As it turns out, setting high DPI awareness in the process fails.

Presumably, "something" is setting it earlier so it can't be set
again because reasons.  To work around this, add a manifest to
ciolib library that asserts the binary is DPI aware and requests
Windows not do GDI scaling.

Not sure if manifest .o files in a lib are linked in by things, but
SyncTERM pulls the .o out and explicitly links it, so this should
fix SyncTERM at least.

src/conio/GNUmakefile

@@ -64,7 +64,7 @@ mtlib: $(MTOBJODIR)$(DIRSEP)ciolib_res${OFILE}
 
 dl-mtlib: $(MTOBJODIR)$(DIRSEP)ciolib_res${OFILE}
 
-$(MTOBJODIR)$(DIRSEP)ciolib_res${OFILE}: ciolib.rc syncicon64.ico
+$(MTOBJODIR)$(DIRSEP)ciolib_res${OFILE}: ciolib.rc syncicon64.ico ciolib.manifest
 	@echo Creating $< ...
 	$(QUIET)${WINDRES} $(WINDRESFLAGS) -O coff -i ciolib.rc -o $@
 endif

src/conio/ciolib.manifest

+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0" xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
+  <asmv3:application>
+    <asmv3:windowsSettings>
+      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true</dpiAware>
+      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2, PerMonitor, System</dpiAwareness>
+      <gdiScaling xmlns="http://schemas.microsoft.com/SMI/2017/WindowsSettings">false</gdiScaling>
+    </asmv3:windowsSettings>
+  </asmv3:application>
+</assembly>

src/conio/ciolib.rc

+#include "windows.h"
+
+/* Manifest */
+1 RT_MANIFEST "ciolib.manifest"
+
 /* ========================================================================= */
 /* Icons.                                                                    */
 /* ========================================================================= */
 
-1	ICON	"syncicon64.ico"
+2 ICON	"syncicon64.ico"

src/conio/win32gdi.c

@@ -1112,9 +1112,6 @@ gdi_init(int mode)
 {
 	CreatePipe(&rch, &wch, NULL, 0);
 
-	bitmap_drv_init(gdi_drawrect, gdi_flush);
-	gdi_textmode(ciolib_initial_mode);
-
 	// code that tells windows we're High DPI aware so it doesn't scale our windows
 	// taken from Yamagi Quake II
 
@@ -1161,6 +1158,9 @@ gdi_init(int mode)
 	else if (SetProcessDPIAware) {
 		SetProcessDPIAware();
 	}
+	bitmap_drv_init(gdi_drawrect, gdi_flush);
+	gdi_textmode(ciolib_initial_mode);
+
 	_beginthread(gdi_thread, 0, (void *)(intptr_t)mode);
 	WaitForSingleObject(init_sem, INFINITE);
 	CloseHandle(init_sem);

src/syncterm/GNUmakefile

@@ -99,7 +99,7 @@ ifeq ($(os),win32)
  EXTRA_LIBS += -luuid
 endif
 
-$(MTOBJODIR)$(DIRSEP)ciolib_res$(OFILE):
+$(MTOBJODIR)$(DIRSEP)ciolib_res$(OFILE): ${CIOLIB-MT}
 	cd ${MTOBJODIR} && $(AR) -x ../${CIOLIB-MT} ciolib_res$(OFILE)
 
 $(SYNCTERM): $(CRYPT_DEPS) $(EXEODIR) $(OBJS) $(BUILD_DEPENDS)