Problems implementing double buffered painting for Windows

Problems implementing double buffered painting for Windows

[Cecilio Pardo]

Hello,

I'm trying to implement double buffered painting for Windows, to
eliminate flicker. I am encountering some problems:

- When to flip buffers? I have tried to attach the flip to
  frame_up_to_date_hook on the 'terminal' struct, but it sometimes get
  called when it should not, producing flicker.

- What portion of the screen has been updated? I have seen no clear way
  to find this out. I'm resorting to intercept calls to w32_fill_rect to
  mark areas as invalidated, as it /seems/ to be always used to clean
  the area before painting, but this is clearly not a solution.

Any ideas welcome. Thank you.

-- 
Cecilio Pardo

Re: Problems implementing double buffered painting for Windows

[Eli Zaretskii]

> From: Cecilio Pardo <cpardo@imayhem.com>
> Date: Mon, 11 May 2020 12:13:50 +0200
> 
> I'm trying to implement double buffered painting for Windows, to
> eliminate flicker.

Thank you very much for working on this.

> - When to flip buffers? I have tried to attach the flip to
>   frame_up_to_date_hook on the 'terminal' struct, but it sometimes get
>   called when it should not, producing flicker.

Did you try doing something similar to what xterm.c does on X?  I mean
the block_buffer_flips trick.  If you did, and it didn't work, why not

> - What portion of the screen has been updated? I have seen no clear way
>   to find this out. I'm resorting to intercept calls to w32_fill_rect to
>   mark areas as invalidated, as it /seems/ to be always used to clean
>   the area before painting, but this is clearly not a solution.

Why not update the entire frame?  That's what the X code does, AFAIU.

Re: Problems implementing double buffered painting for Windows

[chad]

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In addition to Eli's advice, you might find some inspiration in the Mac
port, a version of emacs for macOS that uses a different set of system APIs
than the ns port, which is included in the mainline. It's available
directly via mercurial:
 https://bitbucket.org/mituharu/emacs-mac/src/master/

Hope this helps,
~Chad


On Mon, May 11, 2020 at 9:50 AM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Cecilio Pardo <cpardo@imayhem.com>
> > Date: Mon, 11 May 2020 12:13:50 +0200
> >
> > I'm trying to implement double buffered painting for Windows, to
> > eliminate flicker.
>
> Thank you very much for working on this.
>
> > - When to flip buffers? I have tried to attach the flip to
> >   frame_up_to_date_hook on the 'terminal' struct, but it sometimes get
> >   called when it should not, producing flicker.
>
> Did you try doing something similar to what xterm.c does on X?  I mean
> the block_buffer_flips trick.  If you did, and it didn't work, why not
>
> > - What portion of the screen has been updated? I have seen no clear way
> >   to find this out. I'm resorting to intercept calls to w32_fill_rect to
> >   mark areas as invalidated, as it /seems/ to be always used to clean
> >   the area before painting, but this is clearly not a solution.
>
> Why not update the entire frame?  That's what the X code does, AFAIU.
>
>

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