From 29396415d58b0775d2ca1360362966c75dc4d255 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Wed, 15 Nov 2023 07:51:56 -0500
Subject: [PATCH] LibPDF: Add an initial implementation of type 3 glyph
 rendering

This is a very inefficient implementation: Every time a type 3 font
glyph is drawn, we parse its operator stream and execute all the
operators therein.

We'll want to instead cache the glyphs in bitmaps (at least in most
cases), like we do for other fonts. But it's a good first step, and
all the coordinate math seems to work in the files I've tested.

Good test files from pdfa dataset 0000.zip:

- 0000559.pdf page 1 (and 2): Has a non-default font matrix;
  text appears mirrored if the font matrix isn't handled correctly

- 0000425.pdf, page 1: Draws several glyphs in a single run;
  glyphs overlap if Renderer::render_type3_glyph() ignores the
  passed-in point

- 0000211.pdf, any page: Uses type 3 glyphs for all text.
  Good perf test (already "reasonably fast")

- 0000521.pdf, page 5 (or 7 or or 16): The little red flag in the
  purple box is a type 3 font glyph, and it's colored (which in part
  means the first operator is `d0`, while all the other documents above
  use `d1`)
---
 Userland/Libraries/LibPDF/Fonts/Type3Font.cpp | 10 ++++++----
 Userland/Libraries/LibPDF/Renderer.cpp        | 17 +++++++++++++++++
 Userland/Libraries/LibPDF/Renderer.h          |  3 +++
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibPDF/Fonts/Type3Font.cpp b/Userland/Libraries/LibPDF/Fonts/Type3Font.cpp
index 1cc3f14203..9ff43766b7 100644
--- a/Userland/Libraries/LibPDF/Fonts/Type3Font.cpp
+++ b/Userland/Libraries/LibPDF/Fonts/Type3Font.cpp
@@ -7,6 +7,7 @@
 #include <LibGfx/Painter.h>
 #include <LibPDF/CommonNames.h>
 #include <LibPDF/Fonts/Type3Font.h>
+#include <LibPDF/Renderer.h>
 
 namespace PDF {
 
@@ -53,7 +54,7 @@ void Type3Font::set_font_size(float)
 {
 }
 
-PDFErrorOr<void> Type3Font::draw_glyph(Gfx::Painter&, Gfx::FloatPoint, float, u8 char_code, Renderer const&)
+PDFErrorOr<void> Type3Font::draw_glyph(Gfx::Painter&, Gfx::FloatPoint point, float, u8 char_code, Renderer const& renderer)
 {
     // PDF 1.7 spec, 5.5.4 Type 3 Fonts:
     // "For each character code shown by a text-showing operator that uses a Type 3 font,
@@ -71,8 +72,9 @@ PDFErrorOr<void> Type3Font::draw_glyph(Gfx::Painter&, Gfx::FloatPoint, float, u8
         return {};
 
     // "3. Invokes the glyph description, as described below."
-    // FIXME
-
-    return Error { Error::Type::RenderingUnsupported, "Type3 fonts not yet implemented" };
+    // The Gfx::Painter isn't used because `renderer` paints to it already.
+    // FIXME: Do color things dependent on if the glyph data starts with d0 or d1.
+    // FIXME: Glyph caching.
+    return const_cast<Renderer&>(renderer).render_type3_glyph(point, *char_proc.value(), font_matrix(), m_resources);
 }
 }
diff --git a/Userland/Libraries/LibPDF/Renderer.cpp b/Userland/Libraries/LibPDF/Renderer.cpp
index b2ef3abc3a..1b36eed0da 100644
--- a/Userland/Libraries/LibPDF/Renderer.cpp
+++ b/Userland/Libraries/LibPDF/Renderer.cpp
@@ -1008,4 +1008,21 @@ Gfx::AffineTransform const& Renderer::calculate_text_rendering_matrix() const
     return m_text_rendering_matrix;
 }
 
+PDFErrorOr<void> Renderer::render_type3_glyph(Gfx::FloatPoint point, StreamObject const& glyph_data, Gfx::AffineTransform const& font_matrix, Optional<NonnullRefPtr<DictObject>> resources)
+{
+    ScopedState scoped_state { *this };
+
+    auto text_rendering_matrix = calculate_text_rendering_matrix();
+    text_rendering_matrix.set_translation(point);
+    state().ctm = text_rendering_matrix;
+    state().ctm.scale(text_state().font_size, text_state().font_size);
+    state().ctm.multiply(font_matrix);
+    m_text_rendering_matrix_is_dirty = true;
+
+    auto operators = TRY(Parser::parse_operators(m_document, glyph_data.bytes()));
+    for (auto& op : operators)
+        TRY(handle_operator(op, resources));
+    return {};
+}
+
 }
diff --git a/Userland/Libraries/LibPDF/Renderer.h b/Userland/Libraries/LibPDF/Renderer.h
index 02a174046b..c135593b4a 100644
--- a/Userland/Libraries/LibPDF/Renderer.h
+++ b/Userland/Libraries/LibPDF/Renderer.h
@@ -111,6 +111,9 @@ public:
     ALWAYS_INLINE TextState const& text_state() const { return state().text_state; }
 
     Gfx::AffineTransform const& calculate_text_rendering_matrix() const;
+
+    PDFErrorOr<void> render_type3_glyph(Gfx::FloatPoint, StreamObject const&, Gfx::AffineTransform const&, Optional<NonnullRefPtr<DictObject>>);
+
 private:
     Renderer(RefPtr<Document>, Page const&, RefPtr<Gfx::Bitmap>, RenderingPreferences);