use WorldCoordinates in ArenaView too

src/test/WorldCoordinatesTest.cpp

@@ -10,7 +10,7 @@
 // 40-tile-wide view, so every expectation below is a whole number.
 static WorldCoordinates makeCoordinates(float viewCenterX_tiles)
 {
-    return WorldCoordinates(QSize(800, 400), 20, viewCenterX_tiles);
+    return WorldCoordinates::scrolling(QSize(800, 400), 20, viewCenterX_tiles);
 }
 
 // ---------------------------------------------------------------------------
@@ -22,21 +22,34 @@ TEST_CASE("Tile size makes the world height fill the viewport height", "[coords]
     // REQ-GW-TILE-SIZE: tiles are square and sized so the world height exactly
     // fills the view's height.
     REQUIRE(makeCoordinates(0.0f).getTilePx() == Approx(20.0f));
-    REQUIRE(WorldCoordinates(QSize(800, 600), 20, 0.0f).getTilePx() == Approx(30.0f));
+    REQUIRE(WorldCoordinates::scrolling(QSize(800, 600), 20, 0.0f).getTilePx()
+            == Approx(30.0f));
 }
 
 TEST_CASE("A degenerate world height falls back to a unit tile", "[coords]")
 {
     // Guards the division in every conversion; a zero or negative height would
     // otherwise produce infinities.
-    REQUIRE(WorldCoordinates(QSize(800, 400), 0, 0.0f).getTilePx() == Approx(1.0f));
-    REQUIRE(WorldCoordinates(QSize(800, 400), -5, 0.0f).getTilePx() == Approx(1.0f));
+    REQUIRE(WorldCoordinates::scrolling(QSize(800, 400), 0, 0.0f).getTilePx()
+            == Approx(1.0f));
+    REQUIRE(WorldCoordinates::scrolling(QSize(800, 400), -5, 0.0f).getTilePx()
+            == Approx(1.0f));
+}
+
+TEST_CASE("A zero-size viewport falls back to a unit tile", "[coords]")
+{
+    // A widget that has not been shown yet still has to answer conversions —
+    // the arena hit-tests through the same transform.
+    REQUIRE(WorldCoordinates::scrolling(QSize(0, 0), 20, 0.0f).getTilePx()
+            == Approx(1.0f));
+    REQUIRE(WorldCoordinates::fitToWorld(QSize(0, 0), 40, 20).getTilePx()
+            == Approx(1.0f));
 }
 
 TEST_CASE("Viewport width in tiles follows the widget width", "[coords]")
 {
     REQUIRE(makeCoordinates(0.0f).getViewportWidthTiles() == Approx(40.0f));
-    REQUIRE(WorldCoordinates(QSize(400, 400), 20, 0.0f).getViewportWidthTiles()
+    REQUIRE(WorldCoordinates::scrolling(QSize(400, 400), 20, 0.0f).getViewportWidthTiles()
             == Approx(20.0f));
 }
 
@@ -143,3 +156,48 @@ TEST_CASE("A fractional scroll position widens the viewport rect outward", "[coo
     REQUIRE(rect.left()  == -21);
     REQUIRE(rect.right() == 21);
 }
+
+// ---------------------------------------------------------------------------
+// Fitted (non-scrolling) worlds
+// ---------------------------------------------------------------------------
+
+TEST_CASE("A fitted world takes the tighter of the two axis fits", "[coords]")
+{
+    // Height-limited: 400/20 = 20 px per tile beats 800/30 = 26.67.
+    REQUIRE(WorldCoordinates::fitToWorld(QSize(800, 400), 30, 20).getTilePx()
+            == Approx(20.0f));
+    // Width-limited: 800/80 = 10 px per tile beats 400/20 = 20.
+    REQUIRE(WorldCoordinates::fitToWorld(QSize(800, 400), 80, 20).getTilePx()
+            == Approx(10.0f));
+}
+
+TEST_CASE("A fitted world keeps its whole width on screen", "[coords]")
+{
+    // The point of taking the tighter fit: the far edge must land inside the
+    // viewport, never past it.
+    const WorldCoordinates coordinates =
+        WorldCoordinates::fitToWorld(QSize(800, 400), 80, 20);
+    REQUIRE(coordinates.worldToWidget(QVector2D(80.0f, 0.0f)).x() <= 800.0);
+    REQUIRE(coordinates.worldToWidget(QVector2D(0.0f, 20.0f)).y() <= 400.0);
+}
+
+TEST_CASE("A fitted world puts the origin at the widget's top-left", "[coords]")
+{
+    // No scrolling, so there is no view center to subtract.
+    const WorldCoordinates coordinates =
+        WorldCoordinates::fitToWorld(QSize(800, 400), 40, 20);
+    REQUIRE(coordinates.getViewLeftTiles() == Approx(0.0f));
+    REQUIRE(coordinates.tileToWidget(QPoint(0, 0)) == QPointF(0.0, 0.0));
+    REQUIRE(coordinates.tileToWidget(QPoint(3, 2)) == QPointF(60.0, 40.0));
+}
+
+TEST_CASE("A fitted world round-trips widget points back to world positions",
+          "[coords]")
+{
+    const WorldCoordinates coordinates =
+        WorldCoordinates::fitToWorld(QSize(800, 400), 80, 20);
+    const QVector2D world = coordinates.widgetToWorld(QPoint(120, 55));
+    const QPointF   back  = coordinates.worldToWidget(world);
+    REQUIRE(back.x() == Approx(120.0));
+    REQUIRE(back.y() == Approx(55.0));
+}