Hi devs,
I have started to work on fixing this issue
https://github.com/qgis/QGIS/pull/31930
I was thinking, I have found a solution to force QGIS Server to wait for
loading remote SVG before rendering.
But it seems that I am not able to determine if a task is running or
will be ran.
Just after fetching SVGs, I wrote this code :
if ( QgsApplication::taskManager()->countActiveTasks() > 0 )
{
QEventLoop loop;
QObject::connect( QgsApplication::taskManager(),
&QgsTaskManager::allTasksFinished, &loop, &QEventLoop::quit );
loop.exec();
}
When a task is added, does the number of active tasks increase?
Is the number of active tasks null when all the task has been performed ?
If the number of active tasks is null, are all tasks finished ?
Thansk for your help,
René-Luc
Le 05/07/2019 à 00:48, Nyall Dawson a écrit :
On Thu, 4 Jul 2019 at 23:08, René-Luc Dhont <[email protected]> wrote:
Hi devs,
We encountered a strange issue with QGIS Server, a point layer with a
simple style using a remote SVG.
At the first GetMap request to this layer, QGIS Server rendered an image
with missing symbol, the ?.
At the second same GetMap Request, QGIS Server rendered an image with
the remote SVG.
And sometimes the remote SVG is not drawn and replaced by the ?.
Do you know if the renderer or the styler has a timer to wait for SVG ?
Is It configurable ? or the context can be configured to wait for svg or
an error ?
On the desktop it's done in a background thread, and the svg/raster
image caches fire a signal when the image is downloaded, triggering a
canvas refresh.
I'm not sure how you could address this with server. Maybe either:
1. (ugly) push some flag via the render context to force the renderer
to wait until a required svg is downloaded, and push this flag into
the svg/ raster image caches.
2. (out of the box) use https://github.com/qgis/QGIS/pull/30522 to
check in advance for any remote svg/images required in a project, and
prefetch all these on server startup BEFORE any rendering operation is
requested.
Nyall
Regards,
René-Luc
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