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authorAldrik Ramaekers <aldrikboy@gmail.com>2025-08-03 19:22:36 +0200
committerAldrik Ramaekers <aldrikboy@gmail.com>2025-08-03 19:22:36 +0200
commit853bbb3752a5fa2f58ef456ffb6e3a552e13cb11 (patch)
treece49a533f82a42a65fa6a4771a7b8fbfe33798cf /imgui-1.92.1/backends/imgui_impl_sdlrenderer2.cpp
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+// dear imgui: Renderer Backend for SDL_Renderer for SDL2
+// (Requires: SDL 2.0.17+)
+
+// Note that SDL_Renderer is an _optional_ component of SDL2, which IMHO is now largely obsolete.
+// For a multi-platform app consider using other technologies:
+// - SDL3+SDL_GPU: SDL_GPU is SDL3 new graphics abstraction API. You will need to update to SDL3.
+// - SDL2+DirectX, SDL2+OpenGL, SDL2+Vulkan: combine SDL with dedicated renderers.
+// If your application wants 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 texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
+// [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
+// [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
+// [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.
+
+// 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
+// 2025-06-11: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplSDLRenderer2_CreateFontsTexture() and ImGui_ImplSDLRenderer2_DestroyFontsTexture().
+// 2025-01-18: Use endian-dependent RGBA32 texture format, to match SDL_Color.
+// 2024-10-09: Expose selected render state in ImGui_ImplSDLRenderer2_RenderState, which you can access in 'void* platform_io.Renderer_RenderState' during draw callbacks.
+// 2024-05-14: *BREAKING CHANGE* ImGui_ImplSDLRenderer3_RenderDrawData() requires SDL_Renderer* passed as parameter.
+// 2023-05-30: Renamed imgui_impl_sdlrenderer.h/.cpp to imgui_impl_sdlrenderer2.h/.cpp to accommodate for upcoming SDL3.
+// 2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
+// 2021-12-21: Update SDL_RenderGeometryRaw() format to work with SDL 2.0.19.
+// 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.
+
+#include "imgui.h"
+#ifndef IMGUI_DISABLE
+#include "imgui_impl_sdlrenderer2.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
+#elif defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wfloat-equal" // warning: comparing floating-point with '==' or '!=' is unsafe
+#endif
+
+// SDL
+#include <SDL.h>
+#if !SDL_VERSION_ATLEAST(2,0,17)
+#error This backend requires SDL 2.0.17+ because of SDL_RenderGeometry() function
+#endif
+
+// SDL_Renderer data
+struct ImGui_ImplSDLRenderer2_Data
+{
+ SDL_Renderer* Renderer; // Main viewport's renderer
+
+ ImGui_ImplSDLRenderer2_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_ImplSDLRenderer2_Data* ImGui_ImplSDLRenderer2_GetBackendData()
+{
+ return ImGui::GetCurrentContext() ? (ImGui_ImplSDLRenderer2_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
+}
+
+// Functions
+bool ImGui_ImplSDLRenderer2_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_ImplSDLRenderer2_Data* bd = IM_NEW(ImGui_ImplSDLRenderer2_Data)();
+ io.BackendRendererUserData = (void*)bd;
+ io.BackendRendererName = "imgui_impl_sdlrenderer2";
+ io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+ io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures; // We can honor ImGuiPlatformIO::Textures[] requests during render.
+
+ bd->Renderer = renderer;
+
+ return true;
+}
+
+void ImGui_ImplSDLRenderer2_Shutdown()
+{
+ ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();
+ IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
+ ImGuiIO& io = ImGui::GetIO();
+
+ ImGui_ImplSDLRenderer2_DestroyDeviceObjects();
+
+ io.BackendRendererName = nullptr;
+ io.BackendRendererUserData = nullptr;
+ io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
+ IM_DELETE(bd);
+}
+
+static void ImGui_ImplSDLRenderer2_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_RenderSetViewport(renderer, nullptr);
+ SDL_RenderSetClipRect(renderer, nullptr);
+}
+
+void ImGui_ImplSDLRenderer2_NewFrame()
+{
+ ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();
+ IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDLRenderer2_Init()?");
+ IM_UNUSED(bd);
+}
+
+void ImGui_ImplSDLRenderer2_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_RenderGetScale(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;
+
+ // Catch up with texture updates. Most of the times, the list will have 1 element with an OK status, aka nothing to do.
+ // (This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates).
