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ShaderPlayground / deps / imgui / imgui / backends / imgui_impl_sdlrenderer3.cpp
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1// dear imgui: Renderer Backend for SDL_Renderer for SDL3
2// (Requires: SDL 3.1.8+)
3
4// Note that SDL_Renderer is an _optional_ component of SDL3, which IMHO is now largely obsolete.
5// For a multi-platform app consider using other technologies:
6// - SDL3+SDL_GPU: SDL_GPU is SDL3 new graphics abstraction API.
7// - SDL3+DirectX, SDL3+OpenGL, SDL3+Vulkan: combine SDL with dedicated renderers.
8// If your application wants to render any non trivial amount of graphics other than UI,
9// please be aware that SDL_Renderer currently offers a limited graphic API to the end-user
10// and it might be difficult to step out of those boundaries.
11
12// Implemented features:
13// [X] Renderer: User texture binding. Use 'SDL_Texture*' as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
14// [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
15// [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
16// [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.
17// Missing features:
18// [ ] Renderer: Multi-viewport support (multiple windows).
19
20// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
21// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
22// Learn about Dear ImGui:
23// - FAQ https://dearimgui.com/faq
24// - Getting Started https://dearimgui.com/getting-started
25// - Documentation https://dearimgui.com/docs (same as your local docs/ folder).
26// - Introduction, links and more at the top of imgui.cpp
27
28// CHANGELOG
29// (minor and older changes stripped away, please see git history for details)
30// 2026-04-23: Added support for standard draw callbacks (in platform_io): DrawCallback_ResetRenderState, DrawCallback_SetSamplerLinear, DrawCallback_SetSamplerNearest. (#9378)
31// 2026-03-12: Fixed invalid assert in ImGui_ImplSDLRenderer3_UpdateTexture() if ImTextureID_Invalid is defined to be != 0, which became the default since 2026-03-12. (#9295)
32// 2025-09-18: Call platform_io.ClearRendererHandlers() on shutdown.
33// 2025-06-11: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplSDLRenderer3_CreateFontsTexture() and ImGui_ImplSDLRenderer3_DestroyFontsTexture().
34// 2025-01-18: Use endian-dependent RGBA32 texture format, to match SDL_Color.
35// 2024-10-09: Expose selected render state in ImGui_ImplSDLRenderer3_RenderState, which you can access in 'void* platform_io.Renderer_RenderState' during draw callbacks.
36// 2024-07-01: Update for SDL3 api changes: SDL_RenderGeometryRaw() uint32 version was removed (SDL#9009).
37// 2024-05-14: *BREAKING CHANGE* ImGui_ImplSDLRenderer3_RenderDrawData() requires SDL_Renderer* passed as parameter.
38// 2024-02-12: Amend to query SDL_RenderViewportSet() and restore viewport accordingly.
39// 2023-05-30: Initial version.
40
41#include "imgui.h"
42#ifndef IMGUI_DISABLE
43#include "imgui_impl_sdlrenderer3.h"
44#include <stdint.h> // intptr_t
45
46// Clang warnings with -Weverything
47#if defined(__clang__)
48#pragma clang diagnostic push
49#pragma clang diagnostic ignored "-Wsign-conversion" // warning: implicit conversion changes signedness
50#elif defined(__GNUC__)
51#pragma GCC diagnostic ignored "-Wfloat-equal" // warning: comparing floating-point with '==' or '!=' is unsafe
52#endif
53
54// SDL
55#include <SDL3/SDL.h>
56#if !SDL_VERSION_ATLEAST(3,0,0)
57#error This backend requires SDL 3.0.0+
58#endif
59
60// SDL_Renderer data
61struct ImGui_ImplSDLRenderer3_Data
62{
63 SDL_Renderer* Renderer; // Main viewport's renderer
64 ImVector<SDL_FColor> ColorBuffer;
65
66 // Render State
67 SDL_ScaleMode CurrentScaleMode;
68
69 ImGui_ImplSDLRenderer3_Data() { memset((void*)this, 0, sizeof(*this)); }
70};
71
72// Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts
73// It is STRONGLY preferred that you use docking branch with multi-viewports (== single Dear ImGui context + multiple windows) instead of multiple Dear ImGui contexts.
