SetNextWindowPos: added a ImVec2 pivot parameter for positioning a given a center, bottom-right position, etc. As a generalization of SetNextWindowPosCenter() which is now obsolete. This will be useful for combo-like popups as well.

Demo: Simple-overlay window uses the SetWindowPos pivot to select a corner to position itself at.

imgui.cpp

@@ -204,6 +204,7 @@
  Here is a change-log of API breaking changes, if you are using one of the functions listed, expect to have to fix some code.
  Also read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2017/09/25 (1.52) - removed SetNextWindowPosCenter() because SetNextWindowPos() now has the optional pivot information to do the same and more. Kept redirection function (will obsolete). 
  - 2017/08/25 (1.52) - io.MousePos needs to be set to ImVec2(-FLT_MAX,-FLT_MAX) when mouse is unavailable/missing. Previously ImVec2(-1,-1) was enough but we now accept negative mouse coordinates. In your binding if you need to support unavailable mouse, make sure to replace "io.MousePos = ImVec2(-1,-1)" with "io.MousePos = ImVec2(-FLT_MAX,-FLT_MAX)".
  - 2017/08/22 (1.51) - renamed IsItemHoveredRect() to IsItemRectHovered(). Kept inline redirection function (will obsolete).
                      - renamed IsMouseHoveringAnyWindow() to IsAnyWindowHovered() for consistency. Kept inline redirection function (will obsolete).
@@ -1804,7 +1805,7 @@ ImGuiWindow::ImGuiWindow(const char* name)
     AutoPosLastDirection = -1;
     HiddenFrames = 0;
     SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
-    SetWindowPosCenterWanted = false;
+    SetWindowPosVal = SetWindowPosPivot = ImVec2(FLT_MAX, FLT_MAX);
 
     LastFrameActive = -1;
     ItemWidthDefault = 0.0f;
@@ -3619,11 +3620,15 @@ bool ImGui::BeginPopupModal(const char* name, bool* p_open, ImGuiWindowFlags ext
         return false;
     }
 
+    // Center modal windows by default
+    if ((window->SetWindowPosAllowFlags & g.SetNextWindowPosCond) == 0)
+        SetNextWindowPos(g.IO.DisplaySize * 0.5f, ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
+
     ImGuiWindowFlags flags = extra_flags|ImGuiWindowFlags_Popup|ImGuiWindowFlags_Modal|ImGuiWindowFlags_NoCollapse|ImGuiWindowFlags_NoSavedSettings;
     bool is_open = ImGui::Begin(name, p_open, flags);
     if (!is_open || (p_open && !*p_open)) // NB: is_open can be 'false' when the popup is completely clipped (e.g. zero size display)
     {
-        ImGui::EndPopup();
+        EndPopup();
         if (is_open)
             ClosePopup(id);
         return false;
@@ -3994,9 +3999,12 @@ bool ImGui::Begin(const char* name, bool* p_open, const ImVec2& size_on_first_us
         if (window->Appearing) 
             window->SetWindowPosAllowFlags |= ImGuiCond_Appearing;
         window_pos_set_by_api = (window->SetWindowPosAllowFlags & g.SetNextWindowPosCond) != 0;
-        if (window_pos_set_by_api && ImLengthSqr(g.SetNextWindowPosVal - ImVec2(-FLT_MAX,-FLT_MAX)) < 0.001f)
+        if (window_pos_set_by_api && ImLengthSqr(g.SetNextWindowPosPivot) > 0.00001f)
         {
-            window->SetWindowPosCenterWanted = true;                            // May be processed on the next frame if this is our first frame and we are measuring size
+            // May be processed on the next frame if this is our first frame and we are measuring size
+            // FIXME: Look into removing the branch so everything can go through this same codepath for consistency.
+            window->SetWindowPosVal = g.SetNextWindowPosVal;
+            window->SetWindowPosPivot = g.SetNextWindowPosPivot;
             window->SetWindowPosAllowFlags &= ~(ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing);
         }
         else
@@ -4178,13 +4186,11 @@ bool ImGui::Begin(const char* name, bool* p_open, const ImVec2& size_on_first_us
             window->Size = window->SizeFull = size_on_first_use; // NB: argument name 'size_on_first_use' misleading here, it's really just 'size' as provided by user passed via BeginChild()->Begin().
         }
 