+ if (draw_data->Textures != nullptr)
+ for (ImTextureData* tex : *draw_data->Textures)
+ if (tex->Status != ImTextureStatus_OK)
+ ImGui_ImplSDLRenderer2_UpdateTexture(tex);
+
+ // Backup SDL_Renderer state that will be modified to restore it afterwards
+ struct BackupSDLRendererState
+ {
+ SDL_Rect Viewport;
+ bool ClipEnabled;
+ SDL_Rect ClipRect;
+ };
+ BackupSDLRendererState old = {};
+ old.ClipEnabled = SDL_RenderIsClipEnabled(renderer) == SDL_TRUE;
+ SDL_RenderGetViewport(renderer, &old.Viewport);
+ SDL_RenderGetClipRect(renderer, &old.ClipRect);
+
+ // Setup desired state
+ ImGui_ImplSDLRenderer2_SetupRenderState(renderer);
+
+ // Setup render state structure (for callbacks and custom texture bindings)
+ ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+ ImGui_ImplSDLRenderer2_RenderState render_state;
+ render_state.Renderer = renderer;
+ platform_io.Renderer_RenderState = &render_state;
+
+ // 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
+ for (int n = 0; n < draw_data->CmdListsCount; n++)
+ {
+ const ImDrawList* draw_list = draw_data->CmdLists[n];
+ const ImDrawVert* vtx_buffer = draw_list->VtxBuffer.Data;
+ const ImDrawIdx* idx_buffer = draw_list->IdxBuffer.Data;
+
+ for (int cmd_i = 0; cmd_i < draw_list->CmdBuffer.Size; cmd_i++)
+ {
+ const ImDrawCmd* pcmd = &draw_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_ImplSDLRenderer2_SetupRenderState(renderer);
+ else
+ pcmd->UserCallback(draw_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_RenderSetClipRect(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));
+#if SDL_VERSION_ATLEAST(2,0,19)
+ const SDL_Color* color = (const SDL_Color*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.19+
+#else
+ const int* color = (const int*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.17 and 2.0.18
+#endif
+
+ // 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),
+ draw_list->VtxBuffer.Size - pcmd->VtxOffset,
+ idx_buffer + pcmd->IdxOffset, pcmd->ElemCount, sizeof(ImDrawIdx));
+ }
+ }
+ }
+ platform_io.Renderer_RenderState = nullptr;
+
+ // Restore modified SDL_Renderer state
+ SDL_RenderSetViewport(renderer, &old.Viewport);
+ SDL_RenderSetClipRect(renderer, old.ClipEnabled ? &old.ClipRect : nullptr);
+}
+
+void ImGui_ImplSDLRenderer2_UpdateTexture(ImTextureData* tex)
+{
+ ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();
+
+ if (tex->Status == ImTextureStatus_WantCreate)
+ {
+ // Create and upload new texture to graphics system
+ //IMGUI_DEBUG_LOG("UpdateTexture #%03d: WantCreate %dx%d\n", tex->UniqueID, tex->Width, tex->Height);
+ IM_ASSERT(tex->TexID == ImTextureID_Invalid && tex->BackendUserData == nullptr);
+ IM_ASSERT(tex->Format == ImTextureFormat_RGBA32);
+
+ // Create texture
+ // (Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling)
+ SDL_Texture* sdl_texture = SDL_CreateTexture(bd->Renderer, SDL_PIXELFORMAT_RGBA32, SDL_TEXTUREACCESS_STATIC, tex->Width, tex->Height);
+ IM_ASSERT(sdl_texture != nullptr && "Backend failed to create texture!");
+ SDL_UpdateTexture(sdl_texture, nullptr, tex->GetPixels(), tex->GetPitch());
+ SDL_SetTextureBlendMode(sdl_texture, SDL_BLENDMODE_BLEND);
+ SDL_SetTextureScaleMode(sdl_texture, SDL_ScaleModeLinear);
+
+ // Store identifiers
+ tex->SetTexID((ImTextureID)(intptr_t)sdl_texture);
+ tex->SetStatus(ImTextureStatus_OK);
+ }
+ else if (tex->Status == ImTextureStatus_WantUpdates)
+ {
+ // Update selected blocks. We only ever write to textures regions which have never been used before!
+ // This backend choose to use tex->Updates[] but you can use tex->UpdateRect to upload a single region.
+ SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID;
+ for (ImTextureRect& r : tex->Updates)
+ {
+ SDL_Rect sdl_r = { r.x, r.y, r.w, r.h };
+ SDL_UpdateTexture(sdl_texture, &sdl_r, tex->GetPixelsAt(r.x, r.y), tex->GetPitch());
+ }
+ tex->SetStatus(ImTextureStatus_OK);
+ }
+ else if (tex->Status == ImTextureStatus_WantDestroy)
+ {
+ SDL_Texture* sdl_texture = (SDL_Texture*)(intptr_t)tex->TexID;
+ if (sdl_texture == nullptr)
+ return;
+ SDL_DestroyTexture(sdl_texture);
+
+ // Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
+ tex->SetTexID(ImTextureID_Invalid);
+ tex->SetStatus(ImTextureStatus_Destroyed);
+ }
+}
+
+void ImGui_ImplSDLRenderer2_CreateDeviceObjects()
+{
+}
+
+void ImGui_ImplSDLRenderer2_DestroyDeviceObjects()
+{
+ // Destroy all textures
+ for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
+ if (tex->RefCount == 1)
+ {
+ tex->SetStatus(ImTextureStatus_WantDestroy);
+ ImGui_ImplSDLRenderer2_UpdateTexture(tex);
+ }
+}
+
+//-----------------------------------------------------------------------------
+
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
+#endif // #ifndef IMGUI_DISABLE