Make Plot Legend Wider

Question

I have a pretty plot with a legend

But I want to make the legend the same width as the graph, i.e. causing all the text to be on one line.

Code to make the legend here:

legend = SwatchLegend[{Blue, Orange, Red, Darker[LightGreen, 0.4], 
    Black}, {"Photoemission Signal", "Linear Fit", "Fit Begin", 
    "Fit End", "Baseline" }, LabelStyle -> {FontFamily -> "cmr10"}, 
   LegendMarkers -> {Graphics[{EdgeForm[Black], Opacity[0.6], 
       Disk[]}], Graphics[Line[{{0, 0}, {1, 1}}]], 
     Graphics[Line[{{0, 0}, {0, 1}}]], 
     Graphics[Line[{{0, 0}, {0, 1}}]], 
     Graphics[Line[{{0, 0}, {1, 0}}]]}];

Changing the legend margins does not have the desired effects.

Answer 1

You can set LegendLayout:

legends = 
  SwatchLegend[{Blue, Orange, Red, Darker[LightGreen, 0.4], 
    Black}, {"Photoemission Signal", "Linear Fit", "Fit Begin", 
    "Fit End", "Baseline"}, LabelStyle -> {FontFamily -> "cmr10"}, 
   LegendMarkers -> {Graphics[{EdgeForm[Black], Opacity[0.6], 
       Disk[]}], Graphics[Line[{{0, 0}, {1, 1}}]], 
     Graphics[Line[{{0, 0}, {0, 1}}]], 
     Graphics[Line[{{0, 0}, {0, 1}}]], 
     Graphics[Line[{{0, 0}, {1, 0}}]]}, 
   LegendLayout -> (Row[Flatten[#], Spacer[2]] &)];

ListPlot[RandomInteger[10, 20], Frame -> True, 
 PlotLegends -> Placed[legends, Below], ImageSize -> 500]