Bug report #18892
Scale jump from mouse tremor
|Affected QGIS version:||3.0.2||Regression?:||No|
|Operating System:||Mac OS X 10.12.6||Easy fix?:||No|
|Pull Request or Patch supplied:||No||Resolution:|
|Crashes QGIS or corrupts data:||No||Copied to github as #:||26724|
Previously reported for 2.18.15 but closed as having been fixed for QGIS 3, but unfortunately has not been fixed.
When clicking on the map with the zoom (magnifying glass) tools the slightest inadvertent movement of the mouse while pressed causes the scale factor to jump - e.g., from 1:1,000 to 1:1,000,000 (zoom out tool) or to 1:10 (zoom in tool).
Apparently the smallest movement is interpreted as a request to adjust scale. This is much too "sensitive" and frequently results in large scale jumps from very small hand trembles.
Also occurs in QGIS 3.0.0 and 3.0.1 (and 2.18.15).
This could be avoided by requiring some minimum movement size (perhaps 10x10 pixels) before interpreting the movement as a request to rescale rather than just a normal zoom in or out command.
Also, while being able to select a portion of the map to be rescaled to fit the window using the zoom in tool, I don't understand the logic of the zoom out tool in which selecting a small part of the map causes it to zoom out to a much larger scale? Perhaps this feature should only be implemented for the zoom in tool?
#5 Updated by Garth Fletcher about 2 years ago
open any project, set scale to, say, 1:40,000
select + zoom tool
click down in map canvas
then drag mouse a very very small distance
notice that scaling has jumped by a huge amount, e.g., to 1:100
This occurs frequently due to inadvertent mouse movements ("hand tremor")
and perhaps also due to mouse digitizing jitter (sometimes I'm pretty
sure that I did not actually move the mouse).
The same problem occurs when using the - zoom tool, except in that case
the scale factor jumps to a huge value, e.g., 1:10,000,000
The easy solution is to require some minimum mouse displacement - say 10 screen
pixels in either axis - before accepting the movement as a request to zoom.
Environment (for reference):
Mac OS X 10.12.6
on Mac mini (Mid 2011) 2.3 GHz Intel Core i5, 8 GB 1600 MHz DDR3 RAM
QGIS version 3.2.3-Bonn
QGIS code branch Release 3.2
Compiled against Qt 5.9.6
Running against Qt 5.9.6
Compiled against GDAL/OGR 2.2.4
Running against GDAL/OGR 2.2.4
Compiled against GEOS 3.6.3-CAPI-1.10.3
Running against GEOS 3.6.2-CAPI-1.10.2 4d2925d6
PostgreSQL Client Version 9.4.19
SpatiaLite Version 4.4.0-RC0
QWT Version 6.1.3
QScintilla2 Version 2.10.7
PROJ.4 Version 493