74static ImGui_ImplSDLRenderer3_Data* ImGui_ImplSDLRenderer3_GetBackendData()
75{
76 return ImGui::GetCurrentContext() ? (ImGui_ImplSDLRenderer3_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
77}
78
79// Functions
80static void ImGui_ImplSDLRenderer3_SetupRenderState(SDL_Renderer* renderer)
81{
82 // Clear out any viewports and cliprect set by the user
83 // FIXME: Technically speaking there are lots of other things we could backup/setup/restore during our render process.
84 SDL_SetRenderViewport(renderer, nullptr);
85 SDL_SetRenderClipRect(renderer, nullptr);
86}
87
88void ImGui_ImplSDLRenderer3_NewFrame()
89{
90 ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
91 IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDLRenderer3_Init()?");
92 IM_UNUSED(bd);
93}
94
95// https://github.com/libsdl-org/SDL/issues/9009
96static int SDL_RenderGeometryRaw8BitColor(SDL_Renderer* renderer, ImVector<SDL_FColor>& colors_out, SDL_Texture* texture, const float* xy, int xy_stride, const SDL_Color* color, int color_stride, const float* uv, int uv_stride, int num_vertices, const void* indices, int num_indices, int size_indices)
97{
98 const Uint8* color2 = (const Uint8*)color;
99 colors_out.resize(num_vertices);
100 SDL_FColor* color3 = colors_out.Data;
101 for (int i = 0; i < num_vertices; i++)
102 {
103 color3[i].r = color->r / 255.0f;
104 color3[i].g = color->g / 255.0f;
105 color3[i].b = color->b / 255.0f;
106 color3[i].a = color->a / 255.0f;
107 color2 += color_stride;
108 color = (const SDL_Color*)color2;
109 }
110 return SDL_RenderGeometryRaw(renderer, texture, xy, xy_stride, color3, sizeof(*color3), uv, uv_stride, num_vertices, indices, num_indices, size_indices);
111}
112
113// Draw callbacks
114static void ImGui_ImplSDLRenderer3_DrawCallback_ResetRenderState(const ImDrawList*, const ImDrawCmd*) {} // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
115static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData(); bd->CurrentScaleMode = SDL_SCALEMODE_LINEAR; }
116static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData(); bd->CurrentScaleMode = SDL_SCALEMODE_NEAREST; }
117
118void ImGui_ImplSDLRenderer3_RenderDrawData(ImDrawData* draw_data, SDL_Renderer* renderer)
119{
120 ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
121
122 // If there's a scale factor set by the user, use that instead
123 // If the user has specified a scale factor to SDL_Renderer already via SDL_RenderSetScale(), SDL will scale whatever we pass
124 // to SDL_RenderGeometryRaw() by that scale factor. In that case we don't want to be also scaling it ourselves here.
125 float rsx = 1.0f;
126 float rsy = 1.0f;
127 SDL_GetRenderScale(renderer, &rsx, &rsy);
128 ImVec2 render_scale;
129 render_scale.x = (rsx == 1.0f) ? draw_data->FramebufferScale.x : 1.0f;
130 render_scale.y = (rsy == 1.0f) ? draw_data->FramebufferScale.y : 1.0f;
131
132 // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
133 int fb_width = (int)(draw_data->DisplaySize.x * render_scale.x);
134 int fb_height = (int)(draw_data->DisplaySize.y * render_scale.y);
135 if (fb_width == 0 || fb_height == 0)
136 return;
137
138 // Catch up with texture updates. Most of the times, the list will have 1 element with an OK status, aka nothing to do.
139 // (This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates).
