Resolves tdf#127508 - Flat table header in Calc

Amends 67fd62b3edc86c2891f279b25cf9919c4bbbbca1 with
flat corner button

Change-Id: Ia26aff0844069dd435cf4edd7524c19f5f0f22ea
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/89365
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
diff --git a/sc/source/ui/inc/tabview.hxx b/sc/source/ui/inc/tabview.hxx
index dc65f97..8a8d3e9 100644
--- a/sc/source/ui/inc/tabview.hxx
+++ b/sc/source/ui/inc/tabview.hxx
@@ -71,14 +71,13 @@ class ScCornerButton : public vcl::Window
{
private:
    ScViewData* const     pViewData;
    bool const            bAdd;

protected:
    virtual void    Paint( vcl::RenderContext& rRenderContext, const tools::Rectangle& rRect ) override;
    virtual void    Resize() override;
    virtual void    MouseButtonDown( const MouseEvent& rMEvt ) override;
public:
                    ScCornerButton( vcl::Window* pParent, ScViewData* pData, bool bAdditional );
                    ScCornerButton( vcl::Window* pParent, ScViewData* pData );
                    virtual ~ScCornerButton() override;

    virtual void    StateChanged( StateChangedType nType ) override;
diff --git a/sc/source/ui/view/tabview.cxx b/sc/source/ui/view/tabview.cxx
index 53e03e6..f45a575 100644
--- a/sc/source/ui/view/tabview.cxx
+++ b/sc/source/ui/view/tabview.cxx
@@ -68,10 +68,9 @@ using namespace ::com::sun::star;

//  Corner-Button

ScCornerButton::ScCornerButton( vcl::Window* pParent, ScViewData* pData, bool bAdditional ) :
ScCornerButton::ScCornerButton( vcl::Window* pParent, ScViewData* pData ) :
    Window( pParent, WinBits( 0 ) ),
    pViewData( pData ),
    bAdd( bAdditional )
    pViewData( pData )
{
    EnableRTL( false );
}
@@ -94,32 +93,6 @@ void ScCornerButton::Paint(vcl::RenderContext& rRenderContext, const tools::Rect
    bool bLayoutRTL = pViewData->GetDocument()->IsLayoutRTL( pViewData->GetTabNo() );
    long nDarkX = bLayoutRTL ? 0 : nPosX;

    if (!bAdd)
    {
        // match the shaded look of column/row headers

        Color aFace(rStyleSettings.GetFaceColor());
        Color aWhite(COL_WHITE);
        Color aCenter(aFace);
        aCenter.Merge(aWhite, 0xd0);          // lighten up a bit
        Color aOuter(aFace );
        aOuter.Merge(aWhite, 0xa0);           // lighten up more

        long nCenterX = (aSize.Width() / 2) - 1;
        long nCenterY = (aSize.Height() / 2) - 1;

        rRenderContext.SetLineColor();
        rRenderContext.SetFillColor(aCenter);
        rRenderContext.DrawRect(tools::Rectangle(nCenterX, nCenterY, nCenterX, nPosY));
        rRenderContext.DrawRect(tools::Rectangle(nCenterX, nCenterY, nDarkX, nCenterY));
        rRenderContext.SetFillColor(aOuter);
        rRenderContext.DrawRect(tools::Rectangle(0, 0, nPosX, nCenterY - 1));
        if (bLayoutRTL)
            rRenderContext.DrawRect(tools::Rectangle(nCenterX + 1, nCenterY, nPosX, nPosY));
        else
            rRenderContext.DrawRect(tools::Rectangle(0, nCenterY, nCenterX - 1, nPosY));
    }

    //  both buttons have the same look now - only dark right/bottom lines
    rRenderContext.SetLineColor(rStyleSettings.GetDarkShadowColor());
    rRenderContext.DrawLine(Point(0, nPosY), Point(nPosX, nPosY));
@@ -201,8 +174,8 @@ ScTabView::ScTabView( vcl::Window* pParent, ScDocShell& rDocSh, ScTabViewShell* 
    aVScrollBottom( VclPtr<ScrollBar>::Create( pFrameWin, WinBits( WB_VSCROLL | WB_DRAG ) ) ),
    aHScrollLeft( VclPtr<ScrollBar>::Create( pFrameWin, WinBits( WB_HSCROLL | WB_DRAG ) ) ),
    aHScrollRight( VclPtr<ScrollBar>::Create( pFrameWin, WinBits( WB_HSCROLL | WB_DRAG ) ) ),
    aCornerButton( VclPtr<ScCornerButton>::Create( pFrameWin, &aViewData, false ) ),
    aTopButton( VclPtr<ScCornerButton>::Create( pFrameWin, &aViewData, true ) ),
    aCornerButton( VclPtr<ScCornerButton>::Create( pFrameWin, &aViewData ) ),
    aTopButton( VclPtr<ScCornerButton>::Create( pFrameWin, &aViewData ) ),
    aScrollBarBox( VclPtr<ScrollBarBox>::Create( pFrameWin, WB_SIZEABLE ) ),
    mxInputHintOO(),
    pTimerWindow( nullptr ),