Re: [Qgis-user] Event loop in QGIS3
On Wed, 17 Aug 2022 at 06:54, Tudorache, Marian via Qgis-user
wrote:
>
> Hi Chris,
>
>
>
> I read that article and based on it I found out that I need to put
> processEvents() and I understand the logic in this.
>
>
>
> Someone said:
>
> In more recent QGIS versions the Python console no longer triggers this event
> loop, as it's often quite dangerous to execute the loop in the middle of
> other running code.
>
>
>
> It seems somehow QGIS 2.18 was designed to send automatically updates to the
> GUIs when a loop is running and this capability was eliminated in QGIS 3
That's correct -- there was a forced processEvents in QGIS 2 after
printing anything, but that directly lead to crashes in some
circumstances. processEvents is a potentially very dangerous call, so
now the responsibility is on end users/developers to make sure it's
safe to call after a print.
Nyall
>
> Anyway, thank you for your answer.
>
>
>
> Marian
>
>
>
> From: chris hermansen
> Sent: August 16, 2022 4:40 PM
> To: Tudorache, Marian
> Cc: qgis-user@lists.osgeo.org
> Subject: [EXT] Re: [Qgis-user] Event loop in QGIS3
>
>
>
> Marian and list, On Tue, Aug 16, 2022 at 12: 02 PM Tudorache, Marian via
> Qgis-user wrote: Hello community, A while
> ago I sent a question about a problem with QMessageBox and message bar does
> not get updated
>
> Marian and list,
>
>
>
> On Tue, Aug 16, 2022 at 12:02 PM Tudorache, Marian via Qgis-user
> wrote:
>
> Hello community,
>
>
>
> A while ago I sent a question about a problem with QMessageBox and message
> bar does not get updated during a long process.
>
> In my example I create a script like this.
>
>
>
> from qgis.PyQt import QtWidgets
>
> message = "Wait to open the airspace project..."
>
> msg = QtWidgets.QMessageBox()
>
> msg.setText(message)
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Wait", message)
>
>
>
>
>
> for i in range(1000):
>
> print(i)
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
>
> msg.setText("The process is done")
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
>
>
>
>
>
> When I run the scrip in QGIS 2.18 the QMessageBox displays first the message
> "Wait to open the airspace project...". The same message is pushed to
> messageBar.
>
> Then during the loop it displays the variable i.
>
> At the end of the loop the QMessageBox displays the message "The process is
> done" which is also pushed to the messageBar.
>
>
>
> When I run the same scrip on QGIS 3 the QMessageBox is empty. The message
> "Wait to open the airspace project..." is not displayed by QMessageBox nor by
> messageBar.
>
> The print inside the loop displays the I and when the loop is done the
> QMessageBox displays the message "The process is done".
>
> The messageBar displays also the message "The process is done". And after a
> while it displays the initial message "Wait to open the airspace project..."
>
>
>
> I modified the scrip by adding QApplication.processEvents() inside the loop
> and now everything is fine.
>
> It seems QGIS3 no longer triggers this event loop and I have to do this
> explicitly by calling processEvents from QApplication.
>
>
>
> Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not
> need?
>
>
>
>
>
> Marian, did you read this article?
>
>
>
> https://doc.qt.io/qt-5/qcoreapplication.html#details
>
>
>
> There you will see this:
>
>
>
> The event loop is started with a call to exec(). Long-running operations can
> call processEvents() to keep the application responsive.
>
>
>
> In your case, your "long-running operation" is your for loop. And it is not
> QGIS3 that has the responsibility to trigger processEvents() but your own
> long-running operation, at least the way I'm reading this.
>
>
>
> As to why QGIS 2 did not need this, I don't know.
>
>
> --
>
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
>
>
>
>
> This electronic message, as well as any transmitted files included in the
> electronic message, may contain privileged or confidential information and is
> intended solely for the use of the individual(s) or entity to which it is
> addressed. If you have received this electronic message in error please
> notify the sender immediately and delete the electronic message. Any
> unauthorized copying, disclosure or distribution of the electronic message is
> strictly forbidden. NAV CANADA accepts no liability for any damage caused by
> any virus and/or other malicious code transmitted by this electronic
> communication.
