Purpose: Consider the logic of the "fix layout" operation

Audience: Programmers and interested scientists

The fix layout is intended to correct layout mistakes and provide an easy way to accomplish attractive looking layouts. For example, one can grab on to an axis edge (with shift-click) and drag it down so that it overlaps part of another plot to make it bigger, then run the "fix layout" command to fix the overlap. Also, if ephemeris is added to the top plot of a two-plot layout, then the loaded ticks will overwrite the bottom plot. Fix layout will also fix this.

Another important aspect of fix layout is that it is idempotent, meaning once applied if applied again it should have no effect. We've added a number of options to fix layout now, and there's a remaining bug where a plot with a title grows, breaking the idempotent rule.

So this page is to consider what does the operator mean to do? What spacing should be preserved? A 1-em tall events bar should remain 1-em high, for example. It's y-axis is not used, so maybe it should be turned off.

These are the aspects:

• unused whitespace is recovered.
• the em-height of a plot is preserved.
• the relative sizes of the plots is preserved.
• the margins are used to make the row layout easier to interpret.
• hidden plots which bind together other plots are preserved. A block of X,Y,and Z plots might be linked by a hidden plot.

Define relativeSize which is the size relative to other plots. The relative size is based on the percentage part of the layout, so a plot which is 50%,100% is twice the relativeSize of a plot which is 75%,100%; but this is also true for 50%,100%-1em 75%,100%-1em. This is to preserve the 0%,0%+1em of an events bar.

Define additionalEmSize which is the additional ems added and subtracted to make room for labels. This will be preserved through the operation.

• identify Rows which are actually used.
• implement hideTitles, moveLegendsOutsideNE, hideTimeAxes.
• define totalHeightPixels as the sum of each row (except the margin).
• define relativePlotHeight as the per-row height normalized by totalHeightPixels.
• define MaxUp as the per-row maximum additional pixels needed for the titles attached to the row.
• define MaxDn as the per-row maximum additional pixels needed for the x-axes attached to the row.
• calculate the space available to the plots.
• define newPlotHeight as the new height of each row in pixels.