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fix #983: When scrolling down, consider the height of the horizontal … #1393

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fix #983: When scrolling down, consider the height of the horizontal … #1393

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43 changes: 36 additions & 7 deletions Source/VirtualTrees.BaseTree.pas
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@ interface
{$ELSE}
TVTBaseAncestor = TVTBaseAncestorVcl;
TCanvas = Vcl.Graphics.TCanvas;
TFormatEtcArray = VirtualTrees.Types.TFormatEtcArray;
TFormatEtcArray = VirtualTrees.Types.TFormatEtcArray;
{$ENDIF}

// Alias defintions for convenience
Expand Down Expand Up @@ -540,7 +540,8 @@ TBaseVirtualTree = class abstract(TVTBaseAncestor)
FOffsetY: TDimension; // Determines left and top scroll offset.
FEffectiveOffsetX: TDimension; // Actual position of the horizontal scroll bar (varies depending on bidi mode).
FRangeX,
FRangeY: TNodeHeight; // current virtual width and height of the tree
FRangeY: TNodeHeight; // current virtual width and height of the tree
FScrolling: Boolean; // True while updating scroll bars in reaction to scrolling. See issue #983.
FBottomSpace: TDimension; // Extra space below the last node.

FDefaultPasteMode: TVTNodeAttachMode; // Used to determine where to add pasted nodes to.
Expand Down Expand Up @@ -1855,7 +1856,7 @@ implementation
//These allow us access to protected members in the classes
TVirtualTreeColumnsCracker = class(TVirtualTreeColumns);
TVTHeaderCracker = class(TVTHeader);
TVirtualTreeColumnCracker = class(TVirtualTreeColumn);
TVirtualTreeColumnCracker = class(TVirtualTreeColumn);
TBaseVirtualTreeCracker = class(TBaseVirtualTree);

// streaming support
Expand Down Expand Up @@ -8344,7 +8345,12 @@ procedure TBaseVirtualTree.WMVScroll(var Message: TWMVScroll);
DoStateChange([], [tsThumbTracking]);
// Avoiding to adjust the horizontal scroll position while tracking makes scrolling much smoother
// but we need to adjust the final position here then.
UpdateScrollBars(True);
FScrolling := True; // issue #983, see UpdateHorizontalRange
try
UpdateScrollBars(True);
finally
FScrolling := False;
end;
// Really weird invalidation needed here (and I do it only because it happens so rarely), because
// when showing the horizontal scrollbar while scrolling down using the down arrow button,
// the button will be repainted on mouse up (at the wrong place in the far right lower corner)...
Expand Down Expand Up @@ -11216,7 +11222,14 @@ function TBaseVirtualTree.DoSetOffsetXY(Value: TPoint; Options: TScrollUpdateOpt
UpdateVerticalScrollBar(suoRepaintScrollBars in Options);
if not (FHeader.UseColumns or IsMouseSelecting) and
(FScrollBarOptions.ScrollBars in [System.UITypes.TScrollStyle.ssHorizontal, System.UITypes.TScrollStyle.ssBoth]) then
UpdateHorizontalScrollBar(suoRepaintScrollBars in Options);
begin
FScrolling := True; // issue #983, see UpdateHorizontalRange
try
UpdateHorizontalScrollBar(suoRepaintScrollBars in Options);
finally
FScrolling := False;
end;
end;
end;
end;

Expand Down Expand Up @@ -12289,22 +12302,38 @@ function TBaseVirtualTree.GetMaxRightExtend(): TDimension;

var
Node,
NextNode: PVirtualNode;
NextNode,
PrevNode: PVirtualNode;
TopPosition: TDimension;
CurrentWidth: TDimension;
ScrollBarOffset: TDimension;

begin
Node := GetNodeAt(0, 0, True, TopPosition);
Result := 0;
if not Assigned(Node) then
exit;

if (FScrolling) and ((GetWindowLong(Handle, GWL_STYLE) and WS_HSCROLL) <> 0) then
begin
ScrollBarOffset := GetSystemMetricsForDpi(SM_CYHSCROLL, CurrentPPI);
PrevNode := GetPreviousSibling(Node);
while (ScrollBarOffset > 0) and Assigned(PrevNode) do
begin
CurrentWidth := GetOffset(TVTElement.ofsRightOfText, PrevNode);
if Result < CurrentWidth then
Result := CurrentWidth;
Dec(ScrollBarOffset, PrevNode.NodeHeight);
PrevNode := GetPreviousSibling(PrevNode);
end;
end;

while Assigned(Node) do
begin
if not (vsInitialized in Node.States) then
InitNode(Node);
CurrentWidth := GetOffset(TVTElement.ofsRightOfText, Node);
if Result < (CurrentWidth) then
if Result < CurrentWidth then
Result := CurrentWidth;
Inc(TopPosition, NodeHeight[Node]);
if TopPosition > Height then
Expand Down