From b5145b9596807b62514de6e5c467f76342f47724 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Tue, 3 May 2022 14:24:14 +0300
Subject: [PATCH] Support on_scroll event in ui::scroller

---
 libs/ui/include/psemek/ui/scroller.hpp | 2 ++
 libs/ui/source/scroller.cpp            | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/libs/ui/include/psemek/ui/scroller.hpp b/libs/ui/include/psemek/ui/scroller.hpp
index c764c799..ce62ecca 100644
--- a/libs/ui/include/psemek/ui/scroller.hpp
+++ b/libs/ui/include/psemek/ui/scroller.hpp
@@ -40,6 +40,8 @@ namespace psemek::ui
 
 	protected:
 
+		virtual void on_scroll(geom::vector<float, 2> const & delta);
+
 		virtual float width() const;
 		virtual geom::box<float, 2> visible_range() const;
 
diff --git a/libs/ui/source/scroller.cpp b/libs/ui/source/scroller.cpp
index 74c2cddf..c9700bcb 100644
--- a/libs/ui/source/scroller.cpp
+++ b/libs/ui/source/scroller.cpp
@@ -53,8 +53,10 @@ namespace psemek::ui
 					float c = geom::unlerp<float>(box[0], e.position[0]);
 					c = geom::clamp(c, {0.f, 1.f});
 
+					auto old = shift_tgt_;
 					shift_tgt_[0] = shape_.box[0].length() / 2.f - c * sc[0].min;
 					clamp_shift();
+					on_scroll(shift_tgt_ - old);
 				}
 				break;
 			}
@@ -85,8 +87,10 @@ namespace psemek::ui
 					float c = geom::unlerp<float>(box[1], e.position[1]);
 					c = geom::clamp(c, {0.f, 1.f});
 
+					auto old = shift_tgt_;
 					shift_tgt_[1] = shape_.box[1].length() / 2.f - c * sc[1].min;
 					clamp_shift();
+					on_scroll(shift_tgt_ - old);
 				}
 				break;
 			}
@@ -182,8 +186,10 @@ namespace psemek::ui
 				delta[0] = e.delta;
 			}
 
+			auto old = shift_tgt_;
 			shift_tgt_ += delta * 50.f;
 			clamp_shift();
+			on_scroll(shift_tgt_ - old);
 			post_reshape();
 			return true;
 		}
@@ -291,6 +297,9 @@ namespace psemek::ui
 		p.end_stencil();
 	}
 
+	void scroller::on_scroll(geom::vector<float, 2> const &)
+	{}
+
 	float scroller::width() const
 	{
 		return 0;