Attachment 183655 Details for Bug 143209 – Patch that fixes the bug. Developed against libreoffice-core commit 0eec6d44c65f895c6fe2172792717418627db05d.

[patch] Patch that fixes the bug. Developed against libreoffice-core commit 0eec6d44c65f895c6fe2172792717418627db05d.

0001-vcl-track-partial-scroll-deltas.patch (text/plain), 5.95 KB, created by jeyov45316 on 2022-11-18 03:52:06 UTC

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Creator: jeyov45316

Created: 2022-11-18 03:52:06 UTC

Size: 5.95 KB

patch

obsolete

>From 35c4a884dc3ccf9013b4caa650b96e08e66136dd Mon Sep 17 00:00:00 2001
>From: Jonas Eyov <jeyov45316@singalore.com>
>Date: Fri, 18 Nov 2022 03:40:57 +0000
>Subject: [PATCH] vcl: track partial scroll deltas
>
>previously, Window::HandleScrollCommand only checked each event for
>being a large enough scroll to advance one unit. this happened in
>lcl_HandleScrollHelper by way of o3tl::saturating_cast, which meant
>that nonzero upward/leftward scrolls were always worth at least one
>unit, while downward/rightward scrolls needed to be larger than 1 to
>count.
>
>now, we accumulate partial scroll offsets in WindowImpl and perfor a
>saturating cast on the absolute value, so behavior is symmetric and
>sensitive to accumulated small scroll values. this feels smoother
>and is more correct.
>
>Fixes: https://bugs.documentfoundation.org/show_bug.cgi
>
>Change-Id: Id3692d14edd45ed26f2952e3418e4d82806e1fc4
>---
> vcl/inc/window.h              |  2 ++
> vcl/source/window/window.cxx  |  2 ++
> vcl/source/window/window2.cxx | 38 +++++++++++++++++++++--------------
> 3 files changed, 27 insertions(+), 15 deletions(-)
>
>diff --git a/vcl/inc/window.h b/vcl/inc/window.h
>index 639bee80e..64f404d73 100644
>--- a/vcl/inc/window.h
>+++ b/vcl/inc/window.h
>@@ -256,6 +256,8 @@ public:
>     vcl::Cursor*        mpCursor;
>     PointerStyle        maPointer;
>     Fraction            maZoom;
>+    double              partialScrollX;
>+    double              partialScrollY;
>     OUString            maText;
>     std::optional<vcl::Font>
>                         mpControlFont;
>diff --git a/vcl/source/window/window.cxx b/vcl/source/window/window.cxx
>index 4705fe516..05366d7fb 100644
>--- a/vcl/source/window/window.cxx
>+++ b/vcl/source/window/window.cxx
>@@ -590,6 +590,8 @@ WindowImpl::WindowImpl( vcl::Window& rWindow, WindowType nType )
> {
>     mxOutDev = VclPtr<vcl::WindowOutputDevice>::Create(rWindow);
>     maZoom                              = Fraction( 1, 1 );
>+    partialScrollX                      = 0.0;
>+    partialScrollY                      = 0.0;
>     maWinRegion                         = vcl::Region(true);
>     maWinClipRegion                     = vcl::Region(true);
>     mpWinData                           = nullptr;                      // Extra Window Data, that we don't need for all windows
>diff --git a/vcl/source/window/window2.cxx b/vcl/source/window/window2.cxx
>index b6c4ee254..06dbdd319 100644
>--- a/vcl/source/window/window2.cxx
>+++ b/vcl/source/window/window2.cxx
>@@ -598,12 +598,14 @@ tools::Long Window::GetDrawPixel( OutputDevice const * pDev, tools::Long nPixels
>     return nP;
> }
> 
>-static void lcl_HandleScrollHelper( Scrollable* pScrl, double nN, bool isMultiplyByLineSize )
>+// returns how much was actually scrolled (so that abs(retval) <= abs(nN))
>+static double lcl_HandleScrollHelper( Scrollable* pScrl, double nN, bool isMultiplyByLineSize )
> {
>     if (!pScrl || !nN || pScrl->Inactive())
>-        return;
>+        return 0.0;
> 
>     tools::Long nNewPos = pScrl->GetThumbPos();
>+    double scrolled = nN;
> 
>     if ( nN == double(-LONG_MAX) )
>         nNewPos += pScrl->GetPageSize();
>@@ -616,13 +618,23 @@ static void lcl_HandleScrollHelper( Scrollable* pScrl, double nN, bool isMultipl
>             nN*=pScrl->GetLineSize();
>         }
> 
>-        const double fVal = nNewPos - nN;
>+        // compute how many quantized units to scroll
>+        tools::Long magnitude = o3tl::saturating_cast<tools::Long>(abs(nN));
>+        tools::Long change = copysign(magnitude, nN);
>+
>+        nNewPos = nNewPos - change;
> 
>-        nNewPos = o3tl::saturating_cast<tools::Long>(fVal);
>+        scrolled = double(change);
>+        // convert back to chunked/continuous
>+        if(isMultiplyByLineSize){
>+            scrolled /= pScrl->GetLineSize();
>+        }
>     }
> 
>+    printf("DoScroll %ld, scrolled %lf\n", nNewPos, scrolled);
>     pScrl->DoScroll( nNewPos );
> 
>+    return scrolled;
> }
> 
> bool Window::HandleScrollCommand( const CommandEvent& rCmd,
>@@ -668,6 +680,9 @@ bool Window::HandleScrollCommand( const CommandEvent& rCmd,
>                     {
>                         double nScrollLines = pData->GetScrollLines();
>                         double nLines;
>+                        double* partialScroll = pData->IsHorz()
>+                            ? &mpWindowImpl->partialScrollX
>+                            : &mpWindowImpl->partialScrollY;
>                         if ( nScrollLines == COMMAND_WHEEL_PAGESCROLL )
>                         {
>                             if ( pData->GetDelta() < 0 )
>@@ -676,13 +691,12 @@ bool Window::HandleScrollCommand( const CommandEvent& rCmd,
>                                 nLines = double(LONG_MAX);
>                         }
>                         else
>-                            nLines = pData->GetNotchDelta() * nScrollLines;
>+                            nLines = *partialScroll + pData->GetNotchDelta() * nScrollLines;
>                         if ( nLines )
>                         {
>-                            ImplHandleScroll( nullptr,
>-                                          0L,
>-                                          pData->IsHorz() ? pHScrl : pVScrl,
>-                                          nLines );
>+                            Scrollable* pScrl = pData->IsHorz() ? pHScrl : pVScrl;
>+                            double scrolled = lcl_HandleScrollHelper( pScrl, nLines, true );
>+                            *partialScroll = nLines - scrolled;
>                             bRet = true;
>                         }
>                     }
>@@ -806,12 +820,6 @@ bool Window::HandleScrollCommand( const CommandEvent& rCmd,
>     return bRet;
> }
> 
>-// Note that when called for CommandEventId::Wheel above, despite its name,
>-// pVScrl isn't necessarily the vertical scroll bar. Depending on
>-// whether the scroll is horizontal or vertical, it is either the
>-// horizontal or vertical scroll bar. nY is correspondingly either
>-// the horizontal or vertical scroll amount.
>-
> void Window::ImplHandleScroll( Scrollable* pHScrl, double nX,
>                                Scrollable* pVScrl, double nY )
> {
>-- 
>2.38.1
>

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Attachments on bug 143209: 183655