tdf#168528 sw letter spacing: fix freezing with minimum spacing/scaling

Fix never-ending loop in SwTextFrame::Format_() resulted by bad compression of lines with COMPLETE_STRING cut position.

Note: to test the fix of the rare freezing, a subset font has been
created from Source Serif 4 Variable, and embedded in the test file.

Follow-up to commit 33f20d0a0f
"tdf#168351 sw letter spacing: fix spaces in the last line",
commit 45ec7bd761
"tdf#168251 cui offapi xmloff sw glyph scaling: extend UNO/UX/ODF",
commit 3c53797210
"tdf#167648 sw letter spacing: implement minimum letter spacing"
and commit f83a04c510
"tdf#167648 cui offapi xmloff sw: add DTP-feature maximum letter
spacing".

Change-Id: I517f2b878421df40d69c785155107cf7380f0c0c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/191432
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>

sw/qa/extras/layout/layout3.cxx

@@ -837,6 +837,14 @@ CPPUNIT_TEST_FIXTURE(SwLayoutWriter3, testTdf168448)
     }
 }
 
+CPPUNIT_TEST_FIXTURE(SwLayoutWriter3, testTdf168528)
+{
+    //just care it doesn't freeze
+    // embedded font subset created with:
+    // hb-subset SourceSerif4Variable-Roman.ttf  -u '20,3a,61,64,65,66,67,68,6c,6d,6e,6f,72,73,74,75,79'  -o subset.ttf
+    createSwDoc("tdf168528.odt");
+}
+
 CPPUNIT_TEST_FIXTURE(SwLayoutWriter3, testTdf164499)
 {
     createSwDoc("tdf164499.docx");

sw/source/core/text/guess.cxx

@@ -502,7 +502,9 @@ bool SwTextGuess::Guess( const SwTextPortion& rPor, SwTextFormatInfo &rInf,
         // tdf#168251 minimum glyph scaling allows more text in the line
         // TODO don't be greedy, allow only an extra word or word part
         const sal_Int16 nScaleWidthMinimum = aAdjustItem.GetPropScaleWidthMinimum();
-        if ( nScaleWidthMinimum < 100 )
+        if ( nScaleWidthMinimum < 100 &&
+                    // tdf#168528 avoid freezing
+                    m_nCutPos < TextFrameIndex(rInf.GetText().getLength()) )
         {
             SwTwips nExtraSpace = nLineWidth / (nScaleWidthMinimum / 100.0) - nLineWidth;
             nLineWidth += nExtraSpace;
@@ -512,7 +514,10 @@ bool SwTextGuess::Guess( const SwTextPortion& rPor, SwTextFormatInfo &rInf,
 
         // tdf#167648 minimum letter spacing allows more text in the line
         // TODO don't be greedy, allow only an extra word or word part
-        if ( const sal_Int16 nLetterSpacingMinimum = aAdjustItem.GetPropLetterSpacingMinimum() )
+        const sal_Int16 nLetterSpacingMinimum = aAdjustItem.GetPropLetterSpacingMinimum();
+        if ( nLetterSpacingMinimum &&
+                    // tdf#168528 avoid freezing
+                    m_nCutPos < TextFrameIndex(rInf.GetText().getLength()) )
         {
             SwTwips nExtraSpace = sal_Int32(m_nCutPos - rInf.GetIdx()) *
                                      nSpaceWidth / 10.0 * nLetterSpacingMinimum / 100.0;

vcl/unx/generic/fontmanager/fontconfig.cxx

@@ -1265,6 +1265,9 @@ void PrintFontManager::Substitute(vcl::font::FontSelectPattern &rPattern, OUStri
         }
         if (rPattern.maTargetName == "Linux Libertine G" && rPattern.maSearchName == "Linux Libertine O")
             return;
+        // tdf#168528 allow testing with embedded subset
+        if (rPattern.maTargetName == "Source Serif 4 Variable" && rPattern.maSearchName == "DejaVu Serif")
+            return;
         SAL_WARN("vcl.fonts", "PrintFontManager::Substitute: missing font: '" << rPattern.maTargetName <<
                               "' try: " << rPattern.maSearchName << " instead");
         std::cerr << "terminating test due to missing font: " << rPattern.maTargetName << std::endl;