Different alignment options for map titles (-B+t+s)

[KristofKoch]

See this forum thread for context.

Currently the plot titles are always centered. Other alignments like top right as seen in the following mockup are desirable.

Currently this has to be done with manually placed text. This is difficult when the plot width is not known (e.g. when using a map scale) or the absolute position of the map border on the plot is unknown (e.g. when using annotations outside the map borders). @PaulWessel suggested a new default setting MAP_TITLE_JUST which would allow for maximum flexibility as imagined below:

A --MAP_TITLE_JUST=TR would align the title to the upper-right position as seen in the first figure above.

Minimum code for a simple plot to play with:

gmt begin title_alignment
  gmt coast -RUS.HI+e1 -W0.7p,black -B+f -Bg --MAP_FRAME_TYPE=plain \
    -B+t"HAWAIIAN ISLANDS"+s"Pacific Ocean"
gmt end show

[seisman]

Perhaps MAP_TITLE_JUSTIFICATION is a better name although it's much longer.

[PaulWessel]

While @joa-quim suggestion is not bad it would introduce yet another way of doing things that we have a long-standing way (justification) for doing. Having to add special parsing to decode -: and :- in text string could be lots of work. However, I am not ruling it out but suggest we instead first do the MAP_TITLE_JUSTIFICATION (yes, better name, I was hesitating due to length but I think this might be used sparingly anyway with the default TC). Since the plotting of the title (and subtitle) is isolated in the code somewhere it should just be one or possibly two places to deal with the justification setting.

[PaulWessel]

Looking at gmt_map_title it is not simple to implement this feature since it is dealing with possibly multi-line titles and subtitles etc and doing "line-feed" etc. I have to study how things are done there. Also, the base location point is sometime set by the code before calling gmt_map_title and we just pass 0,0 to flag that. Those steps would change if justification no longer is TC. So not a quick fix I am afraid. Also, just 2 weeks until AGU and 4 talks to work on first.

[PaulWessel]

There are also some inconsistencies in the proposal. For instance, justification codes LT and TL mean the same in GMT but here they are used to distinguish two separate cases. LC and RC are meant to be LM and RM so that is not an issues. But in the TL and TR cases you are using the codes to do two things: Specify a placement and specify a justification for the text. The regular interpretation of justification TL would simply center the text and subtitles on the TL point, not left-justify it. Same with TR. So this would change the meaning of the TR and TL codes as they are used everywhere else in GMT. Not sure what is a good solution here.

[KristofKoch]

Ok, this is something I haven’t thought about. You are right @PaulWessel it should not change/be different to the global behavior of the justification codes.

Maybe it needs two new options:

• MAP_TITLE_JUSTIFICATION
  (maybe now better worded as MAP_TITLE_POSITION) with the known two letter codes and

• MAP_TITLE_TEXT_ALIGN with L, C and R being the options.

The default behavior would be

—MAP_TITLE_JUSTIFICATION=TC
—MAP_TITLE_TEXT_ALIGN=C

The styling for the first figure in my initial post with the title positioned at the top right with text aligned right

—MAP_TITLE_JUSTIFICATION=TR
—MAP_TITLE_TEXT_ALIGN=R

Of course some combinations like LM L wouldn’t be very useful.

Thinking about it lots of old NACA (NASA predecessor) plots have their title inside the plot area in the upper right corner … maybe something worth pursuing as well?

Regarding AGU & your talks: no need to rush, has time until after AGU. Enjoy AGU!

[KristofKoch]

Any comments/ideas on this?

[PaulWessel]

Sorry, reoccupied. But I think we want to accommodate these features:

1. Ability to specify any of the 9 standard justification points, with default TC
2. Ability to override any default text justification as well [centered for TC is default]
3. Ability to place the title inside rather than outside the frame for the given code [outside]

That is three settings. But, is all this necessary? For instance, I often add a string for whatever reason inside the frame and that is simple with text's -F:

echo "My Title" | gmt text -R0/6/0/3 -Jx1i -B -F+cTR+f16p -Dj6p -png map

Certainly, if you consider the title and subtitle block as one item then a -B-related solution might be cleaner. So then we are back to adding new GMT Default settings:

• MAP_TITLE_POSITION: [LCR][BMT] with default TC
• MAP_TITLE_JUSTIFICATION: [LCR][BMT] with default BC (I think)
• MAP_TITLE_INSIDE: Y|N with default N (outside)

Hopefully you and the @GenericMappingTools/core can opine on this proposal.

[KristofKoch]

Hi @PaulWessel,

maybe you are right. The inside case is probably best solved with text -F+c -Dj. Maybe not be perfect ("I can place the title everywhere but inside!") but you get around problems like controlling the distance/spacing to the map frame in case of MAP_TITLE_INSIDE Y ("But I want my title to be exactly 37mm inside from the bottom right corner!"). This is already solved with text -Dj and the last thing -B needs is yet another parameter.

So only MAP_TITLE_POSITION and MAP_TITLE_JUSTIFICATION?