BeginChild: Added ImGuiChildFlags_AlwaysUseWindowPadding, obsoleted ImGuiWindowFlags_AlwaysUseWindowPadding. (#462, (toward #1666, #1496, #1395, #1710)

(bonus: will also eventually free a window flag)

docs/CHANGELOG.txt

@@ -51,7 +51,14 @@ Breaking changes:
       After:   BeginChild("Name", size, ImGuiChildFlags_Border)
       Before:  BeginChild("Name", size, false)
       After:   BeginChild("Name", size) or BeginChild("Name", 0) or BeginChild("Name", size, ImGuiChildFlags_None)
-   Kept inline redirection function with strongly typed bool versions (will obsolete).
+   Kept inline redirection function (will obsolete later) so existing code will work.
+ - BeginChild(): Added child-flag ImGuiChildFlags_AlwaysUseWindowPadding as a replacement for
+   the window-flag ImGuiWindowFlags_AlwaysUseWindowPadding: the feature only ever made sense
+   for use with BeginChild() anyhow, passing it to Begin() had no effect. Now that we accept
+   child-flags we are moving it there. (#462)
+      Before:  BeginChild("Name", size, 0, ImGuiWindowFlags_AlwaysUseWindowPadding);
+      After:   BeginChild("Name", size, ImGuiChildFlags_AlwaysUseWindowPadding, 0);
+   Kept inline redirection enum (will obsolete later) so existing code will work.
  - Debug Tools: Renamed ShowStackToolWindow() ("Stack Tool") to ShowIDStackToolWindow() ("ID Stack Tool"),
    as earlier name was misleading. Kept inline redirection function. (#4631)
  - IO: Removed io.MetricsActiveAllocations introduced in 1.63, was displayed in Metrics and unlikely to

imgui.cpp

@@ -429,6 +429,9 @@ CODE
                            - new: BeginChild("Name", size, ImGuiChildFlags_Border)
                            - old: BeginChild("Name", size, false)
                            - new: BeginChild("Name", size) or BeginChild("Name", 0) or BeginChild("Name", size, ImGuiChildFlags_None)
+ - 2023/11/02 (1.90.0) - BeginChild: added child-flag ImGuiChildFlags_AlwaysUseWindowPadding as a replacement for the window-flag ImGuiWindowFlags_AlwaysUseWindowPadding: the feature only ever made sense for BeginChild() anyhow.
+                           - old: BeginChild("Name", size, 0, ImGuiWindowFlags_AlwaysUseWindowPadding);
+                           - new: BeginChild("Name", size, ImGuiChildFlags_AlwaysUseWindowPadding, 0);
  - 2023/09/27 (1.90.0) - io: removed io.MetricsActiveAllocations introduced in 1.63. Same as 'g.DebugMemAllocCount - g.DebugMemFreeCount' (still displayed in Metrics, unlikely to be accessed by end-user).
  - 2023/09/26 (1.90.0) - debug tools: Renamed ShowStackToolWindow() ("Stack Tool") to ShowIDStackToolWindow() ("ID Stack Tool"), as earlier name was misleading. Kept inline redirection function. (#4631)
  - 2023/09/15 (1.90.0) - ListBox, Combo: changed signature of "name getter" callback in old one-liner ListBox()/Combo() apis. kept inline redirection function (will obsolete).
@@ -5419,6 +5422,8 @@ ImVec2 ImGui::GetItemRectSize()
     return g.LastItemData.Rect.GetSize();
 }
 
+// Prior to v1.90 2023/10/16, the BeginChild() function took a 'bool border = false' parameter instead of 'ImGuiChildFlags child_flags = 0'.
+// ImGuiChildFlags_Border is defined as always == 1 in order to allow old code passing 'true'.
 bool ImGui::BeginChild(const char* str_id, const ImVec2& size_arg, ImGuiChildFlags child_flags, ImGuiWindowFlags window_flags)
 {
     ImGuiID id = GetCurrentWindow()->GetID(str_id);
@@ -5436,10 +5441,23 @@ bool ImGui::BeginChildEx(const char* name, ImGuiID id, const ImVec2& size_arg, I
     ImGuiWindow* parent_window = g.CurrentWindow;
     IM_ASSERT(id != 0);
 
