First commit. Version 0.1.0

tests/vslider_math.rs

@@ -0,0 +1,119 @@
+use ltk::test_support::
+{
+	value_from_y_in_rect,
+	value_from_pos_in_rect,
+	SliderAxis,
+};
+use ltk::{ Point, Rect };
+
+fn rect( x: f32, y: f32, w: f32, h: f32 ) -> Rect
+{
+	Rect { x, y, width: w, height: h }
+}
+
+#[ test ]
+fn top_is_one()
+{
+	let r = rect( 0.0, 0.0, 56.0, 160.0 );
+	assert_eq!( value_from_y_in_rect( r, 0.0 ), 1.0 );
+	assert_eq!( value_from_y_in_rect( r, -50.0 ), 1.0 );
+}
+
+#[ test ]
+fn bottom_is_zero()
+{
+	let r = rect( 0.0, 0.0, 56.0, 160.0 );
+	assert_eq!( value_from_y_in_rect( r, 160.0 ), 0.0 );
+	assert_eq!( value_from_y_in_rect( r, 999.0 ), 0.0 );
+}
+
+#[ test ]
+fn center_returns_half()
+{
+	let r = rect( 0.0, 0.0, 56.0, 160.0 );
+	let v = value_from_y_in_rect( r, 80.0 );
+	assert!( ( v - 0.5 ).abs() < 1e-6, "expected 0.5 got {}", v );
+}
+
+#[ test ]
+fn rect_offset_translates_correctly()
+{
+	let r = rect( 0.0, 500.0, 56.0, 160.0 );
+	assert_eq!( value_from_y_in_rect( r, 500.0 ), 1.0 );
+	assert_eq!( value_from_y_in_rect( r, 660.0 ), 0.0 );
+	let v = value_from_y_in_rect( r, 580.0 );
+	assert!( ( v - 0.5 ).abs() < 1e-6, "expected 0.5 got {}", v );
+}
+
+#[ test ]
+fn output_is_always_in_unit_range()
+{
+	let r = rect( 10.0, 10.0, 56.0, 200.0 );
+	for y in -100i32 ..= 400
+	{
+		let v = value_from_y_in_rect( r, y as f32 );
+		assert!( ( 0.0..= 1.0 ).contains( &v ), "v={} out of range at y={}", v, y );
+	}
+}
+
+#[ test ]
+fn very_short_rect_does_not_divide_by_zero()
+{
+	// Height < 1.0 — track_h is clamped to 1.0 internally so the formula
+	// stays defined.
+	let r = rect( 0.0, 0.0, 56.0, 0.1 );
+	let v = value_from_y_in_rect( r, 0.05 );
+	assert!( v.is_finite() );
+	assert!( ( 0.0..= 1.0 ).contains( &v ) );
+}
+
+#[ test ]
+fn value_is_monotonically_decreasing_along_y()
+{
+	// Moving downward inside the pill must never *increase* the value —
+	// the invariant behind the "drag up = larger" UX contract.
+	let r = rect( 0.0, 0.0, 56.0, 160.0 );
+	let mut prev = value_from_y_in_rect( r, 0.0 );
+	for y in 0 ..= 160
+	{
+		let v = value_from_y_in_rect( r, y as f32 );
+		assert!( v <= prev + 1e-6, "not monotonic: y={} v={} prev={}", y, v, prev );
+		prev = v;
+	}
+}
+
+#[ test ]
+fn value_from_pos_dispatches_horizontal()
+{
+	let r = rect( 0.0, 0.0, 200.0, 36.0 );
+	let v = value_from_pos_in_rect(
+		r,
+		Point { x: 200.0, y: 0.0 },
+		SliderAxis::Horizontal,
+	);
+	assert_eq!( v, 1.0 );
+}
+
+#[ test ]
+fn value_from_pos_dispatches_vertical()
+{
+	let r = rect( 0.0, 0.0, 56.0, 160.0 );
+	let v = value_from_pos_in_rect(
+		r,
+		Point { x: 9_999.0, y: 0.0 },
+		SliderAxis::Vertical,
+	);
+	assert_eq!( v, 1.0 );
+}
+
+#[ test ]
+fn value_from_pos_axes_are_independent()
+{
+	let r = rect( 0.0, 0.0, 200.0, 200.0 );
+	let h = value_from_pos_in_rect(
+		r, Point { x: 100.0, y: 0.0 }, SliderAxis::Horizontal );
+	let v = value_from_pos_in_rect(
+		r, Point { x: 0.0, y: 100.0 }, SliderAxis::Vertical );
+	assert!( ( h - 0.5 ).abs() < 0.1 );
+	assert!( ( v - 0.5 ).abs() < 1e-6 );
+}