Layer effects having unexpected render issues in Print Composer

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Author Name: Jamie Portman (Jamie Portman)
Original Redmine Issue: 15696
Affected QGIS version: 2.14.5
Redmine category:symbology
Assignee: Nyall Dawson

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Hi,

I have search a bit and can't find any previous threads or reports of this issue...
We have encountered on numerous occasions, some bizarre results in the print composer when using layer effects (particularly a drop shadow).

Everything looks fine in the map canvas, but on refreshing the print composer, random triangles are seen (in the base color of the shadow used... black, white, solid blue, etc.)

Frustratingly, it doesn't happen all the time on any particular layer. The screen shots attached are from a project I've been working with no problems for nearly a month, and then today it just starts happening and the only way to get ride of it is to remove the layer effects. Annoying, as this feature is awesome and makes the final map have a much greater impact!

If you export to PDF/JPG the additional, unwanted triangles do transfer to the final result.
The triangles in this particular layer all appear on lines that have a significant change of direction, I'm not sure if this is always the case.

Apologies, if I'm not supposed to assign a ticket to a person... this is one of very few times that I know the developer that came up with the feature!

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• MapComposer.JPG (Jamie Portman)
• PrintComposer-randomtrianglesrendered.JPG (Jamie Portman)
• shadow_project.zip (Jamie Portman)

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Author Name: Nyall Dawson (@nyalldawson)

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Jamie -

I hit this issue once myself but unfortunately lost the project and couldn't find a way to reproduce it. Is there any chance you could share this project file?

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Author Name: Jamie Portman (Jamie Portman)

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there is a LOT in the project... I'll see if I can strip it back but manage to retain the glitch!

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Author Name: Jamie Portman (Jamie Portman)

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Hi Nyall,

I've managed to strip back the project and isolate when the problem occurs a fair bit!
The attached project demonstrates the issue with a single layer.
The problem only occurs when the layer is duplicated (as it is here). Only the top layer has draw effects (shadow) turned on. If the bottom layer is turned off, the issue goes away. If the bottom layer is moved above the other layer, it also goes away!

The issue is only visible in the print composer, it always looks perfectly as expected in the map window :)

Hope this helps.

Jamie

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• 10469 was configured as shadow_project.zip

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• shadow_project.zip (Jamie Portman)

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Author Name: Nyall Dawson (@nyalldawson)

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Perfect - exactly what I needed, thank you. Looks like the issue is caused by the marker line style drawn underneath a layer with effects.

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Author Name: Nyall Dawson (@nyalldawson)

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Fixed in changeset "a0bfc10c568e3e4f54a7f43ca285e2e7b11a194a".

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• status_id was changed from Open to Closed

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Author Name: Jamie Portman (Jamie Portman)

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Thankyou Nyall, you are awesome!
To anyone who says "it's open source, so you just dont have the technical support of commercial software"... well, I am yet to have a bug resolved by Mapinfo or ESRI as quickly as the QGIS developers do!

I take it this fix will flow through into both the next LR and LTR releases?

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Author Name: Nyall Dawson (@nyalldawson)

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Yes, I'll backport it to the current stable releases too so it'll be in the next point releases. Just going to test a few other things first - I think there may be a slightly better way to address this.