LibPDF: Allow operators to receive optional resources

Operators usually assume that the resources its operations will require
will be the Page's. This assumption breaks however when XObjects with
their own resources come into the picture (and maybe other cases too).
In that case, the XObject's resources take precedence, but they should
also contain the Page's resources. Because of this, one can safely use
the XObject resources alone when given, and default to the Page's if
not.

This commit adds all operator calls an extra argument with optional
resources, which will be fed by XObjects as necessary.

Author: rtobar

Userland/Libraries/LibPDF/Renderer.cpp

@@ -10,7 +10,7 @@
 #include <LibPDF/Renderer.h>
 
 #define RENDERER_HANDLER(name) \
-    PDFErrorOr<void> Renderer::handle_##name([[maybe_unused]] Vector<Value> const& args)
+    PDFErrorOr<void> Renderer::handle_##name([[maybe_unused]] Vector<Value> const& args, [[maybe_unused]] Optional<NonnullRefPtr<DictObject>> extra_resources)
 
 #define RENDERER_TODO(name)                                         \
     RENDERER_HANDLER(name)                                          \
@@ -118,20 +118,20 @@ PDFErrorOr<void> Renderer::render()
     return {};
 }
 
-PDFErrorOr<void> Renderer::handle_operator(Operator const& op)
+PDFErrorOr<void> Renderer::handle_operator(Operator const& op, Optional<NonnullRefPtr<DictObject>> extra_resources)
 {
     switch (op.type()) {
-#define V(name, snake_name, symbol)               \
-    case OperatorType::name:                      \
-        TRY(handle_##snake_name(op.arguments())); \
+#define V(name, snake_name, symbol)                                 \
+    case OperatorType::name:                                        \
+        MUST(handle_##snake_name(op.arguments(), extra_resources)); \
         break;
         ENUMERATE_OPERATORS(V)
 #undef V
     case OperatorType::TextNextLineShowString:
-        TRY(handle_text_next_line_show_string(op.arguments()));
+        MUST(handle_text_next_line_show_string(op.arguments()));
         break;
     case OperatorType::TextNextLineShowStringSetSpacing:
-        TRY(handle_text_next_line_show_string_set_spacing(op.arguments()));
+        MUST(handle_text_next_line_show_string_set_spacing(op.arguments()));
         break;
     }
 
@@ -204,9 +204,9 @@ RENDERER_TODO(set_flatness_tolerance)
 
 RENDERER_HANDLER(set_graphics_state_from_dict)
 {
-    VERIFY(m_page.resources->contains(CommonNames::ExtGState));
+    auto resources = extra_resources.value_or(m_page.resources);
     auto dict_name = MUST(m_document->resolve_to<NameObject>(args[0]))->name();
-    auto ext_gstate_dict = MUST(m_page.resources->get_dict(m_document, CommonNames::ExtGState));
+    auto ext_gstate_dict = MUST(resources->get_dict(m_document, CommonNames::ExtGState));
     auto target_dict = MUST(ext_gstate_dict->get_dict(m_document, dict_name));
     TRY(set_graphics_state_from_dict(target_dict));
     return {};
@@ -421,8 +421,9 @@ RENDERER_HANDLER(text_set_leading)
 
 RENDERER_HANDLER(text_set_font)
 {
+    auto resources = extra_resources.value_or(m_page.resources);
     auto target_font_name = MUST(m_document->resolve_to<NameObject>(args[0]))->name();
-    auto fonts_dictionary = MUST(m_page.resources->get_dict(m_document, CommonNames::Font));
+    auto fonts_dictionary = MUST(resources->get_dict(m_document, CommonNames::Font));
     auto font_dictionary = MUST(fonts_dictionary->get_dict(m_document, target_font_name));
 
     text_state().font_size = args[1].to_float();
@@ -527,14 +528,14 @@ RENDERER_TODO(type3_font_set_glyph_width_and_bbox)
 
 RENDERER_HANDLER(set_stroking_space)
 {
-    state().stroke_color_space = TRY(get_color_space(args[0], m_page.resources));
+    state().stroke_color_space = TRY(get_color_space(args[0], extra_resources.value_or(m_page.resources)));
     VERIFY(state().stroke_color_space);
     return {};
 }
 
 RENDERER_HANDLER(set_painting_space)
 {
-    state().paint_color_space = TRY(get_color_space(args[0], m_page.resources));
+    state().paint_color_space = TRY(get_color_space(args[0], extra_resources.value_or(m_page.resources)));
     VERIFY(state().paint_color_space);
     return {};
 }

Userland/Libraries/LibPDF/Renderer.h

@@ -97,13 +97,13 @@ class Renderer {
 
     PDFErrorOr<void> render();
 
-    PDFErrorOr<void> handle_operator(Operator const&);
+    PDFErrorOr<void> handle_operator(Operator const&, Optional<NonnullRefPtr<DictObject>> = {});
 #define V(name, snake_name, symbol) \
-    PDFErrorOr<void> handle_##snake_name(Vector<Value> const& args);
+    PDFErrorOr<void> handle_##snake_name(Vector<Value> const& args, Optional<NonnullRefPtr<DictObject>> = {});
     ENUMERATE_OPERATORS(V)
 #undef V
-    PDFErrorOr<void> handle_text_next_line_show_string(Vector<Value> const& args);
-    PDFErrorOr<void> handle_text_next_line_show_string_set_spacing(Vector<Value> const& args);
+    PDFErrorOr<void> handle_text_next_line_show_string(Vector<Value> const& args, Optional<NonnullRefPtr<DictObject>> = {});
+    PDFErrorOr<void> handle_text_next_line_show_string_set_spacing(Vector<Value> const& args, Optional<NonnullRefPtr<DictObject>> = {});
 
     void begin_path_paint();
     void end_path_paint();