I feel configure events and requests are messed up

Kristian Høgsberg krh at bitplanet.net
Wed Sep 7 13:35:05 PDT 2011

On Wed, Sep 7, 2011 at 4:27 PM, Giovanni Campagna
<scampa.giovanni at gmail.com> wrote:
> Il giorno mer, 07/09/2011 alle 10.33 -0700, Bill Spitzak ha scritto:
>> In Wayland the client allocates the buffer, not the compositor.
>> I think this is what is leading to the confusion here. The compositor
>> has no say over how big the buffer is. Instead the client controls it
>> and tells the compositor what the resulting size is.
>> To cause futher confusion there is an assumption that the compositor
>> will then map this entire buffer onto the screen as a window, thus
>> leading to worry that the client can force the screen to be obscured,
>> and that it can ignore compositor resizing limits, etc. This is not
>> true, the compositor can do anything it wants with the buffer, it is in
>> effect a texture map that it can place part/all of onto the surfaces it
>> composites onto the screen.
> As Kristian said earlier, we need coordination between the compositor
> and the client, which means that when they disagree, we have to decide
> who is right. I say that the compositor is always right, and the
> client-side winsys implementation (that is, libwayland-client + libEGL)
> should enforce this; you say the client is always right and is allowed
> to create and map whatever buffer.
> In your model, if the compositor does not map exactly what the client
> has asked, there is a bug in the compositor; in my model, if the client
> provides a buffer of the wrong size, there is a bug in the client.

I don't think that's what Bill is saying.  If there's a disagreement
between compositor and client, it's typically a broken client. The
disagreement is what happens in that case.  Just because the client
can allocate whatever buffer size it wants doesn't mean that the
compositor has to show all of that.  If the client doesn't behave, you
can still beat the buffer into shape in the compositor when you
present it on screen.  There's no reason to force EGL to allocate a
buffer at the given size.


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