17. FAQ and known problems¶

Known client problems relating directly to CamCOPS
Known client problems relating to third-party software
Known server problems relating directly to CamCOPS
Known server problems relating to the surrounding web server framework
- “Proxy error” or “Website unavailable” whilst downloading big files through Apache
Known server problems relating to other third-party software
- Warnings during “camcops merge_db” relating to the “mysqldb” driver and UTF-8
Hardware FAQs: Sony Xperia Z2 tablet
- The charger doesn’t work
- Where’s the USB port?
Android FAQs

17.1. Known client problems relating directly to CamCOPS ¶

17.2. Known client problems relating to third-party software ¶

17.2.1. Qt: QLabel height ¶

It seems likely that the Qt function QLabel::heightForWidth() sometimes gets heights wrong for some stylesheets, leading to excessive vertical height. See labelwordwrapwide.cpp (and to see the problem: try the demo QuMcqGrid). I think I’ve largely compensated for this, though.

17.2.2. Spinboxes are relatively poor for entering numbers ¶

The spinbox numerical entry fields are weak in terms of NULL values. This is an intrinsic weakness in Qt’s QSpinBox and QDoubleSpinBox that works like this:

if you send a null value to a QSpinBox, it’ll typically show its minimum value; for example, for the range 5–10, if you send it 0, it’ll show 5.
If you then delete the “5” and retype “5”, it doesn’t generate any “changed” signals, either via its string or its integer signals. Therefore, this change isn’t detected by the QuSpinBoxInteger or QuSpinBoxDouble framework. You have to delete it, replace it with something else, and re-enter it, for the change to be noticed and the yellow NULL indicator to disappear.

There’s no clear way round this, except that QuLineEditInteger and QuLineEditDouble do a better job.

17.2.3. QuPickerInline is visually a bit suboptimal ¶

The width requirements of QuPickerInline are a bit much, but then it’s also a bit duff visually compared to QuPickerPopup.

17.2.4. Qt: ScrollMessageBox scrolling under Android ¶

Under Android, ScrollMessageBox scrolls with multi-finger gestures but not with single-finger swipes, even though the single-finger gestures work fine elsewhere. This also varies with device, e.g. Asus Transformer Prime TF201 requires a two-finger swipe in ScrollMessageBox, whereas Samsung Galaxy S5 (?) provides a one-finger swipe. See my thoughts in uifunc::applyScrollGestures(). See also https://forum.qt.io/topic/62385/one-finger-swipe-gestures and https://bugreports.qt.io/browse/QTBUG-40461.

17.2.5. Qt: cursor positioning bug under Android ¶

Sometimes, copy/paste selection cursors appear on screen far removed from the text they relate to. This is a Qt bug; see https://bugreports.qt.io/browse/QTBUG-58503. Related Qt bugs include QTBUG-34867, QTBUG-58700.

Also potentially related to this: when LogBox or LogMessageBox are used with word_wrap = true on Android, the touch-to-scroll goes wrong. These classes use a QPlainTextEdit.

17.2.6. Qt: expand/collapse arrows in tree views are too small on high-DPI screens ¶

The arrow markers for the diagnostic trees don’t scale with DPI. See discussion in diagnosticcodeselector.cpp; the problem is that it’s not obvious how to set them programmatically. In fact, this is very hard indeed; see also my attempts in TreeViewProxyStyle and TreeViewControlDelegate, neither of which can make the changes where they’re needed. Reported as a bug: https://bugreports.qt.io/browse/QTBUG-62323.

17.2.7. Potential Qt performance bug; not recently verified; may have gone ¶

Sometimes there is a delay after clicking on a QuBoolean with an image, like the picture-naming in the ACE-III. The delay occurs whether you click the boolean indicator (with its “you are touching me” shading) or the image. It seems to occur only if the main window is not maximized. The delay is in calling AspectRatioPixmap::mousePressEvent, for example. Using #define DEBUG_CLICK_TIMING shows that the delay is not because the widget’s overridden sizeHint (etc.) code is being called. I’m not sure that this is a problem in my code. Not retested recently; other things have also improved performance (e.g. threaded database writes).

