linux-kernel - Re: [PATCH] fbcon: Use background color for margins

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Date:   Mon, 31 Jul 2017 12:25:28 -0500
From:   David Lechner <david@...hnology.com>
To:     Pavel Machek <pavel@....cz>
Cc:     linux-fbdev@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fbcon: Use background color for margins

On 07/30/2017 04:51 PM, Pavel Machek wrote:
> Hi!
> 
>>>> Screens that don't have a black border around the active area will have
>>>> ugly black bars for the margin when the text background color is not black.
>>>> This is especially noticeable on an LCD screen (not the backlit kind) when
>>>> the terminal colors are inverted.
>>>
>>> Are you sure?
>>
>> Of course I am sure. Otherwise I would not send a patch. ;-)
>>
>> I have attached some pictures to explain it better. The default-console.jpg
>> picture shows what it looks like using just defaults. I think it is hard to
>> read the white text with the black background.
>>
>> So, the solution is to invert the terminal colors. But when you do this, the
>> margins are not inverted, so you are left with black bars on the bottom and
>> the right as seen in inverted-without-patch.jpg.
>>
>> With this patch applied, the margins are also inverted, so you don't have
>> the black bars as seen in inverted-with-patch.jpg. I think this is much
>> nicer.
>>
>>   It is quite common to have different backgrounds in
>>> different parts of the screen, how it is supposed to work there?
>>
>> There will be nothing different in this regard. Only the margins (non-text
>> area) are changed.
> 
> So you have something like midnight commander, which uses colors.
> 
> Lets say top half of screen is normal, bottom one is inverted. What
> color will borders be?
> 
> Will not they do something stupid (such as changing) when the
> curses-based application refreshes?
> 

Ah. I see what you mean now. The margin will be whatever is set for the 
vc_video_erase_char in the kernel, which can be changed by userspace. I 
tried midnight commander and sure enough, I still have the black margins 
when I invert the screen (`setterm -inverse on`). Interestingly, after 
allowing the console to blank after a timeout, the console was blanked 
with white, then after pressing a key to unblank, the margins were also 
white.

So, scratch this one. I will re-evaluate and send a new patch.