Windows: Ready for high-DPI displays (fix BoboTiG#20)

Mickaël Schoentgen · BoboTiG · commit a0df61b6dfed · 2017-08-06T01:27:23.000+02:00
diff --git a/CHANGELOG b/CHANGELOG
@@ -9,6 +9,7 @@ dev     2017/xx/xx
       - MSS: possibility to use custom class to handle screen shot data
       - Mac: handle screenshot's width not divisible by 16 (fix #14, #19, #21)
       - Linux: handle bad display value
+      - Windows: Take into account zoom factor for high-DPI displays (fix #20)
 
 3.0.1   2017/07/06
       - fix examples links
diff --git a/CHANGES.rst b/CHANGES.rst
@@ -9,6 +9,11 @@ darwin.py
 ---------
 - Removed `get_infinity()` function
 
+windows.py
+----------
+- Added `scale_factor` property to `MSS` class
+- Added `scale()` method to `MSS` class
+
 
 3.0.0 (2017-07-06)
 ==================
diff --git a/mss/__main__.py b/mss/__main__.py
@@ -6,19 +6,21 @@
 
 from __future__ import print_function
 
+from .exception import ScreenShotError
 from .factory import mss
 
 
 def main():
     # type: () -> int
     """ Main logic. """
 
-    with mss() as sct:
-        for file_name in sct.save():
-            print(file_name)
-        return 0
-
-    return 1
+    try:
+        with mss() as sct:
+            for file_name in sct.save():
+                print(file_name)
+            return 0
+    except ScreenShotError:
+        return 1
 
 
 if __name__ == '__main__':
diff --git a/mss/darwin.py b/mss/darwin.py
@@ -152,7 +152,7 @@ def monitors(self):
                 # Update AiO monitor's values
                 all_monitors = self.core.CGRectUnion(all_monitors, rect)
 
-            # Update AiO monitor's values
+            # Set the AiO monitor's values
             self._monitors[0] = {
                 'left': int(all_monitors.origin.x),
                 'top': int(all_monitors.origin.y),
diff --git a/mss/windows.py b/mss/windows.py
@@ -4,6 +4,8 @@
 Source: https://github.com/BoboTiG/python-mss
 """
 
+from __future__ import division
+
 import ctypes
 import ctypes.wintypes
 
@@ -41,6 +43,8 @@ class BITMAPINFO(ctypes.Structure):
 class MSS(MSSBase):
     """ Multiple ScreenShots implementation for Microsoft Windows. """
 
+    __scale_factor = None  # type: float
+
     def __init__(self):
         # type: () -> None
         """ Windows initialisations. """
@@ -55,6 +59,32 @@ def __init__(self):
         set_argtypes(self.monitorenumproc)
         set_restypes()
 
+    @property
+    def scale_factor(self):
+        """ Compute the scale factor. """
+
+        if not self.__scale_factor:
+            display = None
+            try:
+                display = ctypes.windll.user32.GetWindowDC(0)
+                width = ctypes.windll.gdi32.GetDeviceCaps(display, 8)
+                width_orig = ctypes.windll.gdi32.GetDeviceCaps(display, 118)
+                scale = (100 + 100 - width * 100 // width_orig) / 100
+                self.__scale_factor = round(scale * 4) / 4
+            finally:
+                if display:
+                    ctypes.windll.gdi32.DeleteObject(display)
+
+        return self.__scale_factor
+
+    def scale(self, value):
+        # type: (float) -> int
+        """ Compute a monitor value at scale, rounded to 2. """
+
+        if self.scale_factor == 1.0:
+            return int(value)
+        return int(value * self.scale_factor * 2 + 0.5) // 2
+
     @property
     def monitors(self):
         # type: () -> List[Dict[str, int]]
@@ -69,10 +99,11 @@ def monitors(self):
             top = ctypes.windll.user32.GetSystemMetrics(sm_yvirtualscreen)
             bottom = ctypes.windll.user32.GetSystemMetrics(sm_cyvirtualscreen)
             self._monitors.append({
-                'left': int(left),
-                'top': int(top),
-                'width': int(right - left),
-                'height': int(bottom - top),
+                'left': self.scale(left),
+                'top': self.scale(top),
+                'width': self.scale(right - left),
+                'height': self.scale(bottom - top),
+                'scale': self.scale_factor,
             })
 
             # Each monitors
@@ -86,10 +117,11 @@ def _callback(monitor, data, rect, dc_):
                 del monitor, data, dc_
                 rct = rect.contents
                 self._monitors.append({
-                    'left': int(rct.left),
-                    'top': int(rct.top),
-                    'width': int(rct.right - rct.left),
-                    'height': int(rct.bottom - rct.top),
+                    'left': self.scale(rct.left),
+                    'top': self.scale(rct.top),
+                    'width': self.scale(rct.right - rct.left),
+                    'height': self.scale(rct.bottom - rct.top),
+                    'scale': self.scale_factor,
                 })
                 return 1
 
@@ -145,6 +177,7 @@ def grab(self, monitor):
             buf_len = monitor['width'] * monitor['height'] * 4  # See [2]
             data = ctypes.create_string_buffer(buf_len)
             srcdc = ctypes.windll.user32.GetWindowDC(0)
+
             memdc = ctypes.windll.gdi32.CreateCompatibleDC(srcdc)
             bmp = ctypes.windll.gdi32.CreateCompatibleBitmap(
                 srcdc, monitor['width'], monitor['height'])
@@ -184,6 +217,8 @@ def set_argtypes(callback):
         callback,
         ctypes.wintypes.LPARAM]
     ctypes.windll.user32.GetWindowDC.argtypes = [ctypes.wintypes.HWND]
+    ctypes.windll.gdi32.GetDeviceCaps.argtypes = [ctypes.wintypes.HWND,
+                                                  ctypes.wintypes.INT]
     ctypes.windll.gdi32.CreateCompatibleDC.argtypes = [ctypes.wintypes.HDC]
     ctypes.windll.gdi32.CreateCompatibleBitmap.argtypes = [
         ctypes.wintypes.HDC,
@@ -219,6 +254,7 @@ def set_restypes():
     ctypes.windll.user32.GetSystemMetrics.restype = ctypes.wintypes.INT
     ctypes.windll.user32.EnumDisplayMonitors.restype = ctypes.wintypes.BOOL
     ctypes.windll.user32.GetWindowDC.restype = ctypes.wintypes.HDC
+    ctypes.windll.gdi32.GetDeviceCaps.restype = ctypes.wintypes.INT
     ctypes.windll.gdi32.CreateCompatibleDC.restype = ctypes.wintypes.HDC
     ctypes.windll.gdi32.CreateCompatibleBitmap.restype = \
         ctypes.wintypes.HBITMAP
