Columns: Improved honoring alignment with various values of ItemSpacing.x and WindowPadding.x. (#125, #2666)

docs/CHANGELOG.txt

@@ -61,6 +61,7 @@ Other Changes:
 - Columns: Made the right-most edge reaches up to the clipping rectangle (removing half of WindowPadding.x
   worth of asymmetrical/extraneous padding, note that there's another half that conservatively has to offset
   the right-most column, otherwise it's clipping width won't match the other column). (#125, #2666)
+- Columns: Improved honoring alignment with various values of ItemSpacing.x and WindowPadding.x. (#125, #2666)
 - Word-wrapping: Fixed overzealous word-wrapping when glyph edge lands exactly on the limit. Because
   of this, auto-fitting exactly unwrapped text would make it wrap. (fixes initial 1.15 commit, 78645a7d).
 - Scrolling: Added SetScrollHereX(), SetScrollFromPosX() for completeness. (#1580) [@kevreco]

imgui_widgets.cpp

@@ -7307,9 +7307,10 @@ void ImGui::BeginColumns(const char* str_id, int columns_count, ImGuiColumnsFlag
     // We aim so that the right-most column will have the same clipping width as other after being clipped by parent ClipRect
     const float column_padding = g.Style.ItemSpacing.x;
     const float half_clip_extend_x = ImFloor(ImMax(window->WindowPadding.x * 0.5f, window->WindowBorderSize));
-    columns->OffMinX = window->DC.Indent.x - column_padding;
+    const float max_1 = window->WorkRect.Max.x + column_padding - ImMax(column_padding - window->WindowPadding.x, 0.0f);
-    columns->OffMaxX = window->WorkRect.Max.x + half_clip_extend_x - window->Pos.x;
+    const float max_2 = window->WorkRect.Max.x + half_clip_extend_x;
-    columns->OffMaxX = ImMax(columns->OffMaxX, columns->OffMinX + 1.0f);
+    columns->OffMinX = window->DC.Indent.x - column_padding + ImMax(column_padding - window->WindowPadding.x, 0.0f);
+    columns->OffMaxX = ImMax(ImMin(max_1, max_2) - window->Pos.x, columns->OffMinX + 1.0f);
     columns->LineMinY = columns->LineMaxY = window->DC.CursorPos.y;
 
     // Clear data if columns count changed
@@ -7351,7 +7352,7 @@ void ImGui::BeginColumns(const char* str_id, int columns_count, ImGuiColumnsFlag
     float offset_1 = GetColumnOffset(columns->Current + 1);
     float width = offset_1 - offset_0;
     PushItemWidth(width * 0.65f);
-    window->DC.ColumnsOffset.x = 0.0f;
+    window->DC.ColumnsOffset.x = ImMax(column_padding - window->WindowPadding.x, 0.0f);
     window->DC.CursorPos.x = (float)(int)(window->Pos.x + window->DC.Indent.x + window->DC.ColumnsOffset.x);
     window->WorkRect.Max.x = window->Pos.x + offset_1 - column_padding;
 }
@@ -7387,7 +7388,7 @@ void ImGui::NextColumn()
     {
         // New row/line
         // Column 0 honor IndentX
-        window->DC.ColumnsOffset.x = 0.0f;
+        window->DC.ColumnsOffset.x = ImMax(column_padding - window->WindowPadding.x, 0.0f);
         window->DrawList->ChannelsSetCurrent(1);
         columns->Current = 0;
         columns->LineMinY = columns->LineMaxY;