>
> Le présent message électronique et tout fichier qui peut y être joint peuvent
> contenir des renseignements privilégiés ou confidentiels destinés à l’usage
> exclusif des personnes ou des organismes à qui ils s’adressent. Si vous avez
> reçu ce message électronique par erreur, veuillez en informer l’expéditeur
> immédiatement et supprimez le. Toute
Re: [Qgis-user] Event loop in QGIS3
Thanks for this question. I had the same issue in my code, but running a
console script in the Qgis application, printing to the console output
would achieve the same thing. Is this applicable to scripts that run in
the console?
On 17/08/22 07:02, Tudorache, Marian via Qgis-user wrote:
Hello community,
A while ago I sent a question about a problem with QMessageBox and
message bar does not get updated during a long process.
In my example I create a script like this.
from qgis.PyQt import QtWidgets
message = "Wait to open the airspace project..."
msg = QtWidgets.QMessageBox()
msg.setText(message)
msg.show()
qgis.utils.iface.messageBar().pushMessage("Wait", message)
for i in range(1000):
print(i)
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
msg.setText("The process is done")
msg.show()
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
When I run the scrip in QGIS 2.18 the QMessageBox displays first the
message "Wait to open the airspace project...". The same message is
pushed to messageBar.
Then during the loop it displays the variable i.
At the end of the loop the QMessageBox displays the message "The
process is done" which is also pushed to the messageBar.
When I run the same scrip on QGIS 3 the QMessageBox is empty. The
message "Wait to open the airspace project..." is not displayed by
QMessageBox nor by messageBar.
The print inside the loop displays the I and when the loop is done the
QMessageBox displays the message "The process is done".
The messageBar displays also the message "The process is done". And
after a while it displays the initial message "Wait to open the
airspace project..."
I modified the scrip by adding QApplication.processEvents() inside the
loop and now everything is fine.
It seems QGIS3 no longer triggers this event loop and I have to do
this explicitly by calling processEvents from QApplication.
*Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does
not need?*
Thank you,
Marian
This electronic message, as well as any transmitted files included in
the electronic message, may contain privileged or confidential
information and is intended solely for the use of the individual(s) or
entity to which it is addressed. If you have received this electronic
message in error please notify the sender immediately and delete the
electronic message. Any unauthorized copying, disclosure or
distribution of the electronic message is strictly forbidden. NAV
CANADA accepts no liability for any damage caused by any virus and/or
other malicious code transmitted by this electronic communication.
Le présent message électronique et tout fichier qui peut y être joint
peuvent contenir des renseignements privilégiés ou confidentiels
destinés à l’usage exclusif des personnes ou des organismes à qui ils
s’adressent. Si vous avez reçu ce message électronique par erreur,
veuillez en informer l’expéditeur immédiatement et supprimez le. Toute
reproduction, divulgation ou distribution du présent message
électronique est strictement interdite. NAV CANADA n’assume aucune
responsabilité en cas de dommage causé par tout virus ou autre
programme malveillant transmis par ce message électronique.
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Re: [Qgis-user] Event loop in QGIS3
Hi Chris,
I read that article and based on it I found out that I need to put
processEvents() and I understand the logic in this.
Someone said:
In more recent QGIS versions the Python console no longer triggers this event
loop, as it's often quite dangerous to execute the loop in the middle of other
running code.
It seems somehow QGIS 2.18 was designed to send automatically updates to the
GUIs when a loop is running and this capability was eliminated in QGIS 3
Anyway, thank you for your answer.
