tdf#115420 fix DC usecount and drop wrong asserts

For DC initialization we check the thread ID to assign a normal
or cached DC to the corresponding WinSalGraphics variable.
The cached DC has a usage count, as there are some limits on
cached DCs count (DCX_CACHE).

But for the WinSalGraphics DC init and release the variable just
matters for the accounting, and generally which thread is doing
the calls: the non-main thread always has to relay them to the
main application thread.

Since we're releasing all WinSalGraphics in ~WinSalFrame and do
all release and re-init in ImplSetParentFrame, there is no way
to correspond the thread ID to the WinSalGraphics variable.

So this drops the wrong assertions based on the WinSalGraphics
variables and renames the GETDC message to GETCACHEDDC to make
usage of a cached DC (DCX_CACHE) more obvious.
As a consequence of the different release DC handling this also
fixes the accounting of the cached DCs, wich was broken in the
initial fix; commit c15ea73f

Change-Id: I11ce52a1b4005f26567f92588437fa37bf227a2e
Reviewed-on: https://gerrit.libreoffice.org/51318Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

vcl/inc/win/saldata.hxx

@@ -215,7 +215,7 @@ int ImplSalWICompareAscii( const wchar_t* pStr1, const char* pStr2 );
 // wParam == 0; lParam == pObject;
 #define SAL_MSG_DESTROYOBJECT       (WM_USER+117)
 // wParam == hWnd; lParam == 0; lResult == hDC
-#define SAL_MSG_GETDC               (WM_USER+120)
+#define SAL_MSG_GETCACHEDDC         (WM_USER+120)
 // wParam == hWnd; lParam == 0
 #define SAL_MSG_RELEASEDC           (WM_USER+121)
 // wParam == newParentHwnd; lParam == oldHwnd; lResult == newhWnd

vcl/inc/win/salframe.h

@@ -33,8 +33,8 @@ public:
     HWND                    mhWnd;                  // Window handle
     HCURSOR                 mhCursor;               // cursor handle
     HIMC                    mhDefIMEContext;        // default IME-Context
-    WinSalGraphics*         mpLocalGraphics;        // current local frame graphics
-    WinSalGraphics*         mpThreadGraphics;       // current frame graphics for other threads
+    WinSalGraphics*         mpLocalGraphics;        // current main thread frame graphics
+    WinSalGraphics*         mpThreadGraphics;       // current frame graphics for other threads (DCX_CACHE)
     WinSalFrame*            mpNextFrame;            // pointer to next frame
     HMENU                   mSelectedhMenu;         // the menu where highlighting is currently going on
     HMENU                   mLastActivatedhMenu;    // the menu that was most recently opened

vcl/win/app/salinst.cxx

@@ -630,7 +630,7 @@ LRESULT CALLBACK SalComWndProc( HWND, UINT nMsg, WPARAM wParam, LPARAM lParam, b
         CASE_NOYIELDLOCK_RESULT( SAL_MSG_CREATEOBJECT, ImplSalCreateObject(
             GetSalData()->mpInstance, reinterpret_cast<WinSalFrame*>(lParam)) )
         CASE_NOYIELDLOCK( SAL_MSG_DESTROYOBJECT, delete reinterpret_cast<SalObject*>(lParam) )
-        CASE_NOYIELDLOCK_RESULT( SAL_MSG_GETDC, GetDCEx(
+        CASE_NOYIELDLOCK_RESULT( SAL_MSG_GETCACHEDDC, GetDCEx(
             reinterpret_cast<HWND>(wParam), nullptr, DCX_CACHE) )
         CASE_NOYIELDLOCK( SAL_MSG_RELEASEDC, ReleaseDC(
             reinterpret_cast<HWND>(wParam), reinterpret_cast<HDC>(lParam)) )

vcl/win/window/salframe.cxx

@@ -920,17 +920,12 @@ bool WinSalFrame::ReleaseFrameGraphicsDC( WinSalGraphics* pGraphics )
     // we don't want to run the WinProc in the main thread directly
     // so we don't hit the mbNoYieldLock assert
     if ( !pSalData->mpInstance->IsMainThread() )
-    {
-        assert( pGraphics == mpThreadGraphics );
         SendMessageW( pSalData->mpInstance->mhComWnd, SAL_MSG_RELEASEDC,
             reinterpret_cast<WPARAM>(mhWnd), reinterpret_cast<LPARAM>(hDC) );
-        pSalData->mnCacheDCInUse--;
-    }
     else
-    {
-        assert( pGraphics == mpLocalGraphics );
         ReleaseDC( mhWnd, hDC );
-    }
+    if ( pGraphics == mpThreadGraphics )
+        pSalData->mnCacheDCInUse--;
     pGraphics->setHDC(nullptr);
     return TRUE;
 }
@@ -994,10 +989,6 @@ bool WinSalFrame::InitFrameGraphicsDC( WinSalGraphics *pGraphics, HDC hDC, HWND
 {
     SalData* pSalData = GetSalData();
     assert( pGraphics );
-    if ( !pSalData->mpInstance->IsMainThread() )
-        assert( pGraphics == mpThreadGraphics );
-    else
-        assert( pGraphics == mpLocalGraphics );
     pGraphics->setHWND( hWnd );
 
     HDC hCurrentDC = pGraphics->getHDC();
@@ -1045,7 +1036,7 @@ SalGraphics* WinSalFrame::AcquireGraphics()
         pGraphics = mpThreadGraphics;
         assert( !pGraphics->getHDC() );
         hDC = reinterpret_cast<HDC>(static_cast<sal_IntPtr>(SendMessageW( pSalData->mpInstance->mhComWnd,
-                                    SAL_MSG_GETDC, reinterpret_cast<WPARAM>(mhWnd), 0 )));
+                                    SAL_MSG_GETCACHEDDC, reinterpret_cast<WPARAM>(mhWnd), 0 )));
     }
     else
     {
@@ -1525,7 +1516,7 @@ void WinSalFrame::ImplSetParentFrame( HWND hNewParentWnd, bool bAsChild )
     {
         HDC hDC = reinterpret_cast<HDC>(static_cast<sal_IntPtr>(
                     SendMessageW( pSalData->mpInstance->mhComWnd,
-                        SAL_MSG_GETDC, reinterpret_cast<WPARAM>(hWnd), 0 )));
+                        SAL_MSG_GETCACHEDDC, reinterpret_cast<WPARAM>(hWnd), 0 )));
         InitFrameGraphicsDC( mpThreadGraphics, hDC, hWnd );
         if ( hDC )
         {