tdf#92982 vcl rendercontext: PaintHelper: restore set buffer properties

If the buffer is persistent, then any member we change on it, so it suit
our needs have to be undone once we're done with the painting.

Change-Id: I7c5491b3b27601fb367af0856ac95cc3f845647a

vcl/source/window/paint.cxx

@@ -40,6 +40,76 @@
 #define IMPL_PAINT_ERASE            ((sal_uInt16)0x0010)
 #define IMPL_PAINT_CHECKRTL         ((sal_uInt16)0x0020)
 
+/// Sets up the buffer to have settings matching the window, and restore the original state in the dtor.
+class PaintBufferGuard
+{
+    ImplFrameData* mpFrameData;
+    bool mbBackground;
+    Wallpaper maBackground;
+    AllSettings maSettings;
+public:
+    PaintBufferGuard(ImplFrameData* pFrameData, vcl::Window* pWindow)
+        : mpFrameData(pFrameData),
+        mbBackground(false)
+    {
+        // transfer various settings
+        // FIXME: this must disappear as we move to RenderContext only,
+        // the painting must become state-less, so that no actual
+        // vcl::Window setting affects this
+        mbBackground = pFrameData->mpBuffer->IsBackground();
+        if (pWindow->IsBackground())
+        {
+            maBackground = pFrameData->mpBuffer->GetBackground();
+            pFrameData->mpBuffer->SetBackground(pWindow->GetBackground());
+        }
+        //else
+            //SAL_WARN("vcl.doublebuffering", "the root of the double-buffering hierarchy should not have a transparent background");
+
+        PushFlags nFlags = PushFlags::NONE;
+        nFlags |= PushFlags::CLIPREGION;
+        nFlags |= PushFlags::FILLCOLOR;
+        nFlags |= PushFlags::FONT;
+        nFlags |= PushFlags::LINECOLOR;
+        nFlags |= PushFlags::MAPMODE;
+        maSettings = pFrameData->mpBuffer->GetSettings();
+        nFlags |= PushFlags::REFPOINT;
+        nFlags |= PushFlags::TEXTCOLOR;
+        nFlags |= PushFlags::TEXTLINECOLOR;
+        nFlags |= PushFlags::OVERLINECOLOR;
+        nFlags |= PushFlags::TEXTFILLCOLOR;
+        nFlags |= PushFlags::TEXTALIGN;
+        nFlags |= PushFlags::RASTEROP;
+        nFlags |= PushFlags::TEXTLAYOUTMODE;
+        nFlags |= PushFlags::TEXTLANGUAGE;
+        pFrameData->mpBuffer->Push(nFlags);
+        pFrameData->mpBuffer->SetClipRegion(pWindow->GetClipRegion());
+        pFrameData->mpBuffer->SetFillColor(pWindow->GetFillColor());
+        pFrameData->mpBuffer->SetFont(pWindow->GetFont());
+        pFrameData->mpBuffer->SetLineColor(pWindow->GetLineColor());
+        pFrameData->mpBuffer->SetMapMode(pWindow->GetMapMode());
+        pFrameData->mpBuffer->SetRefPoint(pWindow->GetRefPoint());
+        pFrameData->mpBuffer->SetSettings(pWindow->GetSettings());
+        pFrameData->mpBuffer->SetTextColor(pWindow->GetTextColor());
+        pFrameData->mpBuffer->SetTextLineColor(pWindow->GetTextLineColor());
+        pFrameData->mpBuffer->SetOverlineColor(pWindow->GetOverlineColor());
+        pFrameData->mpBuffer->SetTextFillColor(pWindow->GetTextFillColor());
+        pFrameData->mpBuffer->SetTextAlign(pWindow->GetTextAlign());
+        pFrameData->mpBuffer->SetRasterOp(pWindow->GetRasterOp());
+        pFrameData->mpBuffer->SetLayoutMode(pWindow->GetLayoutMode());
+        pFrameData->mpBuffer->SetDigitLanguage(pWindow->GetDigitLanguage());
+    }
+    ~PaintBufferGuard()
+    {
+        // Restore buffer state.
+        mpFrameData->mpBuffer->Pop();
+        mpFrameData->mpBuffer->SetSettings(maSettings);
+        if (mbBackground)
+            mpFrameData->mpBuffer->SetBackground(maBackground);
+        else
+            mpFrameData->mpBuffer->SetBackground();
+    }
+};
+
 class PaintHelper
 {
 private:
@@ -88,9 +158,6 @@ public:
     /// Start buffered paint: set it up to have the same settings as m_pWindow.
     void StartBufferedPaint();
 
-    /// Setup the buffer according to the settings of the current m_pWindow.
-    void SetupBuffer();
-
     /// Paint the content of the buffer to the current m_pWindow.
     void PaintBuffer();
 
@@ -134,35 +201,6 @@ void PaintHelper::StartBufferedPaint()
     m_aPaintRectMapMode = m_pWindow->GetMapMode();
 }
 
-void PaintHelper::SetupBuffer()
-{
-    ImplFrameData* pFrameData = m_pWindow->mpWindowImpl->mpFrameData;
-    // transfer various settings
-    // FIXME: this must disappear as we move to RenderContext only,
-    // the painting must become state-less, so that no actual
-    // vcl::Window setting affects this
-    if (m_pWindow->IsBackground())
-        pFrameData->mpBuffer->SetBackground(m_pWindow->GetBackground());
-    //else
-        //SAL_WARN("vcl.doublebuffering", "the root of the double-buffering hierarchy should not have a transparent background");
-
-    pFrameData->mpBuffer->SetClipRegion(m_pWindow->GetClipRegion());
-    pFrameData->mpBuffer->SetFillColor(m_pWindow->GetFillColor());
-    pFrameData->mpBuffer->SetFont(m_pWindow->GetFont());
-    pFrameData->mpBuffer->SetLineColor(m_pWindow->GetLineColor());
-    pFrameData->mpBuffer->SetMapMode(m_pWindow->GetMapMode());
-    pFrameData->mpBuffer->SetRefPoint(m_pWindow->GetRefPoint());
-    pFrameData->mpBuffer->SetSettings(m_pWindow->GetSettings());
-    pFrameData->mpBuffer->SetTextColor(m_pWindow->GetTextColor());
-    pFrameData->mpBuffer->SetTextLineColor(m_pWindow->GetTextLineColor());
-    pFrameData->mpBuffer->SetOverlineColor(m_pWindow->GetOverlineColor());
-    pFrameData->mpBuffer->SetTextFillColor(m_pWindow->GetTextFillColor());
-    pFrameData->mpBuffer->SetTextAlign(m_pWindow->GetTextAlign());
-    pFrameData->mpBuffer->SetRasterOp(m_pWindow->GetRasterOp());
-    pFrameData->mpBuffer->SetLayoutMode(m_pWindow->GetLayoutMode());
-    pFrameData->mpBuffer->SetDigitLanguage(m_pWindow->GetDigitLanguage());
-}
-
 void PaintHelper::PaintBuffer()
 {
     ImplFrameData* pFrameData = m_pWindow->mpWindowImpl->mpFrameData;
@@ -248,7 +286,7 @@ void PaintHelper::DoPaint(const vcl::Region* pRegion)
         if (pFrameData->mbInBufferedPaint && m_pWindow->SupportsDoubleBuffering())
         {
             // double-buffering
-            SetupBuffer();
+            PaintBufferGuard g(pFrameData, m_pWindow);
             m_pWindow->ApplySettings(*pFrameData->mpBuffer.get());
 
             long nOutOffX = pFrameData->mpBuffer->mnOutOffX;