140 if (draw_data->Textures != nullptr)
141 for (ImTextureData* tex : *draw_data->Textures)
142 if (tex->Status != ImTextureStatus_OK)
143 ImGui_ImplSDLRenderer3_UpdateTexture(tex);
144
145 // Backup SDL_Renderer state that will be modified to restore it afterwards
146 struct BackupSDLRendererState
147 {
148 SDL_Rect Viewport;
149 bool ViewportEnabled;
150 bool ClipEnabled;
151 SDL_Rect ClipRect;
152 };
153 BackupSDLRendererState old = {};
154 old.ViewportEnabled = SDL_RenderViewportSet(renderer);
155 old.ClipEnabled = SDL_RenderClipEnabled(renderer);
156 SDL_GetRenderViewport(renderer, &old.Viewport);
157 SDL_GetRenderClipRect(renderer, &old.ClipRect);
158
159 // Setup desired state
160 ImGui_ImplSDLRenderer3_SetupRenderState(renderer);
161
162 // Setup render state structure (for callbacks and custom texture bindings)
163 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
164 ImGui_ImplSDLRenderer3_RenderState render_state;
165 render_state.Renderer = renderer;
166 platform_io.Renderer_RenderState = &render_state;
167
168 // Will project scissor/clipping rectangles into framebuffer space
169 ImVec2 clip_off = draw_data->DisplayPos; // (0,0) unless using multi-viewports
170 ImVec2 clip_scale = render_scale;
171
172 // Render command lists
173 for (const ImDrawList* draw_list : draw_data->CmdLists)
174 {
175 const ImDrawVert* vtx_buffer = draw_list->VtxBuffer.Data;
176 const ImDrawIdx* idx_buffer = draw_list->IdxBuffer.Data;
177
178 for (int cmd_i = 0; cmd_i < draw_list->CmdBuffer.Size; cmd_i++)
179 {
180 const ImDrawCmd* pcmd = &draw_list->CmdBuffer[cmd_i];
181 if (pcmd->UserCallback)
182 {
183 // User callback, registered via ImDrawList::AddCallback()
184 if (pcmd->UserCallback == ImGui_ImplSDLRenderer3_DrawCallback_ResetRenderState)
185 ImGui_ImplSDLRenderer3_SetupRenderState(renderer);
186 else
187 pcmd->UserCallback(draw_list, pcmd);
188 }
189 else
190 {
191 // Project scissor/clipping rectangles into framebuffer space
192 ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
193 ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);
194 if (clip_min.x < 0.0f) { clip_min.x = 0.0f; }
195 if (clip_min.y < 0.0f) { clip_min.y = 0.0f; }
196 if (clip_max.x > (float)fb_width) { clip_max.x = (float)fb_width; }
197 if (clip_max.y > (float)fb_height) { clip_max.y = (float)fb_height; }
198 if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
199 continue;
200
201 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) };
202 SDL_SetRenderClipRect(renderer, &r);
203
204 const float* xy = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, pos));
205 const float* uv = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, uv));
206 const SDL_Color* color = (const SDL_Color*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.19+
207
208 // Bind texture, Draw
209 SDL_Texture* tex = (SDL_Texture*)pcmd->GetTexID();
210 SDL_SetTextureScaleMode(tex, bd->CurrentScaleMode);
211 SDL_RenderGeometryRaw8BitColor(renderer, bd->ColorBuffer, tex,
212 xy, (int)sizeof(ImDrawVert),
213 color, (int)sizeof(ImDrawVert),
214 uv, (int)sizeof(ImDrawVert),
215 draw_list->VtxBuffer.Size - pcmd->VtxOffset,
216 idx_buffer + pcmd->IdxOffset, pcmd->ElemCount, sizeof(ImDrawIdx));
217 }
218 }
219 }
220 platform_io.Renderer_RenderState = nullptr;
221
222 // Restore modified SDL_Renderer state
223 SDL_SetRenderViewport(renderer, old.ViewportEnabled ? &old.Viewport : nullptr);
224 SDL_SetRenderClipRect(renderer, old.ClipEnabled ? &old.ClipRect : nullptr);
225}
226
227void ImGui_ImplSDLRenderer3_UpdateTexture(ImTextureData* tex)
228{
229 ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
230
231 if (tex->Status == ImTextureStatus_WantCreate)
232 {
233 // Create and upload new texture to graphics system
234 //IMGUI_DEBUG_LOG("UpdateTexture #%03d: WantCreate %dx%d\n", tex->UniqueID, tex->Width, tex->Height);
235 IM_ASSERT(tex->TexID == ImTextureID_Invalid && tex->BackendUserData == nullptr);
236 IM_ASSERT(tex->Format == ImTextureFormat_RGBA32);
237
238 // Create texture
239 // (Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling)
240 SDL_Texture* sdl_texture = SDL_CreateTexture(bd->Renderer, SDL_PIXELFORMAT_RGBA32, SDL_TEXTUREACCESS_STATIC, tex->Width, tex->Height);
241 IM_ASSERT(sdl_texture != nullptr && "Backend failed to create texture!");
242 SDL_UpdateTexture(sdl_texture, nullptr, tex->GetPixels(), tex->GetPitch());
243 SDL_SetTextureBlendMode(sdl_texture, SDL_BLENDMODE_BLEND);
244 SDL_SetTextureScaleMode(sdl_texture, SDL_SCALEMODE_LINEAR);
245
246 // Store identifiers
247 tex->SetTexID((ImTextureID)(intptr_t)sdl_texture);
248 tex->SetStatus(ImTextureStatus_OK);
249 }
250 else if (tex->Status == ImTextureStatus_WantUpdates)
251 {
252 // Update selected blocks. We only ever write to textures regions which have never been used before!
