Fonts and text

All text — titles, axis labels, legends, data labels — is rasterized with stb_truetype and decoded as UTF-8. Code points the active font has no glyph for are drawn as ?.

Choosing a font

Source	How	Coverage
Embedded (default)	nothing to do	printable ASCII, ~20 KB in the binary
Embedded Latin	build with -DINSIGHTDOCK_FONT_LATIN=ON (CMake) or FONT_MODE=embedded-latin (Make)	ASCII + Latin-1 + Latin Extended-A, common punctuation, €, ™, − (~22 KB)
Your own TTF	ChartOptions::font	whatever the file covers

#include <insightdock/charts.h>
using namespace insightdock::charts;

auto font = load_font_data("/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf");
if (!font) { /* unreadable, > 64 MiB, or not a TrueType file */ }

BarChart chart;
chart.options().font = font;          // shared_ptr: reuse one font across many charts
chart.options().title = "Café — 25 °C";

load_font_data() validates the file once; ChartOptions::font then holds shared, immutable bytes so copying a chart or building hundreds of charts does not duplicate the font.

FONT_MODE=system (Make)

FONT_MODE=system omits the embedded font entirely, which saves ~20 KB on OpenWrt-class targets. Charts then render no text unless you set ChartOptions::font on every chart:

static auto font = load_font_data("/www/assets/fonts/OpenSans-Regular.ttf");
chart.options().font = font;

Wide x-axis labels

CartesianOptions::x_label_mode chooses how category labels cope with narrow slots:

Mode	Behaviour
Auto (default)	Horizontal; labels are skipped so neighbours never overlap.
Rotate90	Every label is drawn rotated 90° (reads bottom-to-top); the bottom margin grows to fit the longest label.
Truncate	Every label is drawn horizontally, shortened with ... to fit its slot.

max_x_labels still caps the number of labels in every mode.

Multi-line text

Chart titles, category labels and the x-axis title may contain \n:

chart.options().title = "Revenue by quarter\n(thousands of USD)";
chart.set_categories({"Q1\n2024", "Q2\n2024"});

Each line is centred on its own width, and the title / label margins grow to fit. Y-axis titles are single-line. Legend entries support explicit newlines and automatic wrapping.

Colorblind-safe palette

chart.options().palette = PaletteKind::ColorblindSafe; selects the 8-colour Okabe–Ito palette for series added afterwards without an explicit color (set it before add_series).

Legend layout and overflow

Pie, Cartesian and scatter/bubble legends measure labels with the chart font. Top and bottom legends pack entries into centered rows with 10 pixels of canvas padding on each side. Right legends reserve their measured width, up to one third of the canvas, and wrap longer labels. Each legend uses at most one third of the canvas height. Explicit newlines preserve empty lines; long tokens split between UTF-8 code points.

Entries appear in insertion order. When the complete legend exceeds that height, whole trailing entries are replaced by a +N more count. The chart still renders their data. Increase the canvas size, shorten labels or disable the legend to show more data without a summary. If even the count cannot fit (for example, on a very narrow canvas with a large font), the overflow indicator is omitted. An individual code point wider than the available label width also triggers overflow.

Automatic pie centers and radii reserve room for the title and legend at render time, including when dimensions change after set_pie_options(). Explicit coordinates and radii remain caller controlled. Pie callout collisions and arbitrary axis/label collisions still need manual tuning. The same measured legend layout drives PNG, SVG and PDF chart exports; scatter/bubble currently uses raster fallback for vector exports, and the legacy PDF pie report helpers use their own layout.