fix(html): a pdf's selection shows the text it marks

CHANGELOG.md

@@ -16,6 +16,11 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- **Fix**: selecting text in a pdf view hid the words it selected. The
+  `::selection` background v7.2.0 states is `Highlight`, which is opaque, and
+  the layer carrying it paints over the glyph layer. It is see-through now, so
+  the text reads through its own selection.
+
 ## v7.2.0 - 2026-09-20
 
 - **Fix**: a pdf underline and squiggle were drawn through the text rather than

src/odr/internal/html/pdf_file.cpp

@@ -1819,9 +1819,12 @@ class HtmlServiceImpl final : public HtmlService {
       out.out() << ".i{color:transparent;font-family:sf,sans-serif}";
       // A selection paints text in the highlight's own colour, which beats
       // `transparent` and shows this layer over the glyphs it stands for. An
-      // author `::selection` drops the UA background, so state that too.
-      out.out() << ".i::selection,.i *::selection"
-                   "{color:transparent;background-color:Highlight}";
+      // author `::selection` drops the UA background, so state that too - and
+      // state it see-through, because this layer paints over the glyph one.
+      out.out()
+          << ".i::selection,.i *::selection"
+             "{color:transparent;background-color:rgba(70,130,220,.32);"
+             "background-color:color-mix(in srgb,Highlight 45%,transparent)}";
       // Selection-layer run span. `overflow:hidden` clips a wider system font;
       // `.t`'s inherited `pre` blocks wrapping while preserving a run's own
       // leading/trailing space, which is real PDF content.
@@ -2294,10 +2297,12 @@ class HtmlServiceImpl final : public HtmlService {
                    "color:transparent;vertical-align:baseline}";
       // As `.i` in the dual layer above, with `*` reaching a run's own span
       // and a search `mark`.
-      out.out() << ".i::selection,.i *::selection,"
-                   ".ov::selection,.ov *::selection,"
-                   ".sp::selection,.sp *::selection"
-                   "{color:transparent;background-color:Highlight}";
+      out.out()
+          << ".i::selection,.i *::selection,"
+             ".ov::selection,.ov *::selection,"
+             ".sp::selection,.sp *::selection"
+             "{color:transparent;background-color:rgba(70,130,220,.32);"
+             "background-color:color-mix(in srgb,Highlight 45%,transparent)}";
       // A hit in the overlay is clipped away with it, so the glyphs it belongs
       // to carry the highlight instead - the whole run of them, which is as
       // narrow as the overlay can say.
@@ -2872,9 +2877,11 @@ class HtmlServiceImpl final : public HtmlService {
       rule("fn", "color:transparent;");
       // The same guard for a line the embedded font makes invisible; the dual
       // layer's `fnN` rides a `user-select:none` run and needs none.
-      font_styles += ".fn" + n + "::selection,.fn" + n +
-                     " *::selection"
-                     "{color:transparent;background-color:Highlight}";
+      font_styles +=
+          ".fn" + n + "::selection,.fn" + n +
+          " *::selection"
+          "{color:transparent;background-color:rgba(70,130,220,.32);"
+          "background-color:color-mix(in srgb,Highlight 45%,transparent)}";
     }
   }