Add support for downloadable soft fonts (#10011)

This PR adds conhost support for downloadable soft fonts - also known as
dynamically redefinable character sets (DRCS) - using the `DECDLD`
escape sequence.

These fonts are typically designed to work on a specific terminal model,
and each model tends to have a different character cell size. So in
order to support as many models as possible, the code attempts to detect
the original target size of the font, and then scale the glyphs to fit
our current cell size.

Once a font has been downloaded to the terminal, it can be designated in
the same way you would a standard character set, using an `SCS` escape
sequence. The identification string for the set is defined by the
`DECDLD` sequence. Internally we map the characters in this set to code
points `U+EF20` to `U+EF7F` in the Unicode private use are (PUA).

Then in the renderer, any characters in that range are split off into
separate runs, which get painted with a special font. The font itself is
dynamically generated as an in-memory resource, constructed from the
downloaded character bitmaps which have been scaled to the appropriate
size.

If no soft fonts are in use, then no mapping of the PUA code points will
take place, so this shouldn't interfere with anyone using those code
points for something else, as along as they aren't also trying to use
soft fonts. I also tried to pick a PUA range that hadn't already been
snatched up by Nerd Fonts, but if we do receive reports of a conflict,
it's easy enough to change.

## Validation Steps Performed

I added an adapter test that runs through a bunch of parameter
variations for the `DECDLD` sequence, to make sure we're correctly
detecting the font sizes for most of the known DEC terminal models.

I've also tested manually on a wide range of existing fonts, of varying
dimensions, and from multiple sources, and made sure they all worked
reasonably well.

Closes #9164

.github/actions/spelling/allow/apis.txt

@@ -133,6 +133,7 @@ SRWLOCK
 STDCPP
 STDMETHOD
 strchr
+strcpy
 streambuf
 strtoul
 Stubless

.github/actions/spelling/expect/expect.txt

@@ -169,6 +169,7 @@ brandings
 BRK
 Browsable
 bsearch
+Bspace
 bstr
 BTNFACE
 buf
@@ -270,10 +271,12 @@ cmder
 CMDEXT
 Cmdlet
 cmdline
+cmh
 CMOUSEBUTTONS
 cmp
 cmpeq
 cmt
+cmw
 cmyk
 CNL
 cnt
@@ -406,11 +409,13 @@ csbiex
 csharp
 CSHORT
 CSIDL
+Cspace
 csproj
 Csr
 csrmsg
 CSRSS
 csrutil
+css
 cstdarg
 cstddef
 cstdio
@@ -509,6 +514,7 @@ DECAWM
 DECCKM
 DECCOLM
 DECDHL
+DECDLD
 DECDWL
 DECEKBD
 DECID
@@ -789,6 +795,7 @@ FONTENUMPROC
 FONTFACE
 FONTFAMILY
 FONTHEIGHT
+FONTINFO
 fontlist
 FONTOK
 FONTSIZE
@@ -902,6 +909,7 @@ github
 gitlab
 gle
 globals
+GLYPHENTRY
 gmail
 GMEM
 GNUC
@@ -950,6 +958,7 @@ hdrstop
 HEIGHTSCROLL
 hfile
 hfont
+hfontresource
 hglobal
 hhh
 HHmm
@@ -1272,6 +1281,7 @@ locsrc
 locstudio
 Loewen
 LOGFONT
+LOGFONTA
 LOGFONTW
 logissue
 lowercased
@@ -1935,6 +1945,7 @@ realloc
 reamapping
 rects
 redef
+redefinable
 Redir
 redirector
 redist
@@ -1980,6 +1991,7 @@ rfc
 rftp
 rgb
 rgba
+RGBCOLOR
 rgbi
 rgci
 rgfae
@@ -2149,6 +2161,7 @@ SIGDN
 SINGLEFLAG
 SINGLETHREADED
 siup
+sixel
 SIZEBOX
 sizeof
 SIZESCROLL
@@ -2754,6 +2767,7 @@ WTo
 wtof
 wtoi
 WTs
+WTSOFTFONT
 wtw
 wtypes
 Wubi

src/host/getset.cpp

@@ -1639,6 +1639,30 @@ void DoSrvEndHyperlink(SCREEN_INFORMATION& screenInfo)
     screenInfo.GetTextBuffer().SetCurrentAttributes(attr);
 }
 
+// Routine Description:
+// - A private API call for updating the active soft font.
+// Arguments:
+// - bitPattern - An array of scanlines representing all the glyphs in the font.
+// - cellSize - The cell size for an individual glyph.
+// - centeringHint - The horizontal extent that glyphs are offset from center.
+// Return Value:
+// - S_OK if we succeeded, otherwise the HRESULT of the failure.
+[[nodiscard]] HRESULT DoSrvUpdateSoftFont(const gsl::span<const uint16_t> bitPattern,
+                                          const SIZE cellSize,
+                                          const size_t centeringHint) noexcept
+{
+    try
+    {
+        auto* pRender = ServiceLocator::LocateGlobals().pRender;
+        if (pRender)
+        {
+            pRender->UpdateSoftFont(bitPattern, cellSize, centeringHint);
+        }
+        return S_OK;
+    }
+    CATCH_RETURN();
+}
+
 // Routine Description:
 // - A private API call for forcing the renderer to repaint the screen. If the
 //      input screen buffer is not the active one, then just do nothing. We only

src/host/getset.h

@@ -55,6 +55,10 @@ void DoSrvAddHyperlink(SCREEN_INFORMATION& screenInfo,
 
 void DoSrvEndHyperlink(SCREEN_INFORMATION& screenInfo);
 
+[[nodiscard]] HRESULT DoSrvUpdateSoftFont(const gsl::span<const uint16_t> bitPattern,
+                                          const SIZE cellSize,
+                                          const size_t centeringHint) noexcept;
+
 void DoSrvPrivateRefreshWindow(const SCREEN_INFORMATION& screenInfo);
 
 [[nodiscard]] HRESULT DoSrvSetConsoleOutputCodePage(const unsigned int codepage);

src/host/outputStream.cpp

@@ -818,3 +818,18 @@ bool ConhostInternalGetSet::PrivateEndHyperlink() const
     DoSrvEndHyperlink(_io.GetActiveOutputBuffer());
     return true;
 }
+
+// Routine Description:
+// - Replaces the active soft font with the given bit pattern.
+// Arguments:
+// - bitPattern - An array of scanlines representing all the glyphs in the font.
+// - cellSize - The cell size for an individual glyph.
+// - centeringHint - The horizontal extent that glyphs are offset from center.
+// Return Value:
+// - true if successful (see DoSrvUpdateSoftFont). false otherwise.
+bool ConhostInternalGetSet::PrivateUpdateSoftFont(const gsl::span<const uint16_t> bitPattern,
+                                                  const SIZE cellSize,
+                                                  const size_t centeringHint) noexcept
+{
+    return SUCCEEDED(DoSrvUpdateSoftFont(bitPattern, cellSize, centeringHint));
+}

src/host/outputStream.hpp

@@ -147,6 +147,10 @@ class ConhostInternalGetSet final : public Microsoft::Console::VirtualTerminal::
     bool PrivateAddHyperlink(const std::wstring_view uri, const std::wstring_view params) const override;
     bool PrivateEndHyperlink() const override;
 
+    bool PrivateUpdateSoftFont(const gsl::span<const uint16_t> bitPattern,
+                               const SIZE cellSize,
+                               const size_t centeringHint) noexcept override;
+
 private:
     Microsoft::Console::IIoProvider& _io;
 };