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LibGUI: Add a AutoScroll timer to AbstractScrollableWidget

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This commit adds a timer to AbstractScrollableWidget that can be used
when implementing automatic scrolling. By overriding
on_automatic_scrolling_timer_fired() we can calculate the scrolling
delta when dragging objects, and redraw as needed. A helper function,
automatic_scroll_delta_from_position() gives us a delta that
we can use to calculate speed and direction. By default
m_autoscroll_threshold is 20 pixels from the edge, and gives a linear
change in scroll delta.
This commit is contained in:
Marcus Nilsson 2021-09-16 19:00:09 +02:00 • committed by Andreas Kling
parent 522119ab95
commit eec411c508
2 changed files with 47 additions and 0 deletions
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8
Userland/Libraries/LibGUI/AbstractScrollableWidget.h
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@ -51,6 +51,9 @@ public:
void scroll_to_top();
void scroll_to_bottom();
void set_automatic_scrolling_timer(bool active);
Gfx::IntPoint automatic_scroll_delta_from_position(const Gfx::IntPoint&) const;
int width_occupied_by_vertical_scrollbar() const;
int height_occupied_by_horizontal_scrollbar() const;
@ -71,6 +74,7 @@ protected:
virtual void did_scroll() { }
void set_content_size(const Gfx::IntSize&);
void set_size_occupied_by_fixed_elements(const Gfx::IntSize&);
virtual void on_automatic_scrolling_timer_fired() {};
private:
class AbstractScrollableWidgetScrollbar final : public Scrollbar {
@ -103,6 +107,10 @@ private:
Gfx::IntSize m_size_occupied_by_fixed_elements;
bool m_scrollbars_enabled { true };
bool m_should_hide_unnecessary_scrollbars { false };
RefPtr<Core::Timer> m_automatic_scrolling_timer;
bool m_active_scrolling_enabled { false };
int m_autoscroll_threshold { 20 };
};
}