7 files changed, 47 insertions, 15 deletions
diff --git a/dggui/nativewindow.h b/dggui/nativewindow.h
index 07c3559..715d7ca 100644
--- a/dggui/nativewindow.h
+++ b/dggui/nativewindow.h
@@ -59,6 +59,11 @@ public:
 	//! Query size of the native window.
 	virtual std::pair<std::size_t, std::size_t> getSize() const = 0;
 
+	//! While there isn’t a universally agreed-upon meaning for what constitutes
+	//! HiDPI, a common benchmark is that displays with more than double the PPI
+	//! of the old standard (72-96) can arguably be classified as HiDPI.
+	virtual bool isHiDPI() = 0;
+
 	//! Move the window to a new position.
 	//! Note: negative value are allowed.
 	virtual void move(int x, int y) = 0;
diff --git a/dggui/nativewindow_cocoa.h b/dggui/nativewindow_cocoa.h
index e17d4af..0bfa73b 100644
--- a/dggui/nativewindow_cocoa.h
+++ b/dggui/nativewindow_cocoa.h
@@ -42,21 +42,22 @@ public:
 	~NativeWindowCocoa();
 
 	// From NativeWindow:
-	virtual void setFixedSize(std::size_t width, std::size_t height) override;
-	virtual void setAlwaysOnTop(bool always_on_top) override;
-	virtual void resize(std::size_t width, std::size_t height) override;
-	virtual std::pair<std::size_t, std::size_t> getSize() const override;
-	virtual void move(int x, int y) override;
-	virtual std::pair<int, int> getPosition() const override;
-	virtual void show() override;
-	virtual void hide() override;
-	virtual bool visible() const override;
-	virtual void setCaption(const std::string &caption) override;
-	virtual void redraw(const Rect& dirty_rect) override;
-	virtual void grabMouse(bool grab) override;
-	virtual EventQueue getEvents() override;
-	virtual void* getNativeWindowHandle() const override;
-	virtual Point translateToScreen(const Point& point) override;
+	void setFixedSize(std::size_t width, std::size_t height) override;
+	void setAlwaysOnTop(bool always_on_top) override;
+	void resize(std::size_t width, std::size_t height) override;
+	std::pair<std::size_t, std::size_t> getSize() const override;
+	bool isHiDPI() override;
+	void move(int x, int y) override;
+	std::pair<int, int> getPosition() const override;
+	void show() override;
+	void hide() override;
+	bool visible() const override;
+	void setCaption(const std::string &caption) override;
+	void redraw(const Rect& dirty_rect) override;
+	void grabMouse(bool grab) override;
+	EventQueue getEvents() override;
+	void* getNativeWindowHandle() const override;
+	Point translateToScreen(const Point& point) override;
 
 	// Expose friend members of Window to ObjC++ implementation.
 	class Window& getWindow();
diff --git a/dggui/nativewindow_cocoa.mm b/dggui/nativewindow_cocoa.mm
index 3214f57..9484af7 100644
--- a/dggui/nativewindow_cocoa.mm
+++ b/dggui/nativewindow_cocoa.mm
@@ -609,6 +609,12 @@ std::pair<std::size_t, std::size_t> NativeWindowCocoa::getSize() const
 	}
 }
 
+bool NativeWindowCocoa::isHiDPI()
+{
+  float dpi = [priv->window backingScaleFactor];
+  return dpi > 1.0f;
+}
+
 void NativeWindowCocoa::move(int x, int y)
 {
 	NSRect screen = [[NSScreen mainScreen] frame];
diff --git a/dggui/nativewindow_win32.cc b/dggui/nativewindow_win32.cc
index db785e9..45cbd30 100644
--- a/dggui/nativewindow_win32.cc
+++ b/dggui/nativewindow_win32.cc
@@ -489,6 +489,15 @@ std::pair<std::size_t, std::size_t> NativeWindowWin32::getSize() const
 	return std::make_pair(rect.right - rect.left, rect.bottom - rect.top);
 }
 
+bool NativeWindowWin32::isHiDPI()
+{
+	HDC hDC = GetDC(m_hwnd);
+	INT xres = GetDeviceCaps(hDC, LOGPIXELSX);
+	INT yres = GetDeviceCaps(hDC, LOGPIXELSY);
+	ReleaseDC(m_hwnd, hDC);
+	return xres >= 2 * 96 || yres >= 2 * 96;
+}
+
 void NativeWindowWin32::move(int x, int y)
 {
 	SetWindowPos(m_hwnd, always_on_top ? HWND_TOPMOST : nullptr,
diff --git a/dggui/nativewindow_win32.h b/dggui/nativewindow_win32.h
index f4748fe..e8adbfd 100644
--- a/dggui/nativewindow_win32.h
+++ b/dggui/nativewindow_win32.h
@@ -49,6 +49,7 @@ public:
 	void setAlwaysOnTop(bool always_on_top) override;
 	void resize(std::size_t width, std::size_t height) override;
 	std::pair<std::size_t, std::size_t> getSize() const override;
+	bool isHiDPI() override;
 	void move(int x, int y) override;
 	std::pair<int, int> getPosition() const override;
 	void show() override;
diff --git a/dggui/nativewindow_x11.cc b/dggui/nativewindow_x11.cc
index 04f1b35..2f94935 100644
--- a/dggui/nativewindow_x11.cc
+++ b/dggui/nativewindow_x11.cc
@@ -240,6 +240,15 @@ std::pair<std::size_t, std::size_t> NativeWindowX11::getSize() const
 	return {width, height};
 }
 
+bool NativeWindowX11::isHiDPI()
+{
+	auto xres = ((((double) DisplayWidth(display, screen)) * 25.4) /
+	             ((double) DisplayWidthMM(display, screen))) + 0.5;
+	auto yres = ((((double) DisplayHeight(display, screen)) * 25.4) /
+	             ((double) DisplayHeightMM(display, screen))) + 0.5;
+	return xres >= 2 * 96 || yres >= 2 * 96;
+}
+
 void NativeWindowX11::move(int x, int y)
 {
 	if(display == nullptr)
diff --git a/dggui/nativewindow_x11.h b/dggui/nativewindow_x11.h
index bed86bd..94ac6a7 100644
--- a/dggui/nativewindow_x11.h
+++ b/dggui/nativewindow_x11.h
@@ -50,6 +50,7 @@ public:
 	void setAlwaysOnTop(bool always_on_top) override;
 	void resize(std::size_t width, std::size_t height) override;
 	std::pair<std::size_t, std::size_t> getSize() const override;
+	bool isHiDPI() override;;
 	void move(int x, int y) override;
 	std::pair<int, int> getPosition() const override;
 	void show() override;