From ecabcb5c58c3a43e30b49426fea9bfb766827e64 Mon Sep 17 00:00:00 2001
From: SmallJoker <mk939@ymail.com>
Date: Tue, 9 Sep 2025 20:04:40 +0200
Subject: [PATCH] IrrlichtMt: import scrollbar changes

---
 irr/include/CGUIEditBox.h   |  7 ++++++
 irr/include/IGUIScrollBar.h |  5 ++++
 irr/src/CGUIEditBox.cpp     | 49 +++++++++++++++++++++++++++++++++++++
 irr/src/CGUIScrollBar.h     |  3 +++
 4 files changed, 64 insertions(+)

diff --git a/irr/include/CGUIEditBox.h b/irr/include/CGUIEditBox.h
index 6fbb6ff607..44df3f8fbe 100644
--- a/irr/include/CGUIEditBox.h
+++ b/irr/include/CGUIEditBox.h
@@ -10,6 +10,9 @@
 
 namespace gui
 {
+
+class IGUIScrollBar;
+
 class CGUIEditBox : public IGUIEditBox
 {
 public:
@@ -157,6 +160,8 @@ protected:
 	void sendGuiEvent(EGUI_EVENT_TYPE type);
 	//! set text markers
 	void setTextMarkers(s32 begin, s32 end);
+	//! update the vertical scrollBar (visibilty & position)
+	void updateVScrollBar();
 
 	bool processKey(const SEvent &event);
 	//! KEY_LEFT / KEY_RIGHT inputs
@@ -193,6 +198,8 @@ protected:
 	s32 CursorPos;
 	s32 HScrollPos, VScrollPos; // scroll position in characters
 	u32 Max;
+	u32 VScrollBarWidth = 0;
+	IGUIScrollBar *VScrollBar = nullptr;
 
 	bool WordWrap = false,
 		MultiLine = false,
diff --git a/irr/include/IGUIScrollBar.h b/irr/include/IGUIScrollBar.h
index 89a75f619a..2da634c75a 100644
--- a/irr/include/IGUIScrollBar.h
+++ b/irr/include/IGUIScrollBar.h
@@ -51,6 +51,11 @@ public:
 
 	//! sets the current position of the scrollbar
 	virtual void setPos(s32 pos) = 0;
+
+	//! For automatic thumb scaling
+	/** Sets the full height (e.g. content to scroll), in pixels.
+	Set to 0 to disable (default). */
+	virtual void setPageSize(s32 size) = 0;
 };
 
 } // end namespace gui
diff --git a/irr/src/CGUIEditBox.cpp b/irr/src/CGUIEditBox.cpp
index a935463c72..a04cd22514 100644
--- a/irr/src/CGUIEditBox.cpp
+++ b/irr/src/CGUIEditBox.cpp
@@ -7,6 +7,7 @@
 #include "IGUISkin.h"
 #include "IGUIEnvironment.h"
 #include "IGUIFont.h"
+#include "IGUIScrollBar.h"
 #include "IVideoDriver.h"
 #include "rect.h"
 #include "os.h"
@@ -1512,4 +1513,52 @@ void CGUIEditBox::sendGuiEvent(EGUI_EVENT_TYPE type)
 	}
 }
 
+void CGUIEditBox::updateVScrollBar()
+{
+	if (!VScrollBar) {
+		return;
+	}
+
+	// OnScrollBarChanged(...)
+	if (VScrollBar->getPos() != VScrollPos) {
+		s32 deltaScrollY = VScrollBar->getPos() - VScrollPos;
+		CurrentTextRect.UpperLeftCorner.Y -= deltaScrollY;
+		CurrentTextRect.LowerRightCorner.Y -= deltaScrollY;
+
+		s32 scrollymax = getTextDimension().Height - FrameRect.getHeight();
+		if (scrollymax != VScrollBar->getMax()) {
+			// manage a newline or a deleted line
+			VScrollBar->setMax(scrollymax);
+			VScrollBar->setPageSize(s32(getTextDimension().Height));
+			calculateScrollPos();
+		} else {
+			// manage a newline or a deleted line
+			VScrollPos = VScrollBar->getPos();
+		}
+	}
+
+	// check if a vertical scrollbar is needed ?
+	if (getTextDimension().Height > (u32)FrameRect.getHeight()) {
+		FrameRect.LowerRightCorner.X -= VScrollBarWidth;
+
+		s32 scrollymax = getTextDimension().Height - FrameRect.getHeight();
+		if (scrollymax != VScrollBar->getMax()) {
+			VScrollBar->setMax(scrollymax);
+			VScrollBar->setPageSize(s32(getTextDimension().Height));
+		}
+
+		if (!VScrollBar->isVisible()) {
+			VScrollBar->setVisible(true);
+		}
+	} else {
+		if (VScrollBar->isVisible()) {
+			VScrollBar->setVisible(false);
+			VScrollPos = 0;
+			VScrollBar->setPos(0);
+			VScrollBar->setMax(1);
+			VScrollBar->setPageSize(s32(getTextDimension().Height));
+		}
+	}
+}
+
 } // end namespace gui
diff --git a/irr/src/CGUIScrollBar.h b/irr/src/CGUIScrollBar.h
index 4e3cb00e68..260e7b3113 100644
--- a/irr/src/CGUIScrollBar.h
+++ b/irr/src/CGUIScrollBar.h
@@ -59,6 +59,9 @@ public:
 	//! sets the position of the scrollbar
 	void setPos(s32 pos) override;
 
+	//! sets the content height to scroll
+	void setPageSize(s32 size) override { }
+
 	//! updates the rectangle
 	void updateAbsolutePosition() override;