ListBox(): Fixed frame sizing when items_count==1 unnecessarily showing a scrollbar. (#2173). Tweaked frame sizing so list boxes will look more consistent when FramePadding is far from ItemSpacing.

docs/CHANGELOG.txt

@@ -66,6 +66,8 @@ Other Changes:
   introduced in 1.50 and broken in 1.60. (#1698, #894, #713).
 - TextUnformatted(): Fixed a case where large-text path would read bytes past the text_end marker depending
   on the position of new lines in the buffer (it wasn't affecting the output but still not the right thing to do!) 
+- ListBox(): Fixed frame sizing when items_count==1 unnecessarily showing a scrollbar. (#2173) [@luk1337, @ocornut]  
+- ListBox(): Tweaked frame sizing so list boxes will look more consistent when FramePadding is far from ItemSpacing. 
 - RenderText(): Some optimization for very large text buffers, useful for non-optimized builds.
 - BeginMenu(): Fixed menu popup horizontal offset being off the item in the menu bar when WindowPadding=0.0f.
 - ArrowButton(): Fixed arrow shape being horizontally misaligned by (FramePadding.y-FramePadding.x) if they are different.

imgui_widgets.cpp

@@ -4973,7 +4973,7 @@ bool ImGui::CollapsingHeader(const char* label, bool* p_open, ImGuiTreeNodeFlags
 // - Selectable()
 //-------------------------------------------------------------------------
 
-// Tip: pass an empty label (e.g. "##dummy") then you can use the space to draw other text or image.
+// Tip: pass a non-visible label (e.g. "##dummy") then you can use the space to draw other text or image.
 // But you need to make sure the ID is unique, e.g. enclose calls in PushID/PopID or use ##unique_id.
 bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags flags, const ImVec2& size_arg)
 {
@@ -5084,9 +5084,9 @@ bool ImGui::Selectable(const char* label, bool* p_selected, ImGuiSelectableFlags
 // - ListBoxFooter()
 //-------------------------------------------------------------------------
 
-// FIXME: Rename to BeginListBox()
+// 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.
-// Tip: To have a list filling the entire window width, PushItemWidth(-1) and pass an empty label "##empty"
+// Tip: To have a list filling the entire window width, PushItemWidth(-1) and pass an non-visible label e.g. "##empty"
 bool ImGui::ListBoxHeader(const char* label, const ImVec2& size_arg)
 {
     ImGuiWindow* window = GetCurrentWindow();
@@ -5112,24 +5112,26 @@ bool ImGui::ListBoxHeader(const char* label, const ImVec2& size_arg)
     return true;
 }
 
-// FIXME: Rename to BeginListBox()
+// FIXME: In principle this function should be called EndListBox(). We should rename it after re-evaluating if we want to keep the same signature.
 bool ImGui::ListBoxHeader(const char* label, int items_count, int height_in_items)
 {
-    // Size default to hold ~7 items. Fractional number of items helps seeing that we can scroll down/up without looking at scrollbar.
+    // Size default to hold ~7.25 items.
-    // We don't add +0.40f if items_count <= height_in_items. It is slightly dodgy, because it means a dynamic list of items will make the widget resize occasionally when it crosses that size.
+    // We add +25% worth of item height to allow the user to see at a glance if there are more items up/down, without looking at the scrollbar.
+    // We don't add this extra bit if items_count <= height_in_items. It is slightly dodgy, because it means a dynamic list of items will make the widget resize occasionally when it crosses that size.
     // I am expecting that someone will come and complain about this behavior in a remote future, then we can advise on a better solution.
     if (height_in_items < 0)
         height_in_items = ImMin(items_count, 7);
-    float height_in_items_f = height_in_items < items_count ? (height_in_items + 0.40f) : (height_in_items + 0.00f);
+    const ImGuiStyle& style = GetStyle();
+    float height_in_items_f = (height_in_items < items_count) ? (height_in_items + 0.25f) : (height_in_items + 0.00f);
 
     // We include ItemSpacing.y so that a list sized for the exact number of items doesn't make a scrollbar appears. We could also enforce that by passing a flag to BeginChild().
     ImVec2 size;
     size.x = 0.0f;
-    size.y = GetTextLineHeightWithSpacing() * height_in_items_f + GetStyle().ItemSpacing.y;
+    size.y = GetTextLineHeightWithSpacing() * height_in_items_f + style.FramePadding.y * 2.0f;
     return ListBoxHeader(label, size);
 }
 
-// FIXME: Rename to EndListBox()
+// FIXME: In principle this function should be called EndListBox(). We should rename it after re-evaluating if we want to keep the same signature.
 void ImGui::ListBoxFooter()
 {
     ImGuiWindow* parent_window = GetCurrentWindow()->ParentWindow;