Windows: Use the system UI scaling factor

Check for system UI scaling factor via Direct2D DPI values.

3 files changed, 27 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0a54a9eb..1e323d47 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -212,6 +212,9 @@ if (APPLE)
         MACOSX_BUNDLE_COPYRIGHT "© ${COPYRIGHT_YEAR} Jaakko Keränen"
     )
 endif ()
+if (MSYS)
+    target_link_libraries (app PUBLIC d2d1 uuid) # querying DPI
+endif ()
 if (UNIX)
     target_link_libraries (app PUBLIC m)
 endif ()
diff --git a/res/about/version.gmi b/res/about/version.gmi
index f5b38149..788d2ea0 100644
--- a/res/about/version.gmi
+++ b/res/about/version.gmi
@@ -8,6 +8,7 @@
 
 ## 0.4
 * Visual fine-tuning: increased Fira Sans line spacing; list bullets use an accent color.
+* Windows: Support for HiDPI and system UI scaling factor.
 
 ## 0.3
 * Added style customization.
diff --git a/src/ui/window.c b/src/ui/window.c
index 419e6a0a..c0e8fdad 100644
--- a/src/ui/window.c
+++ b/src/ui/window.c
@@ -38,6 +38,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
 #include "../gmutil.h"
 #if defined (iPlatformMsys)
 #   include "../win32.h"
+#   include <d2d1.h>
 #endif
 #if defined (iPlatformApple) && !defined (iPlatformIOS)
 #   include "macos.h"
@@ -491,10 +492,26 @@ static void updateRootSize_Window_(iWindow *d) {
 }
 
 static float pixelRatio_Window_(const iWindow *d) {
+#if defined (iPlatformMsys)
+    /* Query Direct2D for the desktop DPI (not aware of which monitor, though). */ {
+        float ratio = 1.0f;
+        ID2D1Factory *d2dFactory = NULL;
+        HRESULT hr = D2D1CreateFactory(
+            D2D1_FACTORY_TYPE_SINGLE_THREADED, &IID_ID2D1Factory, NULL, (void **) &d2dFactory);
+        if (SUCCEEDED(hr)) {
+            FLOAT dpiX = 96;
+            FLOAT dpiY = 96;
+            ID2D1Factory_GetDesktopDpi(d2dFactory, &dpiX, &dpiY);
+            ratio = (float) (dpiX / 96.0);
+            ID2D1Factory_Release(d2dFactory);
+        }
+    }
+#else
     int dx, x;
     SDL_GetRendererOutputSize(d->render, &dx, NULL);
     SDL_GetWindowSize(d->win, &x, NULL);
     return (float) dx / (float) x;
+#endif
 }
 
 static void drawBlank_Window_(iWindow *d) {
@@ -778,7 +795,13 @@ iInt2 rootSize_Window(const iWindow *d) {
 }
 
 iInt2 coord_Window(const iWindow *d, int x, int y) {
+#if defined (iPlatformMsys)
+    /* On Windows, surface coordinates are in pixels. */
+    return init_I2(x, y);
+#else
+    /* Coordinates are in points. */
     return mulf_I2(init_I2(x, y), d->pixelRatio);
+#endif
 }
 
 iInt2 mouseCoord_Window(const iWindow *d) {