253 // This backend choose to use tex->Updates[] but you can use tex->UpdateRect to upload a single region.
254 SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID;
255 for (ImTextureRect& r : tex->Updates)
256 {
257 SDL_Rect sdl_r = { r.x, r.y, r.w, r.h };
258 SDL_UpdateTexture(sdl_texture, &sdl_r, tex->GetPixelsAt(r.x, r.y), tex->GetPitch());
259 }
260 tex->SetStatus(ImTextureStatus_OK);
261 }
262 else if (tex->Status == ImTextureStatus_WantDestroy)
263 {
264 if (tex->TexID != ImTextureID_Invalid)
265 if (SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID)
266 SDL_DestroyTexture(sdl_texture);
267
268 // Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
269 tex->SetTexID(ImTextureID_Invalid);
270 tex->SetStatus(ImTextureStatus_Destroyed);
271 }
272}
273
274void ImGui_ImplSDLRenderer3_CreateDeviceObjects()
275{
276}
277
278void ImGui_ImplSDLRenderer3_DestroyDeviceObjects()
279{
280 // Destroy all textures
281 for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
282 if (tex->RefCount == 1)
283 {
284 tex->SetStatus(ImTextureStatus_WantDestroy);
285 ImGui_ImplSDLRenderer3_UpdateTexture(tex);
286 }
287}
288
289bool ImGui_ImplSDLRenderer3_Init(SDL_Renderer* renderer)
290{
291 ImGuiIO& io = ImGui::GetIO();
292 IMGUI_CHECKVERSION();
293 IM_ASSERT(io.BackendRendererUserData == nullptr && "Already initialized a renderer backend!");
294 IM_ASSERT(renderer != nullptr && "SDL_Renderer not initialized!");
295
296 // Setup backend capabilities flags
297 ImGui_ImplSDLRenderer3_Data* bd = IM_NEW(ImGui_ImplSDLRenderer3_Data)();
298 io.BackendRendererUserData = (void*)bd;
299 io.BackendRendererName = "imgui_impl_sdlrenderer3";
300 io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
301 io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures; // We can honor ImGuiPlatformIO::Textures[] requests during render.
302
303 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
304 platform_io.DrawCallback_ResetRenderState = ImGui_ImplSDLRenderer3_DrawCallback_ResetRenderState;
305 platform_io.DrawCallback_SetSamplerLinear = ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerLinear;
306 platform_io.DrawCallback_SetSamplerNearest = ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerNearest;
307
308 bd->Renderer = renderer;
309
310 return true;
311}
312
313void ImGui_ImplSDLRenderer3_Shutdown()
314{
315 ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
316 IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
317 ImGuiIO& io = ImGui::GetIO();
318 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
319
320 ImGui_ImplSDLRenderer3_DestroyDeviceObjects();
321
322 io.BackendRendererName = nullptr;
323 io.BackendRendererUserData = nullptr;
324 io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
325 platform_io.ClearRendererHandlers();
326 IM_DELETE(bd);
327}
328
329//-----------------------------------------------------------------------------
330
331#if defined(__clang__)
332#pragma clang diagnostic pop
333#endif
334
335#endif // #ifndef IMGUI_DISABLE