Viewport: Exposing SetNextWindowViewport(). Used in demo and old/obsolete SetNextWindowPosCenter() (which is an interesting case). Fixed back-end likely crash calling GetFocus() after viewport destruction. Fixed metrics crash.

imgui.cpp

@@ -3594,6 +3594,7 @@ void ImGui::UpdatePlatformWindows()
                     g.PlatformIO.Renderer_DestroyWindow(viewport);
                 if (g.PlatformIO.Platform_DestroyWindow)
                     g.PlatformIO.Platform_DestroyWindow(viewport);
+                viewport->CreatedPlatformWindow = false;
                 IM_ASSERT(viewport->RendererUserData == NULL);
                 IM_ASSERT(viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
             }
@@ -7916,6 +7917,15 @@ void ImGui::SetNextWindowPos(const ImVec2& pos, ImGuiCond cond, const ImVec2& pi
     g.NextWindowData.PosCond = cond ? cond : ImGuiCond_Always;
 }
 
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+void ImGui::SetNextWindowPosCenter(ImGuiCond cond) 
+{ 
+    ImGuiViewport* viewport = ImGui::GetMainViewport(); 
+    SetNextWindowPos(viewport->Pos + viewport->Size * 0.5f, cond, ImVec2(0.5f, 0.5f)); 
+    SetNextWindowViewport(viewport->ID); 
+}
+#endif
+
 void ImGui::SetNextWindowSize(const ImVec2& size, ImGuiCond cond)
 {
     ImGuiContext& g = *GImGui;
@@ -14260,7 +14270,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                 else
                     ImGui::BulletText("NavRectRel[0]: <None>");
                 ImGui::BulletText("Viewport: %d, ViewportId: 0x%08X, ViewportPos: (%.1f,%.1f)", window->Viewport ? window->Viewport->Idx : -1, window->ViewportId, window->ViewportPos.x, window->ViewportPos.y);
-                ImGui::BulletText("ViewportMonitor: %d", window->Viewport->PlatformMonitor);
+                ImGui::BulletText("ViewportMonitor: %d", window->Viewport ? window->Viewport->PlatformMonitor : -1);
                 if (window->RootWindow != window) NodeWindow(window->RootWindow, "RootWindow");
                 if (window->ParentWindow != NULL) NodeWindow(window->ParentWindow, "ParentWindow");
                 if (window->DC.ChildWindows.Size > 0) NodeWindows(window->DC.ChildWindows, "ChildWindows");

imgui.h

@@ -206,6 +206,7 @@ namespace ImGui
     IMGUI_API void          SetNextWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                 // set next window collapsed state. call before Begin()
     IMGUI_API void          SetNextWindowFocus();                                                       // set next window to be focused / front-most. call before Begin()
     IMGUI_API void          SetNextWindowBgAlpha(float alpha);                                          // set next window background color alpha. helper to easily modify ImGuiCol_WindowBg/ChildBg/PopupBg.
+    IMGUI_API void          SetNextWindowViewport(ImGuiID viewport_id);                                 // set next window viewport
     IMGUI_API void          SetWindowPos(const ImVec2& pos, ImGuiCond cond = 0);                        // (not recommended) set current window position - call within Begin()/End(). prefer using SetNextWindowPos(), as this may incur tearing and side-effects.
     IMGUI_API void          SetWindowSize(const ImVec2& size, ImGuiCond cond = 0);                      // (not recommended) set current window size - call within Begin()/End(). set to ImVec2(0,0) to force an auto-fit. prefer using SetNextWindowSize(), as this may incur tearing and minor side-effects.    
     IMGUI_API void          SetWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                     // (not recommended) set current window collapsed state. prefer using SetNextWindowCollapsed().
@@ -1148,7 +1149,7 @@ namespace ImGui
     bool                Begin(const char* name, bool* p_open, const ImVec2& size_on_first_use, float bg_alpha_override = -1.0f, ImGuiWindowFlags flags = 0); // Use SetNextWindowSize(size, ImGuiCond_FirstUseEver) + SetNextWindowBgAlpha() instead.
     static inline bool  IsRootWindowOrAnyChildHovered()       { return IsWindowHovered(ImGuiHoveredFlags_RootAndChildWindows); }
     static inline void  AlignFirstTextHeightToWidgets()       { AlignTextToFramePadding(); }
-    static inline void  SetNextWindowPosCenter(ImGuiCond c=0) { ImGuiIO& io = GetIO(); SetNextWindowPos(ImVec2(io.DisplaySize.x * 0.5f, io.DisplaySize.y * 0.5f), c, ImVec2(0.5f, 0.5f)); } // FIXME-VIEWPORT-ABS: Select viewport based on mouse position
+    void                SetNextWindowPosCenter(ImGuiCond cond);
     // OBSOLETED in 1.51 (between Jun 2017 and Aug 2017)
     static inline bool  IsItemHoveredRect()                   { return IsItemHovered(ImGuiHoveredFlags_RectOnly); }
     static inline bool  IsPosHoveringAnyWindow(const ImVec2&) { IM_ASSERT(0); return false; } // This was misleading and partly broken. You probably want to use the ImGui::GetIO().WantCaptureMouse flag instead.

imgui_demo.cpp

@@ -2477,11 +2477,14 @@ static void ShowExampleAppFixedOverlay(bool* p_open)
     // FIXME-VIEWPORT-ABS: Select a default viewport
     const float DISTANCE = 10.0f;
     static int corner = 0;
+    if (corner != -1)
+    {
         ImGuiViewport* viewport = ImGui::GetMainViewport();
         ImVec2 window_pos = ImVec2((corner & 1) ? (viewport->Pos.x + viewport->Size.x - DISTANCE) : (viewport->Pos.x + DISTANCE), (corner & 2) ? (viewport->Pos.y + viewport->Size.y - DISTANCE) : (viewport->Pos.y + DISTANCE));
         ImVec2 window_pos_pivot = ImVec2((corner & 1) ? 1.0f : 0.0f, (corner & 2) ? 1.0f : 0.0f);
-    if (corner != -1)
         ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always, window_pos_pivot);
+        ImGui::SetNextWindowViewport(viewport->ID);
+    }
     ImGui::SetNextWindowBgAlpha(0.3f); // Transparent background
     if (ImGui::Begin("Example: Fixed Overlay", p_open, (corner != -1 ? ImGuiWindowFlags_NoMove : 0) | ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_AlwaysAutoResize|ImGuiWindowFlags_NoSavedSettings|ImGuiWindowFlags_NoFocusOnAppearing|ImGuiWindowFlags_NoNav))
     {

imgui_internal.h

@@ -1080,7 +1080,6 @@ namespace ImGui
 
     // Viewports
     IMGUI_API ImGuiViewportP*       FindViewportByID(ImGuiID id);
-    IMGUI_API void                  SetNextWindowViewport(ImGuiID id);
     IMGUI_API void                  ScaleWindowsInViewport(ImGuiViewportP* viewport, float scale);
     IMGUI_API void                  ShowViewportThumbnails();