Re: [PATCH] HiDPI fixes for squiggly underlines

I wanted to follow up with the underline issue clipping code below and send
a new patch.

I have looked again at the code and did more testing. I started by
commenting out the check again and was able to see problems so I can say
that code is sometimes still important. But it doesn't appear to need a fix
for the yStart++ statement. I didn't increment the nEndY because the value
is currently unused later in the function ;-)

The maMetric.mnWUnderlineSize value is itself a calculated value that tries
to be about 1/2 the descent, and so not entirely to be trusted on how much
space is actually available. Between that logic, and the logic to shrink
the wave line at small descents, it appears fine. At the very least this
bug will only show up on HiDPI computers so that decreases the risk.

Respecting that clipping boundary by setting nStartAddditional = 1 often
makes the spelling underlines only 4 pixels tall at normal zooms with 12
point text on my screen. As I say in the comment, the check should be using
the full descent which gives it more space, but that diff is bigger.

In any case, in this new version I have put in a variable that handles that
issue if someone runs into problems. I'm happy to look at bugs but in here
I've got a fix ready to go. I could consider to fix properly for a future
version, but for now small fixes are best.

Finding the relevant code is often harder than making the fix. It is like
digging in the desert. Opengrok is invaluable. I can fix about 2 places per
session. Yesterday I wrote the code to fix the treeelistview + / - controls
only to eventually find out it was a native one that doesn't seem to allow
being drawn bigger! So I gave up on that issue. If the fix isn't relevant
to Linux, then screw it ;-) Hopefully it is native on all platforms and the
internal bitmaps, etc. can be removed.

-Keith
------------
diff --git a/vcl/source/gdi/outdev3.cxx b/vcl/source/gdi/outdev3.cxx
index f3f5a77..c6de53f 100644
--- a/vcl/source/gdi/outdev3.cxx
+++ b/vcl/source/gdi/outdev3.cxx
@@ -5299,11 +5299,28 @@ void OutputDevice::DrawWaveLine( const Point&
rStartPos, const Point& rEndPos,
     }

     long nWaveHeight;
+    long nStartAdditional = 0;
+
     if ( nStyle == WAVE_NORMAL )
     {
         nWaveHeight = 3;
         nStartY++;
         nEndY++;
+
+        if (1) //hidpi
+        {
+            nWaveHeight = 5;
+            nStartY++; //Shift down an additional pixel for hidpi screens.
+                       //TODO: Probably should be done above, before the
rotation happens
+
+            //Shifting down an additional pixel could cause problems
because the #109280# code below
+            //doesn't know. However, the value itself is about half the
descent and so we do have more
+            //space than we think.
+            //Furthermore, when I did enable nStartAdditional = 1, then
the lines LibreOffice
+            //drew were very frequently just 4 pixels at normal zooms and
don't look as good. If that pixel causes
+            //repaint problems, set this value to 1 and consider to
revisit the below check to do something
+            //based on descent which is a better measure of space
available. Why LO isn't already doing that is beyond me.
+            nStartAdditional = 0;      //Set to 1 if HiDPI redraw problems.
+        }
     }
     else if( nStyle == WAVE_SMALL )
     {
@@ -5316,11 +5333,11 @@ void OutputDevice::DrawWaveLine( const Point&
rStartPos, const Point& rEndPos,

      // #109280# make sure the waveline does not exceed the descent to
avoid paint problems
      ImplFontEntry* pFontEntry = mpFontEntry;
-     if( nWaveHeight > pFontEntry->maMetric.mnWUnderlineSize )
-         nWaveHeight = pFontEntry->maMetric.mnWUnderlineSize;
+     if( nWaveHeight + nStartAdditional >
pFontEntry->maMetric.mnWUnderlineSize )
+         nWaveHeight = pFontEntry->maMetric.mnWUnderlineSize -
nStartAdditional;

      ImplDrawWaveLine( nStartX, nStartY, 0, 0,
-                      nEndX-nStartX, nWaveHeight, 1,
+                      nEndX-nStartX, nWaveHeight, 2,
                       nOrientation, GetLineColor() );
     if( mpAlphaVDev )
         mpAlphaVDev->DrawWaveLine( rStartPos, rEndPos, nStyle );