fix: SG-40934: Defer -eval/-pyeval until display groups exist

[cedrik-fuoco-adsk]

SG-40934: Defer -eval/-pyeval evaluation until display groups exist

Linked issues

SG-40934

Summarize your change.

The -eval (Mu) and -pyeval (Python) command line expressions are no longer evaluated from RvSession::postInitialize(). They are split out into a new RvSession::evalCommandLineScripts() method, which the interactive path calls at the end of RvApplication::newSessionFromFiles(). After setPhysicalDevices() has created the display groups and the session is initialized.

Describe the reason for the change.

postInitialize() runs while the RvDocument is still being constructed, well before RVDisplayGroup nodes exist. Only the default RVOutputGroup is present at that point. When media is loaded via -pyeval, source_setup.py's setDisplayFromProfile() looks for an RVDisplayGroup, finds none, and silently applies nothing — so the Display Transfer Function stays "None" instead of "sRGB".

This is why enabling RV_PROGRESSIVE_SOURCE_LOADING=1 works around the bug: it defers the real media load to an async job, by which time the display groups exist. It also explains the regression window — progressive source loading was on by default before RV 2022.0.0.

Fixing the ordering addresses the root cause, so no workaround is needed in source_setup.py. It also fixes the same problem for -eval, and for the reported case of applying flop to a source from the command line.

Describe what you have tested and on which operating system.

• rv -pyeval "from rv import commands;commands.addSourceVerbose(['some.mov'])"
  → Display Transfer Function is "sRGB", with RV_PROGRESSIVE_SOURCE_LOADING unset

Add a list of changes, and note any that might need special attention during the review.

• RvApp/RvSession.h, RvApp/RvSession.cpp: new evalCommandLineScripts(); the
  -eval/-pyeval logic is moved verbatim out of postInitialize().
• RvCommon/RvDocument.cpp: no longer evaluates the expressions during session
  construction.
• RvCommon/RvApplication.cpp: calls evalCommandLineScripts() at the end of
  newSessionFromFiles().
• rvio/main.cpp, MovieRV/MovieRV.cpp: call it immediately after
  postInitialize(). These are headless, have no display groups to wait for, and
  keep their current timing.

Needs attention:

• Behavior change when a command line expression adds a source and file arguments are given, e.g. rv pyeval "addSourceVerbose(['a.mov'])" b.mov. Previously the expression ran first and its source was then wiped by the clear() in rebuildSessionFromFiles(), leaving only b.mov. Now both sources are loaded. Affects -eval and -pyeval equally.
• The call is placed after the after-progressive-loading block rather than immediately after setPhysicalDevices(). That block is gated on s->loadTotal() == 0 && !files.empty(); evaluating earlier could change loadTotal() and suppress an event that must close a previously emitted before-progressive-loading.
• The rvlink session-reuse path (rebuildSessionFromFiles() via sessionFromUrl) never called postInitialize(), so it already did not run -pyeval. That is unchanged here.
• Pre-existing quirk, intentionally not addressed: m_initEval clears itself after running while m_pyInitEval does not, so -eval is effectively once-per-process and -pyeval is per-session, despite both being documented as "at every session start".

[bernie-laberge]

Nice !
Thank you @cedrik-fuoco-adsk !