYYMMDD_HHMMSS_<STREAM>_<DataType>.txt
-naming convention.
+naming convention. Windows file operations adapt logical paths to the native
+extended-length namespace without exposing that transport spelling in reports.
+
+The phase trace flushes a fixed eleven aggregate success boundaries outside the
+measured frame loop. Only a failure adds a frame-specific boundary, so external
+termination retains progress without per-frame trace I/O.
 
 ## Configuration and CLI
 The executable accepts CLI options for duration, data type, seed, rate, ring
@@ -93,6 +103,7 @@ resolved once at startup to keep runs reproducible.
 - benchmark/include/brownian_generator.h
 - benchmark/include/benchmark_data_source.h
 - benchmark/include/benchmark_profiler.h
+- benchmark/include/path_io.h
 - benchmark/include/benchmark_window.h
 - benchmark/src/benchmark_window.cpp
 - benchmark/src/main.cpp