-        bool window_pos_center = false;
+        const bool window_pos_with_pivot = (window->SetWindowPosVal.x != FLT_MAX && window->HiddenFrames == 0);
-        window_pos_center |= (window->SetWindowPosCenterWanted && window->HiddenFrames == 0);
+        if (window_pos_with_pivot)
-        window_pos_center |= ((flags & ImGuiWindowFlags_Modal) && !window_pos_set_by_api && window_just_appearing_after_hidden_for_resize);
-        if (window_pos_center)
         {
-            // Center (any sort of window)
+            // Position given a pivot (e.g. for centering)
-            SetWindowPos(window, ImMax(style.DisplaySafeAreaPadding, fullscreen_rect.GetCenter() - window->SizeFull * 0.5f), 0);
+            SetWindowPos(window, ImMax(style.DisplaySafeAreaPadding, window->SetWindowPosVal - window->SizeFull * window->SetWindowPosPivot), 0);
         }
         else if (flags & ImGuiWindowFlags_ChildMenu)
         {
@@ -5010,7 +5016,7 @@ static void SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond)
     if (cond && (window->SetWindowPosAllowFlags & cond) == 0)
         return;
     window->SetWindowPosAllowFlags &= ~(ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing);
-    window->SetWindowPosCenterWanted = false;
+    window->SetWindowPosVal = ImVec2(FLT_MAX, FLT_MAX);
 
     // Set
     const ImVec2 old_pos = window->Pos;
@@ -5133,19 +5139,20 @@ void ImGui::SetWindowFocus(const char* name)
     }
 }
 
-void ImGui::SetNextWindowPos(const ImVec2& pos, ImGuiCond cond)
+void ImGui::SetNextWindowPos(const ImVec2& pos, ImGuiCond cond, const ImVec2& pivot)
 {
     ImGuiContext& g = *GImGui;
     g.SetNextWindowPosVal = pos;
+    g.SetNextWindowPosPivot = pivot;
     g.SetNextWindowPosCond = cond ? cond : ImGuiCond_Always;
 }
 
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
 void ImGui::SetNextWindowPosCenter(ImGuiCond cond)
 {
-    ImGuiContext& g = *GImGui;
+    SetNextWindowPos(ImGui::GetIO().DisplaySize * 0.5f, cond, ImVec2(0.5f, 0.5f));
-    g.SetNextWindowPosVal = ImVec2(-FLT_MAX, -FLT_MAX);
-    g.SetNextWindowPosCond = cond ? cond : ImGuiCond_Always;
 }
+#endif
 
 void ImGui::SetNextWindowSize(const ImVec2& size, ImGuiCond cond)
 {

imgui.h

@@ -152,8 +152,7 @@ namespace ImGui
     IMGUI_API bool          IsWindowAppearing();
     IMGUI_API void          SetWindowFontScale(float scale);                                    // per-window font scale. Adjust IO.FontGlobalScale if you want to scale all windows
 
-    IMGUI_API void          SetNextWindowPos(const ImVec2& pos, ImGuiCond cond = 0);            // set next window position. call before Begin()
+    IMGUI_API void          SetNextWindowPos(const ImVec2& pos, ImGuiCond cond = 0, const ImVec2& pivot = ImVec2(0,0)); // set next window position. call before Begin(). use pivot=(0.5f,0.5f) to center on given point, etc.
-    IMGUI_API void          SetNextWindowPosCenter(ImGuiCond cond = 0);                         // set next window position to be centered on screen. call before Begin()
     IMGUI_API void          SetNextWindowSize(const ImVec2& size, ImGuiCond cond = 0);          // set next window size. set axis to 0.0f to force an auto-fit on this axis. call before Begin()
     IMGUI_API void          SetNextWindowSizeConstraints(const ImVec2& size_min, const ImVec2& size_max, ImGuiSizeConstraintCallback custom_callback = NULL, void* custom_callback_data = NULL); // set next window size limits. use -1,-1 on either X/Y axis to preserve the current size. Use callback to apply non-trivial programmatic constraints.
     IMGUI_API void          SetNextWindowContentSize(const ImVec2& size);                       // set next window content size (enforce the range of scrollbars). set axis to 0.0f to leave it automatic. call before Begin()
@@ -489,6 +488,7 @@ namespace ImGui
 
