修复字体过小无法显示下划线

src/qelmt/mod.rs

@@ -1748,7 +1748,9 @@ impl Display for FontInfo {
 impl FontInfo {
     fn apply_height(&mut self, height: f64) {
         self.point_size = height;
-        self.pixel_size = height;
+        // Qt ignores point size when pixel size is set; tiny pixel fonts lose glyph details
+        // so only set pixel size when the height is large enough to render reliably.
+        self.pixel_size = if height >= 3.0 { height } else { 0.0 };
     }
 
     fn scale(&mut self, fact: f64) {