of layout items when exporting (i.e. disabling of cached item render)
The old issue of semi-transparent pixels around the edge of the page
had reared again. This is caused by the antialiasing while rendering
the page symbol. In order to avoid this, we cater to the most common
use case of having pages with a solid, borderless fill and slightly
extend the fill symbol polygon outside the page by 2 pixels
(determined by trial-and-error). The less common use case of having
a page symbol containing a border suffers by this border being
clipped by a couple of pixels, but we must address the much more
common use case over this.
This commit fixes a possible crash when the vector layer renderer
attempts to render a multipolygon containing a polygon without
an exterior ring.
The underlying cause of the creation of this invalid geometry is deeper,
but this commit hardens the renderer and makes it more robust for
handling bad geometries.
Fixes#17365
If file has been modified since the cache, regenerate a new cache
image.
We don't want to check the file modified time too often though,
(e.g., we don't want to check for every point render in a 100k
point file), so use a hardcoded 30 second minimum time between
consecutive file modified checks.
This means that file modifications occuring more often than
every 30 seconds won't be picked up till 30 seconds has elapsed
since the last modification. But at the same time it means that
if the render takes < 30 seconds we'll only check each svg
at most once (and if a render takes > 30 seconds, adding a few
more milliseconds won't hurt!).
Fixes#13565
