On Sun, Jan 23, 2005, Oron Peled wrote about "Re: rant: changing color depth":
> Question: anybody knows why (and how) RANDR made screen-size
>           and refresh-rate dynamic (after all X apps had them
>           static for ages) and why color-depth didn't make
>           it to the list of dynamic parameters?
>           [Please save me the "I never change..." because I
>            really never changed my refresh-rate either. I am
>            looking for technical knowledge not political one]

I don't know anything about this RANDR extension, so I'll just guess.

The screen size was never a very important issue for most X applications,
other than the window manager. An application has a window, and as long as
its size isn't changed without warning (there's a protocol to change its
size, of course), it usually could care less about the size of the screen
around it. Already, there were plenty of window managers that had a "virtual
desktop" implented in various ways, so applications could never really
rely on the size of the screen (virtual or real) anyway.

The Window Manager does need to know the real screen size, so either this
screen-size-change action has to be done inside the Window Manager, or this
RANDR extension would need to send the Window Manager some sort of message
that the screen size has changed (and the Window Manager would have to
support that message - not all of them do).

So that's my guess. I wonder how close I am to the actual truth.

The color depth can't be changed so easily. That is because all X clients
allocate areas of memory that correspond to window contents - either in
the X server's memory, or in their own. The size and the layout of this
memory depends on how many bits it takes to represent a pixel (the color
depth). Theoretically there are ways to handle a color depth change -
e.g., some clients would know how to handle the change, and other clients
would operate in some sort of "old color depth" compatibility mode with
the server - but there is no mechanism in the current X protocol to do
this, so unless the protocol is improved, it cannot be done.

-- 
Nadav Har'El                        |      Sunday, Jan 23 2005, 14 Shevat 5765
[EMAIL PROTECTED]             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |Disclaimer: The opinions expressed above
http://nadav.harel.org.il           |are not my own.

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