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bug#5721: Feature request: Function that returns absolute coordinates


From: Jan Djärv
Subject: bug#5721: Feature request: Function that returns absolute coordinates
Date: Fri, 02 Jul 2010 09:06:49 +0200
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; sv-SE; rv:1.9.2.4) Gecko/20100608 Thunderbird/3.1



YAMAMOTO Mitsuharu skrev 2010-07-02 04.10:

What do you think about the following point?

On Tue, 01 Jun 2010 10:16:08 +0900, YAMAMOTO Mitsuharu<address@hidden>  said:

I'd rather suggest introducing some conversion functions between
relative and absolute coordinate systems.  Newer versions of Mac OS
X provides "Resolution Independence" that allows users to specify a
scale factor:

   
http://developer.apple.com/mac/library/documentation/UserExperience/Conceptual/HiDPIOverview/HiDPIConcepts/HiDPIConcepts.html

With the scale factor, 1 pixel in the relative coordinate system no
longer always correspond to 1 pixel in the absolute one.  Thus one
cannot determine the corresponding absolute coordinates only from
`inside-left' and `inside-top'.

(Maybe "pixel" above should be "unit".)

One can argue that the new API can return enough information to deal
with the scale factor by computing width and height in both relative
and absolute coordinate systems.  But I guess many programmers just
tends to add some offsets for the conversion between these coordinate
systems.  This might cause rewrite of elisp programs when GTK+
supports resolution independence in future.

One could argue that we are always dealing with scaled pixels, and absolute in this context means "absolute scaled" instead of "absolute unscaled". Can't we always use scaled coordinates? When do we need to handle unscsaled?

The new functions use tool bar and title bar height as well as frame top and left. Are these scaled or unscaled pixels? Shouldn't the nextstep specific code just expose scaled pixels to the generic code and do the conversion when needed? I know too little about which API functions that use scaled and which use unscaled.

        Jan D.







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