LibGUI: Factor out scrolling logic from GTableView into a GScrollableWidget.

This then becomes the base class for GTableView. I'd like to share as much
code as possible with GTextEditor and any other scrollable widgets.

1 files changed, 98 insertions, 0 deletions

diff --git a/LibGUI/GScrollableWidget.cpp b/LibGUI/GScrollableWidget.cpp
new file mode 100644
index 0000000000..5f0689d531
--- /dev/null
+++ b/LibGUI/GScrollableWidget.cpp
@@ -0,0 +1,98 @@
+#include <LibGUI/GScrollableWidget.h>
+#include <LibGUI/GScrollBar.h>
+
+GScrollableWidget::GScrollableWidget(GWidget* parent)
+    : GWidget(parent)
+{
+    m_vertical_scrollbar = new GScrollBar(Orientation::Vertical, this);
+    m_vertical_scrollbar->set_step(4);
+    m_vertical_scrollbar->on_change = [this] (int) {
+        update();
+    };
+
+    m_horizontal_scrollbar = new GScrollBar(Orientation::Horizontal, this);
+    m_horizontal_scrollbar->set_step(4);
+    m_horizontal_scrollbar->set_big_step(30);
+    m_horizontal_scrollbar->on_change = [this] (int) {
+        update();
+    };
+
+    m_corner_widget = new GWidget(this);
+    m_corner_widget->set_fill_with_background_color(true);
+}
+
+GScrollableWidget::~GScrollableWidget()
+{
+}
+
+void GScrollableWidget::resize_event(GResizeEvent& event)
+{
+    update_scrollbar_ranges();
+
+    m_vertical_scrollbar->set_relative_rect(event.size().width() - m_vertical_scrollbar->preferred_size().width(), 0, m_vertical_scrollbar->preferred_size().width(), event.size().height() - m_horizontal_scrollbar->preferred_size().height());
+    m_horizontal_scrollbar->set_relative_rect(0, event.size().height() - m_horizontal_scrollbar->preferred_size().height(), event.size().width() - m_vertical_scrollbar->preferred_size().width(), m_horizontal_scrollbar->preferred_size().height());
+
+    m_corner_widget->set_visible(m_vertical_scrollbar->is_visible() && m_horizontal_scrollbar->is_visible());
+    if (m_corner_widget->is_visible()) {
+        Rect corner_rect { m_horizontal_scrollbar->rect().right() + 1, m_vertical_scrollbar->rect().bottom() + 1, m_horizontal_scrollbar->height(), m_vertical_scrollbar->width() };
+        m_corner_widget->set_relative_rect(corner_rect);
+    }
+}
+
+void GScrollableWidget::update_scrollbar_ranges()
+{
+    int available_height = height() - m_size_occupied_by_fixed_elements.height() - m_horizontal_scrollbar->height();
+    int excess_height = max(0, m_content_size.height() - available_height);
+    m_vertical_scrollbar->set_range(0, excess_height);
+
+    int available_width = width() - m_size_occupied_by_fixed_elements.width() - m_vertical_scrollbar->width();
+    int excess_width = max(0, m_content_size.width() - available_width);
+    m_horizontal_scrollbar->set_range(0, excess_width);
+
+    m_vertical_scrollbar->set_big_step(visible_content_rect().height() - m_vertical_scrollbar->step());
+}
+
+void GScrollableWidget::set_content_size(const Size& size)
+{
+    if (m_content_size == size)
+        return;
+    m_content_size = size;
+    update_scrollbar_ranges();
+}
+
+void GScrollableWidget::set_size_occupied_by_fixed_elements(const Size& size)
+{
+    if (m_size_occupied_by_fixed_elements == size)
+        return;
+    m_size_occupied_by_fixed_elements = size;
+    update_scrollbar_ranges();
+}
+
+Rect GScrollableWidget::visible_content_rect() const
+{
+    return {
+        m_horizontal_scrollbar->value(),
+        m_vertical_scrollbar->value(),
+        width() - m_vertical_scrollbar->width(),
+        height() - m_size_occupied_by_fixed_elements.height() - m_horizontal_scrollbar->height()
+    };
+}
+
+void GScrollableWidget::scroll_into_view(const Rect& rect, Orientation orientation)
+{
+    auto visible_content_rect = this->visible_content_rect();
+    if (visible_content_rect.contains(rect))
+        return;
+
+    if (orientation == Orientation::Vertical) {
+        if (rect.top() < visible_content_rect.top())
+            m_vertical_scrollbar->set_value(rect.top());
+        else if (rect.bottom() > visible_content_rect.bottom())
+            m_vertical_scrollbar->set_value(rect.bottom() - visible_content_rect.height());
+    } else {
+        if (rect.left() < visible_content_rect.left())
+            m_horizontal_scrollbar->set_value(rect.left());
+        else if (rect.right() > visible_content_rect.right())
+            m_horizontal_scrollbar->set_value(rect.right() - visible_content_rect.width());
+    }
+}