HackStudio: Show documentation preview in tooltip on identifier hover

When hovering over a C++ token that we have a man page for, we now show
the man page in a tooltip window.

This feels rather bulky at the moment, but the basic mechanism is quite
neat and just needs a bunch of tuning.

3 files changed, 127 insertions, 7 deletions

diff --git a/DevTools/HackStudio/Editor.cpp b/DevTools/HackStudio/Editor.cpp
index fe0666d48f..1ea850b781 100644
--- a/DevTools/HackStudio/Editor.cpp
+++ b/DevTools/HackStudio/Editor.cpp
@@ -1,7 +1,33 @@
 #include "Editor.h"
 #include "EditorWrapper.h"
+#include <AK/FileSystemPath.h>
+#include <LibCore/CDirIterator.h>
+#include <LibCore/CFile.h>
+#include <LibGUI/GApplication.h>
 #include <LibGUI/GPainter.h>
 #include <LibGUI/GScrollBar.h>
+#include <LibGUI/GWindow.h>
+#include <LibHTML/DOM/ElementFactory.h>
+#include <LibHTML/DOM/HTMLHeadElement.h>
+#include <LibHTML/DOM/Text.h>
+#include <LibHTML/HtmlView.h>
+#include <LibHTML/Parser/HTMLParser.h>
+#include <LibMarkdown/MDDocument.h>
+
+Editor::Editor(GWidget* parent)
+    : GTextEditor(GTextEditor::MultiLine, parent)
+{
+    m_documentation_tooltip_window = GWindow::construct();
+    m_documentation_tooltip_window->set_rect(0, 0, 500, 400);
+    m_documentation_tooltip_window->set_window_type(GWindowType::Tooltip);
+
+    m_documentation_html_view = HtmlView::construct(nullptr);
+    m_documentation_tooltip_window->set_main_widget(m_documentation_html_view);
+}
+
+Editor::~Editor()
+{
+}
 
 EditorWrapper& Editor::wrapper()
 {
@@ -20,7 +46,7 @@ void Editor::focusin_event(CEvent& event)
     GTextEditor::focusin_event(event);
 }
 
-void Editor::focusout_event(CEvent & event)
+void Editor::focusout_event(CEvent& event)
 {
     wrapper().set_editor_has_focus({}, false);
     GTextEditor::focusout_event(event);
@@ -42,3 +68,93 @@ void Editor::paint_event(GPaintEvent& event)
         painter.draw_rect(rect, Color::from_rgb(0x955233));
     }
 }
+
+static HashMap<String, String>& man_paths()
+{
+    static HashMap<String, String> paths;
+    if (paths.is_empty()) {
+        // FIXME: This should also search man3, possibly other places..
+        CDirIterator it("/usr/share/man/man2", CDirIterator::Flags::SkipDots);
+        while (it.has_next()) {
+            auto path = String::format("/usr/share/man/man2/%s", it.next_path().characters());
+            auto title = FileSystemPath(path).title();
+            paths.set(title, path);
+        }
+    }
+
+    return paths;
+}
+
+void Editor::show_documentation_tooltip_if_available(const String& hovered_token, const Point& screen_location)
+{
+    auto it = man_paths().find(hovered_token);
+    if (it == man_paths().end()) {
+        dbg() << "no man path for " << hovered_token;
+        m_documentation_tooltip_window->hide();
+        return;
+    }
+
+    dbg() << "opening " << it->value;
+    auto file = CFile::construct(it->value);
+    if (!file->open(CFile::ReadOnly)) {
+        dbg() << "failed to open " << it->value << " " << file->error_string();
+        return;
+    }
+
+    MDDocument man_document;
+    bool success = man_document.parse(file->read_all());
+
+    if (!success) {
+        dbg() << "failed to parse markdown";
+        return;
+    }
+
+    auto html_text = man_document.render_to_html();
+
+    auto html_document = parse_html(html_text);
+    if (!html_document) {
+        dbg() << "failed to parse HTML";
+        return;
+    }
+
+    // FIXME: LibHTML needs a friendlier DOM manipulation API. Something like innerHTML :^)
+    auto style_element = create_element(*html_document, "style");
+    style_element->append_child(adopt(*new Text(*html_document, "body { background-color: #dac7b5; }")));
+
+    // FIXME: This const_cast should not be necessary.
+    auto* head_element = const_cast<HTMLHeadElement*>(html_document->head());
+    ASSERT(head_element);
+    head_element->append_child(style_element);
+
+    m_documentation_html_view->set_document(html_document);
+    m_documentation_tooltip_window->move_to(screen_location.translated(4, 4));
+    m_documentation_tooltip_window->show();
+}
+
+void Editor::mousemove_event(GMouseEvent& event)
+{
+    GTextEditor::mousemove_event(event);
+
+    if (document().spans().is_empty())
+        return;
+
+    auto text_position = text_position_at(event.position());
+    if (!text_position.is_valid()) {
+        GApplication::the().hide_tooltip();
+        return;
+    }
+
+    for (auto& span : document().spans()) {
+        if (span.range.contains(text_position)) {
+            auto adjusted_range = span.range;
+            adjusted_range.end().set_column(adjusted_range.end().column() + 1);
+            auto hovered_span_text = document().text_in_range(adjusted_range);
+#ifdef EDITOR_DEBUG
+            dbg() << "Hovering: " << adjusted_range << " \"" << hovered_span_text << "\"";
+#endif
+            show_documentation_tooltip_if_available(hovered_span_text, event.position().translated(screen_relative_rect().location()));
+            return;
+        }
+    }
+    GApplication::the().hide_tooltip();
+}
diff --git a/DevTools/HackStudio/Editor.h b/DevTools/HackStudio/Editor.h
index 92858b9e69..9d4a9e93ff 100644
--- a/DevTools/HackStudio/Editor.h
+++ b/DevTools/HackStudio/Editor.h
@@ -3,11 +3,12 @@
 #include <LibGUI/GTextEditor.h>
 
 class EditorWrapper;
+class HtmlView;
 
 class Editor final : public GTextEditor {
     C_OBJECT(Editor)
 public:
-    virtual ~Editor() override {}
+    virtual ~Editor() override;
 
     Function<void()> on_focus;
 
@@ -18,9 +19,12 @@ private:
     virtual void focusin_event(CEvent&) override;
     virtual void focusout_event(CEvent&) override;
     virtual void paint_event(GPaintEvent&) override;
+    virtual void mousemove_event(GMouseEvent&) override;
 
-    Editor(GWidget* parent)
-        : GTextEditor(GTextEditor::MultiLine, parent)
-    {
-    }
+    void show_documentation_tooltip_if_available(const String&, const Point& screen_location);
+
+    explicit Editor(GWidget* parent);
+
+    RefPtr<GWindow> m_documentation_tooltip_window;
+    RefPtr<HtmlView> m_documentation_html_view;
 };
diff --git a/DevTools/HackStudio/Makefile b/DevTools/HackStudio/Makefile
index c92fd15e1b..8d874da8cf 100644
--- a/DevTools/HackStudio/Makefile
+++ b/DevTools/HackStudio/Makefile
@@ -19,7 +19,7 @@ DEFINES += -DUSERLAND
 all: $(APP)
 
 $(APP): $(OBJS)
-	$(LD) -o $(APP) $(LDFLAGS) $(OBJS) -lvt -lgui -ldraw -lthread -lcore -lc
+	$(LD) -o $(APP) $(LDFLAGS) $(OBJS) -lvt -lhtml -lmarkdown -lgui -ldraw -lthread -lcore -lc
 
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<