GDK W32: Apply HiDPI scale properly to monitors

Previously HiDPI scale was retrieved and applied too late in the initialization
process to affect monitor size and monitor workarea size, but the code that
initializes these sizes *did* try to use the scale, even though it was always
getting scale=1.

To fix this, move the too-late code into monitor enumeration routine.
This also fixes a probable semantic bug where width and height were divided
by scale, again.

Now monitor and workarea should be in application pixels (i.e. divided by scale),
as intended.

https://bugzilla.gnome.org/show_bug.cgi?id=778835

2 files changed, 39 insertions, 43 deletions

diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index ddc67672cd..a4b40dabf0 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -199,42 +199,6 @@ _gdk_win32_display_init_monitors (GdkWin32Display *win32_display)
       g_ptr_array_insert (win32_display->monitors, 0, primary_to_move);
       changed = TRUE;
     }
-
-  for (i = 0; i < win32_display->monitors->len; i++)
-    {
-      GdkMonitor *monitor;
-      GdkWin32Monitor *win32_monitor;
-
-      monitor = GDK_MONITOR (g_ptr_array_index (win32_display->monitors, i));
-
-      if (win32_display->has_fixed_scale)
-        gdk_monitor_set_scale_factor (monitor, win32_display->window_scale);
-      else
-        {
-          /* First acquire the scale using the current screen */
-          GdkRectangle workarea;
-          POINT pt;
-          guint scale = _gdk_win32_display_get_monitor_scale_factor (win32_display, NULL, NULL, NULL);
-
-          gdk_monitor_get_workarea (monitor, &workarea);
-          workarea.x -= _gdk_offset_x;
-          workarea.y -= _gdk_offset_y;
-          workarea.x += workarea.width / scale;
-          workarea.y += workarea.height / scale;
-          pt.x = workarea.x;
-          pt.y = workarea.y;
-
-          /* acquire the scale using the monitor which the window is nearest on Windows 8.1+ */
-          if (win32_display->have_at_least_win81)
-            {
-              HMONITOR hmonitor = MonitorFromPoint (pt, MONITOR_DEFAULTTONEAREST);
-              scale = _gdk_win32_display_get_monitor_scale_factor (win32_display, hmonitor, NULL, NULL);
-            }
-
-          gdk_monitor_set_scale_factor (monitor, scale);
-        }
-    }
-
   return changed;
 }
 
diff --git a/gdk/win32/gdkmonitor-win32.c b/gdk/win32/gdkmonitor-win32.c
index ea58cb5fc5..56b4a843eb 100644
--- a/gdk/win32/gdkmonitor-win32.c
+++ b/gdk/win32/gdkmonitor-win32.c
@@ -33,6 +33,8 @@
 
 #include "config.h"
 
+#include "gdkprivate-win32.h"
+#include "gdkdisplay-win32.h"
 #include "gdkmonitor-win32.h"
 
 #include <glib.h>
@@ -681,7 +683,43 @@ enum_monitor (HMONITOR hmonitor,
           /* This is the reason this function exists. This data is not available
            * via other functions.
            */
-          scale = gdk_monitor_get_scale_factor (mon);
+          rect.x = monitor_info.rcWork.left;
+          rect.y = monitor_info.rcWork.top;
+          rect.width = (monitor_info.rcWork.right - monitor_info.rcWork.left);
+          rect.height = (monitor_info.rcWork.bottom - monitor_info.rcWork.top);
+          /* This is temporary, scale will be applied below */
+          w32mon->work_rect = rect;
+
+          if (data->display->has_fixed_scale)
+            scale = data->display->window_scale;
+          else
+            {
+              /* First acquire the scale using the current screen */
+              scale = _gdk_win32_display_get_monitor_scale_factor (data->display, NULL, NULL, NULL);
+
+              /* acquire the scale using the monitor which the window is nearest on Windows 8.1+ */
+              if (data->display->have_at_least_win81)
+                {
+                  HMONITOR hmonitor;
+                  POINT pt;
+
+                  /* Not subtracting _gdk_offset_x and _gdk_offset_y because they will only
+                   * be added later on, in _gdk_win32_display_get_monitor_list().
+                   */
+                  pt.x = w32mon->work_rect.x + w32mon->work_rect.width / 2;
+                  pt.y = w32mon->work_rect.y + w32mon->work_rect.height / 2;
+                  hmonitor = MonitorFromPoint (pt, MONITOR_DEFAULTTONEAREST);
+                  scale = _gdk_win32_display_get_monitor_scale_factor (data->display, hmonitor, NULL, NULL);
+                }
+            }
+
+          gdk_monitor_set_scale_factor (mon, scale);
+          /* Now apply the scale to the work rectangle */
+          w32mon->work_rect.x /= scale;
+          w32mon->work_rect.y /= scale;
+          w32mon->work_rect.width /= scale;
+          w32mon->work_rect.height /= scale;
+
           rect.x = monitor_info.rcMonitor.left / scale;
           rect.y = monitor_info.rcMonitor.top / scale;
           rect.width = (monitor_info.rcMonitor.right - monitor_info.rcMonitor.left) / scale;
@@ -689,12 +727,6 @@ enum_monitor (HMONITOR hmonitor,
           gdk_monitor_set_position (mon, rect.x, rect.y);
           gdk_monitor_set_size (mon, rect.width, rect.height);
 
-          rect.x = monitor_info.rcWork.left / scale;
-          rect.y = monitor_info.rcWork.top / scale;
-          rect.width = (monitor_info.rcWork.right - monitor_info.rcWork.left) / scale;
-          rect.height = (monitor_info.rcWork.bottom - monitor_info.rcWork.top) / scale;
-          w32mon->work_rect = rect;
-
           if (monitor_info.dwFlags & MONITORINFOF_PRIMARY && i != 0)
             {
               /* Put primary monitor at index 0, just in case somebody needs