Fix #270337: True dotted lines #6349

elerouxx · 2020-07-19T06:29:02Z

Resolves: https://musescore.org/en/node/270337

Fixes true dotted lines for text lines (with round dots)
Also fixes:

dash-dotted, dash-dot-dotted lines (show real dots)
dotted, dashed and wide dashed slurs and ties.

Before

After

The problem is: the generic Qt DotLine style only shows dots properly when using FlatCaps, and FlatCaps are not always appropriate. Any square or round cap turns dots into short dashes.

This solution replaces default Qt lineStyles dash patterns with MuseScore's own patterns, so it allows real dots, round dots, and also allows the creation of MuseScore's specific dash styles instead of sticking to the generic Qt design.

Other changes:

The minimum dash length set for custom patterns lowered from 1.0 to 0.01 to allow very short dashes (= dots).
The step increments of the spin boxes for custom dash was lowered from 1.0 to 0.25 to improve control.

Code review and feedback will be highly appreciated.

I signed CLA
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I made sure the code compiles on my machine
I made sure there are no unnecessary changes in the code
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[NA] I created the test (mtest, vtest, script test) to verify the changes I made

Jojo-Schmitz · 2020-07-19T08:16:30Z

I guess you mean text lines, not staff lines?

Jojo-Schmitz · 2020-07-19T08:48:00Z

mscore/inspector/inspector_line.ui

@@ -267,7 +267,7 @@
         <double>20.000000000000000</double>
        </property>
        <property name="singleStep">
-         <double>1.000000000000000</double>
+         <double>0.250000000000000</double>


I guess here old gap width steps are still appropriate?

I think you are right. I'll update that.
(I am going to fix dotted slurs and search what else is missing. I think they should be fixed in this PR too).

Yes, agreed, slurs (and ties) should use the same

ecstrema · 2020-07-20T01:23:44Z

Shouldn't this distance be calculated from the right?

Jojo-Schmitz · 2020-07-20T07:28:05Z

libmscore/slur.cpp

@@ -43,7 +43,9 @@ void SlurSegment::draw(QPainter* painter) const
            case 1:
                  painter->setBrush(Qt::NoBrush);
                  pen.setWidthF(score()->styleP(Sid::SlurDottedWidth) * mag);
-                  pen.setStyle(Qt::DotLine);
+                  pen.setStyle(Qt::CustomDashLine);
+                  pen.setDashPattern(QVector<qreal> {0.01, 2.5});


Shouldn't that 'magic' 2.5 rather be expressed in pen width units, pen.widthF() (which in turn relate to Sid::SlurDottedWidth and mag)

See https://doc.qt.io/qt-5/qpen.html#setDashPattern
Seems the pen.setStyle(Qt::CustomDashLine) is implicit, when using pen.setDashPattern()

Your current dotted slur:

When using pen.widthF():

Looks the same, but eliminates that magic number

But then again, making the dots thicker also increases their distance, and by quite a lot. In either case...
Maybe 1.5 or 2 might be a better value?
1.5:

2.0:

I think the dashed and the wide dashed (and customer dashed) lines all should use a Qt::FlatCap BTW, to not make themselves longer by their width.

I will take a look at that pen.widthF() for comparison. About the space between dots, I went from 2.0 to 3.0 and ended up with 2.5 but It's a matter of deciding the design of this dotted "preset".
User can still set a custom dash pattern that looks like dotted and choose a gap - except, no rounded dots.
Ideally, Custom Dash might include an option to choose Round/Square/Flat caps (or maybe the whole thing so user can add rounded cap to solid lines) but either would require adding a property to be saved, and maybe options for Style... so I guess it might be an improvement for later.

Agree with flatCaps so dots in dash-dotted lines really look like dots. Trying this next.

EDIT: the values in the dash patterns (qreal) already refer to pen width, where 1.0 = 1 pen width, so dashes and gaps will scale with the pen (and with mag).

I think we should be using FlatCap on all (dashed) lines and RoundCap on dots, but never SquareCap as it makes the lines longer than expexted

1.5 indeed looks too dense, but 2.0 seems OK to me

Jojo-Schmitz · 2020-07-20T07:28:26Z

libmscore/tie.cpp

@@ -44,7 +44,9 @@ void TieSegment::draw(QPainter* painter) const
            case 1:
                  painter->setBrush(Qt::NoBrush);
                  pen.setWidthF(score()->styleP(Sid::SlurDottedWidth) * mag);
-                  pen.setStyle(Qt::DotLine);
+                  pen.setStyle(Qt::CustomDashLine);
+                  pen.setDashPattern(QVector<qreal> {0.01, 2.5});


elerouxx

The problem with flat caps is that they trend to leave gaps in textline corners (hooks are separated lines so no use for joints here).
IMO, Qt lineStyles (dotted, dash dotted etc) are just internal pattern "presets" that are not well designed for caps other than flat. It would be cleaner and easier if MS just designed its own patterns for dotted/dashed dot/etc and defined them all together somewhere else, then always reference these custom internal patterns instead of using the generic Qt ones. (It would also be prettier than putting curly brackets with "magic" numbers all over the source files).

libmscore/slur.cpp

libmscore/tie.cpp

Jojo-Schmitz · 2020-07-21T07:07:14Z

libmscore/tie.cpp

                  break;
            case 2:
                  painter->setBrush(Qt::NoBrush);
                  pen.setWidthF(score()->styleP(Sid::SlurDottedWidth) * mag);
-                  pen.setStyle(Qt::DashLine);
+                  pen.setStyle(Qt::CustomDashLine);
+                  pen.setDashPattern(dashed);
                  break;
            case 3:
                  painter->setBrush(Qt::NoBrush);
                  pen.setWidthF(score()->styleP(Sid::SlurDottedWidth) * mag);
                  pen.setStyle(Qt::CustomDashLine);


