tdf#95650: Replace wrong assertion with condition

When UniscribeLayout::LayoutText(ImplLayoutArgs & rArgs) is run with
BiDiRtl flag, and some skipped VisualItems was reversed in lines 908-927,
it's possible that they will arrive in reverse order to the code adjusting
mnSubStringMin, so this assertion may fire.

This situation is not erroneous, so simply replacing the assert with "if".

Change-Id: Icb244502dd00b4c08a2c5192369ee66d743b0dcc
Reviewed-on: https://gerrit.libreoffice.org/19835Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>

vcl/qa/cppunit/complextext.cxx

@@ -22,9 +22,15 @@ public:
 
     /// Play with font measuring etc.
     void testArabic();
+#if defined(WNT)
+    void testTdf95650(); // Windows-only issue
+#endif
 
     CPPUNIT_TEST_SUITE(VclComplexTextTest);
     CPPUNIT_TEST(testArabic);
+#if defined(WNT)
+    CPPUNIT_TEST(testTdf95650);
+#endif
     CPPUNIT_TEST_SUITE_END();
 };
 
@@ -77,6 +83,26 @@ void VclComplexTextTest::testArabic()
 #endif
 }
 
+#if defined(WNT)
+void VclComplexTextTest::testTdf95650()
+{
+    const sal_Unicode pTxt[] = {
+        0x0131, 0x0302, 0x0504, 0x4E44, 0x3031, 0x3030, 0x3531, 0x2D30,
+        0x3037, 0x0706, 0x0908, 0x0B0A, 0x0D0C, 0x0F0E, 0x072E, 0x100A,
+        0x0D11, 0x1312, 0x0105, 0x020A, 0x0512, 0x1403, 0x030C, 0x1528,
+        0x2931, 0x632E, 0x7074, 0x0D20, 0x0E0A, 0x100A, 0xF00D, 0x0D20,
+        0x030A, 0x0C0B, 0x20E0, 0x0A0D
+    };
+    OUString aTxt(pTxt, SAL_N_ELEMENTS(pTxt) - 1);
+    VclPtr<vcl::Window> pWin = VclPtr<WorkWindow>::Create(static_cast<vcl::Window *>(nullptr));
+    CPPUNIT_ASSERT(pWin);
+
+    OutputDevice *pOutDev = static_cast< OutputDevice * >(pWin.get());
+    // Check that the following executes without failing assertion
+    pOutDev->ImplLayout(aTxt, 9, 1, Point(), 0, 0, SalLayoutFlags::BiDiRtl, nullptr);
+}
+#endif
+
 CPPUNIT_TEST_SUITE_REGISTRATION(VclComplexTextTest);
 
 CPPUNIT_PLUGIN_IMPLEMENT();

vcl/win/source/gdi/winlayout.cxx

@@ -967,8 +967,8 @@ bool UniscribeLayout::LayoutText( ImplLayoutArgs& rArgs )
             if (rArgs.mnMinCharPos >= rVisualItem.mnEndCharPos)
             {   // fdo#47553 adjust "guessed" min (maybe up to -8 off) to
                 // actual min so it can be used properly in GetNextGlyphs
-                assert(mnSubStringMin <= rVisualItem.mnEndCharPos);
-                mnSubStringMin = rVisualItem.mnEndCharPos;
+                if (mnSubStringMin < rVisualItem.mnEndCharPos)
+                    mnSubStringMin = rVisualItem.mnEndCharPos;
             }
             continue;
         }