Backends: SDL_Renderer: Added support for large meshes (64k+ vertices) with 16-bit indices, enable 'ImGuiBackendFlags_RendererHasVtxOffset' in this backend. (#3926)

backends/imgui_impl_sdlrenderer.cpp

@@ -10,14 +10,15 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
+//  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bit indices.
 // Missing features:
-//  [ ] Renderer: Support for large meshes (64k+ vertices) with 16-bit indices (SDL_RenderGeometryRaw() is missing a vertex offset).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
 // Read online: https://github.com/ocornut/imgui/tree/master/docs
 
 // CHANGELOG
+//  2021-12-03: Added support for large mesh (64K+ vertices), enable ImGuiBackendFlags_RendererHasVtxOffset flag.
 //  2021-10-06: Backup and restore modified ClipRect/Viewport.
 //  2021-09-21: Initial version.
 
@@ -61,6 +62,7 @@ bool ImGui_ImplSDLRenderer_Init(SDL_Renderer* renderer)
     ImGui_ImplSDLRenderer_Data* bd = IM_NEW(ImGui_ImplSDLRenderer_Data)();
     io.BackendRendererUserData = (void*)bd;
     io.BackendRendererName = "imgui_impl_sdlrenderer";
+    io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
 
     bd->SDLRenderer = renderer;
 
@@ -127,7 +129,7 @@ void ImGui_ImplSDLRenderer_RenderDrawData(ImDrawData* draw_data)
         SDL_Rect    ClipRect;
     };
     BackupSDLRendererState old = {};
-    old.ClipEnabled = SDL_RenderIsClipEnabled(bd->SDLRenderer);
+    old.ClipEnabled = SDL_RenderIsClipEnabled(bd->SDLRenderer) == SDL_TRUE;
     SDL_RenderGetViewport(bd->SDLRenderer, &old.Viewport);
     SDL_RenderGetClipRect(bd->SDLRenderer, &old.ClipRect);
 
@@ -170,9 +172,9 @@ void ImGui_ImplSDLRenderer_RenderDrawData(ImDrawData* draw_data)
                 SDL_Rect r = { (int)(clip_min.x), (int)(clip_min.y), (int)(clip_max.x - clip_min.x), (int)(clip_max.y - clip_min.y) };
                 SDL_RenderSetClipRect(bd->SDLRenderer, &r);
 
-                const float* xy = (const float*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, pos));
-                const float* uv = (const float*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, uv));
-                const int* color = (const int*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, col));
+                const float* xy = (const float*)((const char*)(vtx_buffer + pcmd->VtxOffset) + IM_OFFSETOF(ImDrawVert, pos));
+                const float* uv = (const float*)((const char*)(vtx_buffer + pcmd->VtxOffset) + IM_OFFSETOF(ImDrawVert, uv));
+                const int* color = (const int*)((const char*)(vtx_buffer + pcmd->VtxOffset) + IM_OFFSETOF(ImDrawVert, col));
 
                 // Bind texture, Draw
 				SDL_Texture* tex = (SDL_Texture*)pcmd->GetTexID();
@@ -180,7 +182,7 @@ void ImGui_ImplSDLRenderer_RenderDrawData(ImDrawData* draw_data)
                     xy, (int)sizeof(ImDrawVert),
                     color, (int)sizeof(ImDrawVert),
                     uv, (int)sizeof(ImDrawVert),
-                    cmd_list->VtxBuffer.Size,
+                    cmd_list->VtxBuffer.Size - pcmd->VtxOffset,
                     idx_buffer + pcmd->IdxOffset, pcmd->ElemCount, sizeof(ImDrawIdx));
             }
         }

backends/imgui_impl_sdlrenderer.h

@@ -10,8 +10,7 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
-// Missing features:
-//  [ ] Renderer: Support for large meshes (64k+ vertices) with 16-bit indices (SDL_RenderGeometryRaw() is missing a vertex offset).
+//  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bit indices.
 
 #pragma once
 #include "imgui.h"      // IMGUI_IMPL_API

docs/CHANGELOG.txt

@@ -80,6 +80,8 @@ Other Changes:
   likehood of issues with people using VK_DYNAMIC_STATE_SCISSOR in their app without calling
   vkCmdSetScissor() explicitly every frame. (#4644)
 - Backends: DX12: Fixed DRAW_EMPTY_SCISSOR_RECTANGLE warnings. (#4775)
+- Backends: SDL_Renderer: Added support for large meshes (64k+ vertices) with 16-bit indices,
+  enabling 'ImGuiBackendFlags_RendererHasVtxOffset' in the backend. (#3926) [@rokups]
 - Backends: WebGPU: Passing explicit buffer sizes to wgpuRenderPassEncoderSetVertexBuffer() and
   wgpuRenderPassEncoderSetIndexBuffer() functions as validation layers appears to not do what the
   in-flux specs says. (#4766) [@meshula]