17.2.8. VerticalScrollArea layout ¶

VerticalScrollArea is nearly perfect. I’m unclear if any residual minor error relates to VerticalScrollArea itself, or to misreporting of ideal height by e.g. GridLayoutHfw. (Example: PDSS [with no task strings]?) (Note: it’s sometimes worth trying to un-maximize then maximize the window; the error can sometimes go away.)

Update 2017-07-09: I think this is fixed now.

17.3. Known server problems relating directly to CamCOPS ¶

17.4. Known server problems relating to the surrounding web server framework ¶

17.4.1. “Proxy error” or “Website unavailable” whilst downloading big files through Apache ¶

If you perform a very slow operation, creating a very large file to download, the time it takes CamCOPS to respond might exceed the timeout set by Apache. The Apache logs might show an error like “Internal error: proxy: error reading status line from remote server”.

The first thing to check is the gunicorn configuration: to your camcops serve_gunicorn command, try setting the server’s GUNICORN_TIMEOUT_S parameter to e.g. 300 (an increase from the default of 30 s).

This might just change the Apache error to “The timeout specified has expired: proxy: error reading…”, in which case you should also edit the Apache configuration file to add e.g. ProxyTimeout 300.

Then restart CamCOPS and Apache.

17.5. Known server problems relating to other third-party software ¶

17.5.1. Warnings during “camcops merge_db” relating to the “mysqldb” driver and UTF-8 ¶

If, during a camcops merge_db command using the mysqldb driver (a database URL like mysql+mysqldb://…), you get errors like this:

2017-08-25 22:27:23.234 cardinal_pythonlib.sqlalchemy.merge_db:INFO: Processing table 'blobs' via ORM class <class 'camcops_server.cc_modules.cc_blob.Blob'>
/home/rudolf/dev/venvs/camcops/lib/python3.5/site-packages/sqlalchemy/engine/default.py:504: Warning: (1300, "Invalid utf8 character string: '89504E'")
    cursor.execute(statement, parameters)
/home/rudolf/dev/venvs/camcops/lib/python3.5/site-packages/sqlalchemy/engine/default.py:504: Warning: (1300, "Invalid utf8 character string: 'FFD8FF'")
    cursor.execute(statement, parameters)

… or like this, with the charset set to ‘utf8mb4’ for the database and SQLAlchemy URL:

2017-08-25 22:38:36.628 cardinal_pythonlib.sqlalchemy.merge_db:INFO: Processing table 'blobs' via ORM class <class 'camcops_server.cc_modules.cc_blob.Blob'>
/home/rudolf/dev/venvs/camcops/lib/python3.5/site-packages/sqlalchemy/engine/default.py:504: Warning: (1300, "Invalid utf8mb4 character string: '89504E'")
    cursor.execute(statement, parameters)
/home/rudolf/dev/venvs/camcops/lib/python3.5/site-packages/sqlalchemy/engine/default.py:504: Warning: (1300, "Invalid utf8mb4 character string: 'FFD8FF'")
    cursor.execute(statement, parameters)

… then this is likely a mysqldb bug. Potentially related problems:

The problem goes away using “pymysql” rather than “mysqldb”, so try this:

DB_URL = mysql+pymysql://username:password@127.0.0.1:3306/database?charset=utf8mb4

Version

Name

API level

Release date

CamCOPS status

4.1.x

Jelly Bean

16

2012-07-09

Lowest API theoretically supported by Qt 4, though Qt 5.11 doesn’t compile. Too old for CamCOPS (based on 4.4.x failure).

4.2.x

Jelly Bean

17

2012-11-13

Too old for CamCOPS (based on 4.4.x failure).

4.3.x

Jelly Bean

18

2013-07-24

Too old for CamCOPS (based on 4.4.x failure).

4.4.x

KitKat

19

2013-10-31

Fails as of 2018-07-16 (client v2.2.4).

5.0

Lollipop

21

2014-11-12

Untested.

5.1

Lollipop

22

2015-03-09

Untested.

