improve the ezdxf.render.dim_base.Measurement class

Improves the text override feature of the Measurement class.
Replaces the first occurrence of "<>" in then replacement text,
so string interpolation from "$<> xyz" to "$300 xyz" for a
measurement of 300 units is now possible.

Replaces only the first "<>" like BricsCAD.
The override text "<><>" evaluates to "300<>" for the previous
measurement.

examples/render/dimension_linear.py

@@ -145,6 +145,50 @@ def example_background_fill(dxfversion=DXFVERSION):
     doc.saveas(CWD / f"background_fill_example_{dxfversion}.dxf")
 
 
+def example_text_override(dxfversion=DXFVERSION):
+    """This example shows how to override the measurement text."""
+    doc = ezdxf.new(dxfversion, setup=True)
+    msp = doc.modelspace()
+
+    # custom text
+    dim = msp.add_linear_dim(
+        base=(0, 2),
+        p1=(0, 0),
+        p2=(3, 0),
+    )
+    dim.set_text("=<>= <>")  # the first "<>" will be replaced by the measurement text
+    dim.render()
+
+    # suppress text
+    dim = msp.add_linear_dim(
+        base=(5, 2),
+        p1=(5, 0),
+        p2=(8, 0),
+    )
+    dim.set_text(" ")
+    dim.render()
+
+    # regular measurement text
+    dim = msp.add_linear_dim(
+        base=(10, 2),
+        p1=(10, 0),
+        p2=(13, 0),
+    )
+    dim.set_text("")
+    dim.render()
+
+    # regular measurement text
+    dim = msp.add_linear_dim(
+        base=(15, 2),
+        p1=(15, 0),
+        p2=(18, 0),
+    )
+    dim.set_text("<>")
+    dim.render()
+
+    doc.saveas(CWD / f"text_override_example_{dxfversion}.dxf")
+
+
 def example_for_all_text_placings_R12():
     doc = ezdxf.new("R12", setup=True)
     example_for_all_text_placings(doc, "dim_linear_text_placing_R12.dxf")
@@ -788,15 +832,10 @@ def linear_EZ_MM(fmt):
     doc.saveas(CWD / f"dim_linear_R12_{fmt}.dxf")
 
 
-ALL = True
+ALL = False
 
 if __name__ == "__main__":
-    example_for_all_text_placings_ucs_R12()
-    # todo: TEXT entities transformed into 3D space do not work as expected
-    #  for DXF R12!
-    example_for_all_text_placings_in_space_R12()
-    example_for_all_text_placings_ucs_R2007()
-    example_for_all_text_placings_in_space_R2007()
+    example_text_override("R2007")
 
     if ALL:
         linear_tutorial("R2007")
@@ -809,6 +848,8 @@ def linear_EZ_MM(fmt):
         linear_tutorial("R2007")
         linear_tutorial("R12")
         example_background_fill("R2007")
+        example_text_override("R2007")
+
         example_for_all_text_placings_R12()
         example_for_all_text_placings_R2007()
 

src/ezdxf/render/dim_base.py

@@ -451,7 +451,7 @@ def __init__(
         text_style = get_text_style(doc, style_name)
         self.text_height: float = get_char_height(dim_style, text_style) * scale
         self.text_width_factor: float = text_style.get_dxf_attrib("width", 1.0)
-        self.stored_dim_text = dimension.dxf.text
+        self.stored_dim_text: str = dimension.dxf.text
 
         # text_gap: gap between dimension line an dimension text
         self.text_gap: float = get("dimgap", 0.625) * scale
@@ -655,10 +655,11 @@ def text_override(self, measurement: float) -> str:
         text = self.stored_dim_text
         if text == " ":  # suppresses text
             return ""
-        elif text == "" or text == "<>":  # measured distance
-            return self.format_text(measurement)
-        else:  # user override
-            return text
+        formatted_measurement = self.format_text(measurement)
+        if text:
+            # only replace the first "<>", like BricsCAD
+            return text.replace("<>", formatted_measurement, 1)
+        return formatted_measurement
 
     def location_override(self, location: UVec, leader=False, relative=False) -> None:
         """Set user defined dimension text location. ezdxf defines a user

tests/test_07_render/test_704a_render_measurement_text.py

@@ -0,0 +1,64 @@
+# Copyright (c) 2024 Manfred Moitzi
+# License: MIT License
+import pytest
+import ezdxf
+from ezdxf.layouts import Modelspace
+
+
+@pytest.fixture(scope="module")
+def msp() -> Modelspace:
+    doc = ezdxf.new("R2007", setup=True)
+    return doc.modelspace()
+
+
+@pytest.mark.parametrize("text", ["", "<>"])
+def test_regular_measurement_text(msp, text):
+    dim = msp.add_linear_dim(
+        base=(0, 2),
+        p1=(0, 0),
+        p2=(3, 0),
+    )
+    dim.set_text(text)
+
+    block = dim.render().geometry.layout
+    mtext = block.query("MTEXT").first
+    assert mtext.text == "300"
+
+
+def test_suppress_measurement_text(msp):
+    dim = msp.add_linear_dim(
+        base=(0, 2),
+        p1=(0, 0),
+        p2=(3, 0),
+    )
+    dim.set_text(" ")
+
+    block = dim.render().geometry.layout
+    assert len(block.query("MTEXT")) == 0  # no MTEXT entity expected
+
+
+@pytest.mark.parametrize(
+    "text,expected",
+    [
+        ("<>", "300"),
+        ("Ø <>", "Ø 300"),
+        ("<> cm", "300 cm"),
+        ("[ <> ]", "[ 300 ]"),
+        ("<> <>", "300 <>"),  # only the first "<>" will be replaced
+    ],
+)
+def test_override_measurement_text(msp, text, expected):
+    dim = msp.add_linear_dim(
+        base=(0, 2),
+        p1=(0, 0),
+        p2=(3, 0),
+    )
+    dim.set_text(text)
+
+    block = dim.render().geometry.layout
+    mtext = block.query("MTEXT").first
+    assert mtext.text == expected
+
+
+if __name__ == "__main__":
+    pytest.main([__file__])