vcl rendercontext: fix off-by-one error in PaintHelper::PaintBuffer()

With this, Writer no longer has leftover 1-pixel-width/height lines on
scrolling at the right/bottom of the SwEditWin area.

The problem was that PaintBuffer() painted one less row/column of pixels
than intended. This happened because Rectangle::GetSize() uses
GetWidth() and GetHeight(), which return "bound2 - bound1 + 1", but
because the map mode was in twips, the +1 had no effect.

For example, if top=127 and bottom=762 in pixels, then the needed height
is 636, but (assuming e.g. 96 DPI) counting 11430-1905+1 in twips, then
converting to pixels is only 635, so the last row/column is not painted.

Fix the problem by making sure that GetSize() is invoked on a rectangle
that has the size in pixels, that's how e.g.
SdrPreRenderDevice::OutputPreRenderDevice() uses DrawOutDev(), too.

Change-Id: I6f8686e0a91ba402db93982c25be76992c260abe
(cherry picked from commit b3e645cde951906d883f015d342f85fc0eedb2ec)

1 files changed, 13 insertions, 1 deletions

diff --git a/vcl/source/window/paint.cxx b/vcl/source/window/paint.cxx
index 4a6fb2ef114d..e4e7531d5af2 100644
--- a/vcl/source/window/paint.cxx
+++ b/vcl/source/window/paint.cxx
@@ -182,7 +182,19 @@ void PaintHelper::PaintBuffer()
         m_pWindow->SetMapMode(m_aPaintRectMapMode);
         m_pBuffer->SetMapMode(m_aPaintRectMapMode);
 
-        m_pWindow->DrawOutDev(m_aPaintRect.TopLeft(), m_aPaintRect.GetSize(), m_aPaintRect.TopLeft(), m_aPaintRect.GetSize(), *m_pBuffer.get());
+        // Make sure that the +1 value GetSize() adds to the size is in pixels.
+        Size aPaintRectSize;
+        if (m_pWindow->GetMapMode().GetMapUnit() == MAP_PIXEL)
+        {
+            aPaintRectSize = m_aPaintRect.GetSize();
+        }
+        else
+        {
+            Rectangle aRectanglePixel = m_pWindow->LogicToPixel(m_aPaintRect);
+            aPaintRectSize = m_pWindow->PixelToLogic(aRectanglePixel.GetSize());
+        }
+
+        m_pWindow->DrawOutDev(m_aPaintRect.TopLeft(), aPaintRectSize, m_aPaintRect.TopLeft(), aPaintRectSize, *m_pBuffer.get());
     }
 }