Fix positioning of mathtext Rules

anntzer · QuLogic · commit 4bfa0f975042 · 2026-02-06T17:33:06.000-05:00
At the call site https://github.com/matplotlib/matplotlib/blob/51fbfc4eb0e882ef7e95ceab9777c7047f4db819/lib/matplotlib/_mathtext.py#L1706-L1709 the box should clearly go from `cur_v + off_v` to `cur_v + off_v - rule_height` (this is why `cur_v` is shifted by `+ rule_height` just before; also at that point some print debugging indicates that y's go *downwards*), so `Rule.render` should indeed call `render_rect_filled` from `y - h` to `y`.
diff --git a/lib/matplotlib/_mathtext.py b/lib/matplotlib/_mathtext.py
@@ -1453,7 +1453,7 @@ def __init__(self, width: float, height: float, depth: float, state: ParserState
 
     def render(self, output: Output,  # type: ignore[override]
                x: float, y: float, w: float, h: float) -> None:
-        self.fontset.render_rect_filled(output, x, y, w, h)
+        self.fontset.render_rect_filled(output, x, y - h, w, h)
 
 
 class Hrule(Rule):
@@ -2699,12 +2699,11 @@ def _genfrac(self, ldelim: str, rdelim: str, rule: float | None, style: _MathSty
             delta = rule / 2
             num_clr = max((num_shift_up - cnum.depth) - (axis_height + delta), clr)
             den_clr = max((axis_height - delta) - (cden.height - den_shift_down), clr)
-            # Possible bug in fraction rendering. See GitHub PR 22852 comments.
-            vlist = Vlist([cnum,                     # numerator
-                           Vbox(0, num_clr - rule),  # space
-                           Hrule(state, rule),       # rule
-                           Vbox(0, den_clr + rule),  # space
-                           cden                      # denominator
+            vlist = Vlist([cnum,                # numerator
+                           Vbox(0, num_clr),    # space
+                           Hrule(state, rule),  # rule
+                           Vbox(0, den_clr),    # space
+                           cden                 # denominator
                            ])
             vlist.shift_amount = cden.height + den_clr + delta - axis_height
 
