[bug #27782] drawInRect:fromRect:operation:fraction: doesn't work correctly in a flipped view

[Quentin Mathé]

URL:
  <http://savannah.gnu.org/bugs/?27782>

                 Summary: drawInRect:fromRect:operation:fraction: doesn't
work correctly in a flipped view
                 Project: GNUstep
            Submitted by: qmathe
            Submitted on: Thu 22 Oct 2009 06:17:35 PM GMT
                Category: Gui/AppKit
                Severity: 3 - Normal
              Item Group: Bug
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

GNUstep gui and back 28866 on Ubuntu 9.04.

As it is visible in the attached screenshots, -[NSImage
drawInRect:fromRect:operation:fraction:] does not match Mac OS X behavior when
the view coordinates are flipped and is also inconsistent accross backends.

-drawAtPoint:fromRect:operation:fraction: has probably the same issue
although I didn't test it.

With Cocoa Drawing Guide -> Image -> Drawing Versus Compositing explanations,
I tried to figure out where the bug is but I failed to. I don't really
understand why the backend has to know about whether a view is flipped or not.
It seems to me it is not necessary and even undesirable to have the backend
knows about the view notion (e.g. for a graphics editor with its own view-like
hierarchy and which would support various coordinate orientation).
The other thing I don't understand is where the scaling and rotation are
suppressed on the current CTM when -compositeToPoint:XXX methods are used. It
seems to me this should happen directly in these methods by altering the
current CTM and restoring it before the method returns.

I attached the test app which was used to grab the screenshots. It can be
compiled on both GNUstep and Mac OS X (with Xcode).

Quentin.



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File Attachments:


-------------------------------------------------------
Date: Thu 22 Oct 2009 06:17:35 PM GMT  Name: TestDrawInRect.tar.gz  Size:
23kB   By: qmathe

<http://savannah.gnu.org/bugs/download.php?file_id=18926>
-------------------------------------------------------
Date: Thu 22 Oct 2009 06:17:35 PM GMT  Name: drawInRect-screenshots.tar.gz 
Size: 48kB   By: qmathe

<http://savannah.gnu.org/bugs/download.php?file_id=18925>

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