Pango plugin: fix: do not judge empty lines as failing during text layout

Text layout plugins are expected to return failure as `false` from their
`textlayout` function. The Pango plugin considered failure to be anything that
resulted in a horizontal layout width of 0. However, this is not a failure in
the case where the text being laid out is the empty string; its horizontal width
is expected to be 0.

The effect of this was that HTML-like strings like `<<br/>1>` were judged to
fail during text layout and a (redundant) estimation of their text width was
performed. This seems to have been a latent bug present since commit
ad82ef8613b0731806b81f9c0047d0cbf6745470 (~July 2007). This recently became more
visible due to commit 7aa0dcc03ea20b544b2463d97fe4a78af699589c that introduced
warnings during text width estimation if a fallback metric needed to be used.
Users were now presented with “Warning: no hard-coded metrics” when using fonts
that Pango knew of and should not have needed estimation in the first place.

This fix makes the Pango plugin consider 0 width for the layout of an empty
string to be successful. To be clear, this commit is both a functional fix and a
performance improvement.

Gitlab: fixes #2179

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec3c3f614852b423ff883ed80a660b036fe8da94..5484c1d024350b9dfa9263f0d0a3a966173e863c 100644 (file)
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   functions without corrupting their content. Some cases of this were a
   regression in Graphviz 2.46.0. Other cases have existed since the first
   release of `gvpr`. #2185
+- spurious "no hard-coded metrics" warnings on labels with empty lines #2179
 
 ## [3.0.0] – 2022-02-26
 

diff --git a/plugin/pango/gvtextlayout_pango.c b/plugin/pango/gvtextlayout_pango.c
index 3d54670c132371bc97d1a42794e09c4e3431ca23..39e03cb3ee8cde900bf5332d0e75a089a5fec977 100644 (file)
--- a/plugin/pango/gvtextlayout_pango.c
+++ b/plugin/pango/gvtextlayout_pango.c
@@ -289,7 +289,7 @@ static bool pango_textlayout(textspan_t * span, char **fontpath)
     /* The distance below midline for y centering of text strings */
     span->yoffset_centerline = 0.2 * span->font->size;
 
-    return logical_rect.width != 0;
+    return logical_rect.width != 0 || strcmp(text, "") == 0;
 }
 
 static gvtextlayout_engine_t pango_textlayout_engine = {

diff --git a/rtest/test_regression.py b/rtest/test_regression.py
index 679d4fddc6a1e1fbe13c6127c4b46296ff2677a1..cc46c2c60f38bc9172ea1d9bda5f065eadb5a3af 100644 (file)
--- a/rtest/test_regression.py
+++ b/rtest/test_regression.py
@@ -1353,7 +1353,6 @@ def test_2138(examine: str):
     assert "// tok[7]    >>012<<   should NOT include trailing spaces or "     \
       "junk chars" in result, "token 012 not found or has trailing garbage"
 
-@pytest.mark.xfail(strict=True) # FIXME
 def test_2179():
   """
   processing a label with an empty line should not yield a warning