Removed reliance on ImU64 type for the ImDrawList assert. (#1184)

imgui.cpp

@@ -2846,15 +2846,17 @@ static void AddDrawListToRenderList(ImVector<ImDrawList*>& out_render_list, ImDr
     IM_ASSERT(draw_list->IdxBuffer.Size == 0 || draw_list->_IdxWritePtr == draw_list->IdxBuffer.Data + draw_list->IdxBuffer.Size);
     IM_ASSERT((int)draw_list->_VtxCurrentIdx == draw_list->VtxBuffer.Size);
 
-    // Check that draw_list doesn't use more vertices than indexable in a single draw call (default ImDrawIdx = unsigned short = 2 bytes = 64K vertices per window)
-    // If this assert triggers because you are drawing lots of stuff manually, you can:
-    // A) Add '#define ImDrawIdx unsigned int' in imconfig.h to set the index size to 4 bytes. You'll need to handle the 4-bytes indices to your renderer.
-    //    For example, the OpenGL example code detect index size at compile-time by doing:
-    //    'glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);'
+    // Check that draw_list doesn't use more vertices than indexable in a single draw call (default ImDrawIdx = unsigned short = 2 bytes = 64K vertices per ImDrawList = per window)
+    // If this assert triggers because you are drawing lots of stuff manually:
+    // A) Make sure you are coarse clipping, because ImDrawList let all your vertices pass. You can use thre Metrics window to inspect draw list contents.
+    // B) If you need/want meshes with more than 64K vertices, uncomment the '#define ImDrawIdx unsigned int' line in imconfig.h to set the index size to 4 bytes. 
+    //    You'll need to handle the 4-bytes indices to your renderer. For example, the OpenGL example code detect index size at compile-time by doing:
+    //      glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);
     //    Your own engine or render API may use different parameters or function calls to specify index sizes. 2 and 4 bytes indices are generally supported by most API.
-    // B) If for some reason you cannot use 4 bytes indices or don't want to, a workaround is to call BeginChild()/EndChild() before reaching the 64K limit to split your draw commands in multiple draw lists.
-    IM_ASSERT(((ImU64)draw_list->_VtxCurrentIdx >> (sizeof(ImDrawIdx)*8)) == 0);  // Too many vertices in same ImDrawList. See comment above.
-    
+    // C) If for some reason you cannot use 4 bytes indices or don't want to, a workaround is to call BeginChild()/EndChild() before reaching the 64K limit to split your draw commands in multiple draw lists.
+    if (sizeof(ImDrawIdx) == 2)
+        IM_ASSERT(draw_list->_VtxCurrentIdx < (1 << 16) && "Too many vertices in ImDrawList using 16-bit indices. Read comment above");
+
     out_render_list.push_back(draw_list);
     GImGui->IO.MetricsRenderVertices += draw_list->VtxBuffer.Size;
     GImGui->IO.MetricsRenderIndices += draw_list->IdxBuffer.Size;