[PATCH] HiDPI fixes for squiggly underlines

[Keith Curtis]

Hi Kendy,

Good to hear from you. I've got a number of things in progress on my
computer beyond the underlines (
https://wiki.documentfoundation.org/Development/HiDpi) but I wait to get an
API first as I'm just writing "if (1) //hidpi".

I personally don't think a floating point value is a good idea. At the
lowest level, pixel line widths go to 2 or 3 and in the square case go to 4
or 9. I believe anything who wants more resolution should probably be
working based on the system font size. The changes I'm making don't seem to
need more than 3 and even 2 is plenty for all laptops today and into the
distant future. Floating point arithmetic used to be a lot slower than
integer as well but I don't know if that is still true ;-)

I hope it is okay if I can write code that handles the 2x case but has no
guarantees about any other value. I can't test what I can't see and there
is a fair amount of work to get LibreOffice looking good and supporting
variable-sized bitmaps at all. So if it were up to me, I'd just make it a
boolean for a while, and focus / force that part to look great everywhere.
Then when you were ready to further generalize it, the compiler would make
you to validate all the areas. I even have been taking advantage of the
simplicity. I found some arrow drawing logic that wanted an odd-sized
height for best results. And so I just doubled it and subtracted one ;-)

My biggest concern wrt the API is that it has the right value out of the
box. For example, what do normal Macs return for the system font size
versus Retinas? What about on Windows? There is plenty of intelligence that
can go into a bit.

Putting the change in ImplDrawWaveLine is possible. My change is safer in
that it mostly only touches the spelling / grammar which is the most
noticeable issue. With ImplDrawWaveLine you have to worry about more
callers, printers, etc. and possibilities for dirt on screen. I wouldn't
necessarily recommend shifting down 2 pixels for the low-level drawing
code, so maybe you'd still have to have changes in both places.
ImplDrawWaveLine is a routine takes a pixel line width as input, so perhaps
the policy decision should be above it. It seems sort of like putting the
bitmap doubling logic into the BitBlt routine versus in the toolbar which
loads the bitmaps. I could look at the wavy underline character property
logic, but I think it is low priority and still might not change the
ImplDrawWaveLine. I haven't looked into it. I'm happy to fix any bugs in my
simple code, but get concerned about suggestions that complicate it ;-)

Working on this early next week would be great. I've got about 600 more
lines in 14 files to review that make a difference. There is a fair amount
of low-hanging fruit. I am possibly stuck on two issues, but I plug away on
it as I have free time. The hardest part is finding the actual line of code
that have the bug. With my work, they are being marked which makes future
work easier. I did see code that is possibly problematic in places like
DecoView but I'm just focusing on the visible ones. Toolbar bitmaps are the
most important. The Sidebar is the most broken. Do you think they will fix
it?

Anyway, I look forward to working through the issues soon because I have
some time now and hopefully getting this into 4.2.

-Keith
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