Marian
From: chris hermansen
Sent: August 16, 2022 4:40 PM
To: Tudorache, Marian
Cc: qgis-user@lists.osgeo.org
Subject: [EXT] Re: [Qgis-user] Event loop in QGIS3
Marian and list, On Tue, Aug 16, 2022 at 12: 02 PM Tudorache, Marian via
Qgis-user wrote: Hello community, A while ago
I sent a question about a problem with QMessageBox and message bar does not get
updated
Marian and list,
On Tue, Aug 16, 2022 at 12:02 PM Tudorache, Marian via Qgis-user
mailto:qgis-user@lists.osgeo.org>> wrote:
Hello community,
A while ago I sent a question about a problem with QMessageBox and message bar
does not get updated during a long process.
In my example I create a script like this.
from qgis.PyQt import QtWidgets
message = "Wait to open the airspace project..."
msg = QtWidgets.QMessageBox()
msg.setText(message)
msg.show()
qgis.utils.iface.messageBar().pushMessage("Wait", message)
for i in range(1000):
print(i)
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
msg.setText("The process is done")
msg.show()
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
When I run the scrip in QGIS 2.18 the QMessageBox displays first the message
"Wait to open the airspace project...". The same message is pushed to
messageBar.
Then during the loop it displays the variable i.
At the end of the loop the QMessageBox displays the message "The process is
done" which is also pushed to the messageBar.
When I run the same scrip on QGIS 3 the QMessageBox is empty. The message "Wait
to open the airspace project..." is not displayed by QMessageBox nor by
messageBar.
The print inside the loop displays the I and when the loop is done the
QMessageBox displays the message "The process is done".
The messageBar displays also the message "The process is done". And after a
while it displays the initial message "Wait to open the airspace project..."
I modified the scrip by adding QApplication.processEvents() inside the loop and
now everything is fine.
It seems QGIS3 no longer triggers this event loop and I have to do this
explicitly by calling processEvents from QApplication.
Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not need?
Marian, did you read this article?
https://doc.qt.io/qt-5/qcoreapplication.html#details
There you will see this:
The event loop is started with a call to
exec().
Long-running operations can call
processEvents()
to keep the application responsive.
In your case, your "long-running operation" is your for loop. And it is not
QGIS3 that has the responsibility to trigger processEvents() but your own
long-running operation, at least the way I'm reading this.
As to why QGIS 2 did not need this, I don't know.
--
Chris Hermansen · clhermansen "at" gmail "dot" com
C'est ma façon de parler.
This electronic message, as well as any transmitted files included in the
electronic message, may contain privileged or confidential information and is
intended solely for the use of the individual(s) or entity to which it is
addressed. If you have received this electronic message in error please notify
the sender immediately and delete the electronic message. Any unauthorized
copying, disclosure or distribution of the electronic message is strictly
forbidden. NAV CANADA accepts no liability for any damage caused by any virus
and/or other malicious code transmitted by this electronic communication.
Le présent message électronique et tout fichier qui peut y être joint peuvent
contenir des renseignements privilégiés ou confidentiels destinés à l’usage
exclusif des personnes ou des organismes à qui ils s’adressent. Si vous avez
reçu ce message électronique par erreur, veuillez en informer l’expéditeur
immédiatement et supprimez le. Toute reproduction, divulgation ou distribution
du présent message électronique est
Re: [Qgis-user] Event loop in QGIS3
Marian and list,
On Tue, Aug 16, 2022 at 12:02 PM Tudorache, Marian via Qgis-user <
qgis-user@lists.osgeo.org> wrote:
> Hello community,
>
>
>
> A while ago I sent a question about a problem with QMessageBox and message
> bar does not get updated during a long process.
>
> In my example I create a script like this.
>
>
>
> from qgis.PyQt import QtWidgets
>
> message = "Wait to open the airspace project..."
>
> msg = QtWidgets.QMessageBox()
>
> msg.setText(message)
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Wait", message)
>
>
>
>
>
> for i in range(1000):
>
> print(i)
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
>
> msg.setText("The process is done")
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
>
>
>
>
>
> When I run the scrip in QGIS 2.18 the QMessageBox displays first the
> message "Wait to open the airspace project...". The same message is pushed
> to messageBar.