6.0

Marshmallow

23

2015-10-05

Supported; tested 2018-07-16 (client v2.2.4).

7.0

Nougat

24

2016-08-22

Untested; should be fine.

7.1

Nougat

25

2016-10-04

Untested; should be fine.

8.0.0

Oreo

26

2017-08-21

Untested; should be fine.

8.1.0

Oreo

27

2017-12-05

Untested; should be fine.

On Android 4.4.2: Settings ‣ About tablet ‣ Software update ‣ System.
On a Sony Xperia Z2 tablet (model SGP511) that’s not offering an upgrade (e.g. attempting to upgrade from Android 4.4.2 in 2018-07):
1. Check storage space is OK 1.
2. If that doesn’t help, run Sony’s “Xperia Companion” software 2 from a Windows/Mac PC (or virtual machine 3), and run a “Software update” from there. It may be easier from a physical machine.

Footnotes

1: https://support.sonymobile.com/global-en/xperiaz2tablet/kb/80193074525e2538015404fa9ee6007fea/
2: https://support.sonymobile.com/za/xperia-companion/
3: Check that your user is in the vboxusers group to access host USB devices from a VirtualBox guest; see https://unix.stackexchange.com/questions/129305/how-can-i-enable-access-to-usb-devices-within-virtualbox-guests
4: https://doc.qt.io/qt-6.5/android-support.html

17. FAQ and known problems¶

17.1. Known client problems relating directly to CamCOPS ¶

17.2. Known client problems relating to third-party software ¶

17.2.1. Qt: QLabel height ¶

17.2.2. Spinboxes are relatively poor for entering numbers ¶

17.2.3. QuPickerInline is visually a bit suboptimal ¶

17.2.4. Qt: ScrollMessageBox scrolling under Android ¶

17.2.5. Qt: cursor positioning bug under Android ¶

17.2.6. Qt: expand/collapse arrows in tree views are too small on high-DPI screens ¶

17.2.7. Potential Qt performance bug; not recently verified; may have gone ¶

17.2.8. VerticalScrollArea layout ¶

17.3. Known server problems relating directly to CamCOPS ¶

17.4. Known server problems relating to the surrounding web server framework ¶

17.4.1. “Proxy error” or “Website unavailable” whilst downloading big files through Apache ¶

17.5. Known server problems relating to other third-party software ¶

17.5.1. Warnings during “camcops merge_db” relating to the “mysqldb” driver and UTF-8 ¶

17.6. Hardware FAQs: Sony Xperia Z2 tablet ¶

17.6.1. The charger doesn’t work ¶

17.6.2. Where’s the USB port?¶

17.7. Android FAQs ¶

17.7.1. What API levels are offered by different Android versions?¶

17.7.2. I can’t find the beta version of CamCOPS on Google Play ¶

17.7.3. How to remove a Google account from an Android device ¶

17.7.4. How to upgrade Android ¶

Table of Contents

Previous topic

Next topic

This Page

Version	Name	API level	Release date	CamCOPS status
4.1.x	Jelly Bean	16	2012-07-09	Lowest API theoretically supported by Qt 4, though Qt 5.11 doesn’t compile. Too old for CamCOPS (based on 4.4.x failure).
4.2.x	Jelly Bean	17	2012-11-13	Too old for CamCOPS (based on 4.4.x failure).
4.3.x	Jelly Bean	18	2013-07-24	Too old for CamCOPS (based on 4.4.x failure).
4.4.x	KitKat	19	2013-10-31	Fails as of 2018-07-16 (client v2.2.4).
5.0	Lollipop	21	2014-11-12	Untested.
5.1	Lollipop	22	2015-03-09	Untested.
6.0	Marshmallow	23	2015-10-05	Supported; tested 2018-07-16 (client v2.2.4).
7.0	Nougat	24	2016-08-22	Untested; should be fine.
7.1	Nougat	25	2016-10-04	Untested; should be fine.
8.0.0	Oreo	26	2017-08-21	Untested; should be fine.
8.1.0	Oreo	27	2017-12-05	Untested; should be fine.