v0.1.0

Added

• A read-only code view for Gio. View shows one document: monospace rows
  highlighted by chroma from the file name, a line-number gutter (or labels of
  your own), wrapping or sideways scrolling, and one image per visible row, so
  a full screen of code costs a handful of quads. Highlighting runs off the UI
  goroutine; SetContent shows a new document from its top and
  UpdateContent swaps in a new version of it without moving the scroll.
• Side by side. Split shows two documents row for row, scrolling down
  together and sideways each on its own, and it can wrap: a pair of lines takes
  the taller side's rows.
• Decorations and widgets. LineDecoration tints a line and its gutter
  cell, puts a strip down the gutter, rules a separator, hatches a filler row,
  tints spans of characters, and lights a whole hover group under the pointer.
  LineWidget puts a Gio widget on a line (after its text or at the right
  edge, optionally only while hovered); BlockWidget opens space between lines
  for any widget, such as a review thread.
• Selection. Drag, double and triple click, Shift+click, Ctrl+A and Ctrl+C,
  with tabs copied as written. From code: Select, SelectLines,
  Selection, SelectedText and SelectedLines, plus ScrollToLine with
  AlignNearest, AlignCenter and AlignTop, LineCount and LineText.
  A selection dragged past the view's edge scrolls it, faster the farther the
  pointer is beyond (sideways too when unwrapped), and keeps going on frames
  where the pointer does not move.
• A diff view. DiffView diffs two documents itself (SetDocs, line by
  line with Myers' algorithm) or shows a file of a git diff patch
  (ParsePatch, SetPatch). Unified, with an old | new line-number gutter,
  or side by side, with deletions and additions paired and fillers hatched.
  Unchanged runs collapse behind an expander (Collapse, or the gaps of the
  patch, filled through DiffOptions.Expand and FillGap, in parts if need
  be). Each chunk can be reverted through DiffOptions.Revert; Chunks,
  SelectedRange and SelectedChanges read the diff in file line numbers,
  and SetBlocks anchors widgets to file lines. HighlightChanges tints the
  words that changed within a line. The expander and revert affordances are
  drawn by the library and can be replaced.
• Search. View.SetSearch takes a SearchQuery (literal or regexp, case
  sensitivity, whole word) and highlights every match, beneath the text, in
  Theme.SearchMatch; the selected match is the current one, in
  Theme.SearchCurrent. Matches lists them and FindNext and FindPrevious
  select the one after or before the selection, wrapping, and scroll it into
  view, sideways too when lines do not wrap. A match never spans lines, and a
  bad regexp is the only error. DiffView.SetSearch, Matches, FindNext
  and FindPrevious do the same across its unified view and both sides of the
  split.
• Themes. DarkTheme and LightTheme, with the diff colors in
  Theme.Diff. A theme change shows on the next frame.
• Fonts without fontconfig. New resolves a family through fontconfig and
  fails with ErrNoFontconfig where it is missing; NewFromFonts (and
  NewDiffViewFromFonts) take the font files' contents instead. A character no
  font covers is drawn as a box.
• Wide characters take two cells. CJK, fullwidth forms and emoji are laid
  out on the monospace grid as a terminal lays them out, so the columns after
  them line up; a click on either half lands before or after the character,
  wrapping never splits one, and a gutter label's width counts them too.
  Pos.Col and Span still count runes.