TODO and Recommended Fixes

This chapter collects recommendations that emerged from reviewing the code base for this guide. It is meant as a living backlog of technical work — code health, correctness and modernization — complementary to the user-facing backlog analyzed in Open Issue Triage. Items are grouped by theme and tagged with a rough priority (P0 highest). Where an item maps to a tracked issue, the issue is linked.

Toolkit and build modernization

Complete Qt 6 support while keeping Qt 5 (P1). This is a first-class goal with its own chapter, Qt 6 Migration Plan, which is the single source of truth for the audited work items and counts. In short: the CMake build already has a NATRON_QT6 switch and the viewer already uses QOpenGLWidget, so the remaining work is bounded — modernize the removed Qt APIs (QRegExp → QRegularExpression, QDesktopWidget → QScreen, setMargin), bring the qmake build to Qt6 parity, and regenerate the PySide6/Shiboken6 bindings (resolving the enum/flag issue #854). Tracks #1011 and #827.

Keep the two build systems in sync, and pick a long-term direction (P2). Natron maintains both qmake and CMake builds. Every structural change must touch both, which is error-prone. Recommendation: treat CMake as the primary build (it already leads on Qt 6), keep qmake working during the transition, and document a date/criteria for eventually retiring qmake. Until then, add a CI job for each so neither silently rots.

Modernize CI (P1). Migrate CI from Travis to GitHub Actions (#601; the .travis.yml is already disabled). Build both Qt 5 and Qt 6 and run the Tests suite on all three platforms so regressions in the dual-toolkit build are caught automatically.

Adopt a modern C++ baseline consistently (P3). The CMake build already compiles as C++17, and the code has largely moved from C++98 to std::shared_ptr etc. Finish the job opportunistically: prefer override, range-based for (retiring foreach/Q_FOREACH, ~46 uses), nullptr, and enum class where it does not break the Python bindings. Do this file-by-file alongside other work, not as a mass reformat (which would fight the astyle hook and bloat diffs).

Stability and correctness (P0)

These are the code-level counterparts of the P0 issues in Open Issue Triage.

Make the cache respect its limits (P0). #192 reports that Natron does not observe disk/RAM cache size limits and crashes when the disk fills. Audit Cache.h / MemoryFile / TileCacheFile eviction and the disk-space checks; a compositor that fills the disk and crashes loses work.

Diagnose the silent render stall (P0). #248 (rendering silently stalls after N frames) points at the scheduler / abort / thread-pool machinery (OutputSchedulerThread, GenericSchedulerThread, AbortableRenderInfo) or a deadlock around the cache. High value; reproduce under a debug build with FP-exception trapping and thread sanitizer.

Fix launch/teardown crashes (P0). Startup crashes (#845, #1008) and shutdown/lifecycle crashes (#795, #1029, #1057) recur across platforms. Several likely involve OpenGL context creation (#516, amdgpu-pro) — a good place to add defensive checks and clearer diagnostics in OSGLContext_*.

Invest in the crash-reporting pipeline (P1). A large tail of issues are “random crashes” with no stack trace (#557). Making the Breakpad reporter reliably deliver usable minidumps/symbols converts that tail into fixable, evidence-backed bugs. High leverage.

Robustness of critical subsystems

Guard the serialization format (P1). Project loading uses Boost.Serialization (see Design Techniques and Idioms). There is no automated test that round-trips and cross-version-loads real project files. Recommendation: add regression tests that load a corpus of old .ntp files and assert they still open; require a BOOST_CLASS_VERSION bump review for any *Serialization change. This directly protects users from data loss.

Replace deprecated/removed Qt string and regex APIs (P1). Beyond Qt 6 compatibility, QRegExp and the QDesktopWidget family are the concrete deprecated APIs in use; migrating them (details in Qt 6 Migration Plan) improves the Qt 5 build immediately and is low-risk since the replacements exist in Qt 5.15.

Reduce the size of the largest translation units (P3). Several files are enormous (Node.cpp, EffectInstance.cpp and EffectInstanceRenderRoI.cpp, Knob.cpp, RotoContext.cpp, Settings.cpp, OfxParamInstance.cpp — each 100–240 KB). They are hard to navigate and slow to compile. Where a natural seam exists (as the numbered GUI files already show), split them into cohesive units. Do this incrementally and only when already working in the file.

Testing and documentation

Broaden automated test coverage (P2). The Tests suite covers curves, LUT, images, hashing, tracking and the file-system model, but not the render pipeline, the cache, serialization, or knob expressions — the subsystems where the P0 bugs live. Add targeted tests as these areas are touched; a headless NatronRenderer render of a known project compared against a golden image would be a strong end-to-end regression test.

Keep this Maintainer Guide current (P2). Update it when the architecture changes — especially the Qt 6 status in Qt 6 Migration Plan, and re-run the Open Issue Triage analysis periodically (the script used to produce it is simple GitHub-API + label aggregation).

Label and prune the issue tracker (P2). As noted in Open Issue Triage, ~half of issues are untriaged and ~124 are 2018 imports that may already be fixed. A labeling/pruning pass makes the backlog trustworthy and surfaces genuinely actionable work.

Quick-reference: important issues

Priorities as of the July 2026 snapshot (see Open Issue Triage):

Issue	Summary	Priority
#248	Rendering silently stalls after N frames	P0
#516	Won’t open on Ubuntu 20.04 (amdgpu-pro)	P0
#192	Cache ignores size limits; crash on full disk	P0
#845 / #1008	Startup crashes (Linux)	P0
#795 / #1029	Teardown / repeated-open crashes	P0
#864	CLI renders zero frames	P0
#1011 / #854	Qt 6 support / Qt flag binding bug	P1
#827	Qt version tracker	P1
#601	Migrate CI to GitHub Actions	P1
#215 / #990	Ubuntu PPA-Debian repo / Linux binary distrib	P1
#557	Reliable crash reporting	P1
#209	Viewer 8-bit textures	P2
#839	Undo broken for on-screen Transform	P2
#79	Vectorscope & Waveform (top feature)	P2