Add initial support for HiDPI in TkAgg on Windows.

QuLogic · QuLogic · commit c06cc86d47d9 · 2021-05-11T00:39:15.000-04:00
At the moment, Tk does not support updating the 'scaling' value when the
monitor pixel ratio changes, or the window is moved to a different one.
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -167,7 +167,7 @@ def __init__(self, figure=None, master=None, resize_callback=None):
         super().__init__(figure)
         self._idle_draw_id = None
         self._event_loop_id = None
-        w, h = self.figure.bbox.size.astype(int)
+        w, h = self.get_width_height(physical=True)
         self._tkcanvas = tk.Canvas(
             master=master, background="white",
             width=w, height=h, borderwidth=0, highlightthickness=0)
@@ -176,6 +176,7 @@ def __init__(self, figure=None, master=None, resize_callback=None):
         self._tkcanvas.create_image(w//2, h//2, image=self._tkphoto)
         self._resize_callback = resize_callback
         self._tkcanvas.bind("<Configure>", self.resize)
+        self._tkcanvas.bind("<Map>", self._update_device_pixel_ratio)
         self._tkcanvas.bind("<Key>", self.key_press)
         self._tkcanvas.bind("<Motion>", self.motion_notify_event)
         self._tkcanvas.bind("<Enter>", self.enter_notify_event)
@@ -210,6 +211,18 @@ def filter_destroy(event):
         self._master = master
         self._tkcanvas.focus_set()
 
+    def _update_device_pixel_ratio(self, event=None):
+        # Tk gives scaling with respect to 72 DPI, but most (all?) screens are
+        # scaled vs 96 dpi, and pixel ratio settings are given in whole
+        # percentages, so round to 2 digits.
+        ratio = round(self._master.call('tk', 'scaling') / (96 / 72), 2)
+        if self._set_device_pixel_ratio(ratio):
+            # The easiest way to resize the canvas is to resize the canvas
+            # widget itself, since we implement all the logic for resizing the
+            # canvas backing store on that event.
+            w, h = self.get_width_height(physical=True)
+            self._tkcanvas.configure(width=w, height=h)
+
     def resize(self, event):
         width, height = event.width, event.height
         if self._resize_callback is not None:
@@ -845,6 +858,7 @@ def new_figure_manager_given_figure(cls, num, figure):
         with _restore_foreground_window_at_end():
             if cbook._get_running_interactive_framework() is None:
                 cbook._setup_new_guiapp()
+                _c_internal_utils.Win32_SetDpiAwareness()
             window = tk.Tk(className="matplotlib")
             window.withdraw()
 
diff --git a/src/_c_internal_utils.c b/src/_c_internal_utils.c
@@ -124,6 +124,15 @@ mpl_SetForegroundWindow(PyObject* module, PyObject *arg)
 #endif
 }
 
+static PyObject*
+mpl_SetDpiAwareness(PyObject* module)
+{
+#ifdef _WIN32
+    SetProcessDPIAware();
+#endif
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef functions[] = {
     {"display_is_valid", (PyCFunction)mpl_display_is_valid, METH_NOARGS,
      "display_is_valid()\n--\n\n"
@@ -151,6 +160,11 @@ static PyMethodDef functions[] = {
      "Win32_SetForegroundWindow(hwnd, /)\n--\n\n"
      "Wrapper for Windows' SetForegroundWindow.  On non-Windows platforms, \n"
      "a no-op."},
+    {"Win32_SetDpiAwareness",
+     (PyCFunction)mpl_SetDpiAwareness, METH_NOARGS,
+     "Win32_SetDpiAwareness()\n--\n\n"
+     "Set Windows' process DPI awareness to be enabled. On non-Windows\n"
+     "platforms, does nothing."},
     {NULL, NULL}};  // sentinel.
 static PyModuleDef util_module = {
     PyModuleDef_HEAD_INIT, "_c_internal_utils", "", 0, functions, NULL, NULL, NULL, NULL};
