Changed syntax for (very rarely used) IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT mechanism, instead you only need to '#define ImDrawVert MyDrawVert' to use this feature, avoiding the need to declare the entire structure within an awkward macro. Using the old macro will now error with a message pointing you to the new method. (#38, #103, #1172, #1231, #2489)

docs/CHANGELOG.txt

@@ -35,6 +35,10 @@ HOW TO UPDATE?
 Breaking Changes:
 - IO: changed AddInputCharacter(unsigned short c) signature to AddInputCharacter(unsigned int c).
 - Renamed SetNextTreeNodeOpen() to SetNextItemOpen(). Kept inline redirection function (will obsolete).
+- Changed syntax for (very rarely used) IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT mechanism, instead you only
+  need to '#define ImDrawVert MyDrawVert' to use this feature, avoiding the need to declare the entire
+  structure within an awkward macro. Using the old macro will now error with a message pointing you
+  to the new method. (#38, #103, #1172, #1231, #2489)
 
 Other Changes:
 - Window: clarified behavior of SetNextWindowContentSize(). Content size is defined as the size available

examples/imgui_impl_dx9.cpp

@@ -138,8 +138,8 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
 
     // Copy and convert all vertices into a single contiguous buffer, convert colors to DX9 default format.
     // FIXME-OPT: This is a waste of resource, the ideal is to use imconfig.h and
-    //  1) to avoid repacking colors:   #define IMGUI_USE_BGRA_PACKED_COLOR
-    //  2) to avoid repacking vertices: #define IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT struct ImDrawVert { ImVec2 pos; float z; ImU32 col; ImVec2 uv; }
+    //  1) to avoid repacking colors:   use '#define IMGUI_USE_BGRA_PACKED_COLOR'
+    //  2) to avoid repacking vertices: use 'struct ImDrawVertDx9 { ImVec2 pos; float z; ImU32 col; ImVec2 uv; }' + '#define ImDrawVert ImDrawVertDx9'
     CUSTOMVERTEX* vtx_dst;
     ImDrawIdx* idx_dst;
     if (g_pVB->Lock(0, (UINT)(draw_data->TotalVtxCount * sizeof(CUSTOMVERTEX)), (void**)&vtx_dst, D3DLOCK_DISCARD) < 0)

imconfig.h

@@ -68,6 +68,9 @@
 // Read about ImGuiBackendFlags_RendererHasVtxOffset for details.
 //#define ImDrawIdx unsigned int
 
+//---- Override ImDrawVert layout (see comments near ImDrawVert declaration)
+//#define ImDrawVert MyDrawVert
+
 //---- Tip: You can add extra functions within the ImGui:: namespace, here or in your own headers files.
 /*
 namespace ImGui

imgui.cpp

@@ -369,6 +369,8 @@ CODE
  When you are not sure about a old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2019/06/05 (1.71) - changed syntax for (very rarely used) IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT mechanism. instead you only need to '#define ImDrawVert MyDrawVert' to use this feature, 
+                       avoiding the need to declare the entire structure within an awkward macro. Using the old macro will now error and show a message pointing you to the you method.
  - 2019/05/13 (1.71) - renamed SetNextTreeNodeOpen() to SetNextItemOpen(). Kept inline redirection function (will obsolete).
  - 2019/05/11 (1.71) - changed io.AddInputCharacter(unsigned short c) signature to io.AddInputCharacter(unsigned int c).
  - 2019/04/29 (1.70) - improved ImDrawList thick strokes (>1.0f) preserving correct thickness up to 90 degrees angles (e.g. rectangles). If you have custom rendering using thick lines, they will appear thicker now.

imgui.h

@@ -97,7 +97,7 @@ struct ImDrawData;                  // All draw command lists required to render
 struct ImDrawList;                  // A single draw command list (generally one per window, conceptually you may see this as a dynamic "mesh" builder)
 struct ImDrawListSharedData;        // Data shared among multiple draw lists (typically owned by parent ImGui context, but you may create one yourself)
 struct ImDrawListSplitter;          // Helper to split a draw list into different layers which can be drawn into out of order, then flattened back.
-struct ImDrawVert;                  // A single vertex (pos + uv + col = 20 bytes by default. Override layout with IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT)
+struct ImDrawVert;                  // A single vertex (pos + uv + col = 20 bytes by default. You may override layout with a #define.
 struct ImFont;                      // Runtime data for a single font within a parent ImFontAtlas
 struct ImFontAtlas;                 // Runtime data for multiple fonts, bake multiple fonts into a single texture, TTF/OTF font loader
 struct ImFontConfig;                // Configuration data when adding a font or merging fonts
@@ -1803,19 +1803,23 @@ typedef unsigned short ImDrawIdx;
 #endif
 
 // Vertex layout
-#ifndef IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT
+// (You can override the vertex format layout by using e.g. #define ImDrawVert MyDrawVert in imconfig.h
+//  The code expect ImVec2 pos (8 bytes), ImVec2 uv (8 bytes), ImU32 col (4 bytes), but you can re-order them or add other fields 
+//  as needed to simplify integration in your engine. IMPORTANT: dear imgui DOES NOT CLEAR THE STRUCTURE AND DOESN"T CALL ITS CONSTRUCTOR,
+//  so any field other than pos/uv/col will be uninitialized. If you add extra fields (such as a Z coordinate) you will need to either 
+//  ignore them, either set them up yourself.)
+#ifndef ImDrawVert
 struct ImDrawVert
 {
     ImVec2  pos;
     ImVec2  uv;
     ImU32   col;
 };
-#else
-// You can override the vertex format layout by defining IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT in imconfig.h
-// The code expect ImVec2 pos (8 bytes), ImVec2 uv (8 bytes), ImU32 col (4 bytes), but you can re-order them or add other fields as needed to simplify integration in your engine.
-// The type has to be described within the macro (you can either declare the struct or use a typedef)
-// NOTE: IMGUI DOESN'T CLEAR THE STRUCTURE AND DOESN'T CALL A CONSTRUCTOR SO ANY CUSTOM FIELD WILL BE UNINITIALIZED. IF YOU ADD EXTRA FIELDS (SUCH AS A 'Z' COORDINATES) YOU WILL NEED TO CLEAR THEM DURING RENDER OR TO IGNORE THEM.
-IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT;
+#endif
+
+// We previously used IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT that was expanded in this file. Instead please use '#define ImDrawVert MyDrawVert' [OBSOLETED in 1.71]
+#if defined(IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT)
+#error Please use '#define ImDrawVert MyDrawVert' instead!
 #endif
 
 // For use by ImDrawListSplitter.