-    window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_ChildWindow;
-    window_flags |= (parent_window->Flags & ImGuiWindowFlags_NoMove);  // Inherit the NoMove flag
+    // Sanity check as it is likely that some user will accidentally pass ImGuiWindowFlags into the ImGuiChildFlags argument.
+    const ImGuiChildFlags ImGuiChildFlags_SupportedMask_ = ImGuiChildFlags_Border | ImGuiChildFlags_AlwaysUseWindowPadding;
+    IM_UNUSED(ImGuiChildFlags_SupportedMask_);
+    IM_ASSERT((child_flags & ~ImGuiChildFlags_SupportedMask_) == 0 && "Illegal ImGuiChildFlags value. Did you pass ImGuiWindowFlags values instead of ImGuiChildFlags?");
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+    if (window_flags & ImGuiWindowFlags_AlwaysUseWindowPadding)
+        child_flags |= ImGuiChildFlags_AlwaysUseWindowPadding;
+#endif
+
+    window_flags |= ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoSavedSettings;
+    window_flags |= (parent_window->Flags & ImGuiWindowFlags_NoMove); // Inherit the NoMove flag
+
+    // Forward child flags
+    g.NextWindowData.Flags |= ImGuiNextWindowDataFlags_HasChildFlags;
+    g.NextWindowData.ChildFlags = child_flags;
 
-    // Size
+    // Forward size
     const ImVec2 content_avail = GetContentRegionAvail();
     ImVec2 size = ImTrunc(size_arg);
     if (size.x <= 0.0f)
@@ -5538,7 +5556,7 @@ bool ImGui::BeginChildFrame(ImGuiID id, const ImVec2& size, ImGuiWindowFlags ext
     PushStyleVar(ImGuiStyleVar_ChildRounding, style.FrameRounding);
     PushStyleVar(ImGuiStyleVar_ChildBorderSize, style.FrameBorderSize);
     PushStyleVar(ImGuiStyleVar_WindowPadding, style.FramePadding);
-    bool ret = BeginChild(id, size, ImGuiChildFlags_Border, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_AlwaysUseWindowPadding | extra_flags);
+    bool ret = BeginChild(id, size, ImGuiChildFlags_Border | ImGuiChildFlags_AlwaysUseWindowPadding, ImGuiWindowFlags_NoMove | extra_flags);
     PopStyleVar(3);
     PopStyleColor();
     return ret;
@@ -6328,6 +6346,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     {
         UpdateWindowInFocusOrderList(window, window_just_created, flags);
         window->Flags = (ImGuiWindowFlags)flags;
+        window->ChildFlags = (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasChildFlags) ? g.NextWindowData.ChildFlags : 0;
         window->LastFrameActive = current_frame;
         window->LastTimeActive = (float)g.Time;
         window->BeginOrderWithinParent = 0;
@@ -6503,7 +6522,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         else
             window->WindowBorderSize = ((flags & (ImGuiWindowFlags_Popup | ImGuiWindowFlags_Tooltip)) && !(flags & ImGuiWindowFlags_Modal)) ? style.PopupBorderSize : style.WindowBorderSize;
         window->WindowPadding = style.WindowPadding;
-        if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & (ImGuiWindowFlags_AlwaysUseWindowPadding | ImGuiWindowFlags_Popup)) && window->WindowBorderSize == 0.0f)
+        if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup) && !(window->ChildFlags & ImGuiChildFlags_AlwaysUseWindowPadding) && window->WindowBorderSize == 0.0f)
             window->WindowPadding = ImVec2(0.0f, (flags & ImGuiWindowFlags_MenuBar) ? style.WindowPadding.y : 0.0f);
 
         // Lock menu offset so size calculation can use it as menu-bar windows need a minimum size.