>
> Then during the loop it displays the variable i.
>
> At the end of the loop the QMessageBox displays the message "The process
> is done" which is also pushed to the messageBar.
>
>
>
> When I run the same scrip on QGIS 3 the QMessageBox is empty. The message
> "Wait to open the airspace project..." is not displayed by QMessageBox nor
> by messageBar.
>
> The print inside the loop displays the I and when the loop is done the
> QMessageBox displays the message "The process is done".
>
> The messageBar displays also the message "The process is done". And after
> a while it displays the initial message "Wait to open the airspace
> project..."
>
>
>
> I modified the scrip by adding QApplication.processEvents() inside the
> loop and now everything is fine.
>
> It seems QGIS3 no longer triggers this event loop and I have to do this
> explicitly by calling processEvents from QApplication.
>
>
>
> *Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not
> need?*
>
>
>
Marian, did you read this article?
https://doc.qt.io/qt-5/qcoreapplication.html#details
There you will see this:
The event loop is started with a call to exec
> (). Long-running
> operations can call processEvents
> () to keep
> the application responsive.
>
In your case, your "long-running operation" is your for loop. And it is
not QGIS3 that has the responsibility to trigger processEvents() but your
own long-running operation, at least the way I'm reading this.
As to why QGIS 2 did not need this, I don't know.
--
Chris Hermansen · clhermansen "at" gmail "dot" com
C'est ma façon de parler.
___
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Qgis-user@lists.osgeo.org
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[Qgis-user] Event loop in QGIS3
Hello community,
A while ago I sent a question about a problem with QMessageBox and message bar
does not get updated during a long process.
In my example I create a script like this.
from qgis.PyQt import QtWidgets
message = "Wait to open the airspace project..."
msg = QtWidgets.QMessageBox()
msg.setText(message)
msg.show()
qgis.utils.iface.messageBar().pushMessage("Wait", message)
for i in range(1000):
print(i)
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
msg.setText("The process is done")
msg.show()
qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
When I run the scrip in QGIS 2.18 the QMessageBox displays first the message
"Wait to open the airspace project...". The same message is pushed to
messageBar.
Then during the loop it displays the variable i.
At the end of the loop the QMessageBox displays the message "The process is
done" which is also pushed to the messageBar.
When I run the same scrip on QGIS 3 the QMessageBox is empty. The message "Wait
to open the airspace project..." is not displayed by QMessageBox nor by
messageBar.
The print inside the loop displays the I and when the loop is done the
QMessageBox displays the message "The process is done".
The messageBar displays also the message "The process is done". And after a
while it displays the initial message "Wait to open the airspace project..."
I modified the scrip by adding QApplication.processEvents() inside the loop and
now everything is fine.
It seems QGIS3 no longer triggers this event loop and I have to do this
explicitly by calling processEvents from QApplication.
Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not need?
Thank you,
Marian
This electronic message, as well as any transmitted files included in the
electronic message, may contain privileged or confidential information and is
intended solely for the use of the individual(s) or entity to which it is
addressed. If you have received this electronic message in error please notify
the sender immediately and delete the electronic message. Any unauthorized
copying, disclosure or distribution of the electronic message is strictly
forbidden. NAV CANADA accepts no liability for any damage caused by any virus
and/or other malicious code transmitted by this electronic communication.
Le pr?sent message ?lectronique et tout fichier qui peut y ?tre joint peuvent
contenir des renseignements privil?gi?s ou confidentiels destin?s ? l'usage
exclusif des personnes ou des organismes ? qui ils s'adressent. Si vous avez
re?u ce message ?lectronique par erreur, veuillez en informer l'exp?diteur
imm?diatement et supprimez le. Toute reproduction, divulgation ou distribution
du pr?sent message ?lectronique est strictement interdite. NAV CANADA n'assume
aucune responsabilit? en cas de dommage caus? par tout virus ou autre programme
malveillant transmis par ce message ?lectronique.
___
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