LibGUI: Add GInputBox for getting a string from a modal dialog.

Use this to implement some of the toolbar actions in IRCClient. :^)

LibGUI/GInputBox.cpp

@@ -0,0 +1,76 @@
+#include <LibGUI/GInputBox.h>
+#include <LibGUI/GBoxLayout.h>
+#include <LibGUI/GLabel.h>
+#include <LibGUI/GButton.h>
+#include <LibGUI/GTextEditor.h>
+#include <stdio.h>
+
+GInputBox::GInputBox(const String& prompt, const String& title, GObject* parent)
+    : GDialog(parent)
+    , m_prompt(prompt)
+{
+    set_title(title);
+    build();
+}
+
+GInputBox::~GInputBox()
+{
+}
+
+void GInputBox::build()
+{
+    auto* widget = new GWidget;
+    set_main_widget(widget);
+
+    int text_width = widget->font().width(m_prompt);
+
+    set_rect(x(), y(), text_width + 80, 120);
+
+    widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
+    widget->set_fill_with_background_color(true);
+
+    widget->layout()->set_margins({ 8, 8, 8, 8 });
+    widget->layout()->set_spacing(8);
+
+    auto* label = new GLabel(m_prompt, widget);
+    label->set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);
+    label->set_preferred_size({ text_width, 16 });
+
+    auto* text_editor = new GTextEditor(GTextEditor::SingleLine, widget);
+    text_editor->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    text_editor->set_preferred_size({ 0, 16 });
+
+    auto* button_container_outer = new GWidget(widget);
+    button_container_outer->set_layout(make<GBoxLayout>(Orientation::Vertical));
+
+    auto* button_container_inner = new GWidget(button_container_outer);
+    button_container_inner->set_layout(make<GBoxLayout>(Orientation::Horizontal));
+    button_container_inner->layout()->set_spacing(8);
+
+    auto* cancel_button = new GButton(button_container_inner);
+    cancel_button->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    cancel_button->set_preferred_size({ 0, 16 });
+    cancel_button->set_caption("Cancel");
+    cancel_button->on_click = [&] (auto&) {
+        fprintf(stderr, "GInputBox: Cancel button clicked\n");
+        done(1);
+    };
+
+    auto* ok_button = new GButton(button_container_inner);
+    ok_button->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    ok_button->set_preferred_size({ 0, 16 });
+    ok_button->set_caption("OK");
+    ok_button->on_click = [&] (auto&) {
+        fprintf(stderr, "GInputBox: OK button clicked\n");
+        m_text_value = text_editor->text();
+        done(0);
+    };
+
+    text_editor->on_return_pressed = [&] (auto&) {
+        ok_button->click();
+    };
+    text_editor->on_escape_pressed = [&] (auto&) {
+        cancel_button->click();
+    };
+    text_editor->set_focus(true);
+}