DragScalarN, SliderScalarN, InputScalarN, PushMultiItemsWidths: improve multi-components width computation to better distribute the error. (#7120, #7121)

docs/CHANGELOG.txt

@@ -64,6 +64,8 @@ Other changes:
 - Drag and Drop: Fixed drop target highlight on items temporarily pushing a widened clip rect
   (namely Selectables and Treenodes using SpanAllColumn flag) so the highlight properly covers
   all columns. (#7049, #4281, #3272)
+- DragScalarN, SliderScalarN, InputScalarN, PushMultiItemsWidths: improve multi-components
+  width computation to better distribute the error. (#7120, #7121) [@Nahor]
 - Menus: Tweaked hover slack logic, adding a timer to avoid situations where a slow vertical
   movements toward another parent BeginMenu() can keep the wrong child menu open. (#6671, #6926)
 - Debug Tools: Added DebugFlashStyleColor() to identify a style color. Added to Style Editor.

imgui.cpp

@@ -9862,14 +9862,16 @@ void ImGui::PushMultiItemsWidths(int components, float w_full)
     ImGuiWindow* window = g.CurrentWindow;
     IM_ASSERT(components > 0);
     const ImGuiStyle& style = g.Style;
-    const float w_item_one  = ImMax(1.0f, IM_TRUNC((w_full - (style.ItemInnerSpacing.x) * (components - 1)) / (float)components));
-    const float w_item_last = ImMax(1.0f, IM_TRUNC(w_full - (w_item_one + style.ItemInnerSpacing.x) * (components - 1)));
     window->DC.ItemWidthStack.push_back(window->DC.ItemWidth); // Backup current width
-    if (components > 1)
-        window->DC.ItemWidthStack.push_back(w_item_last);
-    for (int i = 0; i < components - 2; i++)
-        window->DC.ItemWidthStack.push_back(w_item_one);
-    window->DC.ItemWidth = (components == 1) ? w_item_last : w_item_one;
+    float w_items = w_full - style.ItemInnerSpacing.x * (components - 1);
+    float prev_split = w_items;
+    for (int i = components - 1; i > 0; i--)
+    {
+        float next_split = IM_TRUNC(w_items * i / components);
+        window->DC.ItemWidthStack.push_back(prev_split - next_split);
+        prev_split = next_split;
+    }
+    window->DC.ItemWidth = prev_split;
     g.NextItemData.Flags &= ~ImGuiNextItemDataFlags_HasWidth;
 }