share the world shapes both views (game and balancing) draw identically

src/ui/WorldPrimitives.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <QColor>
+#include <QPointF>
+
+#include "WorldCoordinates.h"
+
+class QPainter;
+
+// The handful of world-space shapes the game view and the balancing tool's arena
+// view draw identically: a ship, its health bar, a piece of debris, a sensor range.
+//
+// Shared because the arena exists to eyeball combat, which only works while a ship
+// there looks like a ship in the game — if these drift, the balancing tool quietly
+// stops representing what it is measuring. Deliberately kept to shapes that are
+// genuinely the same in both: the two views differ on selection highlights, beams
+// and target lines, and those stay with each view.
+//
+// Free functions taking explicit values, with no state and no simulation: each
+// view keeps its own iteration and layer order. Sizes derive from the tile size so
+// everything scales with the view (REQ-GW-TILE-SIZE).
+
+// Distance from a ship's centre to its nose, in pixels. The selection ring and the
+// health bar are positioned from this, so callers need it whether or not they are
+// the ones drawing the body.
+float getShipForwardExtentPx(const WorldCoordinates& coordinates);
+
+// Radius of a piece of debris, in pixels. Shared so the selection ring around
+// debris cannot drift from the debris it is meant to circle.
+float getDebrisRadiusPx(const WorldCoordinates& coordinates);
+
+// Draws a ship as a triangle at `center` (widget space), pointing along
+// `facing_radians`.
+void drawShipBody(QPainter& painter, const WorldCoordinates& coordinates,
+                  QPointF center, float facing_radians,
+                  const QColor& fill, const QColor& outline);
+
+// Draws a health bar: a dark track with `fraction` of it filled, red for an enemy
+// and green for the player. A negative fraction is clamped to empty.
+void drawHealthBar(QPainter& painter, const WorldCoordinates& coordinates,
+                   qreal left, qreal top, qreal width, float fraction, bool isEnemy);
+
+// Draws a piece of debris as a small brown circle at `center` (widget space).
+void drawDebrisMarker(QPainter& painter, const WorldCoordinates& coordinates,
+                      QPointF center);
+
+// Draws a ship's sensor range as a faint circle in the ship's own outline colour,
+// so overlapping ranges stay distinguishable.
+void drawSensorRange(QPainter& painter, const WorldCoordinates& coordinates,
+                     QPointF center, float range_tiles, const QColor& shipOutline);