     // Obsolete functions (Will be removed! Also see 'API BREAKING CHANGES' section in imgui.cpp)
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+    static void             SetNextWindowPosCenter(ImGuiCond cond = 0);                        // OBSOLETE 1.52+
     static inline bool      IsItemHoveredRect() { return IsItemRectHovered(); }                // OBSOLETE 1.51+
     static inline bool      IsPosHoveringAnyWindow(const ImVec2&) { IM_ASSERT(0); return false; } // OBSOLETE 1.51+. This was partly broken. You probably wanted to use ImGui::GetIO().WantCaptureMouse instead.
     static inline bool      IsMouseHoveringAnyWindow() { return IsAnyWindowHovered(); }        // OBSOLETE 1.51+

imgui_demo.cpp

@@ -2114,20 +2114,30 @@ static void ShowExampleAppConstrainedResize(bool* p_open)
     ImGui::End();
 }
 
-// Demonstrate creating a simple static window with no decoration.
+// Demonstrate creating a simple static window with no decoration + a context-menu to choose which corner of the screen to use.
 static void ShowExampleAppFixedOverlay(bool* p_open)
 {
-    ImGui::SetNextWindowPos(ImVec2(10,10));
+    const float DISTANCE = 10.0f;
+    static int corner = 0;
+    ImVec2 window_pos = ImVec2((corner & 1) ? ImGui::GetIO().DisplaySize.x - DISTANCE : DISTANCE, (corner & 2) ? ImGui::GetIO().DisplaySize.y - DISTANCE : DISTANCE);
+    ImVec2 window_pos_pivot = ImVec2((corner & 1) ? 1.0f : 0.0f, (corner & 2) ? 1.0f : 0.0f);
+    ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always, window_pos_pivot);
     ImGui::PushStyleColor(ImGuiCol_WindowBg, ImVec4(0.0f, 0.0f, 0.0f, 0.3f));
-    if (!ImGui::Begin("Example: Fixed Overlay", p_open, ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoMove|ImGuiWindowFlags_NoSavedSettings))
+    if (ImGui::Begin("Example: Fixed Overlay", p_open, ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_NoMove|ImGuiWindowFlags_NoSavedSettings))
     {
-        ImGui::End();
+        ImGui::Text("Simple overlay\nin the corner of the screen.\n(right-click to change position)");
-        return;
-    }
-    ImGui::Text("Simple overlay\non the top-left side of the screen.");
         ImGui::Separator();
         ImGui::Text("Mouse Position: (%.1f,%.1f)", ImGui::GetIO().MousePos.x, ImGui::GetIO().MousePos.y);
+        if (ImGui::BeginPopupContextWindow())
+        {
+            if (ImGui::MenuItem("Top-left", NULL, corner == 0)) corner = 0;
+            if (ImGui::MenuItem("Top-right", NULL, corner == 1)) corner = 1;
+            if (ImGui::MenuItem("Bottom-left", NULL, corner == 2)) corner = 2;
+            if (ImGui::MenuItem("Bottom-right", NULL, corner == 3)) corner = 3;
+            ImGui::EndPopup();
+        }
         ImGui::End();
+    }
     ImGui::PopStyleColor();
 }
 

imgui_internal.h

@@ -437,6 +437,7 @@ struct ImGuiContext
 
     // Storage for SetNexWindow** and SetNextTreeNode*** functions
     ImVec2                  SetNextWindowPosVal;
+    ImVec2                  SetNextWindowPosPivot;
     ImVec2                  SetNextWindowSizeVal;
     ImVec2                  SetNextWindowContentSizeVal;
     bool                    SetNextWindowCollapsedVal;
@@ -696,7 +697,8 @@ struct IMGUI_API ImGuiWindow
     ImGuiCond               SetWindowPosAllowFlags;             // store condition flags for next SetWindowPos() call.
     ImGuiCond               SetWindowSizeAllowFlags;            // store condition flags for next SetWindowSize() call.
     ImGuiCond               SetWindowCollapsedAllowFlags;       // store condition flags for next SetWindowCollapsed() call.
-    bool                    SetWindowPosCenterWanted;
+    ImVec2                  SetWindowPosVal;                    // store window position when using a non-zero Pivot (position set needs to be processed when we know the window size)
+    ImVec2                  SetWindowPosPivot;                  // store window pivot for positioning. ImVec2(0,0) when positioning from top-left corner; ImVec2(0.5f,0.5f) for centering; ImVec2(1,1) for bottom right.
 
     ImGuiDrawContext        DC;                                 // Temporary per-window data, reset at the beginning of the frame
     ImVector<ImGuiID>       IDStack;                            // ID stack. ID are hashes seeded with the value at the top of the stack