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LibPDF: Mark text rendering matrix as dirty after TJ numbers

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Mostly because I audited all places that assigned to `m_text_matrix`
after #22760.

This one is very difficult to trigger in practice.

`show_text()` marks the text rendering matrix dirty already,
so this only has an effect if the `TJ` array starts with a
number, and the matrix isn't marked dirty going in.

`Tm` caches the text rendering matrix, so I changed text.pdf
to contain:

```
1 0 0 1 45 130 Tm
[ 200 (Hello) -2000 (World) ] TJ T*
```

This first sets an x offset of 5 (on top of the normal 40), and
then undoes it (`200` is multiplied by font size (25) / -1000,
and `200 * 25 / -1000` is -5). Before this change, the topmost
"Hello World" ended up slightly indented.

Likely no behavior change in practice, but makes the code easier
to understand, and maybe it helps in the wild somewhere.
This commit is contained in:
Nico Weber 2024-01-14 21:36:50 -05:00 committed by Sam Atkins
parent f23f5dcd62
commit 9a93f677f4
Notes: sideshowbarker 2024-07-17 12:02:22 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/9a93f677f4
Pull-request: https://github.com/SerenityOS/serenity/pull/22761
2 changed files with 16 additions and 40 deletions
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54
Tests/LibPDF/text.pdf
View file

@ -2,77 +2,51 @@
%µ¶
1 0 obj
<<
/Type /Catalog
/Pages 2 0 R
>>
<</Type/Catalog/Pages 2 0 R>>
endobj
2 0 obj
<<
/Type /Pages
/Kids [ 3 0 R ]
/Count 1
>>
<</Type/Pages/Kids[3 0 R]/Count 1>>
endobj
3 0 obj
<<
/Type /Page
/Parent 2 0 R
/MediaBox [ 0 0 525 250 ]
/Contents 4 0 R
/Resources <<
/Font <<
/F1 5 0 R
>>
>>
>>
<</Type/Page/Parent 2 0 R/MediaBox[0 0 525 250]/Contents 4 0 R/Resources<</Font<</F1 5 0 R>>>>>>
endobj
4 0 obj
<<
/Length 236
>>
<</Length 291>>
stream
BT
/F1 24 Tf
/F1 25 Tf
-30 TL
40 40 Td
[ (Hello) -2000 (World) ] TJ T*
[ (Hello) -1000 -1000 (World) ] TJ T*
[ (Hello) -1000 ] TJ [ -1000 ] TJ [ (World) ] TJ T*
1 0 0 1 45 130 Tm [ 200 (Hello) -2000 (World) ] TJ T*
(should be the same on all lines:) '
(The distance between "Hello" and "World") '
ET
endstream
endobj
5 0 obj
<<
/Type /Font
/Subtype /Type1
/Name /F1
/BaseFont /Helvetica
/Encoding /MacRomanEncoding
>>
<</Type/Font/Subtype/Type1/Name/F1/BaseFont/Helvetica/Encoding/MacRomanEncoding>>
endobj
xref
0 6
0000000000 65536 f
0000000016 00000 n
0000000070 00000 n
0000000136 00000 n
0000000291 00000 n
0000000581 00000 n
0000000062 00000 n
0000000114 00000 n
0000000227 00000 n
0000000568 00000 n
trailer
<<
/Size 6
/Root 1 0 R
>>
<</Size 6/Root 1 0 R>>
startxref
700
666
%%EOF

2
Userland/Libraries/LibPDF/Renderer.cpp
View file

@ -572,9 +572,11 @@ RENDERER_HANDLER(text_show_string_array)
if (element.has<int>()) {
float shift = (float)element.get<int>() / 1000.0f;
m_text_matrix.translate(-shift * text_state().font_size * text_state().horizontal_scaling, 0.0f);
m_text_rendering_matrix_is_dirty = true;
} else if (element.has<float>()) {
float shift = element.get<float>() / 1000.0f;
m_text_matrix.translate(-shift * text_state().font_size * text_state().horizontal_scaling, 0.0f);
m_text_rendering_matrix_is_dirty = true;
} else {
auto str = element.get<NonnullRefPtr<Object>>()->cast<StringObject>()->string();
TRY(show_text(str));