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Commit attr runs less frequently by accumulating length of color run (#…
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…6919)

The act of calling `InsertAttrRuns` is relatively slow. Instead of
calling it a bunch of times to meddle with colors one cell at a time,
we'll accumulate a length of color and call it to make it act all at
once. This is great for when one color full line is getting replaced
with another color full line OR when a line is being replaced with the
same color all at once. There's significantly fewer checks to be made
inside `InsertAttrRuns` if we can help it out by accumulating the length
of each color before asking it to stitch it into the storage.

Validation
----------

- Run `time cat big.txt` and `time cat ls.txt` under VS Performance
  Profiler.
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@miniksa
miniksa authored Jul 17, 2020
1 parent ea2bd42 commit 4351f32
Showing 1 changed file with 77 additions and 45 deletions.
122 changes: 77 additions & 45 deletions src/buffer/out/Row.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -160,66 +160,98 @@ OutputCellIterator ROW::WriteCells(OutputCellIterator it, const size_t index, co
// If we're given a right-side column limit, use it. Otherwise, the write limit is the final column index available in the char row.
const auto finalColumnInRow = limitRight.value_or(_charRow.size() - 1);

while (it && currentIndex <= finalColumnInRow)
if (it)
{
// Fill the color if the behavior isn't set to keeping the current color.
if (it->TextAttrBehavior() != TextAttributeBehavior::Current)
{
const TextAttributeRun attrRun{ 1, it->TextAttr() };
LOG_IF_FAILED(_attrRow.InsertAttrRuns({ &attrRun, 1 },
currentIndex,
currentIndex,
_charRow.size()));
}
// Accumulate usages of the same color so we can spend less time in InsertAttrRuns rewriting it.
auto currentColor = it->TextAttr();
size_t colorUses = 0;
size_t colorStarts = index;

// Fill the text if the behavior isn't set to saying there's only a color stored in this iterator.
if (it->TextAttrBehavior() != TextAttributeBehavior::StoredOnly)
while (it && currentIndex <= finalColumnInRow)
{
const bool fillingLastColumn = currentIndex == finalColumnInRow;

// TODO: MSFT: 19452170 - We need to ensure when writing any trailing byte that the one to the left
// is a matching leading byte. Likewise, if we're writing a leading byte, we need to make sure we still have space in this loop
// for the trailing byte coming up before writing it.

// If we're trying to fill the first cell with a trailing byte, pad it out instead by clearing it.
// Don't increment iterator. We'll advance the index and try again with this value on the next round through the loop.
if (currentIndex == 0 && it->DbcsAttr().IsTrailing())
// Fill the color if the behavior isn't set to keeping the current color.
if (it->TextAttrBehavior() != TextAttributeBehavior::Current)
{
_charRow.ClearCell(currentIndex);
// If the color of this cell is the same as the run we're currently on,
// just increment the counter.
if (currentColor == it->TextAttr())
{
++colorUses;
}
else
{
// Otherwise, commit this color into the run and save off the new one.
const TextAttributeRun run{ colorUses, currentColor };
// Now commit the new color runs into the attr row.
LOG_IF_FAILED(_attrRow.InsertAttrRuns({ &run, 1 },
colorStarts,
currentIndex - 1,
_charRow.size()));
currentColor = it->TextAttr();
colorUses = 1;
colorStarts = currentIndex;
}
}
// If we're trying to fill the last cell with a leading byte, pad it out instead by clearing it.
// Don't increment iterator. We'll exit because we couldn't write a lead at the end of a line.
else if (fillingLastColumn && it->DbcsAttr().IsLeading())

// Fill the text if the behavior isn't set to saying there's only a color stored in this iterator.
if (it->TextAttrBehavior() != TextAttributeBehavior::StoredOnly)
{
_charRow.ClearCell(currentIndex);
_charRow.SetDoubleBytePadded(true);
const bool fillingLastColumn = currentIndex == finalColumnInRow;

// TODO: MSFT: 19452170 - We need to ensure when writing any trailing byte that the one to the left
// is a matching leading byte. Likewise, if we're writing a leading byte, we need to make sure we still have space in this loop
// for the trailing byte coming up before writing it.

// If we're trying to fill the first cell with a trailing byte, pad it out instead by clearing it.
// Don't increment iterator. We'll advance the index and try again with this value on the next round through the loop.
if (currentIndex == 0 && it->DbcsAttr().IsTrailing())
{
_charRow.ClearCell(currentIndex);
}
// If we're trying to fill the last cell with a leading byte, pad it out instead by clearing it.
// Don't increment iterator. We'll exit because we couldn't write a lead at the end of a line.
else if (fillingLastColumn && it->DbcsAttr().IsLeading())
{
_charRow.ClearCell(currentIndex);
_charRow.SetDoubleBytePadded(true);
}
// Otherwise, copy the data given and increment the iterator.
else
{
_charRow.DbcsAttrAt(currentIndex) = it->DbcsAttr();
_charRow.GlyphAt(currentIndex) = it->Chars();
++it;
}

// If we're asked to (un)set the wrap status and we just filled the last column with some text...
// NOTE:
// - wrap = std::nullopt --> don't change the wrap value
// - wrap = true --> we're filling cells as a steam, consider this a wrap
// - wrap = false --> we're filling cells as a block, unwrap
if (wrap.has_value() && fillingLastColumn)
{
// set wrap status on the row to parameter's value.
_charRow.SetWrapForced(wrap.value());
}
}
// Otherwise, copy the data given and increment the iterator.
else
{
_charRow.DbcsAttrAt(currentIndex) = it->DbcsAttr();
_charRow.GlyphAt(currentIndex) = it->Chars();
++it;
}

// If we're asked to (un)set the wrap status and we just filled the last column with some text...
// NOTE:
// - wrap = std::nullopt --> don't change the wrap value
// - wrap = true --> we're filling cells as a steam, consider this a wrap
// - wrap = false --> we're filling cells as a block, unwrap
if (wrap.has_value() && fillingLastColumn)
{
// set wrap status on the row to parameter's value.
_charRow.SetWrapForced(wrap.value());
}
// Move to the next cell for the next time through the loop.
++currentIndex;
}
else

// Now commit the final color into the attr row
if (colorUses)
{
++it;
const TextAttributeRun run{ colorUses, currentColor };
LOG_IF_FAILED(_attrRow.InsertAttrRuns({ &run, 1 },
colorStarts,
currentIndex - 1,
_charRow.size()));
}

// Move to the next cell for the next time through the loop.
++currentIndex;
}

return it;
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