Review Request 127102: Use fixed width for digital clock applet

Daniel Faust hessijames at mailbox.org
Fri Feb 19 14:30:53 GMT 2016



> On Feb. 18, 2016, 1:05 vorm., David Edmundson wrote:
> > applets/digital-clock/package/contents/ui/DigitalClock.qml, line 555
> > <https://git.reviewboard.kde.org/r/127102/diff/1/?file=444552#file444552line555>
> >
> >     rather than looping, can we use FontMetric's maximumCharacterWidth
> >     
> >      * numChars.
> >     
> >     Then we could kill sizeHelper competely (FontMetric's didn't exist when this was written)
> 
> Marco Martin wrote:
>     hoping maximumCharacterWidth is reliable for all fonts, this loop really needs to go
> 
> Daniel Faust wrote:
>     As far as I understand maximumCharacterWidth returns the width of the widest character of the font - which can be ridiculously wide given that the font supports some wild unicode characters.
>     I did a quick test and maximumCharacterWidth returned about twice the width actually needed.
> 
> Martin Klapetek wrote:
>     You still don't need this whole loop though, just find the biggest in 0-9 and use that for all the numbers (except year).
> 
> Daniel Faust wrote:
>     Since I don't know the time format in advance, I have to construct different times and process them with Qt.formatTime.
>     That means, I have to test 0-9 for hours/minutes/seconds, 0-2 for tens of hours and 0-5 for tens of minutes/seconds. Otherwise the constructed times will be invalid.
>     This can be done with three loops and it would bring down the amount of advanceWidth and formatTime calls from 24+60=84 to 3+6+10=19.
> 
> Martin Klapetek wrote:
>     You don't actually need them as a time, you just need them as a placeholder. At which point it doesn't matter if it's a valid time or not. You can even format 12:12 with Qt.formatTime and then replace the numbers with your placeholder number.
>     
>     In other words, the time format /is/ known in advance.
> 
> Daniel Faust wrote:
>     I'm not sure if I understand you, I just tried it with a single loop from 0-9 to construct the time strings:
>     
>     for (var i=0; i<=9; i++) {
>       var str = Qt.formatTime(new Date(2000, 0, 1, i*10 + i, i*10 + i, i*10 + i), main.timeFormat);
>       console.log("hour: " + (i*10 + i) + ", minute: " + (i*10 + i) + " -> " + str);
>     }
>     
>     qml: hour: 0, minute: 0 -> 00:00
>     qml: hour: 11, minute: 11 -> 11:11
>     qml: hour: 22, minute: 22 -> 22:22
>     qml: hour: 33, minute: 33 -> 09:33
>     qml: hour: 44, minute: 44 -> 20:44
>     qml: hour: 55, minute: 55 -> 07:55
>     qml: hour: 66, minute: 66 -> 19:07
>     qml: hour: 77, minute: 77 -> 06:18
>     qml: hour: 88, minute: 88 -> 17:29
>     qml: hour: 99, minute: 99 -> 04:40
> 
> Thomas L├╝bking wrote:
>     Forget about the timeFormat - you iterate from 0-9 and figure the widest glyphs in [0,1], [0,5] and [0,9] - let's reasonably say "0,3 and 7".
>     Then you check the width for 00:37
>     
>     (If you also need the date, you also need to check for the widest glyph in [0,3])
> 
> Daniel Faust wrote:
>     That would work if it wasn't for 12 hour time formats.
>     For 24 hour formats you actually need [0,2], [0,3] and [0,9] for the hour and [0,5] and [0,9] for the minutes/seconds.
>     For 12 hour formats AM you need [0,1], [0,2] and [0,9] for the hour and [0,5] and [0,9] for the minutes/seconds.
>     For 12 hour formats PM you need [1,2], [3,9] and [0,3] for the hour and [0,5] and [0,9] for the minutes/seconds.
>     On top of that you need to account for format changes like hour=0, minute=0 -> "12:00 AM".
>     
>     The code for this logic would be hard to maintain.

Ok, what about this?
Find the widest glyph between 0 and 9.
Use a regex to replace [hmsz] from the format string with the widest number. (This will produce strings like "44:44")
Use Qt.formatTime once with an AM time and once with a PM time and choose the widest of the produced strings.
This code is fairly short and overestimates the total width only slightly.


- Daniel


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On Feb. 17, 2016, 5:23 nachm., Daniel Faust wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/127102/
> -----------------------------------------------------------
> 
> (Updated Feb. 17, 2016, 5:23 nachm.)
> 
> 
> Review request for kde-workspace and Plasma.
> 
> 
> Bugs: 347724
>     https://bugs.kde.org/show_bug.cgi?id=347724
> 
> 
> Repository: plasma-workspace
> 
> 
> Description
> -------
> 
> Currently the width of the date label is not fixed but changes depending on the text. This causes the entire applet to change its width (if the time is the widest displayed item). This in turn can cause all other applets in the same panel to move whenever the displayed time changes.
> 
> This patch uses FontMetrics to iterate over all possible time strings (with different width) and chooses the widest of them as reference for the fixed width of the time label.
> 
> This way the width of the applet stays the same (unless the date is displayed and changes). The text remains centered though, which means that it can still move within the applet when the time changes.
> 
> 
> Diffs
> -----
> 
>   applets/digital-clock/package/contents/ui/DigitalClock.qml 95bb071 
> 
> Diff: https://git.reviewboard.kde.org/r/127102/diff/
> 
> 
> Testing
> -------
> 
> Works with horizontal and vertical panel.
> Also displaying different combinations of "seconds", "date" and "timezone" works.
> 
> 
> Thanks,
> 
> Daniel Faust
> 
>

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