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@ -1,4 +1,65 @@ |
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// Package view implements rendering a graph to a terminal.
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//
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// Steps for rendering
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//
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// - Preprocessing: Disjoin Graph into multiple Graphs, and decide how to
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// arrange them (maybe sort by number of vertices or number of edges (or the
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// sum of both) or something).
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//
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// - Convert Graph into internal representation.
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// - Still uses gg.Graph, but vertices and edge values are wrapped in types
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// internal to this package, and on which further mapping will be done.
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// - Positions unknown at this point.
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// - Junctions are converted to value vertices with set edge order.
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// - Edges contain both their body and their tail/head rune.
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//
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// - Find eligible "root" vertex, probably by one which has the fewest input
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// edges.
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//
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// - Find cycles and reverse edges as needed.
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// - The to/from vertices are reversed, as are the head/tail runes, so the
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// direction will appear consistent with the original graph
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// - TODO this might not be necessary? Or at least may need to be modified.
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// In the paper this is done, but that algorithm allows for edges upward
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// from their tail, whereas this one doesn't. It might only be necessary
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// for the MST stuff, in which case this might only need to take place
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// within Positioning-Part1.
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//
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// - Replace edge bodies with a vertex with a single input/output edge.
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//
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// - Position all vertices
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// - `coord` field on vertices used as row/column coordinates.
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// - Positioning will be done with down being the primary direction and
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// right being the secondary direction.
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// - Part 1) find vertical positions for all vertices (aka assign rows)
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// - This step uses some fancy MST stuff as outlined by (TODO refer to
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// paper here).
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// - Part 2) find horizontal positions within rows (aka assign columns)
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// - Part of this will include creating ephemeral vertices where an
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// edge spans a row without having a vertex on it. These will be
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// removed as the final part of this step.
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// - The jist of this step is to find vertex ordering which reduces
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// number of edge crossings between adjacent rows.
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// - Some extra care is taken for cases where an edge's from vertex is
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// not a lower row than its to vertex.
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// - This is an unavoidable case, as at the least a vertex may
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// connect to itself.
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// - These edges will have their `switchback` field set to true.
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// - For the purposes of calculating edge crossings these edges
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// should be ignored. During the absolute positioning and drawing
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// steps they will be accounted for and dealt with.
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// - Part 3) row/column positions into terminal positions, which are
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// stored on the vertices in the `pos` field. Primary/secondary
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// direction are taken into account here.
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//
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// - Post-processing: any additional absolute positioning and other formatting
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// given by the user for the Graph should be done here
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//
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// - Draw vertices and their edges to buffer
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// - At this point drawing vertices is easy. Edges is more complicated but
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// the start/end positions of each edge should already be known, so while
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// drawing may be complex it's not difficult.
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//
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package view |
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import ( |
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@ -14,7 +75,7 @@ import ( |
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// generates renderable terminal output for it.
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type View struct { |
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g *gg.Graph |
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start gg.Value |
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start gg.Value // TODO shouldn't need this
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primFlowDir, secFlowDir geo.XY |
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} |
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