fix(input): clamp a dragged ruler on an ordered y range and share the orientation test

src/render/renderer.cpp

@@ -939,7 +939,7 @@ void Renderer::draw_cursors(const Plot& plot, const PlotLayout& layout) {
     // stroke (and which axis maps the span it is drawn along), and where the label is
     // written. Everything else -- the skip at the far edge of the axes, the highlight, the
     // text path -- is this one loop's, which is the point of one type rather than two.
-    const bool horizontal = cursor.orientation == CursorOrientation::Horizontal;
+    const bool horizontal = cursor.is_horizontal();
     const f32 at = plot.cursor_screen_coordinate(i);
     // A cursor has no position on the plot when it is strictly outside its range's mapped
     // span -- a marker scrolled past the right edge, a ruler past the bottom -- and the
@@ -985,7 +985,7 @@ void Renderer::draw_cursors(const Plot& plot, const PlotLayout& layout) {
 void Renderer::draw_cursor_label(const Plot& plot, const PlotLayout& layout, const Cursor& cursor,
                                  f32 at) {
   const f32 gap = style_.device(3.0f);
-  if (cursor.orientation == CursorOrientation::Horizontal) {
+  if (cursor.is_horizontal()) {
     // A ruler's text is the value it is *for*, written the way the y axis writes its own
     // tick labels, so a value read off a ruler reads exactly like the tick beside it. The
     // caller's caption, when there is one, is staged first on the same line, so neither the