ImDrawList, ImDrawListSplitter, Columns: Fixed an issue where startin…

…g a split when current VtxOffset was not zero would lead to draw commands with wrong VtxOffset. (#259

docs/CHANGELOG.txt

@@ -56,9 +56,11 @@ Other Changes:
   BeginMenu()/EndMenu() or BeginPopup/EndPopup(). (#3223, #1207) [@rokups]
 - Drag and Drop: Fixed unintended fallback "..." tooltip display during drag operation when
   drag source uses _SourceNoPreviewTooltip flags. (#3160) [@rokups]
-- ImDrawList: Fixed an issue when draw command merging or cancelling while crossing the VtxOffset
-  boundary would lead to draw command being emitted with wrong VtxOffset value. (#3129, #3163, #3232)
+- ImDrawList: Fixed an issue where draw command merging or primitive unreserve while crossing the 
+  VtxOffset boundary would lead to draw commands with wrong VtxOffset. (#3129, #3163, #3232, #2591)
   [@thedmd, @Shironekoben, @sergeyn, @ocornut]
+- ImDrawList, ImDrawListSplitter, Columns: Fixed an issue where starting a split when current 
+  VtxOffset was not zero would lead to draw commands with wrong VtxOffset. (#2591)
 - Misc, Freetype: Fix for rare case where FT_Get_Char_Index() succeed but FT_Load_Glyph() fails.
 - CI: Added CI test to verify we're never accidentally dragging libstdc++ (on some compiler setups,
   static constructors for non-pod data seems to drag in libstdc++ due to thread-safety concerns).
@@ -555,11 +557,11 @@ Other Changes:
 - Log/Capture: Fixed BeginTabItem() label not being included in a text log/capture.
 - ImDrawList: Added ImDrawCmd::VtxOffset value to support large meshes (64k+ vertices) using 16-bit indices.
   The renderer back-end needs to set 'io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset' to enable
-  this, and honor the ImDrawCmd::VtxOffset field. Otherwise the value will always be zero.
+  this, and honor the ImDrawCmd::VtxOffset field. Otherwise the value will always be zero. (#2591)
   This has the advantage of preserving smaller index buffers and allowing to execute on hardware that do not
   support 32-bit indices. Most examples back-ends have been modified to support the VtxOffset field.
 - ImDrawList: Added ImDrawCmd::IdxOffset value, equivalent to summing element count for each draw command.
-  This is provided for convenience and consistency with VtxOffset.
+  This is provided for convenience and consistency with VtxOffset. (#2591)
 - ImDrawCallback: Allow to override the signature of ImDrawCallback by #define-ing it. This is meant to
   facilitate custom rendering back-ends passing local render-specific data to the draw callback.
 - ImFontAtlas: FreeType: Added RasterizerFlags::Monochrome flag to disable font anti-aliasing. Combine
@@ -571,7 +573,7 @@ Other Changes:
   dealing with Win32, and to facilitate integration in custom engines. (#2546) [@andrewwillmott]
 - Backends: OSX: imgui_impl_osx: Added mouse cursor support. (#2585, #1873) [@actboy168]
 - Examples/Backends: DirectX9/10/11/12, Metal, Vulkan, OpenGL3 (Desktop GL only): Added support for large meshes
-  (64k+ vertices) with 16-bit indices, enable 'ImGuiBackendFlags_RendererHasVtxOffset' in those back-ends.
+  (64k+ vertices) with 16-bit indices, enable 'ImGuiBackendFlags_RendererHasVtxOffset' in those back-ends. (#2591)
 - Examples/Backends: Don't filter characters under 0x10000 before calling io.AddInputCharacter(),
   the filtering is done in io.AddInputCharacter() itself. This is in prevision for fuller Unicode
   support. (#2538, #2541)

imgui_draw.cpp

@@ -1359,6 +1359,7 @@ void ImDrawListSplitter::Split(ImDrawList* draw_list, int channels_count)
             ImDrawCmd draw_cmd;
             draw_cmd.ClipRect = draw_list->_ClipRectStack.back();
             draw_cmd.TextureId = draw_list->_TextureIdStack.back();
+            draw_cmd.VtxOffset = draw_list->_VtxCurrentOffset;
             _Channels[i]._CmdBuffer.push_back(draw_cmd);
         }
     }