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Location: kallithea/kallithea/public/js/codemirror_loadmode.js

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Mads Kiilerich

branches: fix performance of branch selectors with many branches - only show the first 200 results

The way we use select2, it will cause browser performance problems when a
select list contains thousands of entries. The primary bottleneck is the DOM
creation, secondarily for the query to filter through the entries and decide
what to show. We thus primarily have to limit how many entries we put in the
drop-down, secondarily limit the iteration over data.

One tricky case is where the user specifies a short but full branch name (like
'trunk') but many other branches contains the same string (not necessarily at
the beginning, like 'for-trunk-next-week') which come before the perfect match
in the branch list. It is thus not a solution to just stop searching when a
fixed amount of matches have been found.

Instead, we limit the amount of ordinary query matches, but always show all
prefix matches. We thus always have to iterate through all entries, but we
start using the (presumably) cheaper prefix search when the limit has been
reached.

There is no filtering initially when there is no query term, so that case has
to be handled specially.

Upstream select2 is now at 4.x. Upgrading is not trivial, and getting this
fixed properly upstream is not a short term solution. Instead, we customize our
copy. The benefit from this patch is bigger than the overhead of "maintaining"
it locally.

(function() {
  var loading = {};
  function splitCallback(cont, n) {
    var countDown = n;
    return function() { if (--countDown == 0) cont(); };
  }
  function ensureDeps(mode, cont) {
    var deps = CodeMirror.modes[mode].dependencies;
    if (!deps) return cont();
    var missing = [];
    for (var i = 0; i < deps.length; ++i) {
      if (!CodeMirror.modes.hasOwnProperty(deps[i]))
        missing.push(deps[i]);
    }
    if (!missing.length) return cont();
    var split = splitCallback(cont, missing.length);
    for (var i = 0; i < missing.length; ++i)
      CodeMirror.requireMode(missing[i], split);
  }

  CodeMirror.requireMode = function(mode, cont) {
    if (typeof mode != "string") mode = mode.mode;
    if (CodeMirror.modes.hasOwnProperty(mode)) return ensureDeps(mode, cont);
    if (loading.hasOwnProperty(mode)) return loading[mode].push(cont);

    var script = document.createElement("script");
    script.src = CodeMirror.modeURL.replace(/%N/g, mode);
    var others = document.getElementsByTagName("script")[0];
    others.parentNode.insertBefore(script, others);
    var list = loading[mode] = [cont];
    var count = 0, poll = setInterval(function() {
      if (++count > 100) return clearInterval(poll);
      if (CodeMirror.modes.hasOwnProperty(mode)) {
        clearInterval(poll);
        loading[mode] = null;
        ensureDeps(mode, function() {
          for (var i = 0; i < list.length; ++i) list[i]();
        });
      }
    }, 200);
  };

  CodeMirror.autoLoadMode = function(instance, mode) {
    if (!CodeMirror.modes.hasOwnProperty(mode))
      CodeMirror.requireMode(mode, function() {
        instance.setOption("mode", instance.getOption("mode"));
      });
    instance.setOption("mode", mode.mime);
  };

  CodeMirror.findExtensionByMode = function(modeInfo) {
    if (modeInfo.ext) {
      return modeInfo.ext[0];
    } else if (modeInfo.mode) {
      return modeInfo.mode;
    } else {
      return "txt";
    }
  };

  CodeMirror.getFilenameAndExt = function(filename){
    var parts = filename.split('.');

    if (parts.length > 1){
        var ext = parts.pop();
        var filename = parts.join("");
    }
    return {"filename": filename, "ext": ext};
  };

}());


//overlay plugin

// Utility function that allows modes to be combined. The mode given
// as the base argument takes care of most of the normal mode
// functionality, but a second (typically simple) mode is used, which
// can override the style of text. Both modes get to parse all of the
// text, but when both assign a non-null style to a piece of code, the
// overlay wins, unless the combine argument was true, in which case
// the styles are combined.

// overlayParser is the old, deprecated name
CodeMirror.overlayMode = CodeMirror.overlayParser = function(base, overlay, combine) {
  return {
    startState: function() {
      return {
        base: CodeMirror.startState(base),
        overlay: CodeMirror.startState(overlay),
        basePos: 0, baseCur: null,
        overlayPos: 0, overlayCur: null
      };
    },
    copyState: function(state) {
      return {
        base: CodeMirror.copyState(base, state.base),
        overlay: CodeMirror.copyState(overlay, state.overlay),
        basePos: state.basePos, baseCur: null,
        overlayPos: state.overlayPos, overlayCur: null
      };
    },

    token: function(stream, state) {
      if (stream.start == state.basePos) {
        state.baseCur = base.token(stream, state.base);
        state.basePos = stream.pos;
      }
      if (stream.start == state.overlayPos) {
        stream.pos = stream.start;
        state.overlayCur = overlay.token(stream, state.overlay);
        state.overlayPos = stream.pos;
      }
      stream.pos = Math.min(state.basePos, state.overlayPos);
      if (stream.eol()) state.basePos = state.overlayPos = 0;

      if (state.overlayCur == null) return state.baseCur;
      if (state.baseCur != null && combine) return state.baseCur + " " + state.overlayCur;
      else return state.overlayCur;
    },

    indent: base.indent && function(state, textAfter) {
      return base.indent(state.base, textAfter);
    },
    electricChars: base.electricChars,

    innerMode: function(state) { return {state: state.base, mode: base}; },

    blankLine: function(state) {
      if (base.blankLine) base.blankLine(state.base);
      if (overlay.blankLine) overlay.blankLine(state.overlay);
    }
  };
};