Jojo-Schmitz · 2020-07-21T07:09:54Z

libmscore/slur.cpp

@@ -33,6 +33,10 @@ void SlurSegment::draw(QPainter* painter) const
      QPen pen(curColor());
      qreal mag = staff() ? staff()->mag(slur()->tick()) : 1.0;

+      QVector<qreal> dotted     = { 0.01, 1.99 }; // tighter than Qt Dotline equivalent { 0.01, 2.99 }
+      QVector<qreal> dashed     = { 3.00, 3.00 };


I wonder whether here too we'd want to increase the gaps by the width to compensate for the SquareCap.
Just like you apparently do for the wide dashed line below

The default Qt::DashLine is { 4.0, 2.0 }. To compensate for caps I changed it to { 3.0, 3.0 } already.
(I had first declared as { 3.01, 2.99 } but that felt a little too geeky since there are no dots involved. If it makes things clear I can do that).

Jojo-Schmitz · 2020-07-21T07:10:33Z

libmscore/textlinebase.cpp

+
+      //Replace generic Qt dash patterns with improved equivalents to show true dots
+      QVector<qreal> dotted        = { 0.01, 1.99 }; // tighter than Qt Dotline equivalent { 0.01, 2.99 }
+      QVector<qreal> dashed        = { 3.0, 3.0 };


see above, compensating for SquareCap?

same. I better add a comment there // Qt DashLine is { 4.0, 2.0 }

Jojo-Schmitz · 2020-07-21T07:11:05Z

libmscore/textlinebase.cpp

+      QVector<qreal> dashed        = { 3.0, 3.0 };
+      QVector<qreal> dashDotted    = { 3.01, 2.99, 0.01, 2.99 };
+      QVector<qreal> dashDotDotted = { 3.01, 2.99, 0.01, 2.99, 0.01, 2.99 };
+      QVector<qreal> customDashes  = { tl->dashLineLen(), tl->dashGapLen() };


Here too, add one line width?

Did better, { 3.0, 3.0 } is a dash with its gap (compensated already from {4,2}) and {0.01, 2.99} is a dot with its gap.

{4.0, 2.0} is DashLine default. Compensated to {3.0, 3.0} for caps.
{1.0, 2.0} is DotLine default. Compensated for caps would be {0.0, 3.0} but zero doesn't work so I give 1 cent back from the gap to the dash - it would be { 0.1, 2.99} but our version of DotLine has smaller gaps { 0.01, 1.99}
The dashDotted and dashDotDotted use nominally 3.0 on every gaps. The 2.99 compensation for 0.01 dashes (ie. dots) is to keep the most consistent output along the line between dash/dashdot etc. so the gaps look aligned between styles when side to side.
Not that someone would tightly compare lines, but it looks neat if the composer wants to add instructions about lines somewhere.

We can't have real dots for the dashDotted and dashDotDotted lines, can we?

Only if we assume RoundCaps for the dashes on these two, leaving SquareCaps only in Dashed and continuous.
Ideally, a new PR could add Cap Style as an option in inspector / styles / etc...
A new property to save to files and deal with and more one decision for the engraver. Would that be overkill?
EDIT: I'd prefer not to offer both flatcaps and squarecaps to final users if that was an option. Behavior is already confusing for us devs.

In any case, mixing straight dashes with round dots in the same line is not possible with Qt styles. Only if we create a method to calculate dashes and dots separately and then draws two overlapping lines. Just for this...

Actually I had a simple idea to draw a line with mixed round dots and sharp dashes. Would it be worth it?
I'll give it a try.

libmscore/tie.cpp

Jojo-Schmitz · 2020-07-21T07:13:02Z

These vtest fails are expected

ecstrema · 2020-07-23T00:53:17Z

Shouldn't this distance be calculated from the right?

I'll clarify a bit:

When the vertical line intersects with the horizontal line, it looks like the corner dots are really close one to each other. Closer than the other dots at least. A solution for this would be to draw the line from the right, instead of from the left, to avoid that thin space.

ecstrema · 2020-07-23T01:12:26Z

Shouldn't this distance be calculated from the right?

I'll clarify a bit:

When the vertical line intersects with the horizontal line, it looks like the corner dots are really close one to each other. Closer than the other dots at least. A solution for this would be to draw the line from the right, instead of from the left, to avoid that thin space.

might be something for another PR though...

elerouxx · 2020-07-23T02:38:29Z

Shouldn't this distance be calculated from the right?

I'll clarify a bit:
When the vertical line intersects with the horizontal line, it looks like the corner dots are really close one to each other. Closer than the other dots at least. A solution for this would be to draw the line from the right, instead of from the left, to avoid that thin space.

might be something for another PR though...

It would be a good idea to draw the hook from the bottom and the line from the right but inverting that direction is not trivial. Also, no perfect solution because if there is a left hook it will have the same problem. Although the right hook is more "important" (more use cases). Maybe another PR indeed.

Fix #270337: True dotted lines

Jojo-Schmitz reviewed Jul 19, 2020

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Jojo-Schmitz approved these changes Jul 19, 2020

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elerouxx force-pushed the real-dotted-lines-3.x branch from b2ce755 to 1b43ec5 Compare July 19, 2020 18:31

Jojo-Schmitz reviewed Jul 20, 2020

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elerouxx commented Jul 21, 2020

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elerouxx force-pushed the real-dotted-lines-3.x branch 2 times, most recently from 9f05247 to 06d4d4f Compare July 21, 2020 05:04