[Windows] make setMinimum/MaximumSize() dpi change awareable (#231)

* save pixel ratio

* [Windows] makes setMin/MaxSize() dpi change awareable

* use pre defined USER_DEFAULT_SCREEN_DPI instead of hard coded 96.0

---------

Co-authored-by: haolinwei <[email protected]>

Author: hlwhl

windows/window_manager.cpp

@@ -52,6 +52,7 @@ class WindowManager {
   double aspect_ratio_ = 0;
   POINT minimum_size_ = {0, 0};
   POINT maximum_size_ = {-1, -1};
+  double pixel_ratio_ = 1;
   bool is_resizable_ = true;
   bool is_skip_taskbar_ = true;
   std::string title_bar_style_ = "normal";
@@ -534,9 +535,10 @@ void WindowManager::SetMinimumSize(const flutter::EncodableMap& args) {
   double height = std::get<double>(args.at(flutter::EncodableValue("height")));
 
   if (width >= 0 && height >= 0) {
+    pixel_ratio_ = devicePixelRatio;
     POINT point = {};
-    point.x = static_cast<LONG>(width * devicePixelRatio);
-    point.y = static_cast<LONG>(height * devicePixelRatio);
+    point.x = static_cast<LONG>(width);
+    point.y = static_cast<LONG>(height);
     minimum_size_ = point;
   }
 }
@@ -548,9 +550,10 @@ void WindowManager::SetMaximumSize(const flutter::EncodableMap& args) {
   double height = std::get<double>(args.at(flutter::EncodableValue("height")));
 
   if (width >= 0 && height >= 0) {
+    pixel_ratio_ = devicePixelRatio;
     POINT point = {};
-    point.x = static_cast<LONG>(width * devicePixelRatio);
-    point.y = static_cast<LONG>(height * devicePixelRatio);
+    point.x = static_cast<LONG>(width);
+    point.y = static_cast<LONG>(height);
     maximum_size_ = point;
   }
 }

windows/window_manager_plugin.cpp

@@ -108,6 +108,10 @@ std::optional<LRESULT> WindowManagerPlugin::HandleWindowProc(HWND hWnd,
                                                              LPARAM lParam) {
   std::optional<LRESULT> result = std::nullopt;
 
+  if (message == WM_DPICHANGED) {
+    window_manager->pixel_ratio_ = (float) LOWORD(wParam) / USER_DEFAULT_SCREEN_DPI;
+  }
+
   if (message == WM_NCCALCSIZE) {
     // This must always be first or else the one of other two ifs will execute
     //  when window is in full screen and we don't want that
@@ -163,13 +167,21 @@ std::optional<LRESULT> WindowManagerPlugin::HandleWindowProc(HWND hWnd,
     MINMAXINFO* info = reinterpret_cast<MINMAXINFO*>(lParam);
     // For the special "unconstrained" values, leave the defaults.
     if (window_manager->minimum_size_.x != 0)
-      info->ptMinTrackSize.x = window_manager->minimum_size_.x;
+      info->ptMinTrackSize.x =
+          static_cast<LONG> (window_manager->minimum_size_.x *
+          window_manager->pixel_ratio_);
     if (window_manager->minimum_size_.y != 0)
-      info->ptMinTrackSize.y = window_manager->minimum_size_.y;
+      info->ptMinTrackSize.y =
+          static_cast<LONG> (window_manager->minimum_size_.y *
+          window_manager->pixel_ratio_);
     if (window_manager->maximum_size_.x != -1)
-      info->ptMaxTrackSize.x = window_manager->maximum_size_.x;
+      info->ptMaxTrackSize.x =
+          static_cast<LONG> (window_manager->maximum_size_.x *
+          window_manager->pixel_ratio_);
     if (window_manager->maximum_size_.y != -1)
-      info->ptMaxTrackSize.y = window_manager->maximum_size_.y;
+      info->ptMaxTrackSize.y =
+          static_cast<LONG> (window_manager->maximum_size_.y *
+          window_manager->pixel_ratio_);
     result = 0;
   } else if (message == WM_NCACTIVATE) {
     if (wParam == TRUE) {