A PDF's body puts each line of the page's text on a line of its own, not a heading and its paragraph run together with a space

MuPDF's text buffer joins the lines of one block with spaces, so a
typst page's heading and the text under it read as one line ("Page one
Hello normal PDF alpha."). The bridge now walks the structured text
itself, structure blocks included, and ends each line with a newline.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2 files changed, 40 insertions, 1 deletions

diff --git a/src/pdf_bridge.c b/src/pdf_bridge.c
index 6fdab46c..594db0f9 100644
--- a/src/pdf_bridge.c
+++ b/src/pdf_bridge.c
@@ -940,6 +940,31 @@ pardes_pdf_highlight_rows(
     return PARDES_PDF_OK;
 }
 
+/* A page's text, a line of it a line of the result: MuPDF's own buffer
+ * joins a block's lines with spaces, which ran a heading into the
+ * paragraph under it. Structure blocks are walked into. */
+static void
+pardes_append_stext_blocks(fz_context *ctx, fz_buffer *buffer, fz_stext_block *block)
+{
+    for (; block != NULL; block = block->next)
+    {
+        if (block->type == FZ_STEXT_BLOCK_STRUCT)
+        {
+            if (block->u.s.down != NULL)
+                pardes_append_stext_blocks(ctx, buffer, block->u.s.down->first_block);
+            continue;
+        }
+        if (block->type != FZ_STEXT_BLOCK_TEXT)
+            continue;
+        for (fz_stext_line *line = block->u.t.first_line; line != NULL; line = line->next)
+        {
+            for (fz_stext_char *ch = line->first_char; ch != NULL; ch = ch->next)
+                fz_append_rune(ctx, buffer, ch->c);
+            fz_append_byte(ctx, buffer, '\n');
+        }
+    }
+}
+
 int
 pardes_pdf_page_text(
     pardes_pdf_document *document,
@@ -961,7 +986,8 @@ pardes_pdf_page_text(
     fz_try(ctx)
     {
         pardes_pdf_cache_page(document, page_number, 1);
-        buffer = fz_new_buffer_from_stext_page(ctx, document->cached_text);
+        buffer = fz_new_buffer(ctx, 1024);
+        pardes_append_stext_blocks(ctx, buffer, document->cached_text->first_block);
         len = fz_buffer_storage(ctx, buffer, &data);
     }
     fz_catch(ctx)
diff --git a/test/pdf.zig b/test/pdf.zig
index d91f50a7..727a1515 100644
--- a/test/pdf.zig
+++ b/test/pdf.zig
@@ -352,6 +352,19 @@ test "a +PdfSections row's first number is the page: a section not there, or on
     }
 }
 
+test "a PDF's body puts each line of its text on a line of its own, never a heading run into the text under it" {
+    if (!pdf_enabled or platform == .web) return;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const p = try PdfLinkTests.init(tmp);
+    defer p.deinit();
+    const text = p.panes[0].?.pdf.?.ensureText(p.pdf_gpa);
+    // The page's three text runs, each its own line.
+    try std.testing.expect(std.mem.indexOf(u8, text, "target.txt\n") != null);
+    try std.testing.expect(std.mem.indexOf(u8, text, "https://example.com/same\n") != null);
+    try std.testing.expect(std.mem.indexOf(u8, text, "label\n") != null);
+}
+
 test "PdfSections Look follows the exact owning PDF, not an equal path" {
     if (!pdf_enabled or platform == .web) return;
     const gpa = std.testing.allocator;