From b4dfe96d85bb7e8e9ca202d6ff8a1a21d20ee3c4 Mon Sep 17 00:00:00 2001
From: nakst <>
Date: Tue, 14 Sep 2021 12:18:08 +0100
Subject: [PATCH] fix fast scroll glitches

---
 desktop/gui.cpp     | 6 +++++-
 kernel/graphics.cpp | 6 +++++-
 kernel/syscall.cpp  | 3 ++-
 kernel/windows.cpp  | 2 +-
 4 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/desktop/gui.cpp b/desktop/gui.cpp
index 7f1b2b8..a90c737 100644
--- a/desktop/gui.cpp
+++ b/desktop/gui.cpp
@@ -2830,6 +2830,10 @@ void ScrollPane::SetPosition(int axis, double newScroll, bool sendMovedMessage)
 	if (newScroll < 0) newScroll = 0;
 	else if (newScroll > limit[axis]) newScroll = limit[axis];
 	if (newScroll == position[axis]) return;
+
+	// Since we might be about to fast scroll, make sure the bits we are scrolling are valid.
+	UIWindowPaintNow(parent->window, nullptr, false);
+
 	double previous = position[axis];
 	position[axis] = newScroll;
 	if (bar[axis]) ScrollbarSetPosition(bar[axis], position[axis], false, false);
@@ -6089,7 +6093,7 @@ void EsElementRepaint(EsElement *element, const EsRectangle *region) {
 }
 
 void EsElementRepaintForScroll(EsElement *element, EsMessage *message) {
-	// TODO Support custom borders sizes.
+	// TODO Support custom border sizes.
 
 	EsRectangle borders = ES_RECT_4(element->internalOffsetLeft, element->internalOffsetRight, 
 			element->internalOffsetTop, element->internalOffsetBottom);
diff --git a/kernel/graphics.cpp b/kernel/graphics.cpp
index 140701b..1888870 100644
--- a/kernel/graphics.cpp
+++ b/kernel/graphics.cpp
@@ -222,7 +222,11 @@ void Surface::Scroll(EsRectangle region, ptrdiff_t delta, bool vertical) {
 				}
 			}
 		} else {
-			// TODO.
+			for (intptr_t i = region.t; i < region.b; i++) {
+				for (intptr_t j = region.r - 1; j >= region.l; j--) {
+					((uint32_t *) bits)[j - delta + i * stride / 4] = ((uint32_t *) bits)[j + i * stride / 4];
+				}
+			}
 		}
 	}
 }
diff --git a/kernel/syscall.cpp b/kernel/syscall.cpp
index d41d422..09a054b 100644
--- a/kernel/syscall.cpp
+++ b/kernel/syscall.cpp
@@ -505,6 +505,7 @@ SYSCALL_IMPLEMENT(ES_SYSCALL_WINDOW_SET_BITS) {
 	if (argument3 == WINDOW_SET_BITS_SCROLL_VERTICAL || argument3 == WINDOW_SET_BITS_SCROLL_HORIZONTAL) {
 		ptrdiff_t scrollDelta = argument2;
 		bool scrollVertical = argument3 == WINDOW_SET_BITS_SCROLL_VERTICAL;
+		EsRectangle originalRegion = region;
 
 		if (scrollVertical) {
 			if (scrollDelta < 0) region.b += scrollDelta;
@@ -522,7 +523,7 @@ SYSCALL_IMPLEMENT(ES_SYSCALL_WINDOW_SET_BITS) {
 				|| region.l >= region.r || region.t >= region.b) {
 		} else {
 			surface->Scroll(region, scrollDelta, scrollVertical);
-			window->Update(&region, true);
+			window->Update(&originalRegion, true);
 			window->queuedScrollUpdate = true;
 			// Don't update the screen until the rest of the window is painted.
 		}
diff --git a/kernel/windows.cpp b/kernel/windows.cpp
index 56d71f3..f8d66b8 100644
--- a/kernel/windows.cpp
+++ b/kernel/windows.cpp
@@ -7,7 +7,7 @@
 // Terminology:
 // 	Dynamic resize - flicker-free resizing in container windows with an embedded window owned by a separate process.
 // 	Direct update - paint first onto the video card's framebuffer, then onto the window manager's; used to reduce latency.
-// 	Fast scroll - scrolling by shifting the bits in the window's surface, rather than repainting the entire area. TODO This is currently a bit broken.
+// 	Fast scroll - scrolling by shifting the bits in the window's surface, rather than repainting the entire area.
 
 struct EmbeddedWindow {
 	void Destroy();