[Qgis-user] QGIS 2.18 -Changing layer rule-based style transparency

[Raymond Nijssen]

Hi Marian,

As I understand you want to set every symbol in your rule based 
classification to 80% transparent (instead of the entire layer)?

I tried to write a qgis (v3.4) script but unfortunately it crashes my 
qgis. So I hope somebody here can correct it, or maybe you will find the 
solution yourself.

I'm doing many prints to see the return values. The crash happens when 
in line 18: symbolItem.setSymbol(symbol)

---

layer = iface.activeLayer()

renderer = layer.renderer()

symbolItems = renderer.legendSymbolItems()
print(symbolItems)

for symbolItem in symbolItems:
     print('---')
     print(symbolItem)
     symbol = symbolItem.symbol()
     print(symbol)
     color = symbol.color()
     print(color.name(1))
     color.setAlpha(255*0.8)
     print(color.name(1))
     symbol.setColor(color)
     symbolItem.setSymbol(symbol) # !!! this makes qgis crash

layer.triggerRepaint()

---

When crashing, qgis outputs:

QGIS died on signal 11Could not attach to process.  If your uid matches 
the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.
No thread selected
No stack.
gdb returned 0
Aborted (core dumped)

---

Kind regards,
Raymond


On 04-01-19 22:32, Tudorache, Marian wrote:
> Hi,
> 
> I have a polygon type vector layer with rule-based style.
> 
> I need to change programmatically the layer transparency.
> 
> I used the following code:
> 
> layer = iface.activeLayer()
> 
> layer.setTransparency(80)
> 
> layer.triggerRepaint()
> 
> This works only if I want to see layers which are under the active one 
> but it does not work for the features inside active layer.
> 
> When there are identical polygons which overlap within active layer, I 
> can only see the top one. If I select a polygon which is underneath it 
> is not displayed as selected.
> 
> I can make it work if I manually open the layer style and double click 
> on rule to open Rule properties and set the transparency for the rule.
> 
> How can I change the rule transparency programmatically?
> 
> Thank you,
> 
> Marian
> 
> 
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