Sparkline

koto::Sparkline renders a sequence of uint64_t values as a compact single-row vertical bar chart using 8 Unicode block characters (Header: koto/sparkline.hpp).

Quick example

Sparkline trend

std::vector<uint64_t> values = {1, 3, 2, 5, 8, 6, 7, 4, 9, 10};
Sparkline()
    .data(values)
    .fg(Color::Cyan)
    .draw(frame, spark_area);

Output

               ▃▂▅▇▅▆▄██

Behavior

• Bottom-row drawing and upper-row clearing: In a multi-row area, Sparkline::draw() renders bars on the bottom row target_row = area.bottom() - 1 and clears all rows above target_row (area.row .. target_row - 1) with Cell{U' ', m_fg, m_bg} (src/sparkline.cpp:60-69).
• Auto-scaling vs. fixed ceiling: If m_max == 0 (the default), effective_max is computed as the maximum element in m_data (clamped to at least 1 if all elements are 0). Otherwise effective_max = m_max (src/sparkline.cpp:80-88).
• Windowing and right alignment: If m_data.size() > area.width, only the last area.width elements are displayed (start_idx = num_points - available_cols). If m_data.size() < area.width and m_align_right == true (the default), leading columns on the left are filled with spaces so the data hugs the right edge (src/sparkline.cpp:93-106).
• 8-level quantization: For each point val:
  • If val == 0, the cell is a space U' '.
  • If val > 0, bar_level = std::min<uint64_t>(7, (val * 8) / effective_max) indexes into SPARKLINE_BARS = {U'▁', U'▂', U'▃', U'▄', U'▅', U'▆', U'▇', U'█'} (src/sparkline.cpp:8-10, src/sparkline.cpp:121-130).

Methods

Method	Description	Default
Sparkline()	Constructs an empty Sparkline.	m_max = 0, m_align_right = true, m_fg = Color::Cyan, m_bg = COLOR_DEFAULT
data(std::span<const uint64_t> values)	Binds a non-owning view over values and clears m_owned_data.	Empty span
data(const std::vector<uint64_t>& values)	Copies values into m_owned_data and points m_data at the copy.	Empty vector
max(uint64_t max_value)	Sets a fixed scaling ceiling (0 enables auto-scaling to the maximum element).	0
align_right(bool right = true)	When true, right-aligns shorter data series; when false, left-aligns them.	true
fg(Color fg)	Sets the foreground color of the sparkline bars.	Color::Cyan
bg(Color bg)	Sets the background color of the sparkline cells.	COLOR_DEFAULT
draw(Frame& frame, Area area)	Draws the sparkline into frame within area.	None

Gotchas

• data(std::span<const uint64_t>) vs. data(const std::vector<uint64_t>&): Passing a std::vector<uint64_t> directly matches the const std::vector<uint64_t>& overload, which copies the vector into m_owned_data (src/sparkline.cpp:21-26). To avoid copying a std::vector<uint64_t> vec on every frame, pass std::span<const uint64_t>(vec).
• Single-row bar height: Even if area.height > 1, Sparkline only draws 1-row-tall bars on area.bottom() - 1 and fills the rows above with blank spaces.

See also

• Gauge
• Performance Deep Dive