Fix applying DX adjustments in CommonSalLayout

By overriding GetCharWidths() and ApplyDXArray() with a simpler and
saner implementation.

This fixes rendering of Awami Nastaliq, as well as subtending marks in
Amiri and potentially other bugs.

Breaks Kashida justification, will need to rewrite that one as well.

Change-Id: I843679e937f2881e77df61f5cbd9516b6df1b3b6

1 files changed, 63 insertions, 0 deletions

diff --git a/vcl/source/gdi/CommonSalLayout.cxx b/vcl/source/gdi/CommonSalLayout.cxx
index a303f707e7dd..2be6dd8a0afa 100644
--- a/vcl/source/gdi/CommonSalLayout.cxx
+++ b/vcl/source/gdi/CommonSalLayout.cxx
@@ -489,3 +489,66 @@ bool CommonSalLayout::LayoutText(ImplLayoutArgs& rArgs)
 
     return true;
 }
+
+bool CommonSalLayout::GetCharWidths(DeviceCoordinate* pCharWidths) const
+{
+    int nCharCount = mnEndCharPos - mnMinCharPos;
+
+    for (int i = 0; i < nCharCount; ++i)
+        pCharWidths[i] = 0;
+
+    for (auto const& aGlyphItem : m_GlyphItems)
+        pCharWidths[aGlyphItem.mnCharPos - mnMinCharPos] += aGlyphItem.mnNewWidth;
+
+    return true;
+}
+
+void CommonSalLayout::ApplyDXArray(ImplLayoutArgs& rArgs)
+{
+    if (rArgs.mpDXArray == nullptr)
+        return;
+
+    int nCharCount = mnEndCharPos - mnMinCharPos;
+    std::unique_ptr<DeviceCoordinate[]> const pOldCharWidths(new DeviceCoordinate[nCharCount]);
+    std::unique_ptr<DeviceCoordinate[]> const pNewCharWidths(new DeviceCoordinate[nCharCount]);
+
+    // Get the natural character widths (i.e. before applying DX adjustments).
+    GetCharWidths(pOldCharWidths.get());
+
+    // Calculate the character widths after DX adjustments.
+    for (int i = 0; i < nCharCount; ++i)
+    {
+        if (i == 0)
+            pNewCharWidths[i] = rArgs.mpDXArray[i];
+        else
+            pNewCharWidths[i] = rArgs.mpDXArray[i] - rArgs.mpDXArray[i - 1];
+    }
+
+    // The accumulated difference in X position.
+    DeviceCoordinate nDelta = 0;
+
+    // Apply the DX adjustments to glyph positions and widths.
+    size_t i = 0;
+    while (i < m_GlyphItems.size())
+    {
+        int nCharPos = m_GlyphItems[i].mnCharPos - mnMinCharPos;
+        DeviceCoordinate nDiff = pNewCharWidths[nCharPos] - pOldCharWidths[nCharPos];
+
+        m_GlyphItems[i].maLinearPos.X() += nDelta;
+        size_t j = i;
+        // Apply the delta to other glyphs belonging to the same character.
+        while (++j < m_GlyphItems.size())
+        {
+            if (m_GlyphItems[j].mnCharPos != m_GlyphItems[i].mnCharPos)
+                break;
+            m_GlyphItems[j].maLinearPos.X() += nDelta;
+        }
+
+        // Increment the delta, the loop above makes sure we do so only once
+        // for every character not for every glyph (otherwise we would apply it
+        // multiple times for each glyphs belonging to the same character which
+        // is wrong since DX adjustments are character based).
+        nDelta += nDiff;
+        i = j;
+    }
+}