From f7ade654491251fa227ea8b2d8c1c7f4b127511e Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Thu, 13 Aug 2026 23:16:20 +0200
Subject: [PATCH] Handle a border case of zero effective text height properly
 by making such texts non-scaling even with non-default font and borrowing the
 dimension from the default font

---
 src/laybasic/laybasic/layBitmapRenderer.cc    |  8 ++++++++
 src/laybasic/laybasic/layRedrawThreadCanvas.h |  2 +-
 src/laybasic/laybasic/layTextInfo.cc          | 11 +++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/laybasic/laybasic/layBitmapRenderer.cc b/src/laybasic/laybasic/layBitmapRenderer.cc
index 0065f836b..0b3e7b6a8 100644
--- a/src/laybasic/laybasic/layBitmapRenderer.cc
+++ b/src/laybasic/laybasic/layBitmapRenderer.cc
@@ -23,6 +23,7 @@
 
 #include "layBitmapRenderer.h"
 #include "layBitmap.h"
+#include "layFixedFont.h"
 
 namespace lay
 {
@@ -398,6 +399,13 @@ BitmapRenderer::draw (const db::Shape &shape, const db::CplxTrans &trans,
         }
       }
 
+      if (h == 0.0) {
+        //  for the special case of zero effective height, borrow the height
+        //  from the default font in an unscaling fashion.
+        const lay::FixedFont &ff = lay::FixedFont::get_font (m_font_resolution);
+        h = ff.height ();
+      }
+
       db::HAlign halign = shape.text_halign ();
       db::VAlign valign = shape.text_valign ();
 
diff --git a/src/laybasic/laybasic/layRedrawThreadCanvas.h b/src/laybasic/laybasic/layRedrawThreadCanvas.h
index 0751d4ab7..99586da9f 100644
--- a/src/laybasic/laybasic/layRedrawThreadCanvas.h
+++ b/src/laybasic/laybasic/layRedrawThreadCanvas.h
@@ -97,7 +97,7 @@ public:
   virtual void prepare (unsigned int /*nlayers*/, unsigned int width, unsigned int height, double resolution, double font_resolution, const db::Vector * /*shift_vector*/, const std::vector<int> * /*planes*/, const lay::Drawings * /*drawings*/)
   {
     m_resolution = resolution;
-    m_resolution = font_resolution;
+    m_font_resolution = font_resolution;
     m_width = width;
     m_height = height;
   }
diff --git a/src/laybasic/laybasic/layTextInfo.cc b/src/laybasic/laybasic/layTextInfo.cc
index b93fea985..17c3143cd 100644
--- a/src/laybasic/laybasic/layTextInfo.cc
+++ b/src/laybasic/laybasic/layTextInfo.cc
@@ -81,15 +81,22 @@ TextInfo::bbox (const db::DText &text, const db::DCplxTrans &vp_trans) const
     fx = -1.0;
   }
 
+  if (h == 0.0) {
+    //  for the special case of zero effective height, borrow the height
+    //  from the default font in an unscaling fashion.
+    const lay::FixedFont &ff = lay::FixedFont::get_font (m_resolution);
+    h = ff.height () / vp_trans.mag ();
+  }
+
   db::DPoint dp1 (fx * offset, fy * offset + (fy - 1) * 0.5 * h);
   db::DPoint dp2 (fx * offset, fy * offset + (fy + 1) * 0.5 * h);
 
   if (font == db::DefaultFont) {
 
-    db::DBox b (dp1 * vp_trans.mag (), dp2 * vp_trans.mag ());
-
     const lay::FixedFont &ff = lay::FixedFont::get_font (m_resolution);
 
+    db::DBox b (dp1 * vp_trans.mag (), dp2 * vp_trans.mag ());
+
     //  count the lines
 
     unsigned int lines = 1;