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List: pykde
Subject: [PyQt] Strange KeyPressEvent behaviour
From: Albert Cervera i Areny <albert () nan-tic ! com>
Date: 2010-05-29 19:12:57
Message-ID: 201005292112.57635.albert () nan-tic ! com
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I've got a strange behaviour with some keypress events which I've been able to
workaround but I'd like to share in case it may be a bug in PyQt.
The situation is a bit complex: I execute a PyQt application using an xrdp (an
open source RDP implementation) server which is being accessed through a
Remote Desktop Client from a Windows Mobile in a handheld. The Handheld has a
barcode reader attached which emulates keyboard strokes.
The thing is I can use the barcode reader without problems using the Remote
Desktop Client against xrdp and with kwrite opened in it. All barcodes are
written correctly. But when I use my own PyQt application some barcodes are
not input correctly. For example, code "00121/1" appears in a QLineEdit (and
QTextEdit too) as "00112/1".
Printing events as they arrive using an event filter shows that the events for
this string come like this: press 0, release 0, press 0, release 0, press 1,
release 1, press 1, press 2, release 2, release 1, press /, release /, press
1, release 1.
As you can see, the strange thing is this part "press 1, press 2, release 2,
release 1". I've worked arround the problem by 'eating' all press events and
sending them only when release event arrives for that key because the order of
release events is correct (00121/1) but not the order of press events
(00112/1).
Does anyone have an explanation for this? Any chance PyQt may not be sending
events in the correct order? Note that this does not happen with all barcodes,
but if a barcode has problems it is *always* printed wrong. Note that I'm
pointing to PyQt because kwrite, which uses Qt too, works correctly with the
same setup.
--
Albert Cervera i Areny
http://www.NaN-tic.com
OpenERP Partner
Mòbil: +34 669 40 40 18
[Attachment #5 (text/html)]
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" \
"http://www.w3.org/TR/REC-html40/strict.dtd"> <html><head><meta name="qrichtext" \
content="1" /><style type="text/css"> p, li { white-space: pre-wrap; }
</style></head><body style=" font-family:'DejaVu Sans'; font-size:12pt; \
font-weight:400; font-style:normal;"> <p style=" margin-top:0px; margin-bottom:0px; \
margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; \
-qt-user-state:0;">I've got a strange behaviour with some keypress events which I've \
been able to workaround but I'd like to share in case it may be a bug in PyQt.</p> <p \
style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">The situation is a bit \
complex: I execute a PyQt application using an xrdp (an open source RDP \
implementation) server which is being accessed through a Remote Desktop Client from a \
Windows Mobile in a handheld. The Handheld has a barcode reader attached which \
emulates keyboard strokes.</p> <p style="-qt-paragraph-type:empty; margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;"></p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">The thing is I can use the barcode reader without \
problems using the Remote Desktop Client against xrdp and with kwrite opened in it. \
All barcodes are written correctly. But when I use my own PyQt application some \
barcodes are not input correctly. For example, code "00121/1" appears in a \
QLineEdit (and QTextEdit too) as "00112/1".</p> <p \
style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Printing events as they \
arrive using an event filter shows that the events for this string come like this: \
press 0, release 0, press 0, release 0, press 1, release 1, press 1, press 2, release \
2, release 1, press /, release /, press 1, release 1.</p> <p \
style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; \
margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></p> <p \
style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">As you can see, the strange \
thing is this part "press 1, press 2, release 2, release 1". I've worked \
arround the problem by 'eating' all press events and sending them only when release \
event arrives for that key because the order of release events is correct (00121/1) \
but not the order of press events (00112/1).</p> <p style="-qt-paragraph-type:empty; \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;"></p> <p style=" \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Does anyone have an \
explanation for this? Any chance PyQt may not be sending events in the correct order? \
Note that this does not happen with all barcodes, but if a barcode has problems it is \
*always* printed wrong. Note that I'm pointing to PyQt because kwrite, which uses Qt \
too, works correctly with the same setup.</p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;"><br />-- </p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;">Albert Cervera i Areny</p> <p style=" \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;"><a \
href="http://www.NaN-tic.com"><span style=" text-decoration: underline; \
color:#0057ae;">http://www.NaN-tic.com</span></a></p> <p style=" margin-top:0px; \
margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; \
text-indent:0px; -qt-user-state:0;"><a href="http://www.NaN-tic.com"><span style=" \
text-decoration: underline; color:#0057ae;">OpenERP Partner</span></a></p> <p style=" \
margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; \
-qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Mòbil: +34 669 40 40 \
18</p></body></html>
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