Win32: center plugin UIs when opening them

source/modules/dgl/src/Window.cpp

@@ -87,7 +87,8 @@ struct Window::PrivateData {
           fWidgets(),
           fModal(),
 #if defined(DISTRHO_OS_WINDOWS)
-          hwnd(0)
+          hwnd(nullptr),
+          hwndParent(nullptr)
 #elif defined(DISTRHO_OS_MAC)
           fNeedsIdle(true),
           mView(nullptr),
@@ -115,7 +116,8 @@ struct Window::PrivateData {
           fWidgets(),
           fModal(parent.pData),
 #if defined(DISTRHO_OS_WINDOWS)
-          hwnd(0)
+          hwnd(nullptr),
+          hwndParent(nullptr)
 #elif defined(DISTRHO_OS_MAC)
           fNeedsIdle(false),
           mView(nullptr),
@@ -132,7 +134,8 @@ struct Window::PrivateData {
 
         // NOTE: almost a 1:1 copy of setTransientWinId()
 #if defined(DISTRHO_OS_WINDOWS)
-        SetWindowLongPtr(hwnd, GWLP_HWNDPARENT, (LONG_PTR)parentImpl->hwnd);
+        hwndParent = parentImpl->hwnd;
+        SetWindowLongPtr(hwnd, GWLP_HWNDPARENT, (LONG_PTR)hwndParent);
 #elif defined(DISTRHO_OS_MAC)
         [mWindow orderWindow:NSWindowBelow relativeTo:parentImpl->window];
 #else
@@ -154,7 +157,8 @@ struct Window::PrivateData {
           fWidgets(),
           fModal(),
 #if defined(DISTRHO_OS_WINDOWS)
-          hwnd(0)
+          hwnd(nullptr),
+          hwndParent(nullptr)
 #elif defined(DISTRHO_OS_MAC)
           fNeedsIdle(parentId == 0),
           mView(nullptr),
@@ -434,9 +438,34 @@ struct Window::PrivateData {
 
 #if defined(DISTRHO_OS_WINDOWS)
         if (yesNo)
-            ShowWindow(hwnd, fFirstInit ? SW_SHOWNORMAL : SW_RESTORE);
+        {
+            if (fFirstInit)
+            {
+                RECT rectChild, rectParent;
+
+                if (hwndParent != nullptr &&
+                    GetWindowRect(hwnd, &rectChild) &&
+                    GetWindowRect(hwndParent, &rectParent))
+                {
+                    SetWindowPos(hwnd, hwndParent,
+                                 rectParent.left + (rectChild.right-rectChild.left)/2,
+                                 rectParent.top + (rectChild.bottom-rectChild.top)/2,
+                                 0, 0, SWP_SHOWWINDOW|SWP_NOSIZE);
+                }
+                else
+                {
+                    ShowWindow(hwnd, SW_SHOWNORMAL);
+                }
+            }
+            else
+            {
+                ShowWindow(hwnd, SW_RESTORE);
+            }
+        }
         else
+        {
             ShowWindow(hwnd, SW_HIDE);
+        }
 
         UpdateWindow(hwnd);
 #elif defined(DISTRHO_OS_MAC)
@@ -624,6 +653,7 @@ struct Window::PrivateData {
         DISTRHO_SAFE_ASSERT_RETURN(winId != 0,);
 
 #if defined(DISTRHO_OS_WINDOWS)
+        hwndParent = (HWND)winId;
         SetWindowLongPtr(hwnd, GWLP_HWNDPARENT, (LONG_PTR)winId);
 #elif defined(DISTRHO_OS_MAC)
         NSWindow* const window = [NSApp windowWithWindowNumber:winId];
@@ -979,7 +1009,8 @@ struct Window::PrivateData {
     } fModal;
 
 #if defined(DISTRHO_OS_WINDOWS)
-    HWND     hwnd;
+    HWND hwnd;
+    HWND hwndParent;
 #elif defined(DISTRHO_OS_MAC)
     bool            fNeedsIdle;
     PuglOpenGLView* mView;

source/utils/CarlaPluginUI.cpp

@@ -599,7 +599,8 @@ class WindowsPluginUI : public CarlaPluginUI
 public:
     WindowsPluginUI(Callback* const cb, const uintptr_t parentId, const bool isResizable) noexcept
         : CarlaPluginUI(cb, isResizable),
-          fWindow(0),
+          fWindow(nullptr),
+          fParentWindow(nullptr),
           fIsVisible(false),
           fFirstShow(true)
      {
@@ -668,9 +669,31 @@ public:
     {
         CARLA_SAFE_ASSERT_RETURN(fWindow != 0,);
 
-        ShowWindow(fWindow, fFirstShow ? SW_SHOWNORMAL : SW_RESTORE);
+        if (fFirstShow)
+        {
+            fFirstShow = false;
+            RECT rectChild, rectParent;
+
+            if (fParentWindow != nullptr &&
+                GetWindowRect(fWindow, &rectChild) &&
+                GetWindowRect(fParentWindow, &rectParent))
+            {
+                SetWindowPos(fWindow, fParentWindow,
+                             rectParent.left + (rectChild.right-rectChild.left)/2,
+                             rectParent.top + (rectChild.bottom-rectChild.top)/2,
+                             0, 0, SWP_SHOWWINDOW|SWP_NOSIZE);
+            }
+            else
+            {
+                ShowWindow(fWindow, SW_SHOWNORMAL);
+            }
+        }
+        else
+        {
+            ShowWindow(fWindow, SW_RESTORE);
+        }
+
         fIsVisible = true;
-        fFirstShow = false;
         UpdateWindow(fWindow);
     }
 
@@ -762,6 +785,7 @@ public:
     {
         CARLA_SAFE_ASSERT_RETURN(fWindow != 0,);
 
+        fParentWindow = (HWND)winId;
         SetWindowLongPtr(fWindow, GWLP_HWNDPARENT, (LONG_PTR)winId);
     }
 
@@ -782,6 +806,7 @@ public:
 
 private:
     HWND     fWindow;
+    HWND     fParentWindow;
     WNDCLASS fWindowClass;
 
     bool fIsVisible;