// dear imgui: Renderer Backend for SDL_Renderer for SDL3
// (Requires: SDL 3.0.0+)
// Note how SDL_Renderer is an _optional_ component of SDL3.
// For a multi-platform app consider using e.g. SDL+DirectX on Windows and SDL+OpenGL on Linux/OSX.
// If your application will want to render any non trivial amount of graphics other than UI,
// please be aware that SDL_Renderer currently offers a limited graphic API to the end-user and
// it might be difficult to step out of those boundaries.
// Implemented features:
// [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!
// [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
// You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
// Learn about Dear ImGui:
// - FAQ https://dearimgui.com/faq
// - Getting Started https://dearimgui.com/getting-started
// - Documentation https://dearimgui.com/docs (same as your local docs/ folder).
// - Introduction, links and more at the top of imgui.cpp
// CHANGELOG
// 2024-05-14: *BREAKING CHANGE* ImGui_ImplSDLRenderer3_RenderDrawData() requires SDL_Renderer* passed as parameter.
// 2024-02-12: Amend to query SDL_RenderViewportSet() and restore viewport accordingly.
// 2023-05-30: Initial version.
#include "imgui.h"
#ifndef IMGUI_DISABLE
#include "imgui_impl_sdlrenderer3.h"
#include <stdint.h> // intptr_t
// Clang warnings with -Weverything
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wsign-conversion" // warning: implicit conversion changes signedness
#endif
// SDL
#include <SDL3/SDL.h>
#if !SDL_VERSION_ATLEAST(3,0,0)
#error This backend requires SDL 3.0.0+
#endif
// SDL_Renderer data
struct ImGui_ImplSDLRenderer3_Data
{
SDL_Renderer* Renderer; // Main viewport's renderer
SDL_Texture* FontTexture;
ImGui_ImplSDLRenderer3_Data() { memset((void*)this, 0, sizeof(*this)); }
};
// Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts
// It is STRONGLY preferred that you use docking branch with multi-viewports (== single Dear ImGui context + multiple windows) instead of multiple Dear ImGui contexts.
static ImGui_ImplSDLRenderer3_Data* ImGui_ImplSDLRenderer3_GetBackendData()
{
return ImGui::GetCurrentContext() ? (ImGui_ImplSDLRenderer3_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
}
// Functions
bool ImGui_ImplSDLRenderer3_Init(SDL_Renderer* renderer)
{
ImGuiIO& io = ImGui::GetIO();
IMGUI_CHECKVERSION();
IM_ASSERT(io.BackendRendererUserData == nullptr && "Already initialized a renderer backend!");
IM_ASSERT(renderer != nullptr && "SDL_Renderer not initialized!");
// Setup backend capabilities flags
ImGui_ImplSDLRenderer3_Data* bd = IM_NEW(ImGui_ImplSDLRenderer3_Data)();
io.BackendRendererUserData = (void*)bd;
io.BackendRendererName = "imgui_impl_sdlrenderer3";
io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
bd->Renderer = renderer;
return true;
}
void ImGui_ImplSDLRenderer3_Shutdown()
{
ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
ImGuiIO& io = ImGui::GetIO();
ImGui_ImplSDLRenderer3_DestroyDeviceObjects();
io.BackendRendererName = nullptr;
io.BackendRendererUserData = nullptr;
io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
IM_DELETE(bd);
}
static void ImGui_ImplSDLRenderer3_SetupRenderState(SDL_Renderer* renderer)
{
// Clear out any viewports and cliprect set by the user
// FIXME: Technically speaking there are lots of other things we could backup/setup/restore during our render process.
SDL_SetRenderViewport(renderer, nullptr);
SDL_SetRenderClipRect(renderer, nullptr);
}
void ImGui_ImplSDLRenderer3_NewFrame()
{
ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDLRenderer3_Init()?");
if (!bd->FontTexture)
ImGui_ImplSDLRenderer3_CreateDeviceObjects();
}
void ImGui_ImplSDLRenderer3_RenderDrawData(ImDrawData* draw_data, SDL_Renderer* renderer)
{
// If there's a scale factor set by the user, use that instead
// If the user has specified a scale factor to SDL_Renderer already via SDL_RenderSetScale(), SDL will scale whatever we pass
// to SDL_RenderGeometryRaw() by that scale factor. In that case we don't want to be also scaling it ourselves here.
