Bug 114127 - Internally set scale factor 1 is not set right.
Summary: Internally set scale factor 1 is not set right.
Status: NEW
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: LibreOffice (show other bugs)
(earliest affected)
Inherited From OOo
Hardware: x86-64 (AMD64) All
: medium minor
Assignee: Not Assigned
Keywords: needsDevAdvice
Depends on:
Blocks: Zoom
  Show dependency treegraph
Reported: 2017-11-29 09:05 UTC by ricky.tigg
Modified: 2023-09-01 03:14 UTC (History)
4 users (show)

See Also:
Crash report or crash signature:

Writer – Manually set scale factor. (21.43 KB, image/png)
2017-11-29 09:05 UTC, ricky.tigg

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Description ricky.tigg 2017-11-29 09:05:04 UTC
Created attachment 138053 [details]
Writer – Manually set scale factor.

Build ID:
CPU threads: 2; OS: Linux 4.13; UI render: default; VCL: gtk3; 
Locale: en-GB (en_GB.UTF-8); Calc: group

Scale factor 1, is not set right (At least on Writer and Calc, only Canonical applications I uses) which means that therefore real sizes are not set correctly for value 1; reasons can be either operating system handled scale factor 1 is not set right, or in case too Libreoffice handles independently its own scale factor, that scale factor 1 is not set right.

Therefore on a 14.1'-inched laptop screen, whose default resolution is 1280 x 800 pix (16:10), while scale is set at value 1, on screen displayed sizes do not match real world sizes. Indeed in order to match real world sizes. value has to be set manually, (8right-click Zoom-level on bottom tool-bar) to 1.18, which as illustrated in attachment corresponds to 118 %.

Expected should be either that system or application that handles scale factor 1 to be set right as it is a requirement to get rights proportions of a document's content. In case Linux operating system and Libreoffice too handle scale factors, and are active at the same time, therefore they mustn't interfere one with another.
Comment 1 Buovjaga 2017-12-03 12:19:15 UTC
So to test you take a physical ruler and measure the dimensions from the screen?
Comment 2 ricky.tigg 2017-12-04 15:01:16 UTC
Correction 13.3-inched WideScreen (13.2" x 7.1").

Physical ruler was not available so package used as application ruler on Fedora 27 is screenruler-0.96-8.fc27.noarch. In order to get a an acceptable accuracy, on Screenruler's I had to make some changes: Settings -> Check Custom settings and set same amount of pixels per inches for both Horizontal and vertical (rights settings for my screen, 1280/13.2" x 800/7.1" which makes at closest 113 x 113, which allows an accuracy of -/+ 1 mm). 

Ruler application's size unit set to cm.
Target paper format set to A4 (in cm. 21.00 x 29.70) in Writer.

Actual results: Ruler indicates 17.9 cm as measure of document horizontal side (corresponds to 118 % on Writer scale) while 21.0 cm is expected.
Comment 3 ricky.tigg 2017-12-05 10:51:15 UTC
Correction: 13.3-inched WideScreen (11.3" x 7.1"), just for information; it has no consequence on results from measured dimensions.
Comment 4 Buovjaga 2017-12-16 11:46:49 UTC
After confirming I had the opposite problem (have to reduce zoom to match reality), I did some digging. It may be fundamentally impossible to fix this without doing a huge renovation.

"the paper size is measured in twips"
Comment 5 ricky.tigg 2018-04-07 11:51:47 UTC
Version: – Build ID: – CPU threads: 2; OS: Linux 4.16; UI render: default; VCL: gtk3; – Locale: en-GB (en_GB.UTF-8); Calc: group

Issue still alive. Upgraded from Fedora v. 27 to v. 28 beta.
Comment 6 QA Administrators 2019-04-08 02:46:36 UTC Comment hidden (obsolete)
Comment 7 V Stuart Foote 2019-04-08 03:42:22 UTC
If the os/DE "Scale factor 1" equates to a zoom of 100% there is no expectation in LibreOffice that zoom to 100% is rendering to screen in "actual" measurements. 

Zoom is to 100% of the applications internal scaling which works in screen independent TWIPS(1/1,440"), or worse PIXELS -- how big is a pixel?

You can adjust the application's zoom so that it will actually measure out on the screen at 100%. 

Or you could adjust your os/DE screen resolution reducing/increasing the effective pixel size--until the applications 100% zoom matches real world measurement. But that will impact other use of the desktop.

Some potential for improvement as LO has been forced for HiDPI support to identify the DPI that a combination of screen size and pixel resolution supports so the UI can be appropriately scaled. But the actual scale of a 100% zoom would still not be directly tested/validated--just rendered "close enough".

Printing & Export, unlike screen rendering, are directly written out with size/scale values relevant to the device/file format.

IMHO, this is not a valid bug and is just a manifestation of the graphics framework and application interface.
Comment 8 QA Administrators 2021-08-31 03:54:51 UTC Comment hidden (obsolete)
Comment 9 ricky.tigg 2021-08-31 09:05:29 UTC
Refer to Comment 7 if internally considered valid.
Comment 10 QA Administrators 2023-09-01 03:14:36 UTC
Dear ricky.tigg,

To make sure we're focusing on the bugs that affect our users today, LibreOffice QA is asking bug reporters and confirmers to retest open, confirmed bugs which have not been touched for over a year.

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