Remove a QgsRectangle from a RectangleMapTool in PyQGIS

Question

In a QGIS plugin, I implemented a RectangleMapTool that I apply to my canvas. Thus, the user has the possibility to select a bounding box to define the spatial processing footprint.

Once he has selected his bounding box, I'd like to delete this QgsRectangle but I can't do it. If the user clicks anywhere after drawing the bounding box, the rectangle disappears but sometimes it remains.

You can run the following code in the Python console. If you run the script a second time, the bounding box will remain drawn:

from processing.gui.RectangleMapTool import RectangleMapTool

# Function
def bbox():
    r = tool.rectangle()
    line_bbox.setText(str(r.xMinimum()))
    line_bbox.show()

# MapTool
canvas = iface.mapCanvas()
tool = RectangleMapTool(canvas)
tool.rectangleCreated.connect(bbox)
canvas.setMapTool(tool)

# QLineEdit
line_bbox = QLineEdit()
line_bbox.hide()

I explored the documentation to be able to delete a QgsRectangle. When it is an entity of a layer I know how to do it but in my case, it is drawn on the canvas.

I also explored several links that ran iface.mapCanvas().scene().items(). I tried to remove the QgsRubberBand objects but my QGIS crashes or no changes are made.

Does this answer help you? Make sure you use a Python variable (e.g., a dict) to store and delete the items. — Germán Carrillo, Jan 14 '20 at 14:59
I read your answer, but in my case I don't have layer sometimes. I draw directly on the canvas. — Vincent Bré, Jan 14 '20 at 15:05
Please provide some code for reproduce your objects and case. — J. Monticolo, Jan 14 '20 at 15:43
You may need to update to new version of QGIS. Crashing issue is fixed in next versions. Link. — Kadir Şahbaz, Jan 14 '20 at 20:28
I saw your post on github saying that it caused a QGIS crash on 3.4. @J. Monticolo solved my problem, thank you. — Vincent Bré, Jan 15 '20 at 07:28
@VincentBré I created a plugin and I want some type of preview window to define a study case using a rectangle. Can I have access to your code to understand how do you did it? — Bárbara Duarte, Oct 09 '20 at 08:15
@BárbaraDuarte I think you have everything you need with my code and the answer of this post — Vincent Bré, Oct 09 '20 at 08:31
So if I understand you have the class RectangleMapTool as in this tutorial (https://docs.qgis.org/3.10/en/docs/pyqgis_developer_cookbook/canvas.html). Then you call it in other scritp using the functions above in this post? Because my doubt is in the interaction with the mouse. It is not drawing the rectangle. — Bárbara Duarte, Oct 09 '20 at 08:44
In a first time, try my code in the Python Console. It works, you should see the rectangle and the minimum x in the QLineEdit widget. — Vincent Bré, Oct 09 '20 at 08:56
I can try. But I want this in my own canvas (a widget created in QtDesigner). When I use your code, gives me this error: "tool.rectangle.connect(bbox) AttributeError: 'function' object has no attribute 'connect'" — Bárbara Duarte, Oct 09 '20 at 12:52
It works fine in the Python console. Now I want to adapted to my plugin that has a widget supposed to be the canvas. — Bárbara Duarte, Oct 09 '20 at 12:53
The easiest way is for you to open a post so that other members and I can help you. You will be able to add your code, screenshots etc. — Vincent Bré, Oct 09 '20 at 13:09
I try and I get it! I will open a question because my rectangle do not close. Thank you. — Bárbara Duarte, Oct 09 '20 at 13:23

score 2 · Accepted Answer · answered Jan 14 '20 at 16:09

2

For me you have just to test if the tool object is already created and call the reset() method for delete the QgsRubberBand displayed :

# MapTool
canvas = iface.mapCanvas()
if tool:
    tool.reset()

tool = RectangleMapTool(canvas)
...

answered Jan 14 '20 at 16:09

J. Monticolo

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Thanks a lot! I was looking for too complicated around QgsRectangle and QgsRubberBand while reset works perfectly well. – Vincent Bré Jan 15 '20 at 07:30

Remove a QgsRectangle from a RectangleMapTool in PyQGIS

1 Answers1