win32: Set the WS_THICKFRAME style on popup windows

Without it, programmatically resizing the window seems to fail. As popup windows are implicitly borderless, calculations taking the frame size into account need to be avoided.

src/video/windows/SDL_windowsevents.c

@@ -1405,7 +1405,7 @@ LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPara
             constrain_max_size = FALSE;
         }
 
-        if (!(SDL_GetWindowFlags(data->window) & SDL_WINDOW_BORDERLESS)) {
+        if (!(SDL_GetWindowFlags(data->window) & SDL_WINDOW_BORDERLESS) && !SDL_WINDOW_IS_POPUP(data->window)) {
             size.top = 0;
             size.left = 0;
             size.bottom = h;
@@ -1991,7 +1991,7 @@ LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPara
             {
                 RECT rect = { 0 };
 
-                if (!(data->window->flags & SDL_WINDOW_BORDERLESS)) {
+                if (!(data->window->flags & SDL_WINDOW_BORDERLESS) && !SDL_WINDOW_IS_POPUP(data->window)) {
                     WIN_AdjustWindowRectForHWND(hwnd, &rect, prevDPI);
                 }
 
@@ -2008,7 +2008,7 @@ LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPara
                 rect.right = query_client_w_win;
                 rect.bottom = query_client_h_win;
 
-                if (!(data->window->flags & SDL_WINDOW_BORDERLESS)) {
+                if (!(data->window->flags & SDL_WINDOW_BORDERLESS) && !SDL_WINDOW_IS_POPUP(data->window)) {
                     WIN_AdjustWindowRectForHWND(hwnd, &rect, nextDPI);
                 }
 

src/video/windows/SDL_windowswindow.c

@@ -162,7 +162,7 @@ static DWORD GetWindowStyle(SDL_Window *window)
     DWORD style = 0;
 
     if (SDL_WINDOW_IS_POPUP(window)) {
-        style |= WS_POPUP;
+        style |= WS_POPUP | WS_THICKFRAME;
     } else if (window->flags & SDL_WINDOW_FULLSCREEN) {
         style |= STYLE_FULLSCREEN;
     } else {
@@ -269,7 +269,7 @@ static bool WIN_AdjustWindowRectWithStyle(SDL_Window *window, DWORD style, DWORD
     /* borderless windows will have WM_NCCALCSIZE return 0 for the non-client area. When this happens, it looks like windows will send a resize message
        expanding the window client area to the previous window + chrome size, so shouldn't need to adjust the window size for the set styles.
      */
-    if (!(window->flags & SDL_WINDOW_BORDERLESS)) {
+    if (!(window->flags & SDL_WINDOW_BORDERLESS) && !SDL_WINDOW_IS_POPUP(window)) {
 #if defined(SDL_PLATFORM_XBOXONE) || defined(SDL_PLATFORM_XBOXSERIES)
         AdjustWindowRectEx(&rect, style, menu, 0);
 #else
@@ -765,6 +765,9 @@ bool WIN_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_Properties
         WIN_ConstrainPopup(window, false);
         WIN_AdjustWindowRectWithStyle(window, style, styleEx, FALSE, &x, &y, &w, &h, SDL_WINDOWRECT_FLOATING);
 
+        int gx, gy;
+        SDL_RelativeToGlobalForWindow(window, window->floating.x, window->floating.y, &gx, &gy);
+        SDL_Log("Create at: %i,%i (%i,%i)", gx, gy, x, y);
         hwnd = CreateWindowEx(styleEx, SDL_Appname, TEXT(""), style,
                               x, y, w, h, parent, NULL, SDL_Instance, NULL);
         if (!hwnd) {