Major update for v1 and tests

src/constants/textMetrics.js

@@ -0,0 +1,54 @@
+/**
+ * Text-rendering constants shared across measurement, bounds, and render code.
+ *
+ * Before this module: `1.2`, `12`, and similar magic numbers were repeated
+ * across `textGeometry.js`, `elementBounds.js`, and `TextElement.jsx`. If
+ * Konva's defaults ever changed (or the design system picked a different
+ * line-height ratio), every site had to be updated in lockstep — and there
+ * was no way to grep for "the line-height ratio" since it was just `1.2`.
+ *
+ * Centralizing here keeps those callers honest. New text-related constants
+ * that show up in 2+ places should land here.
+ *
+ * Note on per-component font-family defaults
+ * ──────────────────────────────────────────
+ * `TextElement.jsx` defaults `fontFamily = 'DM Sans'` (the body face) for
+ * its prop. `textGeometry.js` defaulted to `'Pacifico'` (the display face)
+ * for its measurement-fallback path. Those are intentionally different —
+ * an element rendered without a fontFamily uses DM Sans, but the
+ * measurement helpers fall back to the display face that matches new-text
+ * placement defaults. We keep that distinction by exposing both names
+ * here and letting each call site pick the one that matches its semantics.
+ */
+
+// Konva's default line-height ratio. Multiply by fontSize to get the
+// rendered height of a single text line.
+export const LINE_HEIGHT_RATIO = 1.2;
+
+// Floor for fontSize during scale-down operations. Below this, text becomes
+// hard to read and the rounded display in the Text tab starts losing
+// precision (12 → 11 → 10 each cost ~10% of legibility).
+export const MIN_FONT_SIZE = 12;
+
+// Ceiling for auto-computed fontSize values (e.g. width-preservation
+// when swapping to a narrower font). The Text tab's slider tops out at
+// 120 for typical fine-tuning, but width-preservation can legitimately
+// land above that when going from a wide display face to a very
+// condensed one. 200 gives plenty of headroom (about 2/3 of the
+// 300-design-unit canvas height) while preventing pathological growth
+// on a font whose measureText returns near-zero for a particular glyph.
+// The user can still corner-drag the text on canvas past this value;
+// the cap only governs the auto-preserve math.
+export const MAX_FONT_SIZE = 200;
+
+// Default fontSize when an element doesn't specify one. Matches the
+// historical TEXT default in textGeometry.placeTextCentered.
+export const DEFAULT_FONT_SIZE = 32;
+
+// Display face used by the freeform "Add text" button and as the
+// measurement fallback when an element has no explicit fontFamily.
+export const DEFAULT_DISPLAY_FONT = 'Pacifico';
+
+// Body face used by TextElement's prop default (so Konva renders something
+// reasonable when the prop is omitted).
+export const DEFAULT_BODY_FONT = 'DM Sans';