imgui.h

@@ -994,7 +994,6 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_NoBringToFrontOnFocus  = 1 << 13,  // Disable bringing window to front when taking focus (e.g. clicking on it or programmatically giving it focus)
     ImGuiWindowFlags_AlwaysVerticalScrollbar= 1 << 14,  // Always show vertical scrollbar (even if ContentSize.y < Size.y)
     ImGuiWindowFlags_AlwaysHorizontalScrollbar=1<< 15,  // Always show horizontal scrollbar (even if ContentSize.x < Size.x)
-    ImGuiWindowFlags_AlwaysUseWindowPadding = 1 << 16,  // Ensure child windows without border uses style.WindowPadding (ignored by default for non-bordered child windows, because more convenient)
     ImGuiWindowFlags_NoNavInputs            = 1 << 18,  // No gamepad/keyboard navigation within the window
     ImGuiWindowFlags_NoNavFocus             = 1 << 19,  // No focusing toward this window with gamepad/keyboard navigation (e.g. skipped by CTRL+TAB)
     ImGuiWindowFlags_UnsavedDocument        = 1 << 20,  // Display a dot next to the title. When used in a tab/docking context, tab is selected when clicking the X + closure is not assumed (will wait for user to stop submitting the tab). Otherwise closure is assumed when pressing the X, so if you keep submitting the tab may reappear at end of tab bar.
@@ -1009,6 +1008,11 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_Popup                  = 1 << 26,  // Don't use! For internal use by BeginPopup()
     ImGuiWindowFlags_Modal                  = 1 << 27,  // Don't use! For internal use by BeginPopupModal()
     ImGuiWindowFlags_ChildMenu              = 1 << 28,  // Don't use! For internal use by BeginMenu()
+
+    // Obsolete names
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+    ImGuiWindowFlags_AlwaysUseWindowPadding = 1 << 30,  // Obsoleted in 1.90: Use ImGuiChildFlags_AlwaysUseWindowPadding in BeginChild() call.
+#endif
 };
 
 // Flags for ImGui::BeginChild()
@@ -1017,6 +1021,7 @@ enum ImGuiChildFlags_
 {
     ImGuiChildFlags_None                    = 0,
     ImGuiChildFlags_Border                  = 1 << 0,   // Show an outer border and enable WindowPadding. (Important: this is always == 1 for legacy reason)
+    ImGuiChildFlags_AlwaysUseWindowPadding  = 1 << 1,   // Pad with style.WindowPadding even if no border are drawn (no padding by default for non-bordered child windows because it makes more sense)
 };
 
 // Flags for ImGui::InputText()

imgui_internal.h

@@ -1161,6 +1161,7 @@ enum ImGuiNextWindowDataFlags_
     ImGuiNextWindowDataFlags_HasFocus           = 1 << 5,
     ImGuiNextWindowDataFlags_HasBgAlpha         = 1 << 6,
     ImGuiNextWindowDataFlags_HasScroll          = 1 << 7,
+    ImGuiNextWindowDataFlags_HasChildFlags      = 1 << 8,
 };
 
 // Storage for SetNexWindow** functions
@@ -1175,6 +1176,7 @@ struct ImGuiNextWindowData
     ImVec2                      SizeVal;
     ImVec2                      ContentSizeVal;
     ImVec2                      ScrollVal;
+    ImGuiChildFlags             ChildFlags;
     bool                        CollapsedVal;
     ImRect                      SizeConstraintRect;
     ImGuiSizeCallback           SizeCallback;
@@ -2394,6 +2396,7 @@ struct IMGUI_API ImGuiWindow
     char*                   Name;                               // Window name, owned by the window.
     ImGuiID                 ID;                                 // == ImHashStr(Name)
     ImGuiWindowFlags        Flags;                              // See enum ImGuiWindowFlags_
+    ImGuiChildFlags         ChildFlags;                         // Set when window is a child window. See enum ImGuiChildFlags_
     ImGuiViewportP*         Viewport;                           // Always set in Begin(). Inactive windows may have a NULL value here if their viewport was discarded.
     ImVec2                  Pos;                                // Position (always rounded-up to nearest pixel)
     ImVec2                  Size;                               // Current size (==SizeFull or collapsed title bar size)