float rsx = 1.0f;
float rsy = 1.0f;
SDL_GetRenderScale(renderer, &rsx, &rsy);
ImVec2 render_scale;
render_scale.x = (rsx == 1.0f) ? draw_data->FramebufferScale.x : 1.0f;
render_scale.y = (rsy == 1.0f) ? draw_data->FramebufferScale.y : 1.0f;
// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
int fb_width = (int)(draw_data->DisplaySize.x * render_scale.x);
int fb_height = (int)(draw_data->DisplaySize.y * render_scale.y);
if (fb_width == 0 || fb_height == 0)
return;
// Backup SDL_Renderer state that will be modified to restore it afterwards
struct BackupSDLRendererState
{
SDL_Rect Viewport;
bool ViewportEnabled;
bool ClipEnabled;
SDL_Rect ClipRect;
};
BackupSDLRendererState old = {};
old.ViewportEnabled = SDL_RenderViewportSet(renderer) == SDL_TRUE;
old.ClipEnabled = SDL_RenderClipEnabled(renderer) == SDL_TRUE;
SDL_GetRenderViewport(renderer, &old.Viewport);
SDL_GetRenderClipRect(renderer, &old.ClipRect);
// Will project scissor/clipping rectangles into framebuffer space
ImVec2 clip_off = draw_data->DisplayPos; // (0,0) unless using multi-viewports
ImVec2 clip_scale = render_scale;
// Render command lists
ImGui_ImplSDLRenderer3_SetupRenderState(renderer);
for (int n = 0; n < draw_data->CmdListsCount; n++)
{
const ImDrawList* cmd_list = draw_data->CmdLists[n];
const ImDrawVert* vtx_buffer = cmd_list->VtxBuffer.Data;
const ImDrawIdx* idx_buffer = cmd_list->IdxBuffer.Data;
for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
{
const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
if (pcmd->UserCallback)
{
// User callback, registered via ImDrawList::AddCallback()
// (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)
if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)
ImGui_ImplSDLRenderer3_SetupRenderState(renderer);
else
pcmd->UserCallback(cmd_list, pcmd);
}
else
{
// Project scissor/clipping rectangles into framebuffer space
ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);
if (clip_min.x < 0.0f) { clip_min.x = 0.0f; }
if (clip_min.y < 0.0f) { clip_min.y = 0.0f; }
if (clip_max.x > (float)fb_width) { clip_max.x = (float)fb_width; }
if (clip_max.y > (float)fb_height) { clip_max.y = (float)fb_height; }
if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
continue;
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_SetRenderClipRect(renderer, &r);
const float* xy = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, pos));
const float* uv = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, uv));
const SDL_Color* color = (const SDL_Color*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.19+
// Bind texture, Draw
SDL_Texture* tex = (SDL_Texture*)pcmd->GetTexID();
SDL_RenderGeometryRaw(renderer, tex,
xy, (int)sizeof(ImDrawVert),
color, (int)sizeof(ImDrawVert),
uv, (int)sizeof(ImDrawVert),
cmd_list->VtxBuffer.Size - pcmd->VtxOffset,
idx_buffer + pcmd->IdxOffset, pcmd->ElemCount, sizeof(ImDrawIdx));
}
}
}
// Restore modified SDL_Renderer state
SDL_SetRenderViewport(renderer, old.ViewportEnabled ? &old.Viewport : nullptr);
SDL_SetRenderClipRect(renderer, old.ClipEnabled ? &old.ClipRect : nullptr);
}
// Called by Init/NewFrame/Shutdown
bool ImGui_ImplSDLRenderer3_CreateFontsTexture()
{
ImGuiIO& io = ImGui::GetIO();
ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
// Build texture atlas
unsigned char* pixels;
int width, height;
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height); // Load as RGBA 32-bit (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.
// Upload texture to graphics system
// (Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling)
bd->FontTexture = SDL_CreateTexture(bd->Renderer, SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STATIC, width, height);
if (bd->FontTexture == nullptr)
{
SDL_Log("error creating texture");
return false;
}
SDL_UpdateTexture(bd->FontTexture, nullptr, pixels, 4 * width);
SDL_SetTextureBlendMode(bd->FontTexture, SDL_BLENDMODE_BLEND);
SDL_SetTextureScaleMode(bd->FontTexture, SDL_SCALEMODE_LINEAR);
// Store our identifier
io.Fonts->SetTexID((ImTextureID)(intptr_t)bd->FontTexture);
return true;
}
void ImGui_ImplSDLRenderer3_DestroyFontsTexture()
{
ImGuiIO& io = ImGui::GetIO();
ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
if (bd->FontTexture)
{
io.Fonts->SetTexID(0);
SDL_DestroyTexture(bd->FontTexture);
bd->FontTexture = nullptr;
}
}
bool ImGui_ImplSDLRenderer3_CreateDeviceObjects()
{
return ImGui_ImplSDLRenderer3_CreateFontsTexture();
}
void ImGui_ImplSDLRenderer3_DestroyDeviceObjects()
{
ImGui_ImplSDLRenderer3_DestroyFontsTexture();
}
//-----------------------------------------------------------------------------
#if defined(__clang__)
#pragma clang diagnostic pop
#endif
#endif // #ifndef IMGUI_DISABLE
