Initialize the main renderer, then the sub renderer. Because.

Extract the main rendering into a separate component.

Some renderer clean up was done after the call to DeleteRenderer().
Move it to DeleteRenderer to simplify further refactorings.

Some renderer initialization was done after the call to
CreateRenderer(). Move it to CreateRenderer to simplify further
refactorings.

Replace opengl_init_program() and opengl_deinit_program() by
CreateRenderer() and DeleteRenderer(), independant of
vout_display_opengl_t.

Use struct vlc_gl_renderer directly instead of vout_display_opengl_t
when possible.

This paves the way to extract the renderer into a separate component.

The field is an array of textures.

Move fields related to the renderer from vout_display_opengl_t to
vlc_gl_renderer.

This paves the way to move rendering to a separate renderer component.

The struct prgm contains some locations of the program, the struct
vlc_gl_renderer contains some others.

There are no reason to keep two separate structures.

Rename renderer callbacks from tc_ to renderer_. There is no tex
converter (tc) anymore.

The opengl_tex_converter_t is not a converter anymore: it is only used
to communicate between the renderer (currently managed in vout_helper.c)
and the fragment shader generation code (fragment_shaders.c).

The field was used only from vout_display_opengl_New().

The vout_helper now only manages the rendering of the "main" pictures,
so it never renders subpictures anymore (this has been moved to
vlc_gl_sub_renderer).

The new subpictures renderer did not apply the alpha value.

Extract the subpictures rendering into a separate component, using its
own simplified vertex and fragment shaders.

This simplifies vout_helper.c.

The functions GenerateTextures() and DeleteTextures() apply to interop,
move them to the relevant file.

These util functions will be called from other files.

Expose a function to align a value to the next power of 2.

It will be called from other files.

Move subpictures rendering to separate functions.

The macro will be used from several files.

Expose functions to create and delete a vlc_gl_interop.

This avoids the callers to handle internal details about interop
creation and destruction.

Extract interop creation into a separate function.

This will allow to create an interop without an opengl_tex_converter_t.

Do not pass extensions to opengl_init_program().

This was an optimization not to retrieve the extensions list twice.
However, since the initialization will be moved into a separate
component (the renderer), we don't want to expose this internal detail.

Use a callback to close an interop instead of relying on closing the
module.

This allows to properly close interop_sw, which is not a module.

Since vlc_gl_interop has been introduced, the fragment shader is built
by vout_helper instead of the converter module.

Therefore, there is no need to keep it exposed in the
opengl_tex_converter_t instance.

In the initial patchset, vlc_gl_interop was named vlc_gl_importer.

It had been incorrectly replaced.

The transform matrix provided by Android was applied only on the first
plane.

cf. 28f8c56d

Fixes:
  modules/codec/webvtt/webvtt.c:155:33: warning: implicit conversion from ‘enum <anonymous>’ to ‘enum webvtt_header_line_e’

A lock is overkill to swap a variable: use an atomic variable.
Also fix a corner case double free (and racy memory read) at exit,
by freeing the outstanding title only after the thread exits.

Use ToWide() which converts from UTF-8 provide by the core to UTF-16
expected by the Win32 GUI. mbstowcs() converts from the local 8-bit
character set, which is typically not UTF-8 on Windows.

While at it, avoid one string copy.

It was written (and signaled) without proper locking, and it duplicated
the thread-join anyway since it was the very last observable action.

This is the 21st century. The C run-time threading subsystem knows better
than you how to optimise condition variables.

This is the 21st century. The C run-time threading subsystem knows better
than you how to optimise condition variables.

Use C++20 draft-like names instead of custom neither-Linux-nor-Windows
ones.

Note though that C++ has no timed variant for its atomic wait method.

As things stood, it works on Android (where the code is actually used)
but not on desktop. There is a latent bug where cancellation is not
acted up, leading to dead locks.