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Re: redisplay system of emacs

From: Jan Djärv
Subject: Re: redisplay system of emacs
Date: Fri, 12 Feb 2010 13:49:56 +0100
User-agent: Thunderbird (X11/20090817)

alin.s skrev:
An improvement in redisplay for X can be done by defining in the edit area of
every window a subwindow for every character. For a window of geometry
200x70 of characters, it would be 1400 windows registered in X-server.

You are mad. Everything would be 1400 times more. 1400 times more calls to the X server, 1400 times more GC:s created, 1400 times more events from the X server, 1400 times more Xft structures (XftDraws for example) created.
Emacs would be at least 1400 times slower.

The advantage is that redisplay would work automatically; every character
has associated its own expose event; the event PointerMotionMask would
simply signify LeaveWindow and EnterWindow; so it will always be able to be
captured without resource consuming.

But Emacs still needs to figure out what character that is in that window in order to redraw it.

To say more, in order to clear a character it would require no computation,
but only a simply call of XClearWindow().

Every window could have its own font.

So say we have 1400 windows each with a different font with a different size? How do you purpose we lay this out? Instead of laying out characters we are now laying out windows. Same problem, but with an enormous overhead.

And to say more, an image of high dimension will be divided in many
subwindows, and emacs will be able to display images normally, not as a huge

Again, making the display of an image to be so much slower, because instead of one (ideally), call to the X server, we now have one per window. And what a nightmare to figure out what part of an image that needs to be redrawn and moved if the user changes the size of the Emacs frame...

And finally, because this structure is identical to the geometry of the
console, the code for X and console can be unified in many places.

Not very likely.

Did 1:st of April arrive early?

        Jan D.

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