Windows: clicking on a window close button doesn't claim focus and bring to front. (#8683)

Added ImGuiItemFlags_NoFocus, ImGuiButtonFlags_NoFocus. Neither are well specified so marking as experimental.

docs/CHANGELOG.txt

@@ -302,6 +302,7 @@ Other changes:
   codepath that preserve last contents size when collapsed, resulting in
   programmatically uncollapsing auto-sizing windows having them flicker size
   for a frame. (#7691) [@achabense]
+- Windows: clicking on a window close button doesn't claim focus and bring to front. (#8683)
 - Windows: loosened code to allow hovering of resize grips, borders, and table
   borders while hovering a sibling child window, so that the code in master matches
   one in docking (they accidentally diverged). (#8554)

imgui.cpp

@@ -7126,8 +7126,12 @@ void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& titl
 
     // Close button
     if (has_close_button)
+    {
+        g.CurrentItemFlags |= ImGuiItemFlags_NoFocus;
         if (CloseButton(window->GetID("#CLOSE"), close_button_pos))
             *p_open = false;
+        g.CurrentItemFlags &= ~ImGuiItemFlags_NoFocus;
+    }
 
     window->DC.NavLayerCurrent = ImGuiNavLayer_Main;
     g.CurrentItemFlags = item_flags_backup;

imgui_internal.h

@@ -946,6 +946,7 @@ enum ImGuiItemFlagsPrivate_
     ImGuiItemFlags_AllowOverlap             = 1 << 14, // false     // Allow being overlapped by another widget. Not-hovered to Hovered transition deferred by a frame.
     ImGuiItemFlags_NoNavDisableMouseHover   = 1 << 15, // false     // Nav keyboard/gamepad mode doesn't disable hover highlight (behave as if NavHighlightItemUnderNav==false).
     ImGuiItemFlags_NoMarkEdited             = 1 << 16, // false     // Skip calling MarkItemEdited()
+    ImGuiItemFlags_NoFocus                  = 1 << 17, // false     // [EXPERIMENTAL: Not very well specced] Clicking doesn't take focus. Automatically sets ImGuiButtonFlags_NoFocus + ImGuiButtonFlags_NoNavFocus in ButtonBehavior().
 
     // Controlled by widget code
     ImGuiItemFlags_Inputable                = 1 << 20, // false     // [WIP] Auto-activate input mode when tab focused. Currently only used and supported by a few items before it becomes a generic feature.
@@ -1023,6 +1024,7 @@ enum ImGuiButtonFlagsPrivate_
     ImGuiButtonFlags_NoHoveredOnFocus       = 1 << 19,  // don't report as hovered when nav focus is on this item
     ImGuiButtonFlags_NoSetKeyOwner          = 1 << 20,  // don't set key/input owner on the initial click (note: mouse buttons are keys! often, the key in question will be ImGuiKey_MouseLeft!)
     ImGuiButtonFlags_NoTestKeyOwner         = 1 << 21,  // don't test key/input owner when polling the key (note: mouse buttons are keys! often, the key in question will be ImGuiKey_MouseLeft!)
+    ImGuiButtonFlags_NoFocus                = 1 << 22,  // [EXPERIMENTAL: Not very well specced]. Don't focus parent window when clicking.
     ImGuiButtonFlags_PressedOnMask_         = ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_PressedOnClickRelease | ImGuiButtonFlags_PressedOnClickReleaseAnywhere | ImGuiButtonFlags_PressedOnRelease | ImGuiButtonFlags_PressedOnDoubleClick | ImGuiButtonFlags_PressedOnDragDropHold,
     ImGuiButtonFlags_PressedOnDefault_      = ImGuiButtonFlags_PressedOnClickRelease,
 };

imgui_widgets.cpp

@@ -548,6 +548,8 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
     ImGuiItemFlags item_flags = (g.LastItemData.ID == id ? g.LastItemData.ItemFlags : g.CurrentItemFlags);
     if (flags & ImGuiButtonFlags_AllowOverlap)
         item_flags |= ImGuiItemFlags_AllowOverlap;
+    if (item_flags & ImGuiItemFlags_NoFocus)
+        flags |= ImGuiButtonFlags_NoFocus | ImGuiButtonFlags_NoNavFocus;
 
     // Default only reacts to left mouse button
     if ((flags & ImGuiButtonFlags_MouseButtonMask_) == 0)
@@ -623,7 +625,7 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
                         SetFocusID(id, window);
                         FocusWindow(window);
                     }
-                    else
+                    else if (!(flags & ImGuiButtonFlags_NoFocus))
                     {
                         FocusWindow(window, ImGuiFocusRequestFlags_RestoreFocusedChild); // Still need to focus and bring to front, but try to avoid losing NavId when navigating a child
                     }
@@ -641,7 +643,7 @@ bool ImGui::ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool
                         SetFocusID(id, window);
                         FocusWindow(window);
                     }
-                    else
+                    else if (!(flags & ImGuiButtonFlags_NoFocus))
                     {
                         FocusWindow(window, ImGuiFocusRequestFlags_RestoreFocusedChild); // Still need to focus and bring to front, but try to avoid losing NavId when navigating a child
                     }