Internals: Moved CalcItemSize next to CalcItemWidth, added comments to clarify their respective intent. Should have no side effect.

imgui.cpp

@@ -2973,19 +2973,6 @@ void ImGui::FocusableItemUnregister(ImGuiWindow* window)
     window->DC.FocusCounterTab--;
 }
 
-ImVec2 ImGui::CalcItemSize(ImVec2 size, float default_x, float default_y)
-{
-    ImGuiContext& g = *GImGui;
-    ImVec2 content_max;
-    if (size.x < 0.0f || size.y < 0.0f)
-        content_max = g.CurrentWindow->Pos + GetContentRegionMax();
-    if (size.x <= 0.0f)
-        size.x = (size.x == 0.0f) ? default_x : ImMax(content_max.x - g.CurrentWindow->DC.CursorPos.x, 4.0f) + size.x;
-    if (size.y <= 0.0f)
-        size.y = (size.y == 0.0f) ? default_y : ImMax(content_max.y - g.CurrentWindow->DC.CursorPos.y, 4.0f) + size.y;
-    return size;
-}
-
 float ImGui::CalcWrapWidthForPos(const ImVec2& pos, float wrap_pos_x)
 {
     if (wrap_pos_x < 0.0f)
@@ -5785,13 +5772,13 @@ void ImGui::PopItemWidth()
     window->DC.ItemWidth = window->DC.ItemWidthStack.empty() ? window->ItemWidthDefault : window->DC.ItemWidthStack.back();
 }
 
+// Calculate default item width given value passed to PushItemWidth()
 float ImGui::CalcItemWidth()
 {
     ImGuiWindow* window = GetCurrentWindowRead();
     float w = window->DC.ItemWidth;
     if (w < 0.0f)
     {
-        // Align to a right-side limit. We include 1 frame padding in the calculation because this is how the width is always used (we add 2 frame padding to it), but we could move that responsibility to the widget as well.
         float width_to_right_edge = GetContentRegionAvail().x;
         w = ImMax(1.0f, width_to_right_edge + w);
     }
@@ -5799,6 +5786,22 @@ float ImGui::CalcItemWidth()
     return w;
 }
 
+// [Internal] Calculate full item size given user provided 'size' parameter and default width/height. Default width is often == CalcItemWidth().
+// Those two functions CalcItemWidth vs CalcItemSize are awkwardly named because they are not fully symmetrical.
+// Note that only CalcItemWidth() is publicly exposed.
+ImVec2 ImGui::CalcItemSize(ImVec2 size, float default_w, float default_h)
+{
+    ImGuiWindow* window = GetCurrentWindowRead();
+    ImVec2 content_max;
+    if (size.x < 0.0f || size.y < 0.0f)
+        content_max = window->Pos + GetContentRegionMax();
+    if (size.x <= 0.0f)
+        size.x = (size.x == 0.0f) ? default_w : ImMax(content_max.x - window->DC.CursorPos.x, 4.0f) + size.x;
+    if (size.y <= 0.0f)
+        size.y = (size.y == 0.0f) ? default_h : ImMax(content_max.y - window->DC.CursorPos.y, 4.0f) + size.y;
+    return size;
+}
+
 void ImGui::SetCurrentFont(ImFont* font)
 {
     ImGuiContext& g = *GImGui;

imgui_internal.h

@@ -1438,7 +1438,7 @@ namespace ImGui
     IMGUI_API bool          IsClippedEx(const ImRect& bb, ImGuiID id, bool clip_even_when_logged);
     IMGUI_API bool          FocusableItemRegister(ImGuiWindow* window, ImGuiID id);   // Return true if focus is requested
     IMGUI_API void          FocusableItemUnregister(ImGuiWindow* window);
-    IMGUI_API ImVec2        CalcItemSize(ImVec2 size, float default_x, float default_y);
+    IMGUI_API ImVec2        CalcItemSize(ImVec2 size, float default_w, float default_h);
     IMGUI_API float         CalcWrapWidthForPos(const ImVec2& pos, float wrap_pos_x);
     IMGUI_API void          PushMultiItemsWidths(int components, float width_full = 0.0f);
     IMGUI_API void          PushItemFlag(ImGuiItemFlags option, bool enabled);

imgui_widgets.cpp

@@ -5440,6 +5440,9 @@ bool ImGui::Selectable(const char* label, bool* p_selected, ImGuiSelectableFlags
 // - ListBoxHeader()
 // - ListBoxFooter()
 //-------------------------------------------------------------------------
+// FIXME: This is an old API. We should redesign some of it, rename ListBoxHeader->BeginListBox, ListBoxFooter->EndListBox
+// and promote using them over existing ListBox() functions, similarly to change with combo boxes.
+//-------------------------------------------------------------------------
 
 // FIXME: In principle this function should be called BeginListBox(). We should rename it after re-evaluating if we want to keep the same signature.
 // Helper to calculate the size of a listbox and display a label on the right.