Always scale HarfBuzz font before using it

We cache and reuse the HarfBuzz font, so we need to make sure it always
has the right font size before using it.

Change-Id: I332c7f51f6495effde529c63485cb4ec658b2ca5

2 files changed, 17 insertions, 13 deletions

diff --git a/vcl/inc/CommonSalLayout.hxx b/vcl/inc/CommonSalLayout.hxx
index 97002926af31..20130ee3dc28 100644
--- a/vcl/inc/CommonSalLayout.hxx
+++ b/vcl/inc/CommonSalLayout.hxx
@@ -53,6 +53,8 @@ class CommonSalLayout : public GenericSalLayout
     OString                 msLanguage;
     std::vector<hb_feature_t> maFeatures;
 
+    hb_font_t*              getHbFont();
+
 public:
 #if defined(_WIN32)
     explicit                CommonSalLayout(HDC, WinFontInstance&, const WinFontFace&);
diff --git a/vcl/source/gdi/CommonSalLayout.cxx b/vcl/source/gdi/CommonSalLayout.cxx
index 239486ef2e37..61395bdc620f 100644
--- a/vcl/source/gdi/CommonSalLayout.cxx
+++ b/vcl/source/gdi/CommonSalLayout.cxx
@@ -85,10 +85,12 @@ static hb_font_t* createHbFont(hb_face_t* pHbFace)
     return pHbFont;
 }
 
-static void scaleHbFont(hb_font_t* pHbFont, const FontSelectPattern& aFontSelData)
+// We cache and re-use the HarfBuzz font for different layout instances, so we
+// need sure to set the correct scale (font size) before using the font.
+hb_font_t* CommonSalLayout::getHbFont()
 {
-    unsigned int nXScale = aFontSelData.mnWidth << 6;
-    unsigned int nYScale = aFontSelData.mnHeight << 6;
+    unsigned int nXScale = mrFontSelData.mnWidth << 6;
+    unsigned int nYScale = mrFontSelData.mnHeight << 6;
 
 #if defined(_WIN32)
     // HACK to get stretched/shrunken text. TODO: Get rid of HACK
@@ -99,8 +101,10 @@ static void scaleHbFont(hb_font_t* pHbFont, const FontSelectPattern& aFontSelDat
     if (!nXScale)
       nXScale = nYScale;
 
-    hb_font_set_ppem(pHbFont, nXScale, nYScale);
-    hb_font_set_scale(pHbFont, nXScale, nYScale);
+    hb_font_set_ppem(mpHbFont, nXScale, nYScale);
+    hb_font_set_scale(mpHbFont, nXScale, nYScale);
+
+    return mpHbFont;
 }
 
 #if !HB_VERSION_ATLEAST(1, 1, 0)
@@ -181,7 +185,6 @@ CommonSalLayout::CommonSalLayout(HDC hDC, WinFontInstance& rWinFontInstance, con
         hb_face_destroy(pHbFace);
     }
 
-    scaleHbFont(mpHbFont, mrFontSelData);
     ParseFeatures(mrFontSelData.maTargetName);
 }
 
@@ -208,7 +211,6 @@ CommonSalLayout::CommonSalLayout(const CoreTextStyle& rCoreTextStyle)
         hb_face_destroy(pHbFace);
     }
 
-    scaleHbFont(mpHbFont, mrFontSelData);
     ParseFeatures(mrFontSelData.maTargetName);
 }
 
@@ -228,7 +230,6 @@ CommonSalLayout::CommonSalLayout(FreetypeFont& rFreetypeFont)
         hb_face_destroy(pHbFace);
     }
 
-    scaleHbFont(mpHbFont, mrFontSelData);
     ParseFeatures(mrFontSelData.maTargetName);
 }
 #endif
@@ -374,7 +375,8 @@ static int GetVerticalFlagsForScript(UScriptCode aScript)
 
 bool CommonSalLayout::LayoutText(ImplLayoutArgs& rArgs)
 {
-    hb_face_t* pHbFace = hb_font_get_face(mpHbFont);
+    hb_font_t* pHbFont = getHbFont();
+    hb_face_t* pHbFace = hb_font_get_face(pHbFont);
     hb_script_t aHbScript = HB_SCRIPT_INVALID;
 
     int nGlyphCapacity = 2 * (rArgs.mnEndCharPos - rArgs.mnMinCharPos);
@@ -486,7 +488,7 @@ bool CommonSalLayout::LayoutText(ImplLayoutArgs& rArgs)
             hb_segment_properties_t aHbProps;
             hb_buffer_get_segment_properties(pHbBuffer, &aHbProps);
             hb_shape_plan_t* pHbPlan = hb_shape_plan_create_cached(pHbFace, &aHbProps, maFeatures.data(), maFeatures.size(), pHbShapers);
-            bool ok = hb_shape_plan_execute(pHbPlan, mpHbFont, pHbBuffer, maFeatures.data(), maFeatures.size());
+            bool ok = hb_shape_plan_execute(pHbPlan, pHbFont, pHbBuffer, maFeatures.data(), maFeatures.size());
             assert(ok);
             (void) ok;
             hb_buffer_set_content_type(pHbBuffer, HB_BUFFER_CONTENT_TYPE_GLYPHS);
@@ -650,9 +652,9 @@ void CommonSalLayout::ApplyDXArray(ImplLayoutArgs& rArgs)
     if (rArgs.mnFlags & SalLayoutFlags::KashidaJustification)
     {
         // Find Kashida glyph width and index.
-        scaleHbFont(mpHbFont, mrFontSelData);
-        if (hb_font_get_glyph(mpHbFont, 0x0640, 0, &nKashidaIndex))
-            nKashidaWidth = hb_font_get_glyph_h_advance(mpHbFont, nKashidaIndex) / 64;
+        hb_font_t* pHbFont = getHbFont();
+        if (hb_font_get_glyph(pHbFont, 0x0640, 0, &nKashidaIndex))
+            nKashidaWidth = hb_font_get_glyph_h_advance(pHbFont, nKashidaIndex) / 64;
         bKashidaJustify = nKashidaWidth != 0;
     }