Dpi unaware placement bug (#2121)

Fix for bug when placing dpi unaware window such as Notepad++ in left of right part of monitor. In that application gap of about 7px was left or right.
This fixes only single-monitor scenario
It skips correction for dpi unaware window that leaves a gap

src/common/monitors.cpp

@@ -38,6 +38,11 @@ std::vector<MonitorInfo> MonitorInfo::GetMonitors(bool include_toolbar)
     return monitors;
 }
 
+int MonitorInfo::GetMonitorsCount()
+{
+    return GetMonitors(true).size();
+}
+
 static BOOL CALLBACK get_primary_display_enum_cb(HMONITOR monitor, HDC hdc, LPRECT rect, LPARAM data)
 {
     MONITORINFOEX monitor_info;

src/common/monitors.h

@@ -32,6 +32,7 @@ struct MonitorInfo : ScreenSize
 
     // Returns monitor rects ordered from left to right
     static std::vector<MonitorInfo> GetMonitors(bool include_toolbar);
+    static int GetMonitorsCount();
     // Return primary display
     static MonitorInfo GetPrimaryMonitor();
     // Return monitor on which hwnd window is displayed

src/modules/fancyzones/lib/Zone.cpp

@@ -6,6 +6,8 @@
 #include "Settings.h"
 #include "util.h"
 
+#include "common/monitors.h"
+
 struct Zone : winrt::implements<Zone, IZone>
 {
 public:
@@ -78,14 +80,15 @@ RECT Zone::ComputeActualZoneRect(HWND window, HWND zoneWindow) noexcept
 
     const auto level = DPIAware::GetAwarenessLevel(GetWindowDpiAwarenessContext(window));
     const bool accountForUnawareness = level < DPIAware::PER_MONITOR_AWARE;
+
     if (SUCCEEDED(DwmGetWindowAttribute(window, DWMWA_EXTENDED_FRAME_BOUNDS, &frameRect, sizeof(frameRect))))
     {
-        const auto left_margin = frameRect.left - windowRect.left;
-        const auto right_margin = frameRect.right - windowRect.right;
-        const auto bottom_margin = frameRect.bottom - windowRect.bottom;
-        newWindowRect.left -= left_margin;
-        newWindowRect.right -= right_margin;
-        newWindowRect.bottom -= bottom_margin;
+        LONG leftMargin = frameRect.left - windowRect.left;
+        LONG rightMargin = frameRect.right - windowRect.right;
+        LONG bottomMargin = frameRect.bottom - windowRect.bottom;
+        newWindowRect.left -= leftMargin;
+        newWindowRect.right -= rightMargin;
+        newWindowRect.bottom -= bottomMargin;
     }
 
     // Map to screen coords
@@ -97,7 +100,8 @@ RECT Zone::ComputeActualZoneRect(HWND window, HWND zoneWindow) noexcept
         const auto taskbar_left_size = std::abs(mi.rcMonitor.left - mi.rcWork.left);
         const auto taskbar_top_size = std::abs(mi.rcMonitor.top - mi.rcWork.top);
         OffsetRect(&newWindowRect, -taskbar_left_size, -taskbar_top_size);
-        if (accountForUnawareness)
+
+        if (accountForUnawareness && MonitorInfo::GetMonitorsCount() > 1)
         {
             newWindowRect.left = max(mi.rcMonitor.left, newWindowRect.left);
             newWindowRect.right = min(mi.rcMonitor.right - taskbar_left_size, newWindowRect.right);