Why QDeclarativeGeoMap::visibleRegion is non-NOTIFYable in QtLocation Map?
I'm using QtLocation QML Map to display a big amount of items on a map. As with the number of items visible on the map the performance decreases, i would like to set visible only the items actually visible on the viewport. For this it would be handy to just calculate the visibility based on whether the item's coordinate is within the viewport, like:
visible: mapBase.visibleRegion.contains(model.item.coordinate)
But unfortunately the visibleRegion property is non-NOTIFYable, as stated in the documentation at http://doc.qt.io/qt-5/qml-qtlocation-map.html#visibleRegion-prop.
Is there any specific reason (like performance-issues) to not implement a notify signal for this property? Is there any way to workaround this, and set the visibility of a map item based on whether it's within the viewport?
qt qml qtlocation
asked Nov 21 '18 at 13:07
zgyarmati
30729
add a comment |
I'm using QtLocation QML Map to display a big amount of items on a map. As with the number of items visible on the map the performance decreases, i would like to set visible only the items actually visible on the viewport. For this it would be handy to just calculate the visibility based on whether the item's coordinate is within the viewport, like:
visible: mapBase.visibleRegion.contains(model.item.coordinate)
But unfortunately the visibleRegion property is non-NOTIFYable, as stated in the documentation at http://doc.qt.io/qt-5/qml-qtlocation-map.html#visibleRegion-prop.
Is there any specific reason (like performance-issues) to not implement a notify signal for this property? Is there any way to workaround this, and set the visibility of a map item based on whether it's within the viewport?
qt qml qtlocation
asked Nov 21 '18 at 13:07
zgyarmati
30729
add a comment |
I'm using QtLocation QML Map to display a big amount of items on a map. As with the number of items visible on the map the performance decreases, i would like to set visible only the items actually visible on the viewport. For this it would be handy to just calculate the visibility based on whether the item's coordinate is within the viewport, like:
visible: mapBase.visibleRegion.contains(model.item.coordinate)
But unfortunately the visibleRegion property is non-NOTIFYable, as stated in the documentation at http://doc.qt.io/qt-5/qml-qtlocation-map.html#visibleRegion-prop.
Is there any specific reason (like performance-issues) to not implement a notify signal for this property? Is there any way to workaround this, and set the visibility of a map item based on whether it's within the viewport?
qt qml qtlocation
asked Nov 21 '18 at 13:07
zgyarmati
30729
I'm using QtLocation QML Map to display a big amount of items on a map. As with the number of items visible on the map the performance decreases, i would like to set visible only the items actually visible on the viewport. For this it would be handy to just calculate the visibility based on whether the item's coordinate is within the viewport, like:
visible: mapBase.visibleRegion.contains(model.item.coordinate)
But unfortunately the visibleRegion property is non-NOTIFYable, as stated in the documentation at http://doc.qt.io/qt-5/qml-qtlocation-map.html#visibleRegion-prop.
Is there any specific reason (like performance-issues) to not implement a notify signal for this property? Is there any way to workaround this, and set the visibility of a map item based on whether it's within the viewport?
qt qml qtlocation
qt qml qtlocation
asked Nov 21 '18 at 13:07
zgyarmati
30729
asked Nov 21 '18 at 13:07
zgyarmati
30729
asked Nov 21 '18 at 13:07
zgyarmati
30729
asked Nov 21 '18 at 13:07
zgyarmati
30729
asked Nov 21 '18 at 13:07
zgyarmati
30729
30729
add a comment |
add a comment |
1 Answer
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I suppose the reason could be that it's expensive to calculate.
But visibleRegion changes when one of the following properties change: zoomLevel, center, bearing, tilt, fieldOfView. You could, for example, define your own "property var visRegion", and update it when reacting on those properties above by fetching visibleRegion and assigning it to visRegion.
answered Nov 29 '18 at 14:10
Pa_
392313
add a comment |
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1 Answer
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active
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
I suppose the reason could be that it's expensive to calculate.
But visibleRegion changes when one of the following properties change: zoomLevel, center, bearing, tilt, fieldOfView. You could, for example, define your own "property var visRegion", and update it when reacting on those properties above by fetching visibleRegion and assigning it to visRegion.
answered Nov 29 '18 at 14:10
Pa_
392313
add a comment |
I suppose the reason could be that it's expensive to calculate.
But visibleRegion changes when one of the following properties change: zoomLevel, center, bearing, tilt, fieldOfView. You could, for example, define your own "property var visRegion", and update it when reacting on those properties above by fetching visibleRegion and assigning it to visRegion.
answered Nov 29 '18 at 14:10
Pa_
392313
add a comment |
I suppose the reason could be that it's expensive to calculate.
But visibleRegion changes when one of the following properties change: zoomLevel, center, bearing, tilt, fieldOfView. You could, for example, define your own "property var visRegion", and update it when reacting on those properties above by fetching visibleRegion and assigning it to visRegion.
answered Nov 29 '18 at 14:10
Pa_
392313
I suppose the reason could be that it's expensive to calculate.
But visibleRegion changes when one of the following properties change: zoomLevel, center, bearing, tilt, fieldOfView. You could, for example, define your own "property var visRegion", and update it when reacting on those properties above by fetching visibleRegion and assigning it to visRegion.
answered Nov 29 '18 at 14:10
Pa_
392313
answered Nov 29 '18 at 14:10
Pa_
392313
answered Nov 29 '18 at 14:10
Pa_
392313
answered Nov 29 '18 at 14:10
Pa_
392313
392313
add a comment |
add a comment |
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