LibWeb: Add a "select all" action to the Web::PageView

This works by finding the very first and very last LayoutText nodes
in the layout tree and then setting the selection bounds to those two
nodes. For some reason it gets glitchy if we set the very first and
very last *LayoutNode* as the selection bounds, but I didn't feel like
investigating that too closely right now.

Libraries/LibWeb/PageView.cpp

@@ -67,12 +67,51 @@ PageView::PageView()
     m_copy_action = GUI::CommonActions::make_copy_action([this](auto&) {
         GUI::Clipboard::the().set_data(selected_text(), "text/plain");
     });
+
+    m_select_all_action = GUI::CommonActions::make_select_all_action([this](auto&) {
+        select_all();
+    });
 }
 
 PageView::~PageView()
 {
 }
 
+void PageView::select_all()
+{
+    auto* layout_root = this->layout_root();
+    if (!layout_root)
+        return;
+
+    const LayoutNode* first_layout_node = layout_root;
+
+    for (;;) {
+        auto* next = first_layout_node->next_in_pre_order();
+        if (!next)
+            break;
+        first_layout_node = next;
+        if (is<LayoutText>(*first_layout_node))
+            break;
+    }
+
+    const LayoutNode* last_layout_node = first_layout_node;
+
+    for (const LayoutNode* layout_node = first_layout_node; layout_node; layout_node = layout_node->next_in_pre_order()) {
+        if (is<LayoutText>(*layout_node))
+            last_layout_node = layout_node;
+    }
+
+    ASSERT(first_layout_node);
+    ASSERT(last_layout_node);
+
+    int last_layout_node_index_in_node = 0;
+    if (is<LayoutText>(*last_layout_node))
+        last_layout_node_index_in_node = to<LayoutText>(*last_layout_node).text_for_rendering().length() - 1;
+
+    layout_root->selection().set({ first_layout_node, 0 }, { last_layout_node, last_layout_node_index_in_node });
+    update();
+}
+
 String PageView::selected_text() const
 {
     StringBuilder builder;

Libraries/LibWeb/PageView.h

@@ -73,8 +73,11 @@ public:
 
     virtual bool accepts_focus() const override { return true; }
 
+    GUI::Action& select_all_action() { return *m_select_all_action; }
     GUI::Action& copy_action() { return *m_copy_action; }
+
     String selected_text() const;
+    void select_all();
 
 private:
     PageView();
@@ -119,6 +122,7 @@ private:
     NonnullOwnPtr<Page> m_page;
 
     RefPtr<GUI::Action> m_copy_action;
+    RefPtr<GUI::Action> m_select_all_action;
 };
 
 }